[geo] Designing a scenario of unilateral climate intervention—Preprint

[Geoengineering News]

https://eartharxiv.org/repository/view/7673/

*Authors*
Patrick W Keys, Curtis M Bell

https://doi.org/10.31223/X56T3P

*11 September 2024*

*Abstract*
Climate change is causing increasingly alarming global impacts, such as
rising temperatures and more severe storms. Despite this, current
multilateral initiatives and agreements to systematically reduce greenhouse
gas emissions are completely incommensurate with the scale of the problem.
Thus, we explore the potential that some unilateral actor, finding present
and near-future climate changes intolerable, may seek to respond to these
changes through its own deliberate intervention in the climate. Focusing
specifically on stratospheric aerosol injection (SAI), which is the
dispersal of reflective particles in the stratosphere to reflect some of
the sun’s energy away from Earth, we seek to identify the characteristics
of states that might be most likely to modify the climate without broad
international consensus. We develop a framework of geopolitically-relevant
conditions that progressively reduce the number of candidate states, with
the aim of identifying plausible unilateral SAI initiators. These
conditions consider the state’s capacity to deploy SAI, variability in
states’ motivations to change their local climates, the confidence that a
deployment could be sustained and might produce the intended effects, and
the state’s insensitivity to global condemnation, should the international
community disapprove of this action. We provide a detailed explanation of
each of these conditions along with discussion of potential candidate
states. Our results highlight a concentration of states meeting all or most
of these conditions in the vicinity of the Arabian Sea. Based on this
finding, we conclude with a discussion of how this type of geopolitical
scenario development can be integrated into social-physical simulations of
geopolitically plausible climate intervention scenarios.

*Source: ArXiv*

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[geo] Emulating SAI Scenarios in CESM2 and the Effects on the Southern Hemisphere Large-Scale Atmospheric Circulation—Thesis

[Geoengineering News]

https://studenttheses.uu.nl/handle/20.500.12932/47764

*Author*
Lingbeek, Simone

2024

*Abstract*
The implementation of adequate and timely policies to prevent the further
increase of green- house gases in our atmosphere and the most disastrous
effects of global warming is becoming increasingly unlikely. In this
context, stratospheric aerosol injections (SAI) could provide a solution by
(temporarily) decreasing global mean surface temperature. The study of SAI
as a climate intervention requires earth system models capable of resolving
comprehensive at- mospheric chemistry and dynamics. Here we validate a
method that makes use of the results of the comprehensive atmospheric model
CESM2(WACCM6) to simulate SAI with the sim- pler CESM2(CAM6). We show that
this method is succesful in replicating the experiment, reproducing surface
temperature and precipitation trends within the range of model-variability.
The atmospheric thermodynamical changes caused by SAI are replicated in our
model as well, especially for the Southern Hemisphere. We then use our
model to conduct experiments with two SAI scenarios - a gradual SAI
starting in 2020 and a rapid cooling SAI scenario starting in 2080, both
with SSP5-8.5 as background. We study the effects of SAI on the large-scale
atmospheric circulation of the Southern Hemisphere. We find that both SAI
scenarios are able to prevent the changes in the lower stratosphere
observed under SSP5-8.5. In the upper strato- sphere SAI leads to a much
stronger polar night jet. SAI is also not able to prevent the strong
decrease in the frequency of sudden stratospheric warming events as
observed under SSP5-8.5. We find a slightly weaker response to SAI in the
rapid cooling SAI scenario, but overall trends are identical to the gradual
SAI scenario.

*Source: Utrecht University*

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[geo] Future Seasonal Surface Temperature Predictability with and without ARISE-Stratospheric Aerosol Injection-1.5

[Geoengineering News]

https://essopenarchive.org/doi/full/10.22541/essoar.172616142.24081869/v1

*Authors*
Kirsten J. Mayer,Elizabeth A. Barnes,James Wilson Hurrell

*12 September 2024*

*Cite as*: Kirsten J. Mayer, Elizabeth A. Barnes, James Wilson Hurrell.
Future Seasonal Surface Temperature Predictability with and without
ARISE-Stratospheric Aerosol Injection-1.5. ESS Open Archive . September 12,
2024.
DOI: 10.22541/essoar.172616142.24081869/v1

*Abstract*
To help reduce anthropogenic climate change impacts, various forms of solar
radiation modification have been proposed to reduce the rate of warming.
One method to intentionally reflect sunlight into space is through the
introduction of reflective particles into the stratosphere, known as
stratospheric aerosol injection (SAI). Previous research has shown that SAI
implementation could lead to future climate impacts beyond surface
temperature, including changes in the distribution of future tropical
precipitation. This response has the potential to modulate midlatitude
variability and predictability through atmospheric teleconnections. Here,
we explore possible differences in seasonal surface temperature
predictability under a future with and without SAI implementation, using
the ARISE-SAI-1.5 simulations. We find significant future predictability
changes in both boreal summer and winter under SSP2-4.5 with and without
SAI. However, during boreal winter, some of the increases in future
predictability under SS2-4.5 are mitigated by SAI, particularly in regions
impacted by ENSO teleconnections.

*Source: ESS OPEN ARCHIVE *

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[geo] SOLAR GEOENGINEERING WEEKLY SUMMARY (09 SEPTEMBER - 15 SEPTEMBER 2024)

[Geoengineering News]

SOLAR GEOENGINEERING WEEKLY SUMMARY (09 SEPTEMBER - 15 SEPTEMBER 2024)
*Subscribe to our newsletter to receive monthly updates on Solar
Geoengineering:*
Solar Geoengineering Updates

Monthly news summaries about solar geoengineering. Links to scientific
papers, news articles, jobs, podcasts, and videos.

By Andrew Lockley

--
DEADLINESCall for Abstract—YHYS Colloquium 2024

|
Deadline: 16 September 2024

Session: Climate interventions as a phenomenon of the Anthropocene:
Environmental social sciences research into the suggested stopgap measures.

*Call for Proposals—WCRP Climate Global South Fellowship provides young
researchers the opportunity to develop their own research initiatives,
including on SRM

|
Deadline for submitting applications: 30 September 2024*(NEW) Call for
Proposals—Exploring Climate Cooling
 | Deadline to submit
concept paper by 07 October 2024 | Full Proposal deadline is 09 December
2024*Funding opportunity: Modelling environmental responses to solar
radiation management by Natural Environment Research Council (NERC) |
Deadline to apply: 08 October 202
4*Call
for Submission—Repair Conference 2025 by Centre for Climate Repair

|
Deadline: 31 October 2024

Applications for presentations and posters are required in the following
areas:-Stratospheric Aerosol Injection-Marine Cloud Brightening-Seabed
Curtains-Sea Ice Thickening-Space Sun Shades-Other Arctic Repair Topics
(e.g. glacier drainage, land surface albedo enhancement, cirrus cloud
thinning, ocean foaming etc.)

*Submit your recent research on Solar Radiation Management to new ES:
Atmospheres collection

|
Deadline: 31 January 2025*
--
RESEARCH PAPERS*An investigation of the relationship between tropical
monsoon precipitation changes and stratospheric sulfate aerosol optical
depth
*

Xavier, A., Bala, G., Roose, S., & Kh, U. (2024). An investigation of the
relationship between tropical monsoon precipitation changes and
stratospheric sulfate aerosol optical depth. *Oxford Open Climate Change*,
*4*(1), kgae016.

*Abstract*

Stratospheric aerosol geoengineering (SAG) is one of the several solar
geoengineering options that have been proposed to counteract climate
change. In the case of SAG, reflective aerosols injected into the
stratosphere would reflect more sunlight and cool the planet. When
assessing the potential efficacy and risks of SAG, the sensitivity of
tropical monsoon precipitation changes should be also considered. Using a
climate model, we perform several stylized simulations with different
meridional distributions and amounts of volcanic sulfate aerosols in the
stratosphere. Because tropical monsoon precipitation responds to global
mean and interhemispheric difference in radiative forcing or temperature,
we quantify the sensitivity of tropical monsoon precipitation to SAG in
terms of two parameters: global mean aerosol optical depth (GMAOD) and
interhemispheric AOD difference (IHAODD). For instance, we find that the
simulated northern hemisphere monsoon precipitation has a sensitivity of
−1.33 ± 0.95% per 0.1 increase in GMAOD and −7.62 ± 0.27% per 0.1 increase
in IHAODD. Our estimated precipitation changes in terms of the two
sensitivity parameters for the global mean precipitation and for the
indices of tropical, northern hemisphere, southern hemisphere and Indian
summer monsoon precipitation are in good agreement with the model simulated
precipitation changes. Similar sensitivity estimates are also made for unit
changes in global mean and interhemispheric differences in effective
radiative forcing and surface temperature. Our study based on planetary
energetics provides a simpler framework for understanding the tropical
monsoon precipitation response to external forcing agents.

[image: (a) The meridional distribution of zonal mean concentrat

[geo] Call for Proposals: Exploring Climate Cooling—Backed by £56.8m, this programme will explore whether approaches designed to delay, or avert, climate tipping points could be feasible, scalable, an

[Geoengineering News]

*Poster's note: Submit your concept paper by 7 October*

https://www.aria.org.uk/exploring-climate-cooling/

*13 September 2024*

ARIA announced the launch of *Exploring Climate Cooling* programme.

Climate change could cause global temperatures to increase by several
degrees by the end of the century, precipitating climate tipping points
with serious and irreversible consequences.

While the only sustainable way to reduce the risk of such tipping events is
through decarbonisation, the risk of crossing one or more tipping points in
the near future has driven increased interest in approaches to actively
reduce global temperatures in the shorter term. In the absence of robust
data, we have little understanding of whether such interventions are
scientifically sound, effective, or what their full range of impacts might
be,

Backed by £56.8m, this programme will collect essential missing data and
seek to answer the fundamental scientific questions required to reach more
definitive conclusions on whether any potential approaches for cooling the
Earth could be feasible, scalable, and safe.

Find out more about the programme, our approach to responsible governance,
and apply for funding *here* .

*Key submission dates*

Concept paper window:* 13th September - 7th October*
We are now accepting three-page concept papers, which we’ll assess and
feedback whether applicants are encouraged or discouraged from submitting a
full proposal. We strongly encourage teams to do this as it has produced
substantially stronger proposals across ARIA’s other programmes.

Full proposal window: *8th November - 9th December*
Applicants can submit an eight page, full proposal during these dates. You
can still submit a full proposal if you miss the concept paper window or if
you are discouraged from a full application. However, I highly recommend
submitting a concept paper.

*Teaming*
Our teaming tool is still live, so if you would like to submit a combined
proposal with potential collaborators, register your interest for our
teaming platform
.
If you have already registered your interest, you can find a list of
pseudonymised collaborators in ARIA’s confirmation email. Please make sure
to check your junk folders.

*Clarifications*
For any questions relating to the call, please submit your question to
clarificati...@aria.org. uk. Please note that
Programme Directors cannot answer questions about live calls.

*Source: ARIA*

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[geo] Cloud Brightening Over Oceans May Stave off Climate Change, but With Risk

[Geoengineering News]

https://goodmenproject.com/featured-content/cloud-brightening-over-oceans-may-stave-off-climate-change-but-with-risk/

Ongoing efforts to include marine cloud brightening under an international
anti-marine pollution treaty, the London Protocol, could be one effective
route to setting standards for research and field experiments.



By Sean Mowbray 

*06 September 2024*

   - *• Marine cloud brightening (MCB), the spraying of sea salt aerosols
   or other fine particles into clouds to artificially brighten them and
   increase the sun’s reflectivity, is a proposed strategy to ward off the
   full effects of climate change.*
   -
- *• However, this solar radiation management (SRM) geoengineering
   technique is highly controversial, and experts say governance of MCB field
   experiments and deployment is needed now at the national and international
   levels.*
   -
- *• Ongoing efforts to include marine cloud brightening under an
   international anti-marine pollution treaty, the London Protocol, could be
   one effective route to setting standards for research and field
   experiments.*
   -
- *• But if MCB is deployed on a large scale, some experts say there is the
   potential for serious negative effects on the global climate system. These
   impacts could be especially severe if deployment is uncontrolled and lacks
   science-based governance.*
   -

Regional deployment of marine cloud brightening off the U.S. West Coast
would be far less effective in the warmer world of 2050, and if
implemented, could unleash higher temperatures in Europe and other regions,
warns recent research .

The June 2024 modeling study of the controversial geoengineering technique
shows “that a regional intervention will have large scale implications. So
even though you’re applying [MCB] in a smaller space, the impacts [end up
being] global,” says Jessica Wan, first author on the paper and a climate
sciences Ph.D. candidate at California’s Scripps Institution of
Oceanography.

Marine cloud brightening is a form of solar radiation management. According
to the theory, spraying sea salt aerosols, or other tiny particles, into
clouds over the world’s oceans could make those clouds brighter, reflecting
more of the sun’s rays back into space and leading to a cooling effect on
the Earth below.

MCB is viewed as a geoengineering technology that could buy time
, while the
world drastically slashes its carbon emissions, and as a “painkiller
”
to ward off the worst impacts of greenhouse gas-induced warming, while
those deep cuts are made.

But MCB experimentation and implementation are highly controversial, with
opponents calling for an outright ban

on
marine geoengineering technologies, which they describe as a “dangerous
distraction
”
from tackling climate change emission reductions.

Others argue MCB research is needed now to keep all options on the table,
in case aggressive carbon-cutting measures fail to quickly materialize.
Adding to the debate, experts warn of the risk posed by the dearth of
national and international regulations to guide marine cloud brightening
testing and use.
A future fraught with unknowns

Studies like Wan’s highlight the major knowledge gaps that remain in a
field that’s been mostly confined thus far to modeling, and point up the
vast uncertainties of how MCB should and could be deployed.

For Wan, the “big picture” takeaway is that “the widespread climate impacts
of a regional intervention will change under different climate conditions,”
meaning that testing and deployment impacts in today’s climate could be
very different from those in the more globally warmed future.

“I think the paper shows convincingly that the effectiveness of marine
cloud brightening in a certain region can change with continued global
warming. [But] I’m not convinced that the change will always be to diminish
efficacy,” said Michael Diamond, assistant professor of meteorology and
environmental science at Florida State University, who was not involved in
the study. “Other work has found that very local deployments (like just
over the Great Barrier Reef )
don’t seem to have detectable remote effects.”

In Diamond’s view, one conclusion could be that marine cloud brightening
may be an option for either large-scale or small-scale deployment to
protect fragile ecosystems, but not appropriate at the regional scale
.
A tale of two tests

Earlier this year, a small-scale MCB field te

[geo] The disappearance of ship tracks – on the impact of sulfur reduction in marine fuel on the climate—Thesis

[Geoengineering News]

https://repositum.tuwien.at/handle/20.500.12708/200234

*Authors*
Mirčetić, Nikola

*Citation*: Mirčetić, N. (2024). The disappearance of ship tracks – on the
impact of sulfur reduction in marine fuel on the climate [Master Thesis,
Technische Universität Wien; Diplomatische Akademie Wien]. reposiTUm.
https://doi.org/10.34726/hss.2024.123161

*Abstract*
In response to concerns regarding human health and environmental
protection, the International Maritime Organization (IMO) adopted the IMO
2020 regulation, which reduced the sulfur content in marine fuel from 3.5%
to 0.5%. This regulation, effective since 2020, has significantly reduced
sulfur dioxide (SO2) emissions from ships by more than 80%. However, this
reduction has led to the unintended consequence of diminishing the
atmospheric cooling effects provided by sulfate aerosols, which previously
contributed to the formation of clouds known as ship tracks, cloud
brightening, and the scattering of solar radiation. This loss has
potentially exacerbated global warming. This thesis investigates the
climatic impact of the IMO 2020 regulation through a comparative literature
review, analyzing divergent views within the scientific community. Key
discrepancies are highlighted between the Intergovernmental Panel on
Climate Change (IPCC) and climate scientist James E. Hansen and his
colleagues. The IPCC's 6th Assessment Report downplays the cooling effect
of pre-2020 shipping emissions, whereas other studies indicate a
significant cooling influence for the same period. In particular, recent
publications co-authored by Hansen demonstrate that the IMO 2020 regulation
has considerably reduced the formation of ship tracks and contributed to
recent warming. There is now compelling evidence that the IMO 2020
regulation has led to an increase in absorbed solar radiation, resulting in
an acceleration of global warming rates. *This indicates that sulfur
reductions are contributing to the occurrence of more extreme weather
events. The thesis concludes that while sulfur reductions are intended to
improve human health and reduce premature deaths attributable to ship
emissions, the climatic repercussions necessitate reevaluation. The
findings call for an improved understanding of aerosol impacts to enhance
climate models and propose deliberate geoengineering measures, such as
marine cloud brightening via aerosol injection, to mitigate the unintended
warming effects of sulfur emission reductions.*

*Source: Tuwien*

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[geo] Implications for governance of Stardust’s activities in relation to Stratospheric Aerosol Injection— A report by Janos Pasztor

[Geoengineering News]

https://www.linkedin.com/posts/janos-pasztor-85465421_report-to-stardust-on-governance-implications-activity-7239141519784378369-1Oms

*Janos Pasztor*

*10 September 2024*

“On 2 May I posted about my work as an independent consultant to Stardust
Solutions, a USA/Israeli startup, to provide views and recommendations on
the governance implications of their work on stratospheric aerosol
injection. As promised, my report (attached below) would be made public.

Beyond Stardust, I hope that the ideas in this report will be of use for
other startups, whether for- or non-profit, but also for relevant state and
non-state actors.

In some ways, this is uncharted territory. But I do believe the report
addresses some key issues. I also hope that by making this available
publicly, it will encourage different actors to reflect on these, and to
come up with their ideas on what the governance implications are, and what
can be done about them.

I look forward to your feedback on this report.”— Janos Pasztor












*Source: LinkedIn*

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[geo] Opportunities and Risks: Solar Geoengineering Scenarios for Climate Change Mitigation by 2050

[Geoengineering News]

https://www.politics-dz.com/opportunities-and-risks-solar-geoengineering-scenarios-for-climate-change-mitigation-by-2050/

*07 September 2024*

With warnings of rising planetary temperatures and the international
community’s failure to implement preventative policies to combat climate
change, the importance of developing technological solutions like solar
geoengineering has increased. Solar geoengineering aims to reduce global
temperatures by modifying solar radiation (SRM) or by decreasing
atmospheric carbon dioxide through capture and storage in oceans or on land
(CDR). In the absence of a genuine commitment to reducing emissions,
scientists propose solar geoengineering as a last-ditch effort to tackle
global warming.

In this context, a recent report by the French Defense and Climate
Observatory highlighted the developments in the widespread deployment of
solar geoengineering technologies in the coming decades, the associated
natural and human risks, key actors, and the role of major powers in this
field. The report also presented potential scenarios and recommendations
for deploying these technologies by 2050.
*Nature of Technologies and Risks:*

Solar geoengineering, or solar radiation management (SRM), involves
techniques designed to reflect sunlight to cool the Earth through
large-scale, deliberate intervention in the Earth’s climate system to
mitigate the harmful effects of global warming. However, using these
techniques involves both human and natural risks. Several types of SRM
technologies are designed, including:

*Local Solar Geoengineering:* Two local techniques have been developed:
marine cloud brightening (MCB) and cloud thinning (CCT). Marine cloud
brightening involves injecting tiny droplets into marine clouds to make
them brighter and more reflective by spraying sea salt into low marine
clouds. Brighter clouds help reduce the amount of solar radiation reaching
the Earth’s surface, thereby lowering atmospheric and ocean temperatures.

*Planetary Solar Geoengineering:* This involves injecting aerosols into the
stratosphere (SAI) on a planetary scale. This method disperses reflective
particles via aircraft or balloons in the stratosphere, targeting the
release of sulfate particles to reduce the amount of sunlight reaching the
Earth and the heat trapped in the atmosphere. This approach aims to create
cooling conditions similar to those following major volcanic eruptions.
While this technique is the most studied for modifying radiative balance,
it is also the most controversial due to its planetary scope and associated
scientific uncertainties.

*Space-Based Solar Geoengineering:* Some solar geoengineering projects plan
to deploy reflective devices (mirrors) in outer space to reflect about 2%
of sunlight. This technique is less advanced and less studied due to its
complexity and high costs, estimated in billions of dollars. Mirrors would
need to be launched by rocket and positioned about 1,500,000 kilometers
from Earth at the “Lagrange L1” point, where Earth’s gravity
counterbalances the Sun’s gravity, allowing objects to be stable in orbit.

According to a 2023 United Nations report on solar geoengineering, the
mirrors would last about 20 years. Currently, there is only one space-based
geoengineering project, titled “Space Bubbles,” being carried out by a team
from MIT, aimed at dispersing some sunlight away from Earth. However, it
remains theoretical.

There are several natural risks associated with the three solar
geoengineering techniques, including: persistent effects related to
increased carbon dioxide levels, reduced photosynthesis affecting humidity,
rainfall, and local oxygen concentrations (e.g., drought in South America,
increased tropical rainfall), ozone layer degradation, increased
hurricanes, and extreme climate changes with severe impacts on temperatures
and ecosystems due to solar radiation.

Human risks include: reduced agricultural yields, decreased primary
productivity in the Amazon, slight increases in rainfall disruption in
Africa, health risks associated with temperature changes, declining air
quality, and loss of ecosystem services (e.g., decreased photosynthesis).


Additionally, there is a common risk known as “social and technical
lock-in,” where developed technologies become entrenched due to economic
and political interests, making it difficult to reverse their deployment
even if they prove ineffective or harmful, leading to what is known as
“terminal shock.” This risk is particularly relevant for space mirrors,
which might become targets in military conflicts, potentially causing an
immediate increase in global temperatures. This risk also applies to
geoengineering operations requiring ongoing chemical interventions.
*Network of Actors:*

The actors in the field of solar geoengineering vary between major
countries, the scientific community, as well as the private sector,
international bodies, and non-governmental organizations. However, major
powers remain the mo

[geo] Africa's Climate Response to Marine Cloud Brightening Strategies Is Highly Sensitive to Deployment Region

[Geoengineering News]

https://par.nsf.gov/biblio/10538156

*Authors*
Romaric_C Odoulami, Haruki Hirasawa, Kouakou Kouadio, Trisha_D Patel,
Kwesi_A Quagraine, Izidine Pinto, Temitope_S Egbebiyi, Babatunde_J Abiodun,
Christopher Lennard, Mark_G

*01 September 2024*

*Abstract*
Solar climate intervention refers to a group of methods for reducing
climate risks associated with anthropogenic warming by reflecting sunlight.
Marine cloud brightening (MCB), one such approach, proposes to inject
sea‐salt aerosol into one or more regional marine boundary layer to
increase marine cloud reflectivity. Here, we assess the potential influence
of various MCB experiments on Africa's climate using simulations from the
Community Earth System Model (CESM2) with the Community Atmosphere Model
(CAM6) as its atmospheric component. We analyzed four idealized MCB
experiments under a medium‐range background forcing scenario (SSP2‐4.5),
which brighten clouds over three subtropical ocean regions: (a) Northeast
Pacific (MCBNEP); (b) Southeast Pacific (MCBSEP); (c) Southeast Atlantic
(MCBSEA); and (d) these three regions simultaneously (MCBALL). Our results
suggest that the climate impacts of MCB in Africa are highly sensitive to
the deployment region. MCBSEPwould produce the strongest global cooling
effect and thus could be the most effective in decreasing temperatures,
increasing precipitation, and reducing the intensity and frequency of
temperature and precipitation extremes across most parts of Africa,
especially West Africa, in the future (2035–2054) compared to the
historical climate (1995–2014). MCB in other regions produces less cooling
and wetting despite similar radiative forcings. While the projected changes
under MCBALLare similar to those of MCBSEP, MCBNEPand MCBSEAcould see more
residual warming and induce a warmer future than under SSP2‐4.5 in some
regions across Africa. All MCB experiments are more effective in cooling
maximum temperature and related extremes than minimum temperature and
related extremes.

*Source: Nsf*

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[geo] SOLAR GEOENGINEERING WEEKLY SUMMARY (26 AUGUST - 01 SEPTEMBER 2024)

[Geoengineering News]

SOLAR GEOENGINEERING WEEKLY SUMMARY (26 AUGUST - 01 SEPTEMBER 2024)

Subscribe to our newsletter to receive monthly updates on Solar
Geoengineering:
Solar Geoengineering Updates

Monthly news summaries about solar geoengineering. Links to scientific
papers, news articles, jobs, podcasts, and videos.

By Andrew Lockley

--
RESEARCH PAPERSEffectiveness of Using Calcite as an Aerosol to Remediate
the Urban Heat Island 

Hoback, A. (2024). Effectiveness of Using Calcite as an Aerosol to
Remediate the Urban Heat Island. Urban Science, 8(3), 124.

*Abstract*

The purpose of this study was to develop analytical tools to find the
effectiveness of using aerosols to mitigate the urban heat island effect.
Specifically, mineral calcite would be placed in a plume over cities to
reflect solar radiation. A secondary goal is to compare the relative
efficiencies of releasing the particles from tower heights or from aircraft
heights. The aim is to reduce daytime temperatures at the surface. The
method was to use a one-dimensional model or a single-column model to
predict temperatures and weather conditions at all altitudes over a period
of one month. The SCAM6 code was altered to incorporate the new
capabilities for introduced aerosols. The pre-existing code considered only
windblown dust, so the code was enhanced to handle aerosols that were
intentionally produced. The key findings are that calcite as an aerosol
does affect the weather. The models predict that in humid regions, calcite
is less effective because it interacts with water clouds. In arid regions,
calcite should be more effective since there are fewer water clouds to
interact with. The result is that it is possible to predict reductions in
air temperatures if solar insolation can be reduced. It was shown that
temperatures can be reduced by 4 °C in arid regions. The conclusions are
that calcite aerosol should be effective at mitigating urban heat islands.
However, further work is needed related to economic, health, and ecological
concerns.

South Asian Summer Monsoon under Stratospheric Aerosol Intervention


Tilmes, S., Acharya, A., Bednarz, E., & Fadnavis, S. (2024). South Asian
Summer Monsoon under Stratospheric Aerosol Intervention.

*Abstract*

The South Asian summer monsoon (SAM) bears significant importance for
agriculture, water resources, economy, and environmental aspects of the
region for more than 1.5 billion people. To minimize the adverse impacts of
global warming, Stratospheric Aerosol Intervention (SAI) has been proposed
to lower surface temperatures by reflecting a portion of solar radiation
back into space. However, the effects of SAI on SAM are still very
uncertain and demand more research. We investigate this using the
Stratospheric Aerosol Geoengineering Large Ensemble datasets. Our study
reveals a reduction in the mean and extreme summer monsoon precipitation
under SAI in this scenario, driven by a combination of the SAI-induced
lower stratospheric warming and the associated weakening of the northern
hemispheric subtropical jet, changes in the upper-tropospheric wave
activities, geopotential height anomalies, and the strength of the Asian
Summer Monsoon Anticyclone. Local dust changes that can otherwise be
important for SAM rainfall variability under climate change also contribute
to changes under SAI. As the interest in SAI research grows, our results
demonstrate the urgent need to understand SAM variability under different
SAI scenarios, which is essential for sustainable development and disaster
preparedness in South Asia.

Cirrus formation regimes – Data driven identification and quantification of
mineral dust effect


Jeggle, K., Neubauer, D., Binder, H., & Lohmann, U. (2024). Cirrus
formation regimes–Data driven identification and quantification of mineral
dust effect. *EGUsphere*, *2024*, 1-25.

*Abstract*

The microphysical and radiative properties of cirrus clouds are strongly
dependent on the ice nucleation mechanism and origin of the ice crystals.
Due to sparse temporal coverage of satellite data and limited observations
of ice nucleating particles (INPs) at cirrus levels it is notoriously hard
to determine the origin of the ice and the nucleation mechanism of cirrus
clouds in satellite observations. In this work we combine three years of
satellite observations of cirrus clouds from the DARDAR-Nice retrieval
product with Lagrangian trajectories of reanalysis data of meteorological
and aerosol vari

[geo] Effectiveness of Using Calcite as an Aerosol to Remediate the Urban Heat Island

[Geoengineering News]

https://www.mdpi.com/2413-8851/8/3/124

*Author*
Alan Hoback

https://doi.org/10.3390/urbansci8030124

*27 August 2024*

*Abstract*
The purpose of this study was to develop analytical tools to find the
effectiveness of using aerosols to mitigate the urban heat island effect.
Specifically, mineral calcite would be placed in a plume over cities to
reflect solar radiation. A secondary goal is to compare the relative
efficiencies of releasing the particles from tower heights or from aircraft
heights. The aim is to reduce daytime temperatures at the surface. The
method was to use a one-dimensional model or a single-column model to
predict temperatures and weather conditions at all altitudes over a period
of one month. The SCAM6 code was altered to incorporate the new
capabilities for introduced aerosols. The pre-existing code considered only
windblown dust, so the code was enhanced to handle aerosols that were
intentionally produced. The key findings are that calcite as an aerosol
does affect the weather. The models predict that in humid regions, calcite
is less effective because it interacts with water clouds. In arid regions,
calcite should be more effective since there are fewer water clouds to
interact with. The result is that it is possible to predict reductions in
air temperatures if solar insolation can be reduced. It was shown that
temperatures can be reduced by 4 °C in arid regions. The conclusions are
that calcite aerosol should be effective at mitigating urban heat islands.
However, further work is needed related to economic, health, and ecological
concerns.

*Source: MDPI*

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[geo] Cirrus formation regimes – Data driven identification and quantification of mineral dust effect

[Geoengineering News]

https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2559/

*Authors*
Kai Jeggle, David Neubauer, Hanin Binder, and Ulrike Lohmann

*Citations*: Jeggle, K., Neubauer, D., Binder, H., and Lohmann, U.: Cirrus
formation regimes – Data driven identification and quantification of
mineral dust effect, EGUsphere [preprint],
https://doi.org/10.5194/egusphere-2024-2559, 2024.

*Received: 13 Aug 2024 – Discussion started: 26 Aug 2024*

*Abstract*
The microphysical and radiative properties of cirrus clouds are strongly
dependent on the ice nucleation mechanism and origin of the ice crystals.
Due to sparse temporal coverage of satellite data and limited observations
of ice nucleating particles (INPs) at cirrus levels it is notoriously hard
to determine the origin of the ice and the nucleation mechanism of cirrus
clouds in satellite observations. In this work we combine three years of
satellite observations of cirrus clouds from the DARDAR-Nice retrieval
product with Lagrangian trajectories of reanalysis data of meteorological
and aerosol variables calculated 24 h backward in time for each observed
cirrus cloud. In a first step, we identify typical cirrus cloud formation
regimes by clustering the Lagrangian trajectories and characterize observed
microphysical properties for in situ and liquid origin cirrus clouds in
midlatitudes and the tropics. On average, in situ cirrus clouds have
smaller ice water content (IWC) and lower ice crystal number concentration
(Nice) and a strong negative temperature dependence of Nice, while liquid
origin cirrus have a larger IWC and higher Nice and a strong positive
temperature dependence of IWC. In a second step, we use MERRA2 reanalysis
data to quantify the sensitivity of cirrus cloud microphysical properties
to a change in the concentration of dust particles that may act as INPs. By
identifying similar cirrus cloud formation pathways, we can condition on
ice-origin, region, and meteorological dependencies, and quantify the
impact of dust particles for different formation regimes. We find that at
cloud top median Nice decreases with increasing dust concentrations for
liquid origin cirrus. Specifically, the sensitivities are between 5 % and
11 % per unit increase of dust concentration in logarithmic space in the
tropics and between 12 % and 18 % in the mid-latitudes. The decrease in
Nice can be explained by increased heterogeneous ice nucleation in the
mixed-phase regime, leading to fewer cloud droplets freezing homogeneously
once the cloud enters the cirrus temperatures and glaciates. The resulting
fewer, but larger ice crystals are more likely to sediment, leading to
reduced IWC, as for example observed for liquid origin cirrus in the
mid-latitudes. In contrast, for in situ cirrus in the tropics, we find an
increase of Nice median values of 21 % per unit increase of dust aerosol in
logarithmic space. We assume that this is caused by heterogeneous
nucleation of ice initiated by dust INPs in INP limited conditions with
supersaturations between the heterogeneous and homogeneous freezing
thresholds. Such conditions frequently occur at high altitudes, especially
in tropical regions at temperatures below 200 K. Our results provide an
observational line of evidence that the climate intervention method of
seeding cirrus clouds with potent INPs may result in an undesired positive
cloud radiative effect (CRE), i.e. a warming effect. Instead of producing
fewer but larger ice crystals, which would lead to the desired negative
CRE, we show that additional INPs can lead to an increase in Nice, an
effect called overseeding.

*Source: EGUsphere *

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[geo] South Asian Summer Monsoon under Stratospheric Aerosol Intervention

[Geoengineering News]

https://www.researchsquare.com/article/rs-4631758/v1

*Authors*
Simone Tilmes, Asutosh Acharya, Ewa Bednarz, Suvarna Fadnavis

*26 August 2024*

https://doi.org/10.21203/rs.3.rs-4631758/v1

*Abstract*
The South Asian summer monsoon (SAM) bears significant importance for
agriculture, water resources, economy, and environmental aspects of the
region for more than 1.5 billion people. To minimize the adverse impacts of
global warming, Stratospheric Aerosol Intervention (SAI) has been proposed
to lower surface temperatures by reflecting a portion of solar radiation
back into space. However, the effects of SAI on SAM are still very
uncertain and demand more research. We investigate this using the
Stratospheric Aerosol Geoengineering Large Ensemble datasets. Our study
reveals a reduction in the mean and extreme summer monsoon precipitation
under SAI in this scenario, driven by a combination of the SAI-induced
lower stratospheric warming and the associated weakening of the northern
hemispheric subtropical jet, changes in the upper-tropospheric wave
activities, geopotential height anomalies, and the strength of the Asian
Summer Monsoon Anticyclone. Local dust changes that can otherwise be
important for SAM rainfall variability under climate change also contribute
to changes under SAI. As the interest in SAI research grows, our results
demonstrate the urgent need to understand SAM variability under different
SAI scenarios, which is essential for sustainable development and disaster
preparedness in South Asia.

*Source: Research Square*

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[geo] Projected changes to Arctic shipping routes after stratospheric aerosol deployment in the ARISE-SAI scenarios

[Geoengineering News]

https://www.frontiersin.org/journals/climate/articles/10.3389/fclim.2024.1426679/abstract

*Authors*
Ariel L. Morrison, Debanjali Pathak, Elizabeth A. Barnes, James W. Hurrell

*26 August 2024*

DOI: 10.3389/fclim.2024.1426679

*Abstract*
Rapid reductions in Arctic sea ice in response to warming have led to
increased interest in using the Arctic Ocean for commercial shipping. As
the world warms, however, different strategies are being considered to
stabilize or reduce surface temperatures in order to prevent critical
climate change impacts. One such strategy is stratospheric aerosol
injection (SAI), a form of solar climate intervention. Projected changes to
Arctic sea ice under SAI with specific regards to shipping have not yet
been assessed. We compare output from two SAI simulations that have
different global mean temperature targets with a non-SAI control simulation
to provide the first assessment of Arctic Ocean navigability under
potential SAI scenarios. We find that sea ice concentration and thickness
quickly stabilize or increase after SAI deployment. When sea ice thickness
stabilizes in response to SAI, the number of days when the Arctic Ocean is
navigable remains fairly constant, but increasing sea ice thickness leads
to reduced navigability compared to the non-SAI simulation. From 2035-2069,
both the Northwest Passage and Northern Sea Route are accessible from
July-November in all three simulations, but there are no navigable routes
under either SAI scenario from April-June. When the Arctic is navigable, it
can take 2-12 days longer to cross the Arctic Ocean in the SAI simulations
than in the non-SAI control simulation, and there are large year-to-year
variations in travel time. Overall, Arctic shipping may take longer and be
more difficult in an SAI vs a non-SAI world because of relatively thicker
sea ice, but the degree to which Arctic shipping may change in response to
SAI is dependent on the particular climate intervention strategy.

*Source: Frontiers *

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[geo] A Mathematical Modelling for Solar Irradiance Reduction of Sunshades and Some Near-future Albedo Modification Approaches for Mitigation of Global Warming

[Geoengineering News]

https://www.sciencedirect.com/science/article/abs/pii/S1364682624001652

*Authors*
Baris Baykant Alagoz, Cemal Keles, Abdullah Ates, Burhan Baran

https://doi.org/10.1016/j.jastp.2024.106337

*24 August 2024*

*Highlights*
•This study revisits mathematical modeling of the solar irradiance
reduction rate

•Solar irradiance reduction model based on the solar flux blockading is
improved

•The model discusses climate control via adjustable parameters of sunshades

•A group of feasible solutions for the global warming problem is discussed


*Abstract*
To address the global warming problem, one of the space-based
geoengineering solutions suggests the construction of an occluding disc
that can work as a solar curtain to mitigate solar irradiation penetration
to the earth atmosphere. A widely discussed concept needs the construction
of a large-scale sunshade system near the Sun–Earth L1 equilibrium point in
order to control the average global temperature. However, to improve the
accuracy of theoretical estimations, more consistent modeling of the
Sun-Curtain-Earth system and solar irradiance reduction rate are required.
This study revisits the mathematical modeling of the solar irradiance
reduction system and considers the fundamentals of shading physics.
Simplified mathematical modeling of solar irradiance reduction rate is
derived based on the solar flux density. For the climate control,
controllability of the reduction rate by using some physical parameters
(e.g., flux reflection rate and angle of the curtain) is discussed. Based
on the results of this model, the technical challenges and feasibility of
constructing a sunshade system at L1 Lagrange point are evaluated. Some
technologically feasible, near-future options for the warming problem are
discussed briefly.

*Source: ScienceDirect *

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[geo] SOLAR GEOENGINEERING WEEKLY SUMMARY (19 AUGUST - 25 AUGUST 2024)

[Geoengineering News]

SOLAR GEOENGINEERING WEEKLY SUMMARY (19 AUGUST - 25 AUGUST 2024)



Subscribe to our newsletter to receive monthly updates on Solar
Geoengineering:
Solar Geoengineering Updates

Monthly news summaries about solar geoengineering. Links to scientific
papers, news articles, jobs, podcasts, and videos.

By Andrew Lockley

--
RESEARCH PAPERSSolar Geoengineering: History, Methods, Governance, Prospects


Parson, E. A., & Keith, D. W. (2024). Solar Geoengineering: History,
Methods, Governance, Prospects. *Annual Review of Environment and Resources*,
*49*.

*Abstract*

Solar geoengineering, also called sunlight reflection or solar radiation
modification (SRM), is a potential climate response that would cool the
Earth's surface and reduce many other climate changes by scattering on
order 1% of incoming sunlight back to space. SRM can only imperfectly
correct for elevated greenhouse gases, but it might complement other
climate responses to reduce risks, while also bringing new risks and new
challenges to global governance. As climate alarm and calls for effective
near-term action mount, SRM is attracting sharply increased attention and
controversy, with many calls for expanded research and governance
consultations along with ongoing concerns about risks, misuse, or
overreliance. We review SRM's history, methods, potential uses and impacts,
and governance needs, prioritizing the approach that is most prominent and
promising, stratospheric aerosol injection. We identify several
policy-relevant characteristics of SRM interventions and identify four
narratives that capture current arguments over how SRM might be developed
or used in socio-political context to either beneficial or destructive
effect, with implications for near-term research, assessment, and
governance activity.

Baseline Climate Variables for Earth System Modelling


Juckes, M., Taylor, K. E., Antonio, F., Brayshaw, D., Buontempo, C., Cao,
J., ... & Dingley, B. (2024). Baseline Climate Variables for Earth System
Modelling. *EGUsphere*, *2024*, 1-37.

*Abstract*

The Baseline Climate Variables for Earth System Modelling (ESM-BCVs) are
defined as a list of 132 variables which have high utility for the
evaluation and exploitation of climate simulations. The list reflects the
most heavily used elements of the Coupled Model Intercomparison Project
phase 6 (CMIP6) archive. Successive phases of CMIP have supported strong
results in science and substantial influence in international climate
policy formulation. This paper responds both to interest in exploiting CMIP
data standards in a broader range of climate modelling activities and a
need to achieve greater clarity about the significance and intention of
variables in the CMIP Data Request. As Earth System Modelling (ESM)
archives grow in scale and complexity there are emerging problems
associated with weak standardisation at the variable collection level. That
is, there are good standards covering how specific variables should be
archived, but this paper fills a gap in the standardisation of which
variables should be archived. The ESM-BCV list is intended as a resource
for ESM Model INtercomparison Projects (MIPs) developing requests to enable
greater consistency among MIPs, and as a reference for modelling centres to
enhance consistency within MIPs. Provisional planning for the CMIP7 Data
Request exploits the ESM-BCVs as a core element. The baseline variables
list includes 98 variables which have modest or minor data volume
footprints and could be generated systematically when simulations are
produced and archived for exploitation by the WCRP community. A further 34
variables are classed as high volume and are only suitable for production
when the resource implications are justified.

Securing the ‘great white shield’? Climate change, Arctic security and the
geopolitics of solar geoengineering


Kornbech, N., Corry, O., & McLaren, D. (2024). Securing the ‘great white
shield’? Climate change, Arctic security and the geopolitics of solar
geoengineering. *Cooperation and Conflict*, 00108367241269629.

*Abstract*

The Arctic has been identified by scientists as a relatively promising
venue for controversial ‘solar geo

[geo] Solar Geoengineering: History, Methods, Governance, Prospects

[Geoengineering News]

https://www.annualreviews.org/content/journals/10.1146/annurev-environ-112321-081911

*Authors*
Edward A. Parson, and David W. Keith

*August 21, 2024*

*Abstract*
Solar geoengineering, also called sunlight reflection or solar radiation
modification (SRM), is a potential climate response that would cool the
Earth's surface and reduce many other climate changes by scattering on
order 1% of incoming sunlight back to space. SRM can only imperfectly
correct for elevated greenhouse gases, but it might complement other
climate responses to reduce risks, while also bringing new risks and new
challenges to global governance. As climate alarm and calls for effective
near-term action mount, SRM is attracting sharply increased attention and
controversy, with many calls for expanded research and governance
consultations along with ongoing concerns about risks, misuse, or
overreliance. We review SRM's history, methods, potential uses and impacts,
and governance needs, prioritizing the approach that is most prominent and
promising, stratospheric aerosol injection. We identify several
policy-relevant characteristics of SRM interventions and identify four
narratives that capture current arguments over how SRM might be developed
or used in socio-political context to either beneficial or destructive
effect, with implications for near-term research, assessment, and
governance activity.

*Source: Annual Reviews*

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[geo] Scientists propose guidelines for solar geoengineering research

[Geoengineering News]

https://phys.org/news/2024-08-scientists-guidelines-solar-geoengineering.html


*Author*
David Hosansky , NCAR & UCAR

*23 August 2024*
[image: Scientists propose guidelines for solar geoengineering research]


The proposed eight interconnected research criteria are grouped into three
main categories (different colors). The order of the criteria shown is not
meant to imply a ranking of importance. Credit: *Oxford Open Climate
Change* (2024).
DOI: 10.1093/oxfclm/kgae010
Scientists propose guidelines for solar geoengineering research
The proposed eight interconnected research criteria are grouped into three
main categories (different colors). The order of the criteria shown is not
meant to imply a ranking of importance. Credit: Oxford Open Climate Change
(2024). DOI: 10.1093/oxfclm/kgae010

Scientists for several years have studied the theoretical effectiveness of
injecting sulfur dioxide into the stratosphere to reflect heat from the sun
and offset Earth's warming temperatures. But they also want to ensure that
the solar geoengineering approaches being studied are evaluated for their
technical feasibility, as well as their cooling potential and possible
ecological and societal side effects.


To guide future work, an international team of scientists led by the U.S.
National Science Foundation National Center for Atmospheric Research (NSF
NCAR) has published a paper in Oxford Open Climate Change with specific
recommendations for evaluating proposals to inject sulfur dioxide, which is
known as stratospheric aerosol intervention (SAI).

The paper also suggests criteria for discontinuing those scenarios that are
not feasible because of scientific, technical, or societal issues.

"The goal is to work toward an assessment that can be used to identify the
most feasible and legitimate scenarios, based on both how much they reduce
natural and societal risks as well as any unwanted side effects," said NSF
NCAR scientist Simone Tilmes, the lead author.

"If society were to ever consider implementing SAI, it is imperative that
we provide the best possible scientific understanding to policy makers and
the public."

Mimicking volcanic eruptions
Once injected into the stratosphere, sulfur dioxide would form
sunlight-reflecting sulfate aerosols. Previous studies, drawing on computer
modeling and observations of large volcanic eruptions, have shown these
aerosols would have a cooling effect similar to that of a major volcanic
eruption.


The injections could continue to cool Earth for decades or even centuries,
buying time until heat-trapping greenhouse gases in the atmosphere return
to lower levels.

The previous research, however, has also emphasized the potential risks of
SAI, such as changing the stratospheric ozone layer and altering global
precipitation patterns.

Since such injections cannot perfectly offset the impacts of greenhouse gas
emissions, Tilmes and her co-authors write that informed policy decisions
require a comprehensive understanding of the benefits and risks of SAI.
They emphasize the need for a research and governance structure, with fair
representation from both the Global South and North, to oversee SAI
research and technology developments.

"Research on various solar geoengineering methods has been going on for a
few decades now, but there hasn't been a formal assessment collating all
the information in one place suitable for policy makers and the public,"
said NOAA scientist Karen Rosenlof, a co-author of the new paper.

"It's time for such an assessment to occur, covering the criteria described
in this paper, and repeated on a regular basis."

The paper proposes eight research criteria for assessing SAI developments.
The criteria are:


   - Technical and economic limitations
   - Cooling potential
   - Ability to meet climate objectives
   - Infrastructure for monitoring, detection, and attribution
   - Large-scale and regional climate response
   - Impacts on human and natural systems
   - Societal risks
   - Mitigation of risks through governance


"The goal of these criteria is to promote optimal approaches from a climate
perspective while carefully weighing the benefits and risks and making sure
to include the perspectives of underrepresented groups and the Global
South," Tilmes said.


*More information*: Simone Tilmes et al, Research criteria towards an
interdisciplinary Stratospheric Aerosol Intervention assessment, Oxford
Open Climate Change (2024). DOI: 10.1093/oxfclm/kgae010

*Source: Phys.Org*

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[geo] Baseline Climate Variables for Earth System Modelling

[Geoengineering News]

https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2363/

*Authors*
Martin Juckes, Karl E. Taylor, Fabrizio Antonio, David Brayshaw, Carlo
Buontempo, Jian Cao, Paul J. Durack, Michio Kawamiya, Hyungjun Kim, Tomas
Lovato, Chloe Mackallah, Matthew Mizielinski, Alessandra Nuzzo, Martina
Stockhause, Daniele Visioni, Jeremy Walton, Briony Turner, Eleanor
O’Rourke, and Beth Dingley

*Citations: *Juckes, M., Taylor, K. E., Antonio, F., Brayshaw, D.,
Buontempo, C., Cao, J., Durack, P. J., Kawamiya, M., Kim, H., Lovato, T.,
Mackallah, C., Mizielinski, M., Nuzzo, A., Stockhause, M., Visioni, D.,
Walton, J., Turner, B., O’Rourke, E., and Dingley, B.: Baseline Climate
Variables for Earth System Modelling, EGUsphere [preprint],
https://doi.org/10.5194/egusphere-2024-2363, 2024.

*Received: 25 Jul 2024 – Discussion started: 22 Aug 2024*

*Abstract*
The Baseline Climate Variables for Earth System Modelling (ESM-BCVs) are
defined as a list of 132 variables which have high utility for the
evaluation and exploitation of climate simulations. The list reflects the
most heavily used elements of the Coupled Model Intercomparison Project
phase 6 (CMIP6) archive. Successive phases of CMIP have supported strong
results in science and substantial influence in international climate
policy formulation. This paper responds both to interest in exploiting CMIP
data standards in a broader range of climate modelling activities and a
need to achieve greater clarity about the significance and intention of
variables in the CMIP Data Request. As Earth System Modelling (ESM)
archives grow in scale and complexity there are emerging problems
associated with weak standardisation at the variable collection level. That
is, there are good standards covering how specific variables should be
archived, but this paper fills a gap in the standardisation of which
variables should be archived. The ESM-BCV list is intended as a resource
for ESM Model INtercomparison Projects (MIPs) developing requests to enable
greater consistency among MIPs, and as a reference for modelling centres to
enhance consistency within MIPs. Provisional planning for the CMIP7 Data
Request exploits the ESM-BCVs as a core element. The baseline variables
list includes 98 variables which have modest or minor data volume
footprints and could be generated systematically when simulations are
produced and archived for exploitation by the WCRP community. A further 34
variables are classed as high volume and are only suitable for production
when the resource implications are justified.


*Source: EGUSphere*

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[geo] Securing the ‘great white shield’? Climate change, Arctic security and the geopolitics of solar geoengineering

[Geoengineering News]

https://journals.sagepub.com/doi/abs/10.1177/00108367241269629

*Authors*
Nikolaj Kornbech, Olaf Corry, and Duncan McLaren

https://doi.org/10.1177/00108367241269629

*18 August 2024*

*Abstract*
The Arctic has been identified by scientists as a relatively promising
venue for controversial ‘solar geoengineering’ – technical schemes to
reflect more sunlight to counteract global warming. Yet contemporary
regional security dynamics and the relative (in)significance of climate
concerns among the key Arctic states suggest a different conclusion. By
systematically juxtaposing recently published schemes for Arctic
geoengineering with Arctic security strategies published by the littoral
Arctic states and China, we reveal and detail two conflicting security
imaginaries. Geoengineering schemes scientifically securitise (and seek to
maintain) the Arctic’s ‘great white shield’ to protect ‘global’ humanity
against climate tipping points and invoke a past era of Arctic
‘exceptionality’ to suggest greater political feasibility for research
interventions here. Meanwhile, state security imaginaries understand the
contemporary Arctic as an increasingly contested region of considerable
geopolitical peril and economic opportunity as temperatures rise. Alongside
the entangled history of science with geopolitics in the region, this
suggests that geoengineering schemes in the Arctic are unlikely to follow
scientific visions, and unless co-opted into competitive, extractivist
state security imaginaries, may prove entirely infeasible. Moreover, if the
Arctic is the ‘best-case’ for geoengineering politics, this places a huge
question mark over the feasibility of other, more global prospects.

*Source: Sage Journals*

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[geo] Quantifying the Direct Radiative Effect of Stratospheric Aerosols Using Radiative Kernels

[Geoengineering News]

https://essopenarchive.org/doi/pdf/10.22541/essoar.172374105.56686934

*Authors*
Qiurun Yu, Yi Huang

*15 August 2024*

*Abstract *
To facilitate the quantification of the stratospheric aerosol radiative
effect, this study generates a set of aerosol direct radiative effect
(ADRE) kernels based on MERRA-2 reanalysis data. These radiative kernels
measure the sensitivities of ADRE to perturbations in scattering and
absorbing aerosol optical depth (AOD), respectively. Both broadband and
band-by-band radiative kernels are developed to account for the wavelength
dependency of ADRE. The broadband kernels are then emulated by a
multivariate regression model, which predicts the kernel values from a
handful of predictors, including the top-of-atmosphere (TOA) insolation,
TOA reflectance, and stratospheric AOD. These kernels offer an efficient
and versatile way to assess the ADRE of stratospheric aerosols. The ADREs
of the 2022 Hunga volcano eruption and the 2020 Australia wildfire are
estimated from the kernels and validated against radiative transfer
model-calculated results. The Hunga eruption induced a global mean cooling
forcing of -0.46 W/m² throughout 2022, while the Australia wildfire caused
a warming forcing of +0.28 W/m² from January to August. The kernel
estimation can capture over 90% of the ADRE variance with relative error
within 10%, in these assessments. The results demonstrate the spectral
dependencies of stratospheric ADRE and highlight the distinct radiative
sensitivity of stratospheric aerosols, which differs significantly from
that of tropospheric aerosols.

*Plain Language Summary *
Stratospheric aerosols influence the Earth's energy balance by scattering
and absorbing solar radiation, making it crucial to accurately measure
their radiative impact. However, quantifying the aerosol radiative impact
is computationally expensive if using radiative transfer models. In this
work, we develop a set of aerosol radiative kernels, which can provide a
flexible and efficient means for calculating the radiative effects of
stratospheric aerosols. The kernels have been demonstrated to effectively
quantify the radiative impacts of stratospheric aerosols resulting from
wildfire and volcanic eruption events.

*Source: ESS OPEN ARCHIVE *

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[geo] SOLAR GEOENGINEERING WEEKLY SUMMARY (12 AUGUST - 18 AUGUST 2024)

[Geoengineering News]

SOLAR GEOENGINEERING WEEKLY SUMMARY (12 AUGUST - 18 AUGUST 2024

)

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RESEARCH PAPERSHSW-V v1.0: localized injections of interactive volcanic
aerosols and their climate impacts in a simple general circulation model


Hollowed, J. P., Jablonowski, C., Brown, H. Y., Hillman, B. R., Bull, D.
L., & Hart, J. L. (2024). HSW-V v1. 0: localized injections of interactive
volcanic aerosols and their climate impacts in a simple general circulation
model. *Geoscientific Model Development*, *17*(15), 5913-5938.

*Abstract*

A new set of standalone parameterizations is presented for simulating the
injection, evolution, and radiative forcing by stratospheric volcanic
aerosols against an idealized Held–Suarez–Williamson (HSW) atmospheric
background in the Energy Exascale Earth System Model version 2 (E3SMv2). In
this model configuration (HSW with enabled volcanism, HSW-V), sulfur
dioxide (SO2) and ash are injected into the atmosphere with a specified
profile in the vertical, and they proceed to follow a simple exponential
decay. The SO2 decay is modeled as a perfect conversion to a long-living
sulfate aerosol which persists in the stratosphere. All three species are
implemented as tracers in the model framework and are transported by the
dynamical core's advection algorithm. The aerosols contribute
simultaneously to local heating of the stratosphere and cooling of the
surface by a simple plane-parallel Beer–Lambert law applied on two zonally
symmetric radiation broadbands in the longwave and shortwave ranges. It is
shown that the implementation parameters can be tuned to produce realistic
temperature anomaly signatures of large volcanic events. In particular,
results are shown for an ensemble of runs that mimic the volcanic eruption
of Mt. Pinatubo in 1991. The design requires no coupling to microphysical
subgrid-scale parameterizations and thus approaches the computational
affordability of prescribed aerosol forcing strategies. The idealized
simulations contain a single isolated volcanic event against a
statistically uniform climate, where no background aerosols or other
sources of externally forced variability are present. HSW-V represents a
simpler-to-understand tool for the development of climate source-to-impact
attribution methods.

IMO2020 Regulations Accelerate Global Warming by up to 3 Years in UKESM1


Jordan, G., & Henry, M. (2024). IMO2020 regulations accelerate global
warming by up to 3 years in UKESM1. *Earth's Future*, *12*(8),
e2024EF005011.

*Abstract*

The International Maritime Organization (IMO) introduced new regulations on
the sulfur content of shipping emissions in 2020 (IMO2020). Estimates of
the climatic impact of this global reduction in anthropogenic sulfate
aerosols vary widely. Here, we contribute to narrowing this uncertainty
with two sets of climate model simulations using UKESM1. Using fixed
sea-surface temperature atmosphere-only simulations, we estimate an IMO2020
global effective radiative forcing of 0.139 ± 0.019 Wm−2 and show that most
of this forcing is due to aerosol-induced changes to cloud properties.
Using coupled ocean-atmosphere simulations, we note significant changes in
cloud top droplet number concentration and size across regions with high
shipping traffic density, and—in the North Atlantic and North Pacific—these
microphysical changes translate to a decrease in cloud albedo. We show that
IMO2020 increases global annual surface temperature on average by 0.046 ±
0.010°C across 2020–2029; approximately 2–3 years of global warming.
Furthermore, our model simulations show that IMO2020 helps to explain the
exceptional warming in 2023, but other factors are needed to fully account
for it. The year 2023 also had an exceptionally large decrease in reflected
shortwave radiation at the top-of-atmosphere. Our results show that IMO2020
made that more likely, yet the observations are within the variability of
simulations without the reduction in shipping emissions. To better
understand the climatic impacts of IMO2020, a model intercomparison pro

[geo] Vanguard for a Blue Sky —Analysing Stratospheric Aerosol Injection and London’s Climate Movement: An Ecological Leninist Strategy —Thesis

[Geoengineering News]

https://lup.lub.lu.se/student-papers/record/9163109/file/9163123.pdf

*Author*
James Mace-Moore

*Spring 2024*

*Abstract*
The world continues to boil due to capital’s incapacity to resolve its
climatic contradictions. Stratospheric Aerosol Injection (SAI), a
technological process theorised to instantly reduce global temperatures,
has piqued the interest of a now desperate ruling class. Given its
worldwide impacts, enormous risks, and capitalistimperialist reproductive
capacities, it is crucial to engage with SAI while it is still in early
development. Troublingly, there has thus far been little public
consultation. In the UK, an emergent site of SAI development, the climate
movement intersects at this critical juncture. The concern is that a
historically depoliticised climate movement may uncritically accept SAI as
a symptomatic fix to the crisis. Grounded in Marxist theory and departing
from the conception of SAI as a spatiotemporal fix, this thesis addresses
three primary objectives: assessing current perceptions of SAI among
London’s climate movement; evaluating the impact of political education in
fostering a critical perspective of the technology, connecting this
educational intervention to the Leninist concept of the vanguard layer; and
considering how the vanguard layer can assist in counter-hegemonic
struggle. The research involved a mixed-method qualitative experiment with
members of London’s climate movement. Findings reveal that while there is
awareness of SAI’s functionality, participants exhibited technological
neutralism and misplaced optimism in liberal governance structures. This
underscores the need for more critical education to challenge these
perspectives. It likewise highlights the potential benefits of an
ecological-Leninist approach to building a counter-hegemonic coalition of
forces, capable of addressing the root cause of the ecological crisis.

*Source: Lund University*

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[geo] HSW-V v1.0: localized injections of interactive volcanic aerosols and their climate impacts in a simple general circulation model

[Geoengineering News]

https://gmd.copernicus.org/articles/17/5913/2024/

*Authors*
Joseph P. Hollowed, Christiane Jablonowski, Hunter Y. Brown, Benjamin R.
Hillman, Diana L. Bull, and Joseph L. Hart

*Citations*: Hollowed, J. P., Jablonowski, C., Brown, H. Y., Hillman, B.
R., Bull, D. L., and Hart, J. L.: HSW-V v1.0: localized injections of
interactive volcanic aerosols and their climate impacts in a simple general
circulation model, Geosci. Model Dev., 17, 5913–5938,
https://doi.org/10.5194/gmd-17-5913-2024, 2024.

*Published: 08 August 2024*

*Abstract*
A new set of standalone parameterizations is presented for simulating the
injection, evolution, and radiative forcing by stratospheric volcanic
aerosols against an idealized Held–Suarez–Williamson (HSW) atmospheric
background in the Energy Exascale Earth System Model version 2 (E3SMv2). In
this model configuration (HSW with enabled volcanism, HSW-V), sulfur
dioxide (SO2) and ash are injected into the atmosphere with a specified
profile in the vertical, and they proceed to follow a simple exponential
decay. The SO2 decay is modeled as a perfect conversion to a long-living
sulfate aerosol which persists in the stratosphere. All three species are
implemented as tracers in the model framework and are transported by the
dynamical core's advection algorithm. The aerosols contribute
simultaneously to local heating of the stratosphere and cooling of the
surface by a simple plane-parallel Beer–Lambert law applied on two zonally
symmetric radiation broadbands in the longwave and shortwave ranges. It is
shown that the implementation parameters can be tuned to produce realistic
temperature anomaly signatures of large volcanic events. In particular,
results are shown for an ensemble of runs that mimic the volcanic eruption
of Mt. Pinatubo in 1991. The design requires no coupling to microphysical
subgrid-scale parameterizations and thus approaches the computational
affordability of prescribed aerosol forcing strategies. The idealized
simulations contain a single isolated volcanic event against a
statistically uniform climate, where no background aerosols or other
sources of externally forced variability are present. HSW-V represents a
simpler-to-understand tool for the development of climate source-to-impact
attribution methods.

*Source: EGU*

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[geo] Governing cloud seeding in Australia and the United States : lessons for regional solar radiation management—Thesis

[Geoengineering News]

https://figshare.utas.edu.au/articles/thesis/Governing_cloud_seeding_in_Australia_and_the_United_States_lessons_for_regional_solar_radiation_management/26625061?file=48455422

*Author*
Manon Simon

*18 August 2024*

*Abstract*
This thesis investigates the extent to which cloud seeding laws can be used
as a basis for governing regional solar radiation management activities.
Solar radiation management (SRM) is being proposed to reflect a portion of
sunlight away from Earth, to delay temperature increases while the
international community accelerates mitigation actions. It includes
planetary-scale interventions, as well as regional-scale activities, such
as marine cloud brightening (MCB). Research and deployment of these novel
technologies will require the development of governance frameworks to
manage associated risks and uncertainties. Whereas attempts to influence
the climate system at a global scale will require international governance,
domestic arrangements may be more appropriate to govern small-scale field
testing and regional SRM applications.

Cloud seeding is an established technology, developed after World War II to
modify precipitation patterns to enhance rain and snow, or suppress hail.
In the context of climate change, cloud seeding continues to be used as a
long-term water management strategy to increase freshwater resources in key
locations for water, food, and energy security. Governments across the
world have long invested in these technologies and developed legal
frameworks to govern cloud seeding activities. Cloud seeding and regional
SRM bear enough similarities to warrant an in-depth assessment of existing
legal and institutional arrangements for cloud seeding, and the extent to
which they can inform the governance of SRM technologies, such as MCB.

This thesis assesses the relevance of a legal analogy between cloud seeding
and regional SRM through the analytical and normative lens of adaptive
governance. Using adaptive governance principles, it examines the
governance of cloud seeding in two Australian states and two American
states. These case studies show that regional SRM regimes require (1) legal
arrangements to facilitate greater interactions between institutions across
scales of governance, to account both for the scale of deployment and the
scale of impacts; (2) broader participation of relevant stakeholders at an
early stage of research; (3) flexible legal mechanisms built into the
decision-making to foster iterative learning; and (4) mechanisms to prevent
and resolve potential conflicts.

*Source: University of Tasmania *

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[geo] IMO2020 Regulations Accelerate Global Warming by up to 3 Years in UKESM1

[Geoengineering News]

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024EF005011

*Authors*
G. Jordan, M. Henry

*First published: 14 August 2024*

https://doi.org/10.1029/2024EF005011

*Abstract*
The International Maritime Organization (IMO) introduced new regulations on
the sulfur content of shipping emissions in 2020 (IMO2020). Estimates of
the climatic impact of this global reduction in anthropogenic sulfate
aerosols vary widely. Here, we contribute to narrowing this uncertainty
with two sets of climate model simulations using UKESM1. Using fixed
sea-surface temperature atmosphere-only simulations, we estimate an IMO2020
global effective radiative forcing of 0.139 ± 0.019 Wm−2 and show that most
of this forcing is due to aerosol-induced changes to cloud properties.
Using coupled ocean-atmosphere simulations, we note significant changes in
cloud top droplet number concentration and size across regions with high
shipping traffic density, and—in the North Atlantic and North Pacific—these
microphysical changes translate to a decrease in cloud albedo. We show that
IMO2020 increases global annual surface temperature on average by 0.046 ±
0.010°C across 2020–2029; approximately 2–3 years of global warming.
Furthermore, our model simulations show that IMO2020 helps to explain the
exceptional warming in 2023, but other factors are needed to fully account
for it. The year 2023 also had an exceptionally large decrease in reflected
shortwave radiation at the top-of-atmosphere. Our results show that IMO2020
made that more likely, yet the observations are within the variability of
simulations without the reduction in shipping emissions. To better
understand the climatic impacts of IMO2020, a model intercomparison project
would be valuable whilst the community waits for a more complete
observational record.

*Key Points*
Recent regulations on the sulfur content of ship emissions has accelerated
global warming by approximately 2–3 years

Reduced ship emissions induce responses in cloud properties,
top-of-atmosphere radiation, and surface temperatures

The regulations contribute to the exceptional warming observed in 2023, yet
other factors are needed to fully account for it

*Plain Language Summary*
In 2020, the International Maritime Organization introduced new regulations
decreasing the sulfur content of shipping emissions (IMO2020). Since sulfur
is a pollutant, it is expected that IMO2020 will improve air quality and
health outcomes. These emissions, however, also lead to the formation of
tiny particles in the air which brighten clouds, resulting in more sunlight
reflected to space which helps cool the planet. Hence, by reducing sulfur
emissions, IMO2020 will lead to planetary warming, yet the magnitude of
this effect is hotly debated. In this work, we use a state-of-the-art Earth
system model to assess the warming impact of IMO2020. We find that IMO2020
increases the global average temperature by around 0.05°C; the equivalent
to 2–3 years of global warming. Thus, IMO2020 helps to explain the
exceptional warmth observed in 2023, yet other factors are needed to fully
account for it. The year 2023 also had a record decrease in reflected
sunlight contributing to the record temperatures, and our results show that
IMO2020 made that more likely. Finally, we emphasize that IMO2020 has
simply brought forward the warming from reductions in pollutants that are
factored in favorable future climate scenarios.

*Source: AGU*

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[geo] On Thin Ice: Solar Geoengineering to Manage Tipping Element Risks in the Cryosphere by 2040

[Geoengineering News]

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024EF004797

*Authors*
Wake Smith, Madeline F. Bartels, Jasper G. Boers, Christian V. Rice

*First published: 13 August 2024*

https://doi.org/10.1029/2024EF004797

*Abstract*
Tipping elements are features of the climate system that can display
self-reinforcing and non-linear responses if pushed beyond a certain
threshold (the “tipping point”). Models suggest that we may surpass several
of these tipping points in the next few decades, irrespective of which
emissions pathway humanity follows. Some tipping elements reside in the
Arctic and Antarctic and could potentially be avoided or arrested via a
stratospheric aerosol injection (SAI) program applied only at the poles.
This paper considers the utility of proactively developing the capacity to
respond to emergent tipping element threats at the poles as a matter of
risk management. It then examines both the air and ground infrastructure
that would be required to operationalize such capability by 2040 and finds
that this would require a funded launch decision by a financially credible
actor by roughly 2030.

*Key Points*
We risk crossing tipping thresholds in mid-century that mitigation could
not prevent, though geoengineering could rescue the situation

A polar solar geoengineering program potentially delay or avoid crossing
tipping thresholds

Polar solar geoengineering capability by 2040 would require a funded
program launch by or before roughly 2030

*Plain Language Summary*
Stratospheric aerosol injection is a solar geoengineering method by which
tiny particles cast into the stratosphere reflect a portion of incoming
sunlight away from Earth. Recent work has demonstrated that SAI may be
effective in preventing components of the climate system known as “tipping
elements” from collapsing by cooling the atmosphere and thereby preventing
the crossing of dangerous temperature thresholds. In particular, many of
the highest risk tipping elements reside in the cryosphere and their
minimum temperature thresholds are estimated to be passed in coming decades
regardless of global mitigation pathways. An SAI program at high latitudes
could effectively manage some of the associated risks by cooling the Arctic
and Antarctic, thereby preventing tipping elements from collapsing. This
paper investigates the ground and air infrastructure that would be required
to operate such a solar geoengineering program by the year 2040. We first
describe the logistics of such a program, including airport base location
choice, plane procurement and modification strategies, and projected costs.
We find that infrastructure development for a polar solar geoengineering
program would need to commence by 2030 or sooner in order to successfully
safeguard cryospheric tipping elements, suggesting that research and
decision-making processes for a stratospheric aerosol injection program
should be approached with urgency.

*Source: AGU*

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[geo] The effectiveness of solar radiation management for marine cloud brightening geoengineering by fine sea spray in worldwide different climatic regions

[Geoengineering News]

https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2263/

*Authors*
Zhe Song, Ningning Yao, Lang Chen, Yuhai Sun, Boqiong Jiang, Pengfei Li,
Daniel Rosenfeld, and Shaocai Yu

*Citations: *Song, Z., Yao, N., Chen, L., Sun, Y., Jiang, B., Li, P.,
Rosenfeld, D., and Yu, S.: The effectiveness of solar radiation management
for marine cloud brightening geoengineering by fine sea spray in worldwide
different climatic regions, EGUsphere [preprint],
https://doi.org/10.5194/egusphere-2024-2263, 2024.

*Received: 20 Jul 2024 – Discussion started: 09 Aug 2024*

*Abstract*
Marine Cloud Brightening (MCB) geoengineering aims to inject aerosols over
oceans to brighten clouds and reflect more sunlight to offset the impacts
of global warming or to achieve localized climate cooling. There is still
controversy about the contributions of direct and indirect effects of
aerosols in implementing MCB and the lack of quantitative assessments of
both. Here, we conducted experiments with injected sea-salt aerosols in the
same framework for five open oceans around the globe. Our results show that
a uniform injection strategy that did not depend on wind speed captured the
sensitive areas of the regions that produced the largest radiative
perturbations during the implementation of MCB. When the injection amounts
were low, the sea-salt aerosols dominated the shortwave radiation mainly
through the indirect effects of brightening clouds, showing obvious spatial
heterogeneity. As the indirect effects of aerosols saturated with
increasing injection rates, the direct effects still increased linearly and
exceeded the indirect effects, producing a consistent increase in the
spatial distributions of top-of-atmosphere upward shortwave radiation. Our
research emphasizes that MCB was best implemented in areas with extensive
cloud cover, while the aerosol direct scattering effects remained dominant
when clouds were scarce.

*Source: EGUsphere *

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[geo] SOLAR GEOENGINEERING WEEKLY SUMMARY (05 AUGUST - 11 AUGUST 2024)

[Geoengineering News]

SOLAR GEOENGINEERING WEEKLY SUMMARY (05 AUGUST - 11 AUGUST 2024)




Subscribe to our newsletter to receive monthly updates on Solar
Geoengineering:
Solar Geoengineering Updates

Monthly news summaries about solar geoengineering. Links to scientific
papers, news articles, jobs, podcasts, and videos.

By Andrew Lockley

--
RESEARCH PAPERSThe effectiveness of solar radiation management for marine
cloud brightening geoengineering by fine sea spray in worldwide different
climatic regions


Song, Z., Yao, N., Chen, L., Sun, Y., Jiang, B., Li, P., ... & Yu, S.
(2024). The effectiveness of solar radiation management for marine cloud
brightening geoengineering by fine sea spray in worldwide different
climatic regions. *EGUsphere*, *2024*, 1-40.

*Abstract*

Marine Cloud Brightening (MCB) geoengineering aims to inject aerosols over
oceans to brighten clouds and reflect more sunlight to offset the impacts
of global warming or to achieve localized climate cooling. There is still
controversy about the contributions of direct and indirect effects of
aerosols in implementing MCB and the lack of quantitative assessments of
both. Here, we conducted experiments with injected sea-salt aerosols in the
same framework for five open oceans around the globe. Our results show that
a uniform injection strategy that did not depend on wind speed captured the
sensitive areas of the regions that produced the largest radiative
perturbations during the implementation of MCB. When the injection amounts
were low, the sea-salt aerosols dominated the shortwave radiation mainly
through the indirect effects of brightening clouds, showing obvious spatial
heterogeneity. As the indirect effects of aerosols saturated with
increasing injection rates, the direct effects still increased linearly and
exceeded the indirect effects, producing a consistent increase in the
spatial distributions of top-of-atmosphere upward shortwave radiation. Our
research emphasizes that MCB was best implemented in areas with extensive
cloud cover, while the aerosol direct scattering effects remained dominant
when clouds were scarce.

Do small outdoor geoengineering experiments require governance?


Jinnah, S., Talati, S., Bedsworth, L., Gerrard, M., Kleeman, M., Lempert,
R., ... & Sugiyama, M. (2024). Do small outdoor geoengineering experiments
require governance?. *Science*, *385*(6709), 600-603.

*Abstract*

In March 2024, Harvard University publicly announced the cancellation of
its proposed Stratospheric Controlled Perturbation Experiment (SCoPEx),
which would have been the world’s first outdoor stratospheric aerosol
injection (SAI) experiment. SAI, a type of solar geoengineering (SG), seeks
to cool the planet by releasing aerosols into the stratosphere to reflect
sunlight. The co-authors here are members of the independent advisory
committee (AC) convened by Harvard in 2019 to develop a research governance
framework for SCoPEx. We frame below the importance of SCoPEx and SG
governance and summarize the governance framework developed by the AC
[detailed in (1)]. We then move beyond the report to reflect on the process
of developing that framework, the challenges we encountered, and the
sources of tension encountered in its implementation.

Projected global sulfur deposition with climate intervention


Rubin, H. J., Yang, C. E., Hoffman, F. M., & Fu, J. S. (2024). Projected
global sulfur deposition with climate intervention. *Global Environmental
Change Advances*, *3*, 100011.

*Abstract*

Even with immediate implementation of global policies to mitigate carbon
dioxide emissions, the impacts of climate change will continue to worsen
over the next decades. One potential response is stratospheric aerosol
injection (SAI), where sulfur dioxide is released into the stratosphere to
block incoming solar radiation. SAI does not reduce the level of carbon
dioxide in the atmosphere, but it can slow warming and act as a stopgap
measure to give the world more time to pursue effective carbon reduction
strategies. While SAI is controversial, it remains a technically feasible
proposition. It ought to be thoroughly modeled both to characterize global
risks better and to further the scientific community’s understand

[geo] The effectiveness of solar radiation management for marine cloud brightening geoengineering by fine sea spray in worldwide different climatic regions

[Geoengineering News]

https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2263/

*Authors*
Zhe Song, Ningning Yao, Lang Chen, Yuhai Sun, Boqiong Jiang, Pengfei Li,
Daniel Rosenfeld, and Shaocai Yu

*Citations*: Song, Z., Yao, N., Chen, L., Sun, Y., Jiang, B., Li, P.,
Rosenfeld, D., and Yu, S.: The effectiveness of solar radiation management
for marine cloud brightening geoengineering by fine sea spray in worldwide
different climatic regions, EGUsphere [preprint],
https://doi.org/10.5194/egusphere-2024-2263, 2024.

*Received: 20 Jul 2024 – Discussion started: 09 Aug 2024*

*Abstract*
Marine Cloud Brightening (MCB) geoengineering aims to inject aerosols over
oceans to brighten clouds and reflect more sunlight to offset the impacts
of global warming or to achieve localized climate cooling. There is still
controversy about the contributions of direct and indirect effects of
aerosols in implementing MCB and the lack of quantitative assessments of
both. Here, we conducted experiments with injected sea-salt aerosols in the
same framework for five open oceans around the globe. Our results show that
a uniform injection strategy that did not depend on wind speed captured the
sensitive areas of the regions that produced the largest radiative
perturbations during the implementation of MCB. When the injection amounts
were low, the sea-salt aerosols dominated the shortwave radiation mainly
through the indirect effects of brightening clouds, showing obvious spatial
heterogeneity. As the indirect effects of aerosols saturated with
increasing injection rates, the direct effects still increased linearly and
exceeded the indirect effects, producing a consistent increase in the
spatial distributions of top-of-atmosphere upward shortwave radiation. Our
research emphasizes that MCB was best implemented in areas with extensive
cloud cover, while the aerosol direct scattering effects remained dominant
when clouds were scarce.

*Source: EGU Sphere*

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[geo] Do small outdoor geoengineering experiments require governance?

[Geoengineering News]

https://www.science.org/doi/10.1126/science.adn2853

*Authors*
Sikina Jinnah , Shuchi Talati, Louise Bedsworth, Michael Gerrard, Michael
Kleeman, Robert Lempert, Katharine Mach, Leonard Nurse, Hosea Olayiwola
Patrick, and Masahiro Sugiyama

*8 August 2024*

DOI: 10.1126/science.adn2853

*Abstract*
In March 2024, Harvard University publicly announced the cancellation of
its proposed Stratospheric Controlled Perturbation Experiment (SCoPEx),
which would have been the world’s first outdoor stratospheric aerosol
injection (SAI) experiment. SAI, a type of solar geoengineering (SG), seeks
to cool the planet by releasing aerosols into the stratosphere to reflect
sunlight. The co-authors here are members of the independent advisory
committee (AC) convened by Harvard in 2019 to develop a research governance
framework for SCoPEx. We frame below the importance of SCoPEx and SG
governance and summarize the governance framework developed by the AC
[detailed in (1)]. We then move beyond the report to reflect on the process
of developing that framework, the challenges we encountered, and the
sources of tension encountered in its implementation.

*Source: Science *

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[geo] Projected global sulfur deposition with climate intervention

[Geoengineering News]

https://www.sciencedirect.com/science/article/pii/S29501385247X

*Authors*
H.J. Rubin, C.-E. Yang, F.M. Hoffman, J.S. Fu

*01 August 2024*

https://doi.org/10.1016/j.gecadv.2024.100011

*Abstract*
Even with immediate implementation of global policies to mitigate carbon
dioxide emissions, the impacts of climate change will continue to worsen
over the next decades. One potential response is stratospheric aerosol
injection (SAI), where sulfur dioxide is released into the stratosphere to
block incoming solar radiation. SAI does not reduce the level of carbon
dioxide in the atmosphere, but it can slow warming and act as a stopgap
measure to give the world more time to pursue effective carbon reduction
strategies. While SAI is controversial, it remains a technically feasible
proposition. It ought to be thoroughly modeled both to characterize global
risks better and to further the scientific community’s understanding of
stratospheric aerosol dynamics. SAI relies on sulfate aerosols which have a
lifetime of several years in the stratosphere but will eventually be
deposited back onto Earth’s surface. While sulfate is an important nutrient
for many ecosystems, high concentrations can cause acidification,
eutrophication, and biodiversity loss. We use model outputs from the
Geoengineering Model Intercomparison Project (GeoMIP) to track the impacts
of sulfur deposition from SAI to various ecoregions through comparison with
historical climate and future Shared Socioeconomic Pathway (SSP) scenarios.
Our results demonstrate that dry sulfur deposition will continue to decline
worldwide, regardless of scenario, from a high of 41 Tg S/yr in 1981 to
under 20 Tg S/yr by 2100. Wet sulfur deposition, however, is much more
uncertain and further work needs to be done in this area to harmonize model
estimates. Under SAI, many ecoregions will experience notably different
sulfur deposition regimes by the end of the century compared to historical
trends. In some places, this will not be substantially different than the
impacts of climate change under SSP2–4.5 or SSP5–8.5. However, in some
ecoregions the model projections disagree dramatically on the magnitude of
future trends in both emissions and deposition, with, for example,
UKESM1–0-LL projecting that SO42- deposition in deciduous needleleaf
forests under G6 Sulfur will reach 394 % of SSP2–4.5 deposition by the
2080 s while CESM2-WACCM projects that SO42- deposition will remain at
170 % of SSP2–4.5 deposition during that same time period. Our work
emphasizes the lack of agreement between models and the importance of
improving our understanding of SAI impacts for future climate
decision-making.

*Source: ScienceDirect *

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[geo] Building capacity to govern emerging climate intervention technologies

[Geoengineering News]

https://online.ucpress.edu/elementa/article/12/1/00124/202924/Building-capacity-to-govern-emerging-climate

*Authors*
Zachary Dove, Sikina Jinnah, Shuchi Talati

https://doi.org/10.1525/elementa.2023.00124

*01 June 2024*

*Abstract*
Capacity building is needed to enable effective and inclusive governance of
emerging climate intervention technologies. Here we use solar
geoengineering (SG) as a case of an emerging climate intervention
technology to highlight the importance of focusing attention on building
capacity to govern these and similar technologies. We propose the concept
of “governance capacity building” to help focus research and practice
toward building and strengthening the knowledge, skills, tools, practices,
or resources needed to govern SG. Centrally, we argue that “governance
capacity building” is needed to enable multiple types of actors to
contribute to all stages of the governance process, should be owned by
recipients, and aimed toward building long term and durable forms of
capacity. These capacity building efforts must center climate vulnerable
communities and countries that stand to gain or lose the most from
decisions about whether and how research and deployment of these
technologies will move forward. To ensure governance capacity remains with
these populations over the long term, governance capacity building should
embrace a new model of capacity building envisioned primarily by actors in
the Global South. We use these insights to demonstrate that gaps and
limitations in how capacity building is understood in the SG governance
literature and implemented in practice are stifling the potential for
capacity building to enable effective and inclusive governance in the SG
issue area. To help rectify this, we chart a path toward building
successful governance capacity building programs for climate intervention
technologies.

*Source: Elementa Science of the Anthropocene*

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[geo] Peak Shaving with Solar Radiation Management Would Shorten Global Temperature Overshoot

[Geoengineering News]

https://essopenarchive.org/doi/full/10.22541/essoar.172253206.64448528/v1

*Authors*
Linus Boselius, Alistair Duffey, Peter James Irvine

*Cite as:* Linus Boselius, Alistair Duffey, Peter James Irvine. Peak
Shaving with Solar Radiation Management Would Shorten Global Temperature
Overshoot. ESS Open Archive . August 01, 2024.
DOI: 10.22541/essoar.172253206.64448528/v1

*01 August 2024*

*Abstract*
Projected rates of emissions reductions are unlikely to keep global
temperatures from crossing the Paris Agreement temperature targets.
Large-scale carbon dioxide removal (CDR) could help recover a target
temperature after it has been exceeded, producing an overshoot scenario.
Solar radiation management (SRM) is the proposal to cool the planet by
increasing the reflection of incoming solar radiation. It could be used in
an overshoot scenario for peak shaving, where SRM is deployed to maintain a
temperature target during the overshoot. Here, we quantify the effect of
peak shaving on the duration of the overshoot using an adapted extension of
the SSP2-4.5 scenario and an ensemble of variants of the FaIR simple
climate model. We find a substantial reduction in overshoot duration, which
ranges from ∼5% for decadal overshoots up to ∼20% for multi-century
overshoots. The shortening is predominantly driven by the ocean response to
peak shaving. Peak shaving results in lower ocean temperatures relative to
the overshoot scenario, inducing a stronger surface temperature response to
decreasing and negative emissions, driving overshoot shortening. Our
results also indicate that peak shaving with SRM would reduce the
cumulative net negative emissions needed to end temperature overshoot by
∼27%. Thus, SRM, when deployed as a complement to emissions reductions and
CDR, could end overshoot decades earlier than otherwise and at a
substantially lower cost.

Source:

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[geo] SOLAR GEOENGINEERING WEEKLY SUMMARY (29 JULY - 04 AUGUST 2024)

[Geoengineering News]

SOLAR GEOENGINEERING WEEKLY SUMMARY (29 JULY - 04 AUGUST 2024)




*Subscribe to our newsletter to receive monthly updates on Solar
Geoengineering:*
Solar Geoengineering Updates

Monthly news summaries about solar geoengineering. Links to scientific
papers, news articles, jobs, podcasts, and videos.

By Andrew Lockley

--
RESEARCH PAPERSFirst simulations of feedback algorithm-regulated marine
cloud brightening


Lee, W. R., Chen, C. C., Richter, J. H., MacMartin, D. G., & Kravitz, B.
(2024). First simulations of feedback algorithm-regulated marine cloud
brightening. *Authorea Preprints*.

*Abstract*

Feedback control algorithms, an important tool in climate intervention
strategy design, are widely used in stratospheric aerosol injection (SAI)
simulations but have never been implemented for marine cloud brightening
(MCB). Using the Community Earth System Model (CESM2), we present the first
simulations of feedback control-regulated MCB. Our controller, which
regulates global mean temperature (T0) by varying the area of MCB coverage
over time, successfully maintains the desired T0 of 1.5°C above the
preindustrial in the SSP2-4.5 global warming scenario comparably to a
contemporary SAI controller. After 35 years of intervention, the surface
temperature response when MCB has been gradually ramped up over time in
this way is similar to a constant intervention with similar global mean
temperature (including strong regional heterogeneity), but system memory
may cause differences in Arctic sea ice and the Atlantic Meridional
Overturning Circulation (AMOC).

Shading responses are species-specific in thermally stressed corals


Ellis, S. L., Butcherine, P., Tagliafico, A., Hendrickson, C. A., Kelaher,
B. P., Schulz, K. G., & Harrison, D. P. Shading responses are
species-specific in thermally stressed corals. *Frontiers in Marine Science*,
*11*, 1333806.

*Authors*

Light is critical to coral growth through endosymbiont photosynthesis but
can also act with elevated temperatures to cause coral bleaching. When more
light is absorbed than can be used for photosynthesis, elevated irradiance
can damage symbiont photosynthetic machinery.Hence, solar-radiation
management through shading has been suggested to alleviate coral bleaching
during marine heatwaves. Acropora divaricata and Acropora kenti were tested
at two temperatures with 30% shading and an unshaded control to determine
the relative impacts of light and temperature on coral bleaching severity.
The coral bleaching response was assessed by photochemical (pulse amplitude
modulated fluorometry), physiological (symbiont density, chlorophyll a
concentration, catalase activity, and lipid peroxidation), and physical
(mean intensity of grey or 'percentage whiteness') markers. Shading
significantly reduced the bleaching response in A. divaricata, whilst for
some parameters A. kenti responded negatively to shade. In A. divaricata,
shading prevented photochemical collapse up to the experiment's maximum 4.4
degree-heating weeks (DHW). Biomarkers of coral bleaching stress responded
to shade and water temperature at 4.4 DHW; catalase activity was greatest
in the shaded and ambient temperature treatment. Shading did not reduce the
effects of bleaching in A. kenti; the mean intensity of grey and light
saturation coefficient was greatest in the shaded treatment. Shading did,
however, reduce lipid peroxidation at 3 DHW.Our results suggest shading
during thermal stress may only protect some coral species, highlighting the
need to consider species-specific responses when evaluating the potential
efficacy of coral bleaching interventions.

Projected Thermally Driven Elderly Mortality for Beijing Under Greenhouse
Gas and Stratospheric Aerosol Geoengineering Scenarios


Wang, J., Zhao, L., & Moore, J. C. (2024). Projected thermally driven
elderly mortality for Beijing under greenhouse gas and stratospheric
aerosol geoengineering scenarios. *Earth's Future*, *12*(7), e2024EF004422.

*Abstract*

Beijing is undergoing multiple challenges including urbanization, warming
and aging. The Beijing megalopolis of 20 million people now suffers more
cold-related than heat-related dea

[geo] This Scientist Has a Risky Plan to Cool Earth. There’s Growing Interest (David Keith wants to spray a pollutant into the sky to block some sunlight. He says the benefits would outweigh the dange

[Geoengineering News]

https://www.nytimes.com/2024/08/01/climate/david-keith-solar-geoengineering.html?unlocked_article_code=1._k0.yLu-.cNXlfBXRq3Z3&smid=url-share

*By David Gelles*

*01 August 2024*

David Keith was a graduate student in 1991 when a volcano erupted in the
Philippines, sending a cloud of ash toward the edge of space.

Seventeen million tons of sulfur dioxide released from Mount Pinatubo
spread across the stratosphere, reflecting some of the sun’s energy away
from Earth. The result was a drop in average temperatures in the Northern
Hemisphere by roughly one degree Fahrenheit in the year that followed.

Today, Dr. Keith cites that event as validation of an idea that has become
his life’s work: He believes that by intentionally releasing sulfur dioxide
into the stratosphere, it would be possible to lower temperatures
worldwide, blunting global warming.

Such radical interventions are increasingly being taken seriously as the
effects of climate change grow more intense. Global temperatures have hit
record highs for 13 months in a row, unleashing violent weather, deadly
heat waves and raising sea levels. Scientists expect the heat to keep
climbing for decades. The main driver of the warming, the burning of fossil
fuels, continues more or less unabated.

Against this backdrop, there is growing interest in efforts to
intentionally alter the Earth’s climate, a field known as geoengineering.

Already, major corporations are operating enormous facilities to vacuum up
the carbon dioxide that’s heating up the atmosphere

and
bury it underground. Some scientists are performing experiments designed to
brighten clouds
,
another way to bounce some solar radiation back to space. Others are
working on efforts to make oceans and plants absorb more carbon dioxide.

But of all these ideas, it is stratospheric solar geoengineering that
elicits the greatest hope and the greatest fear.

Proponents see it as a relatively cheap and fast way to reduce temperatures
well before the world has stopped burning fossil fuels. Harvard University
has a solar geoengineering program that has received grants from the
Microsoft co-founder Bill Gates, the Alfred P. Sloan Foundation and the
William and Flora Hewlett Foundation. It’s being studied by the
Environmental Defense Fund along with the World Climate Research Program,
an international scientific effort. The European Union last year called for
a thorough analysis
 of
the risks of geoengineering and said countries should discuss how to
regulate an eventual deployment of the technology.

But many scientists and environmentalists fear that it could result in
unpredictable calamities.

Because it would be used in the stratosphere and not limited to a
particular area, solar geoengineering could affect the whole world,
possibly scrambling natural systems, like creating rain in one arid region
while drying out the monsoon season elsewhere. Opponents worry it would
distract from the urgent work of transitioning away from fossil fuels. They
object to intentionally releasing sulfur dioxide, a pollutant that would
eventually move from the stratosphere to ground level, where it can
irritate the skin, eyes, nose and throat and can cause respiratory
problems. And they fear that once begun, a solar geoengineering program
would be difficult to stop.

“The whole notion of spraying sulfur compounds to reflect sunlight is
arrogant and simplistic,” the Canadian environmentalist

David
Suzuki said. “There are unintended consequences of powerful technologies
like these, and we have no idea what they will be.”

Raymond Pierrehumbert, an atmospheric physicist at the University of
Oxford, said he considered solar geoengineering a grave threat to human
civilization.

“It’s not only a bad idea in terms of something that would never be safe to
deploy,” he said. “But even doing research on it is not just a waste of
money, but actively dangerous*.”*

[image: David Suzuki in a wooded area. He is wearing a long-sleeved shirt
and jeans and is backlit by sunshine.]
The Canadian environmentalist David Suzuki. “There are unintended
consequences of powerful technologies like these,” he said.Credit...Melissa
Renwick for The New York Times


Shuchi Talati, the founder of a nonprofit organization called the Alliance
for Just Deliberation on Solar Geoengineering, called the technology “a
double-edged sword.”


“It could be a way to limit human suffering,” she said. “At the same time,
I think it can also exacerbate suffering if used in a bad way.”

In a series of interviews, Dr. Keith, a professor in the University of
Chicago’s department of geophysical sciences, countered that the risks
posed by solar geoe

[geo] First simulations of feedback algorithm-regulated marine cloud brightening

[Geoengineering News]

https://essopenarchive.org/doi/full/10.22541/essoar.172107989.92419868

*Authors*
Walker Raymond Lee, Chih-Chieh Chen, Jadwiga H. Richter, Douglas G
MacMartin, Ben Kravitz

*15 July 2024*

*Abstract*
Feedback control algorithms, an important tool in climate intervention
strategy design, are widely used in stratospheric aerosol injection (SAI)
simulations but have never been implemented for marine cloud brightening
(MCB). Using the Community Earth System Model (CESM2), we present the first
simulations of feedback control-regulated MCB. Our controller, which
regulates global mean temperature (T0) by varying the area of MCB coverage
over time, successfully maintains the desired T0 of 1.5°C above the
preindustrial in the SSP2-4.5 global warming scenario comparably to a
contemporary SAI controller. After 35 years of intervention, the surface
temperature response when MCB has been gradually ramped up over time in
this way is similar to a constant intervention with similar global mean
temperature (including strong regional heterogeneity), but system memory
may cause differences in Arctic sea ice and the Atlantic Meridional
Overturning Circulation (AMOC).

*Source: ESS OPEN ARCHIVE *

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[geo] Shading responses are species-specific in thermally stressed corals

[Geoengineering News]

https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2024.1333806/abstract

*Authors*
Sophia L. Ellis, Peter Butcherine, Alejandro Tagliafico, Conor A.
Hendrickson, Brendan P. Kelaher, Kai G. Schulz, Daniel P. Harrison

*31 July 2024*

doi: 10.3389/fmars.2024.1333806

*Authors*
Light is critical to coral growth through endosymbiont photosynthesis but
can also act with elevated temperatures to cause coral bleaching. When more
light is absorbed than can be used for photosynthesis, elevated irradiance
can damage symbiont photosynthetic machinery.Hence, solar-radiation
management through shading has been suggested to alleviate coral bleaching
during marine heatwaves. Acropora divaricata and Acropora kenti were tested
at two temperatures with 30% shading and an unshaded control to determine
the relative impacts of light and temperature on coral bleaching severity.
The coral bleaching response was assessed by photochemical (pulse amplitude
modulated fluorometry), physiological (symbiont density, chlorophyll a
concentration, catalase activity, and lipid peroxidation), and physical
(mean intensity of grey or 'percentage whiteness') markers. Shading
significantly reduced the bleaching response in A. divaricata, whilst for
some parameters A. kenti responded negatively to shade. In A. divaricata,
shading prevented photochemical collapse up to the experiment's maximum 4.4
degree-heating weeks (DHW). Biomarkers of coral bleaching stress responded
to shade and water temperature at 4.4 DHW; catalase activity was greatest
in the shaded and ambient temperature treatment. Shading did not reduce the
effects of bleaching in A. kenti; the mean intensity of grey and light
saturation coefficient was greatest in the shaded treatment. Shading did,
however, reduce lipid peroxidation at 3 DHW.Our results suggest shading
during thermal stress may only protect some coral species, highlighting the
need to consider species-specific responses when evaluating the potential
efficacy of coral bleaching interventions.

*Source: Frontiers *

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[geo] Projected Thermally Driven Elderly Mortality for Beijing Under Greenhouse Gas and Stratospheric Aerosol Geoengineering Scenarios

[Geoengineering News]

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2024EF004422

*Authors*
Jun Wang, Liyun Zhao, John C. Moore

*First published*: *15 July 2024*

https://doi.org/10.1029/2024EF004422

*Abstract*
Beijing is undergoing multiple challenges including urbanization, warming
and aging. The Beijing megalopolis of 20 million people now suffers more
cold-related than heat-related deaths. Stratospheric aerosol injection
(SAI) geoengineering is designed to lower surface temperatures, so if SAI
were ever done, it may reduce future heat-related mortality, while also
increasing cold-related mortality. Here we use four Earth System Models
(ESM) downscaled to 10 km resolution with the Weather Research and
Forecasting (WRF) system to capture urban temperature, humidity and wind
speeds. Temperature-related mortality risk were calculated using a
distributed lag nonlinear model (DLNM) of the elderly (over 65s) under the
dynamically downscaled moderate (RCP4.5) and extreme (RCP8.5) greenhouse
gas, and the G4 SAI scenarios. We used population demographics for all five
shared socioeconomic pathways (SSP) and various adaptation measures.
Heat-related excess deaths under G4 are 630∼3,160 per year fewer than
RCP4.5, while cold-related deaths are 370∼1,990 more than RCP4.5 during
2060–2069, with a marginally significant net reduction. G4 significantly
reduces the excess deaths relative to RCP8.5. Both heat-related and
cold-related mortality will increase by 240∼490% when the aging population
is accounted for, and decrease by 11%, 23% and 44% under low, medium and
high adaptation relative to a no adaptation scenario. Dynamical downscaling
produces better quality climate simulations than commonly used statistical
approaches, and in the case of Beijing, significantly fewer heat-related
deaths. The marginal health benefits of modest future SAI in Beijing may be
representative of the population impacts in the extra-tropics where deaths
due to cold are more than those caused by heat.

*Key Points*
Stratospheric aerosol injection (SAI) geoengineering on both heat-related
and cold-related mortality for the elderly in Beijing was simulated

GeoMIP G4 SAI reduces heat-related excess deaths, but also increases
cold-related excess deaths, with little net negative differences from RCP4.5

Dynamical downscaling significantly reduces projecting future heat-related
excess deaths relative to statistical methods

*Plain Language Summary*
Climate warming has increased the intensity and frequency of extreme
weather has consequences for human health in the 21st century.
Stratospheric aerosol injection (SAI) geoengineering can, to some extent,
slow down global warming, but its impact on human health is unclear.
Beijing is one of the most populous and developed cities in China and is
undergoing dual challenges of warming and aging which amplify the health
risks to the elderly population. It is therefore of both local significance
and wider relevance for developing world cities to explore the impact of
SAI geoengineering on the mortality of elderly people in Beijing. We
project heat-related and cold-related excess deaths under different
climate, population and adaptation scenarios in Beijing during the 2060s.
SAI geoengineering could reduce approximately 630∼3,160 heat-related excess
deaths, but it could also increase 370∼1,990 cold-related excess deaths.
There are large uncertainties in projection of excess deaths under
different shared socioeconomic pathways.

*Source: AGU*

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[geo] Degrees announces nine new teams to research the socio-political dimensions of SRM

[Geoengineering News]

https://www.degrees.ngo/nine-new-teams-to-research-the-socio-political-dimensions-of-srm/

*30 July 2024*

The Degrees Initiative today announced a major expansion in
developing-country research on solar radiation modification (SRM),
supporting nine new teams of social scientists to explore the
socio-political dimensions of SRM.

These new projects—based in Argentina, Bangladesh, Brazil (x2), Ghana,
India, Mexico, Pakistan, and the Philippines—mark the beginning of the
first international SRM research programme aimed exclusively at social
scientists in developing countries.

After the research teams were selected earlier this year, they joined us in
Istanbul for a research-planning workshop alongside SRM experts
volunteering their time as research collaborators. During the workshop, the
teams presented their research plans, shared insights and discussed
challenges from their regions, and then worked with the research
collaborators to refine their proposals.

With the projects now finalised, the new cohort will begin their research,
working to better understand how the use of SRM relates to a range of
topics, including economics, ethics, health justice, public perception, and
governance.

The nine new projects will now form a key part of building the evidence
base on SRM, alongside the 150+ Degrees-funded climate scientists modelling
the impacts of SRM and climate change. These scientists have gone on to
become experts in the field, publishing groundbreaking research, serving on
UN expert panels, and leading regional conversations on the potential and
the risks of SRM.

Now the Degrees Initiative hopes to do the same for social sciences. Many
observers believe that the social, political, and ethical dimensions of SRM
could prove even more challenging than the physical ones. Who gets to
decide if SRM is used or rejected? What ethical considerations should guide
research and its governance? How do the socio-political impacts of further
warming compare to those of SRM? Over the next few years, Degrees will
support teams from around the world as they delve into these questions and
take their place at the heart of the global conversation.

The world’s most climate-vulnerable regions have the most to gain or to
lose from SRM. The new social science research projects will help
stakeholders better understand the risks of implementing or rejecting SRM.
This in turn will nudge the world towards more equitable and informed
evaluation of the options for addressing climate change.

As ever with Degrees Initiative grants, the researchers were free to define
their own research questions, and funding selections were based on
independent peer review.

*Learn more about the projects*


*Source: The Degrees Initiative *

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[geo] Strategic dimensions of solar geoengineering: Economic theory and experiments

[Geoengineering News]

https://www.sciencedirect.com/science/article/abs/pii/S2214804324001083

*Authors*
Daniel Heyen, Alessandro Tavoni

https://doi.org/10.1016/j.socec.2024.102271

*25 July 2024*

*Highlights*
•Solar Geoengineering could reduce global temperatures fast and at low
direct cost.

•An important concern is the strategic implications of solar geoengineering.

•We review theoretical and experimental contributions on strategic issues
of solar geoengineering.

•We outline fruitful topics for future economic research.

*Abstract*
Solar geoengineering denotes a set of technologies that would enable a fast
and relatively cheap global temperature reduction. Besides potential
physical side-effects, a major concern is the strategic dimension: Who is
going to use solar geoengineering and how would it affect others? How does
the presence of solar geoengineering change the strategic incentives
surrounding other climate policy instruments such as mitigation? We review
the existing theoretical and experimental contributions to those questions
and outline promising lines of future economic research.

*Source: ScienceDirect *

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[geo] Projected impact of solar radiation modification geoengineering on water deficit risk over major Central African river basins

[Geoengineering News]

https://iopscience.iop.org/article/10.1088/1748-9326/ad657d/meta

*Authors*
Thierry C. Fotso-Nguemo, Steven Chouto, Jean Pierre Nghond, Arona Diedhiou,
Ben Kravitz, Zéphirin D. Yepdo1, Flore K. Djuidje and Babatunde J Abiodun

*Accepted Manuscript online 19 July 2024*

DOI 10.1088/1748-9326/ad657d

*Abstract*
The economy of Central African countries strongly depends on rain-fed
agriculture and hydropower generation. However, most countries in this
subregion do not yet have the irrigation technologies that are already
applied in many more advanced nations, which further exposes them to the
serious risk of severe drought caused by global warming. This study
investigates the potential impact of solar radiation modification (SRM)
geoengineering on the water availability over the four major river basins
that cross most of Central African countries (i.e., Niger Basin, Lake Chad
Basin, Cameroon Atlantic Basin and Congo Basin). For this purpose a
potential water availability index was computed based on an ensemble-mean
simulations carried out in the framework of Phase 6 of the Geoengineering
Model Intercomparison Project (GeoMIP6), considering two SRM simulation
experiments: the stratospheric sulphate aerosol injection (G6sulfur) and
the global solar dimming (G6solar). The climate change simulation results
in a robust decreases by up to 60% in water availability, most pronounced
over the Cameroon Atlantic Basin under the hight radiative forcing
scenario. Therefore, in a business-as-usual world, the reduction in water
availability combined with the rapid population growth expected by 2050 in
the studied region, could result in a significant water deficit over
Central African countries towards the end of the 21st century. This water
deficit can affect all activities that depend on water resources, such as
water supply, agriculture and hydropower generation. Furthermore, the
results also show that SRM methods have the potential to significantly
reduce this deficit by increasing water availability (as compared to
climate change) by up to 50% over the affected river basins, with a more
accentuated increase found in the Cameroon Atlantic Basin when the global
solar dimming is applied. These results suggest good possibilities of
adaptation for populations living in the geographical areas of these river
basins.

*Source: IOP SCIENCE *

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[geo] Size-resolved process understanding of stratospheric sulfate aerosol following the Pinatubo eruption

[Geoengineering News]

https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2227/

*Authors*
Allen Hu, Xiaohong Liu, Ziming Ke, Benjamin Wagman, Hunter Brown, Zheng Lu,
Diana Bull, and Kara Peterson

*Citations*. Hu, A., Liu, X., Ke, Z., Wagman, B., Brown, H., Lu, Z., Bull,
D., and Peterson, K.: Size-resolved process understanding of stratospheric
sulfate aerosol following the Pinatubo eruption, EGUsphere [preprint],
https://doi.org/10.5194/egusphere-2024-2227, 2024.

*Received: 17 Jul 2024 – Discussion started: 24 Jul 2024*

*Abstract*
Stratospheric sulfate aerosol produced by volcanic eruptions plays
important roles in atmospheric chemistry and the global radiative balance
of the atmosphere. The simulation of stratospheric sulfate concentrations
and optical properties is highly dependent on the chemistry scheme and
microphysical treatment. In this work, we implemented a sophisticated
gas-phase chemistry scheme (full chemistry, FC) and a 5-mode version of the
Modal Aerosol Module (MAM5) for the treatment of stratospheric sulfate
aerosol in the Department of Energy’s Energy Exascale Earth System Model
version 2 (E3SMv2) model to better simulate the chemistry-aerosol feedback
following the Pinatubo eruption, and to compare it against a simulation
using simplified chemistry (SC) and the default 4-mode version of the Modal
Aerosol Module (MAM4). MAM5 experiments were found to better capture the
stratospheric sulfate burden from the eruption of the volcano to the end of
1992 as compared to the High-resolution Infra Red Sounder (HIRS)
observations, and the formation of sulfate in MAM5FC was significantly
faster than in MAM4FC due to the addition of a OH replenishment reaction.
Analyses of microphysical processes indicate that more sulfate aerosol mass
was generated in total in FC experiments than in SC experiments. MAM5
performs better than MAM4 in simulation of aerosol optical depth (AOD); AOD
anomalies from the MAM5 experiment have better agreement with AVHRR. The
simulated largest changes in global mean net radiative flux at the top of
the atmosphere following the eruption were about -3 W/m2 in MAM5
experiments and roughly -1.5 W/m2 in MAM4 experiments.


*Source: EGUsphere*

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[geo] Strategic dimensions of solar geoengineering: economic theory and experiments

[Geoengineering News]

https://www.sciencedirect.com/science/article/abs/pii/S2214804324001083

*Authors*
Daniel Heyen, Alessandro Tavoni

https://doi.org/10.1016/j.socec.2024.102271

*19 July 2024*

*Highlights*
•Solar Geoengineering could reduce global temperatures fast and at low
direct cost

•An important concern is the strategic implications of solar geoengineering

•We review theoretical and experimental contributions on strategic issues
of solar geoengineering

•We outline fruitful topics for future economic research

*Abstract*
Solar geoengineering denotes a set of technologies that would enable a fast
and relatively cheap global temperature reduction. Besides potential
physical side-effects, a major concern is the strategic dimension: Who is
going to use solar geoengineering and how would it affect others? How does
the presence of solar geoengineering change the strategic incentives
surrounding other climate policy instruments such as mitigation? We review
the existing theoretical and experimental contributions to those questions
and outline promising lines of future economic research.

*Source: ScienceDirect *

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[geo] On the credibility of threats to avoid the deployment of solar geoengineering

[Geoengineering News]

https://link.springer.com/article/10.1007/s10018-024-00407-2

*Authors*
Michael Finus, Francesco Furini

*Published: 17 July 2024*

*Citations*: Finus, M., Furini, F. On the credibility of threats to avoid
the deployment of solar geoengineering. Environ Econ Policy Stud (2024).
https://doi.org/10.1007/s10018-024-00407-2

*Abstract*
We analyze how geoengineering in the form of solar radiation management
(SRM), associated with the potential of high collateral damages, affects
the governance architecture of climate agreements. We investigate under
which conditions signatories to a climate agreement can avoid the
deployment of SRM and implement a climate agreement on mitigation. We show
that a climate agreement with all countries can be stable with the threat
to deploy SRM in case a country free-rides. The threat is deterrent if
collateral damages are perceived to be sufficiently high (lower threshold),
but only credible if those damages are not too high (upper threshold). SRM
deployment is the only threat available to signatories if they choose
mitigation levels simultaneously with non-signatories (Nash–Cournot
scenario). However, if signatories choose mitigation levels before
non-signatories (Stackelberg scenario), an additional punishment option
arises. Then if collateral damages are sufficiently large, signatories can
reduce their mitigation levels and impose a heavier burden on
non-signatories that would find it profitable to avoid the deployment of
SRM. We show that our results are robust in two analytical frameworks
frequently employed in the game-theoretic analysis of international
environmental agreements.

*Source: SpringerLink*

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[geo] Planetary Sunshade Foundation Brings its Message to DC

[Geoengineering News]

https://payloadspace.com/planetary-sunshade-foundation-brings-its-message-to-dc/

By Jacqueline Feldscher 
*July 21, 2024*
A rendering of NASA’s Solar Cruiser mission. Image: NASA

Advocates for placing a sunshade in space to address global warming were in
DC last week educating officials on Capitol Hill and beyond about the
benefits of the technology.

Wait, what? Some climate change activists argue that cutting emissions and
removing carbon dioxide from the atmosphere won’t be enough to stop global
warming. These officials argue for a third step: sending a planetary
sunshade into space to cut solar radiation.

The idea is to station a giant structure at a stable point between the Sun
and Earth to provide some shade and reduce temperature rise. While this
tech has previously only been the purview of science fiction and cartoons,
advocates argue that advancements in solar sail tech and the rise of heavy
lift launchers are now making it possible.

The teachers: The Planetary Sunshade Foundation is an advocacy group
founded in 2021 to bring together experts to teach policymakers and the
public about the benefits of a sunshade, Morgan Goodwin, the executive
director of the group, told Payload.

The students: Five representatives of the foundation met with three
congressional offices on both sides of the aisle, Goodwin said. They also
met with the House space subcommittee, the State Department’s space policy
team, and the National Space Council, he said.

“It’s an exciting moment because I think we are stepping into a world where
this kind of a project is possible to consider,” he said. “We do have the
capability, we do have the sorts of space activities that would support
this, and the increasing urgency of the global warming crisis is
encouraging people to bring more and more options to the table.”

The ask: Goodwin said the group had two main goals in their conversations
with government officials:

   - Long term, the foundation is pushing for more overlap between the
   space and climate sectors, breaking down silos to allow for consideration
   of ideas like this.
   - Short term, the group is asking Congress to fund NASA’s Solar Cruiser
   mission, which is currently grounded. The mission would advance solar sail
   tech and teach engineers how to operate at the Lagrange points between the
   Sun and Earth.

*Source: Payload*

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[geo] SOLAR GEOENGINEERING WEEKLY SUMMARY (15 JULY - 21 JULY 2024)

[Geoengineering News]

*SOLAR GEOENGINEERING WEEKLY SUMMARY (15 JULY - 21 JULY 2024)*


*Subscribe to our newsletter to receive monthly updates on Solar
Geoengineering:*
Solar Geoengineering Updates

Monthly news summaries about solar geoengineering. Links to scientific
papers, news articles, jobs, podcasts, and videos.

By Andrew Lockley

--
*DEADLINES*(NEW) Registration Form for Virtual Workshops on Solar Radiation
Modification: Science and Governance Perspectives for Africa by DSG

| Registration Deadline: 25 July 2024*Call for Abstracts—AGU Conference |
Submissions are open until 31 July 2024
*

*SRM Sessions at AGU2024:**GC009-Advances in Climate Engineering Science
**A081-Exploring
the Interplay of Weather Modification and Climate Intervention: Modeling,
Observations, and Field Campaigns
**GC004-Advancements
in Climate Intervention Research Technologies, Policies and Practices:
Opportunities and Issues
**GC048-Climate
Intervention, Mitigation, Adaptation, and Restoration: Assessing the Risks
and Benefits of Using Earth System Models for Guidance on Climate Action
*

*Call for Abstract—Cloud and precipitation responses to aerosol pollution,
weather modification and climate intervention
 | Deadline to apply: 15 August
2024**Funding opportunity: Modelling environmental responses to solar
radiation management by Natural Environment Research Council (NERC) |
Deadline to apply: 08 October 202
4**Submit
your recent research on Solar Radiation Management to new ES: Atmospheres
collection

| Deadline: 31 January 2025*
--
RESEARCH PAPERSWhy Conceptions of Scale Matter to Artificity Arguments in
SRM Ethics


Clark, C. J. (2024). Why Conceptions of Scale Matter to Artificity
Arguments in SRM Ethics. *Ethics, Policy & Environment*, 1-13.

*Abstract*

Ethicists have raised a variety of concerns about solar radiation
management (SRM). This essay investigates the specific worries associated
with artificity: Does SRM transform the planet into an artifact? Should
experimental SRM strategies be implemented if the consequences are
unpredictable? These worries have led some to strongly reject SRM. But the
conceptual framework used by environmental scientists to understand the
scope of management interventions might offer a way to adequately defuse
the perceived ethical concerns about artificity. Concepts from theories of
scale, like discontinuity and panarchy, are discussed to demonstrate how
the artificity arguments appear to depend on disputable premises.

Sensitivity of the global hydrological cycle to the altitude of
stratospheric sulphate aerosol layer


KH, U., Bala, G., & Xavier, A. (2024). Sensitivity of the global
hydrological cycle to the altitude of stratospheric sulphate aerosol
layer. *Environmental
Research Letters*.

*Abstract*

Stratospheric aerosol geoengineering (SAG) has been proposed as one of the
potential options to offset the impacts of anthropogenically induced
climate change. Previous modelling studies have shown that the efficacy of
the cooling via SAG increases with altitude of the aerosol layer. It has
been also shown that the stratospheric heating associated with SAG could
stabilize the tropical atmosphere and weaken the tropical hydrological
cycle. Using a global climate model, we perform a systematic study by
prescribing volcanic sulphate aerosols at three different altitudes (22 km,
18 km and 16 km) and assess the sensitivity of the global and tropical mean
precipitation to the altitude. We find that even though the efficacy of
cooling increases with altitude of the aerosol layer, the global and
tropical mean precipitation changes are less sensitive to the height of the
aerosol layer. This is because the magnitude of both the global and
tropical mean precipitation reduction increases with aerosol altitude in
response to increasing efficacy of aerosols, but

[geo] Why Conceptions of Scale Matter to Artificity Arguments in SRM Ethics

[Geoengineering News]

https://www.tandfonline.com/doi/full/10.1080/21550085.2024.2381417

*Authors*
Colby J. Clark

*Published online: 18 Jul 2024*

https://doi.org/10.1080/21550085.2024.2381417

*Abstract*
Ethicists have raised a variety of concerns about solar radiation
management (SRM). This essay investigates the specific worries associated
with artificity: Does SRM transform the planet into an artifact? Should
experimental SRM strategies be implemented if the consequences are
unpredictable? These worries have led some to strongly reject SRM. But the
conceptual framework used by environmental scientists to understand the
scope of management interventions might offer a way to adequately defuse
the perceived ethical concerns about artificity. Concepts from theories of
scale, like discontinuity and panarchy, are discussed to demonstrate how
the artificity arguments appear to depend on disputable premises.

*Source: Taylor & Francis *

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[geo] Assessment of solar geoengineering impact on precipitation and temperature extremes in the Muda River Basin, Malaysia using CMIP6 SSP and GeoMIP6 G6 simulations

[Geoengineering News]

https://www.sciencedirect.com/science/article/abs/pii/S0048969724049660

*Authors*
Mou Leong Tan, Yi Lin Tew, Juneng Liew, Govindasamy Bala, Mari R. Tye, Chun
Kiat Chang, Nurfashareena Muhamad

*15 July 2024*

https://doi.org/10.1016/j.scitotenv.2024.174817

*Highlights*
•G6sulfur may exacerbate dry spells of the Muda River basin (MRB) in the
future.

•G6solar and G6sulfur modulate the MRB's climate increases of SSP585 to
match SSP245.

•G6solar, G6sulfur and SSP245 project ~2 °C temperature increase in the MRB.

•G6solar and G6sulfur modulate increases precipitation extremes to match
SSP245.

•Future studies should consider more SRM experiments and hydro-climatic
modelling.

*Abstract*
The concept of solar geoengineering remains a topic of debate, yet it may
be an effective way for cooling the Earth's temperature. Nevertheless, the
impact of solar geoengineering on regional or local climate patterns is an
active area of research. This study aims to evaluate the impact of solar
geoengineering on precipitation and temperature extremes of the Muda River
Basin (MRB), a very important agricultural basin situated in the northern
Peninsular Malaysia. The analysis utilized the multi-model ensemble mean
generated by four models that contributed to the Geoengineering Model
Intercomparison Project (GeoMIP6). These models were configured to simulate
the solar irradiance reduction (G6solar) and stratospheric sulfate aerosols
(G6sulfur) strategies as well as the moderate (SSP245) and high emission
(SSP585) experiments. Prior to the computation of extreme indices, a linear
scaling approach was employed to bias correct the daily precipitation,
maximum and minimum temperatures. The findings show that the G6solar and
G6sulfur experiments, particularly the latter, could be effective in
holding the increases in both annual and monthly mean precipitation totals
and temperature extremes close to the increases projected under SSP245. For
example, both G6solar and G6sulfur experiments project increases of
temperature over the basin of 2 °C at the end of the 21st century as
compared to 3.5 °C under SSP585. The G6solar and G6sulfur experiments also
demonstrate some reliability in modulating the increases in precipitation
extreme indices associated with flooding to match those under SSP245.
However, the G6sulfur experiment may exacerbate dry conditions in the
basin, as monthly precipitation is projected to decrease during the dry
months from January to May and consecutives dry days are expected to
increase, particularly during the 2045–2064 and 2065–2084 periods.
Increases dry spells could indirectly affect agricultural and freshwater
supplies, and pose considerable challenges to farmers.
Graphical abstract

[image: Unlabelled Image]


*Source: ScienceDirect *

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[geo] New airborne research facility observes sensitivity of cumulus cloud microphysical properties to aerosol regime over the great barrier reef

[Geoengineering News]

https://pubs.rsc.org/en/content/articlelanding/2024/ea/d4ea9a

*Authors*
Diana C. Hernandez-Jaramillo, Chris Medcraft, Ramon Campos Braga, Peter
Butcherine, Adrian Doss, Brendan Kelaher, Daniel Rosenfeldb and Daniel P.
Harrisona

*26 JUNE 2024*

*Abstract*
Our work on aerosol–cloud–radiation interactions became hamstrung by the
lack of a suitable aerosol and cloud microphysics equipped aircraft in
Australia. To address this infrastructure gap, we have established a new
airborne research platform, designed primarily for Marine Cloud Brightening
(MCB) field studies but with broader applicability across diverse airborne
research domains. This platform, comprising a Cessna 337 aircraft was
outfitted with a comprehensive suite of meteorological, aerosol, and cloud
microphysical instrumentation normally only found on much larger aircrafts.
The aircraft has completed its first field deployment over the Great
Barrier Reef (GBR) supporting the Reef Restoration and Adaptation Program.
Here we present details of the platform configuration, a flight summary of
its first campaign and a case study illustrating the capabilities of the
new platform. In the case study presented, data was collected from two
well-developed cumulus cloud cells which were similar in macrophysical
properties but formed under markedly different aerosol regimes. We observed
a strong difference in cloud microphysical properties. Higher aerosol
concentrations led to more numerous and smaller cloud drops and suppressed
warm rain. Our observations are consistent with the hypothesis that cumulus
clouds, dominant over the GBR during summer, are amenable to marine cloud
brightening. Our results demonstrate the practical utility of the new
research aircraft through a focused case study, laying the groundwork for
future scientific investigations of aerosol–cloud interactions.

Fig.
1 Conceptual design of the aircraft sampling platform showing major
external instrumentation and photo of the final configuration

*Source: ACS PUBLICATIONS *

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[geo] Research criteria towards an interdisciplinary stratospheric aerosol intervention assessment

[Geoengineering News]

https://academic.oup.com/oocc/advance-article/doi/10.1093/oxfclm/kgae010/7701783

*Authors*
Simone Tilmes, Karen Rosenlof, Daniele Visioni, Ewa M Bednarz, Tyler
Felgenhauer, Wake Smith, Chris Lennard, Michael S Diamond, Matthew Henry,
Cheryl Harrison, Chelsea Thompson

 https://doi.org/10.1093/oxfclm/kgae010

*Published: 29 June 2024*

*Abstract*
With surface temperatures already reaching unprecedented highs, resulting
in significant adverse consequences for societies and ecosystems, there is
an increasing call to expand research into climate interventions, including
Stratospheric Aerosol Intervention (SAI). However, research and
dissemination are currently fragmented and would benefit from a
comprehensive international assessment of the current state of knowledge
regarding impacts, risks, and recommendations for future SAI research
directions. The goals of a scientific assessment would be to describe the
current state of SAI research and evaluate proposed scenario-strategy
combinations through well-designed evaluation guidelines. The suggested
iterative approach would integrate natural and social science
considerations to guide future research toward more plausible scenarios and
strategy development to reduce uncertainties and minimize the risks of SAI.
Here, we outline multidisciplinary research criteria to guide the
assessment process and provide an overview of the benefits and risks of
proposed SAI applications. We group these criteria into three categories:
1) technical and design requirements, 2) response and impacts, and 3)
societal considerations. Including all three categories in a comprehensive
assessment of potential SAI applications outlined here promotes enhanced
interdisciplinary and international collaborations, intentionally engaging
the underrepresented Global South. The assessment structure further
promotes the need for recurring reports every few years with globally
representative participation and could also be applicable to other Solar
Radiation Modification methods or combined approaches. Such assessments are
necessary to align research with considerations for decision-makers and the
public on the feasibility of SAI in reducing the impacts of climate change
and its potential societal and ecological trade-offs.

*Source: Oxford Open Climate Change *

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[geo] Incorporating Climate Engineering into Secondary Education: A New Direction for Indiana’s Science Classrooms

[Geoengineering News]

https://scholarworks.iu.edu/journals/index.php/thst/article/view/37892

*Authors*
Paul Goddard
Ben Kravitz
Adam Scribner
Kirstin Milks
Catherine Peterson

*08 July 2024*

*Abstract*
Climate change represents a significant existential challenge in modern
times, with widespread anxiety over its impacts. There's a growing desire
among students to explore climate solutions and identify actions they can
personally undertake to address climate change. Despite mitigation efforts,
current greenhouse gas emission reduction measures are insufficient, and
the development of negative emission technologies is both slow and costly.
Consequently, the past two decades have witnessed an escalating interest in
alternative strategies to temporarily and intentionally cool the planet.
These strategies include injecting reflective particles into the
stratosphere or increasing the reflectivity of low-lying ocean clouds.
Collectively known as climate engineering, also called geoengineering,
these approaches could serve as a temporary shield against the most severe
outcomes of climate change, buying time while efforts to mitigate emissions
and enhance carbon sequestration reach the required scale.
In line with the Indiana state science standards (HS-ESS3-4), this article
presents the Climate Engineering Teaching Module (CETM) and recounts
firsthand experiences from its application in high school settings.
Launched over three years ago, the CETM has been effectively integrated
into fifteen Indiana classrooms. As the future citizens and leaders of
Indiana, it is crucial that students are well-informed on climate
engineering. Educating them about the scientific, ethical, political, and
economic facets of climate engineering is imperative for fostering
responsible decision-making. By examining the trade-offs associated with
climate engineering and encouraging students to conceptualize ways to
implement these technologies beneficially while minimizing risks, the CETM
offers an innovative and practical approach to teaching climate change and
engineering design. This method not only prepares students for active
engagement in future discussions on climate engineering but also equips
them with a comprehensive understanding of its complexities.

*Source: HASTI*

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[geo] Scientists call for ‘major initiative’ to study whether geoengineering should be used on glaciers — Report

[Geoengineering News]

https://news.uchicago.edu/story/scientists-call-major-initiative-study-whether-geoengineering-should-be-used-glaciers

*By Louise Lerner *

*11 July, 2024*

Report finds many questions remain around technology to address glacier
melting and sea-level rise

A group of scientists has released a landmark report (
https://climateengineering.uchicago.edu/wp-content/uploads/2024/05/Glacial-Climate-Intervention_A-Research-Vision.pdf)
on glacial geoengineering—an emerging field studying whether technology
could halt the melting of glaciers and ice sheets as climate change
progresses.

The white paper

represents
the first public efforts by glaciologists to assess possible technological
interventions that could help address catastrophic sea-level rise scenarios.

While it does not endorse any specific interventions, it calls for a “major
initiative” in the next decades to research which, if any, interventions
could and should be used.

“Everyone who is a scientist hopes that we don’t have to do this research,”
said Douglas MacAyeal, a professor of geophysical sciences with the
University of Chicago who has studied glaciers for nearly 50 years and is a
co-author on the white paper. “But we also know that if we don’t think
about it, we could be missing an opportunity to help the world in the
future.”

The paper is the result of two recent conferences at the University of
Chicago and Stanford University on geoengineering—catalyzed and encouraged
by the newly formed Climate Systems Engineering initiative at UChicago,
which seeks to understand the benefits, risks, and governance of
technologies that might reduce the impacts of accumulated greenhouse gases.
[image: Tyndall Glacier in Taan Fiord, Alaska]
Tyndall Glacier in Taan Fiord, Alaska.
Photo by Peter J Haeussler, U.S. Geological Survey
*Tipping points*

Scientists have documented major changes in every major glacier system
worldwide. As climate change continues, these massive ice sheets will
release more and more water, which will lead to rising global sea
levels—the oceans have already risen by 8 to 9 inches since the late 1800s.

Most of the ice that would affect global sea levels is concentrated in a
few areas in the Arctic and Antarctic. This has prompted speculation
whether it would be possible to slow or halt this melting, such as by
installing walls around ice sheets to insulate them from warming ocean
water.

But any such intervention could have major consequences, ranging from
costing large amounts of money for little effect to majorly disturbing
Arctic ecosystems and livelihoods—and there are many questions to answer
before any such effort could be undertaken.

“It will take 15 to 30 years for us to understand enough to recommend or
rule out any of these interventions,” said co-author John Moore, a
professor with the Arctic Center at the University of Lapland.

“Our argument is that we should start funding this research now, so that we
aren’t making panicked decisions down the road when the water is already
lapping at our ankles,” said MacAyeal.

The report is also clear that the first order of business is to stop
emitting carbon into the atmosphere. “We can never say often enough that
that is the first priority,” said Moore.

But it is also possible that ice sheets have a tipping point for
collapsing—and that we have already passed it.

“Humans have already released so much carbon dioxide that we are seeing
profound changes in every glacier system around the world,” said MacAyeal.
“Many of these are likely to have a tipping point where even if we were to
stop emitting all carbon worldwide tomorrow, the system would still
collapse. And we are not in a position now to say that we haven’t already
crossed those points.”
[image: Large icebergs break away from Matusevich Glacier]
Large icebergs break away from Matusevich Glacier in east Antarctica in
2010.
Photo courtesy of NASA Earth Observatory image by Jesse Allen and Robert
Simmon
*Types of interventions*

The two conferences, one held at the University of Chicago last October and
the other at Stanford University in December, brought together dozens of
glaciologists, engineers and related disciplines.

The participants summarized our current knowledge of glacier science, and
discussed two major categories of glacier interventions that have been
proposed to date.

The first category consists of some type of berms or fiber-based “curtains”
moored on the seabed around the feet of ice shelves, which would prevent
warm water from undermining them. (The biggest threat to ice sheets is
actually warmer ocean water, rather than hotter air temperatures.)

“From preliminary studies, the actual engineering required might be smaller
than you might think,” said MacAyeal. “For example, the Thwaites Glacier in
Antarctica might require as little as 50 miles of seabed nets and curtains
to make a difference.

[geo] Current State of Geoengineering

[Geoengineering News]

https://link.springer.com/referenceworkentry/10.1007/978-3-031-30231-2_20-1

*Author*
Joshua Luczak

*First Online: 14 June 2024*

*Abstract*
There are, broadly speaking, three ways in which scientists and
policymakers talk about responding to the anthropogenic climate change. We
can mitigate the effects, adapt to it, or we can utilize geoengineering
techniques to offset its harmful impacts. As it currently stands, most
reasonable scientists, policymakers, and thinkers hold that some
combination of adaptation together with an aggressive mitigation strategy
is the most appropriate, all things considered, way to respond to the
problem. Since we are already committed to some climate change, any
response to the problem must include some kind of adaptation strategy. But,
for a collection of reasons, aggressive mitigation has to be the focus of
our policy response. It is the best, safest, and most fair way to resolve
the problem in the long run. Despite this, talk of incorporating forms of
geoengineering into our overall response strategy have grown in recent
times. In light of this trend, this chapter provides an overview of
geoengineering that is relevant for policymakers and lawmakers. This
chapter describes the most common and influential geoengineering techniques
that have been proposed and gives the reader a sense of where
geoengineering techniques sit in the minds of scientists and policymakers.
There is currently a dearth of laws and regulations that are directly aimed
at ensuring the safe development, testing, and deployment of geoengineering
techniques. There is also a lack of governance overseeing the research and
development of these techniques. This chapter serves as a partial primer
for anyone interested in wading into policy and legal issues surrounding
geoengineering.

*Source: SpringerLink*

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[geo] Validating a microphysical prognostic stratospheric aerosol implementation in E3SMv2 using observations after the Mount Pinatubo eruption

[Geoengineering News]

https://gmd.copernicus.org/articles/17/5087/2024/

*Authors*
Hunter York Brown, Benjamin Wagman, Diana Bull, Kara Peterson, Benjamin
Hillman, Xiaohong Liu, Ziming Ke, and Lin Lin

https://doi.org/10.5194/gmd-17-5087-2024

*03 July 2024*

*Abstract*
This paper describes the addition of a stratospheric prognostic aerosol
(SPA) capability – developed with the goal of accurately simulating sulfate
aerosol formation and evolution in the stratosphere – in the Department of
Energy (DOE) Energy Exascale Earth System Model, version 2 (E3SMv2). The
implementation includes changes to the four-mode Modal Aerosol Module
microphysics in the stratosphere to allow for larger particle growth and
more accurate stratospheric aerosol lifetime following the Pinatubo
eruption. E3SMv2-SPA reasonably reproduces stratospheric aerosol lifetime,
burden, aerosol optical depth, and top-of-atmosphere flux when compared to
remote sensing observations. E3SMv2-SPA also has close agreement with the
interactive chemistry–climate model CESM2-WACCM (Community Earth System
Model version 2–Whole Atmosphere Community Climate Model) – which has a
more complete chemical treatment – and the observationally constrained,
prescribed volcanic aerosol treatment in E3SMv2. Global stratospheric
aerosol size distributions identify the nucleation and growth of sulfate
aerosol from volcanically injected SO2 from both major and minor volcanic
eruptions from 1991 to 1993. The modeled aerosol effective radius is
consistently lower than satellite and in situ measurements (max differences
of ∼ 30 %). Comparisons with in situ size distribution samples indicate
that this simulated underestimation in both E3SMv2-SPA and CESM2-WACCM is
due to overly small accumulation and coarse-mode aerosols 6–18 months
post-eruption, with E3SMv2-SPA simulating ∼ 50 % of the coarse-mode
geometric mean diameters of observations 11 months post-eruption. Effective
radii from the models and observations are used to calculate offline
scattering and absorption efficiencies to explore the implications of
smaller simulated aerosol size for the Pinatubo climate impacts. Scattering
efficiencies at wavelengths of peak solar irradiance (∼ 0.5 µm) are 10 %–80
% higher for daily samples in models relative to observations through 1993,
suggesting higher diffuse radiation at the surface and a larger cooling
effect in the models due to the smaller simulated aerosol; absorption
efficiencies at the peak wavelengths of outgoing terrestrial radiation (∼
10 µm) are 15 %–40 % lower for daily samples in models relative to
observations, suggesting an underestimation in stratospheric heating in the
models due to the smaller simulated aerosol. These potential biases are
based on aerosol size alone and do not take into account differences in the
aerosol number. The overall agreement of E3SMv2-SPA with observations and
its similar performance to the well-validated CESM2-WACCM makes E3SMv2-SPA
a viable alternative to simulating climate impacts from stratospheric
sulfate aerosols.

*Source: EGU*

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[geo] Governing Prometheus Ethical Reflections On Risk & Uncertainty In Solar Climate Engineering Research

[Geoengineering News]

https://research.tudelft.nl/files/204271932/Dissertation_Ben_Hofbauer_Governing_Prometheus_final.pdf






*Source: TU Delft University *

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[geo] SOLAR GEOENGINEERING WEEKLY SUMMARY (01 JULY - 07 JULY 2024)

[Geoengineering News]

SOLAR GEOENGINEERING WEEKLY SUMMARY (01 JULY - 07 JULY 2024)


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Geoengineering:
Solar Geoengineering Updates

Monthly news summaries about solar geoengineering. Links to scientific
papers, news articles, jobs, podcasts, and videos.

By Andrew Lockley

--
RESEARCH PAPERSDrone-Based Measurement of the Size Distribution and
Concentration of Marine Aerosols above the Great Barrier Reef


Eckert, C., Hernandez-Jaramillo, D. C., Medcraft, C., Harrison, D. P., &
Kelaher, B. P. (2024). Drone-Based Measurement of the Size Distribution and
Concentration of Marine Aerosols above the Great Barrier Reef.
*Drones*, *8*(7),
292.

*Abstract*

Marine aerosol particles can act as cloud condensation nuclei and influence
the atmospheric boundary layer by scattering solar radiation. The
interaction of ocean waves and coral reefs may affect the distribution and
size of marine aerosol particles. Measuring this effect has proven
challenging. Here, we tested the hypothesis that the distribution and size
of marine aerosol particles would vary over three distinct zones (i.e.,
coral lagoon, surf break, and open water) near One Tree Island in the Great
Barrier Reef, which is approximately 85 km off the east coast of Australia.
We used a modified DJI Agras T30 drone fitted with a miniaturised scanning
electrical mobility sizer and advanced mixing condensation particle counter
to collect data on aerosol size distribution between 30 and 300 nm at 20 m
above the water surface. We conducted 30 flights over ten days during the
Austral summer/autumn of 2023. The fitted bimodal lognormal curves indicate
that the number concentrations for aerosols below 85 nm diameter are more
than 16% higher over the lagoon than over open water. The average mean mode
diameters remained constant across the different zones, indicating no
significant influence of breaking waves on the detected aerosol size modes.
The most influential explanatory variable for aerosol size distribution was
the difference between air temperature and the underlying sea surface,
explaining around 40% of the variability. Salinity also exhibited a
significant influence, explaining around 12% of the measured variability in
the number concentration of aerosols throughout the campaign. A calculated
wind stress magnitude did not reveal significant variation in the measured
marine aerosol concentrations. Overall, our drone-based aerosol
measurements near the water surface effectively characterise the dynamics
of background marine aerosols around One Tree Island Reef, illustrating the
value of drone-based systems for providing size-dependent aerosol
information in difficult-to-access and environmentally sensitive areas.

Measurement report: Aerosol vertical profiling over the Southern Great
Barrier Reef using lidar and MAX-DOAS measurements


Ryan, R. G., Toms-Hardman, L., Smirnov, A., Harrison, D., & Schofield, R.
(2024). Measurement report: Aerosol vertical profiling over the Southern
Great Barrier Reef using lidar and MAX-DOAS measurements. *EGUsphere*,
*2024*, 1-20.

*Abstract*

Aerosol vertical profile measurements were made using multi-axis
differential optical absorption spectroscopy (MAX-DOAS) and mini-Micropulse
LiDAR (MPL) at One Tree Island in the Southern Great Barrier Reef from
February to April 2023. This is an understudied location in terms of
atmospheric aerosols and chemistry but is growing in importance as multiple
research streams examine the influence of aerosols on radiation over the
Great Barrier Reef. Solar radiation management proposals require
regional-scale aerosol modelling, which is evaluated against aerosol
extinction and optical depth measurements, necessitating a thorough
understanding of measurements of these quantities. MPL aerosol retrieval
showed extinction-to-backscatter ratios (0.031 on average) and
depolarization ratios (0.015 on average) consistent with clean, unpolluted
Southern hemispheric marine aerosol. The maximum depolarization ratio
tended to be above the layer of maximum MPL backscatter, which is
attributed to dried sea-salt layers above the boundary layer. MAX-DOAS and
MPL extinction profiles show aerosol layers extending beyond 2 km altitude
in the middle of the day, but predominantly below 1 k

[geo] Uncertainties and confidence in stratospheric aerosol injection modelling: a systematic literature review

[Geoengineering News]

https://academic.oup.com/oocc/advance-article/doi/10.1093/oxfclm/kgae007/7699797

*Authors*
Anni Määttänen, Thibaut Lameille, Carola Kloeck, Olivier Boucher, François
Ravetta

https://doi.org/10.1093/oxfclm/kgae007

*Published: 26 June 2024*

*Abstract*
Model projections performed to evaluate the efficacy and impacts of solar
geoengineering interventions, such as Stratospheric Aerosol Injection
(SAI), include multiple sources of uncertainty, namely scenario, model, and
natural variability uncertainty. It is well accepted that a quantitative
uncertainty assessment related to SAI modelling is required to provide
robust and policy-relevant information on SAI. This study investigates how
and to what extent articles using a climate modelling approach on SAI
quantify and communicate uncertainty sources.

*Methods*
We conducted a systematic literature review of a sample of 60 peer-reviewed
articles in order to (a) analyse whether uncertainties were addressed, and
if yes, which methods were used to characterize uncertainties, and (b)
study how the articles communicated assumptions and limits that contribute
to the estimation of confidence in the used models and the resulting
projections.

*Results*
We present statistics on the uncertainty quantification methods used in the
articles and we discuss the vocabulary employed for conveying these
uncertainties and model confidence. In the studied article sample, the
attention paid to uncertainty estimations in the SAI literature increased
with time, and overall, uncertainties were treated using a variety of
methods. Model confidence was not always explicitly communicated as the
models used are already tested in the literature and their strengths and
weaknesses are known to the community although this is often implicit.

*Conclusion*
Our results show that it is currently difficult to perform global,
quantitative assessments of uncertainty related to SAI research, in line
with recent review reports on solar geoengineering.

*Source: Oxford Open Climate Change*

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[geo] Is cloud brightening a sensible way to combat climate change?

[Geoengineering News]

https://illuminem.com/illuminemvoices/is-cloud-brightening-a-sensible-way-to-combat-climate-change

*By Wil Burns*

*05 July 2024*

*Introduction*

Two months ago, a team of scientists helmed by researchers from the
University of Washington initiated a field test on the deck of the U.S.S.
Hornet , a decommissioned aircraft carrier
docked off Alameda, California. The experiment entailed spraying extremely
tiny sea salt particles into the air using a device that resembles a
snow-making device. The researchers wanted to determine if they could
consistently spray the right size of particles to ultimately facilitate a
process called “marine cloud brightening (MCB).” However, after a public
meeting in June to review the experiment, the Alameda City Council voted
unanimously to stop the operation

.

Marine Cloud Brightening is one approach in a suite of options to combat
climate change denominated as “solar radiation modification

(SRM),”
often called solar geoengineering
. SRM
approaches seek to reduce the amount of solar (shortwave) energy that
reaches the Earth’s surface. Reducing radiative forcing can offset some of
the warming effects associated with greenhouse gas emissions. Other SRM
approaches include injecting sulfur dioxide or other materials into the
stratosphere, or placing highly reflective sunshades in space
.

MCB aims to increase the albedo, or reflectivity, of low-level maritime
clouds. Increasing cloud albedo could result in deflection of more incoming
solar radiation back to space, thus exerting a cooling effect. The approach
seeks to accomplish this by injecting seawater spray into the lower marine
atmosphere. Ideally, the spray would be converted to fine particles
(approximately 50 nanometers) by evaporation and conveyed to clouds by
turbulent and convective air motions. The higher aerosol load associated
with such operations could lead to a greater number of cloud droplets,
smaller in diameter. This phenomenon, known as the “Twomey effect
,” could
substantially increase the reflectivity of the clouds
. Smaller cloud
droplets could also extend the lifetime of such clouds
.

One leading proponent of this approach has proposed the deployment of a
fleet of unmanned wind-powered ships
. These vessels would be equipped
with underwater turbines to produce the necessary seawater particles, and
devices to inject the particles into the atmosphere.

Given the failure of the world community in arresting climate change, it is
likely that the drum beat for deployment of SRM approaches will grow ever
louder in the next decade. This piece will focus on marine cloud
brightening in terms of potential benefits and risks.
*Potential effectiveness of marine cloud brightening*

To date, virtually all assessments of the potential effectiveness of MCB to
combat climate change are derived from modeling, and the results reflect
high levels of uncertainty and heterogeneous results. For example, one study
 concluded
that delivering a 50-100% increase in droplet concentrations in all marine
stratiform clouds could offset the warming associated with a doubling of
the concentrations of greenhouse gases in the atmosphere.

However, another study concluded that increases in droplet concentrations
would have to be much higher to achieve that objective, and ultimately
might fail to increase albedo sufficiently
.
Moreover, other studies
 have
found no substantial changes in temperature over wide ranges of the globe,
or have concluded that positive temperature impacts might diminish over time
.
Some models have also suggested that MCB could largely restore sea ice
coverage in both the Northern and Southern Hemispheres
.
*Potential risks associated with marine cloud brightening*

MCB research to date has raised serious concerns that deployment might
ultimately create regional “winners” and “losers,” which could undermine
principles of equity and justice and exacerbate international tensions. In one
study

[geo] Stratospheric aerosol injection for controlling greenhouse gas emission

[Geoengineering News]

https://www.sciencedirect.com/science/article/abs/pii/B9780443192319000120

*Authors*
Muhammad Irfan, Muhammad Ali Musarat, Saba Ayub, Wesam Salah Alaloul

*28 June 2025*

https://doi.org/10.1016/B978-0-443-19231-9.00012-0

*Abstract*
An artificial method of injecting sulfate aerosols into the stratosphere to
reduce greenhouse gas emissions (GHGs) is called stratospheric aerosol
injection (SAI). By releasing sulfates into the atmosphere, volcanic
eruptions naturally disperse sunlight and lower the temperature of the
Earth’s surface. This technique attempts to replicate that process. SAI has
drawn interest as a possible geoengineering technique to mitigate the
effects of climate change. It does, however, present important ethical,
technical, and environmental issues that need to be properly resolved
before deployment is ever discussed. Regional climate alteration, ozone
layer depletion, disruption of precipitation patterns, and negative health
consequences on humans are among the possible dangers linked to solar
radiation exposure. Concerns about consent, equity, governance frameworks,
and unexpected repercussions are all included in the category of ethical
considerations. Moreover, there are unknowns about the best injection
heights and aerosol volume needed for efficient cooling while reducing
additional hazards. To make informed judgments in the future regarding the
sustainability and practicality of using SAI as a tool to reduce greenhouse
gas emissions, it is imperative to have a thorough grasp of these intricate
concerns. Therefore, the current chapter will analyze the concept of SAI
and its anticipated benefits and challenges.

*Source: ScienceDirect*

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[geo] Drone-Based Measurement of the Size Distribution and Concentration of Marine Aerosols above the Great Barrier Reef

[Geoengineering News]

https://www.mdpi.com/2504-446X/8/7/292

*Authors*
Christian Eckert, Diana C. Hernandez-Jaramillo,Chris Medcraft, Daniel P.
Harrison and Brendan P. Kelaher

https://doi.org/10.3390/drones8070292

*Published: 27 June 2024*

*Abstract*
Marine aerosol particles can act as cloud condensation nuclei and influence
the atmospheric boundary layer by scattering solar radiation. The
interaction of ocean waves and coral reefs may affect the distribution and
size of marine aerosol particles. Measuring this effect has proven
challenging. Here, we tested the hypothesis that the distribution and size
of marine aerosol particles would vary over three distinct zones (i.e.,
coral lagoon, surf break, and open water) near One Tree Island in the Great
Barrier Reef, which is approximately 85 km off the east coast of Australia.
We used a modified DJI Agras T30 drone fitted with a miniaturised scanning
electrical mobility sizer and advanced mixing condensation particle counter
to collect data on aerosol size distribution between 30 and 300 nm at 20 m
above the water surface. We conducted 30 flights over ten days during the
Austral summer/autumn of 2023. The fitted bimodal lognormal curves indicate
that the number concentrations for aerosols below 85 nm diameter are more
than 16% higher over the lagoon than over open water. The average mean mode
diameters remained constant across the different zones, indicating no
significant influence of breaking waves on the detected aerosol size modes.
The most influential explanatory variable for aerosol size distribution was
the difference between air temperature and the underlying sea surface,
explaining around 40% of the variability. Salinity also exhibited a
significant influence, explaining around 12% of the measured variability in
the number concentration of aerosols throughout the campaign. A calculated
wind stress magnitude did not reveal significant variation in the measured
marine aerosol concentrations. Overall, our drone-based aerosol
measurements near the water surface effectively characterise the dynamics
of background marine aerosols around One Tree Island Reef, illustrating the
value of drone-based systems for providing size-dependent aerosol
information in difficult-to-access and environmentally sensitive areas.

*Source: MDPI*

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[geo] Measurement report: Aerosol vertical profiling over the Southern Great Barrier Reef using lidar and MAX-DOAS measurements

[Geoengineering News]

https://egusphere.copernicus.org/preprints/2024/egusphere-2024-/

*Authors*
Robert G. Ryan, Lilani Toms-Hardman, Alexander Smirnov, Daniel Harrison,
and Robyn Schofield

*How to cite. *Ryan, R. G., Toms-Hardman, L., Smirnov, A., Harrison, D.,
and Schofield, R.: Measurement report: Aerosol vertical profiling over the
Southern Great Barrier Reef using lidar and MAX-DOAS measurements,
EGUsphere [preprint], https://doi.org/10.5194/egusphere-2024-, 2024.

*Received: 12 Apr 2024 – Discussion started: 28 Jun 2024*

*Abstract*
Aerosol vertical profile measurements were made using multi-axis
differential optical absorption spectroscopy (MAX-DOAS) and mini-Micropulse
LiDAR (MPL) at One Tree Island in the Southern Great Barrier Reef from
February to April 2023. This is an understudied location in terms of
atmospheric aerosols and chemistry but is growing in importance as multiple
research streams examine the influence of aerosols on radiation over the
Great Barrier Reef. Solar radiation management proposals require
regional-scale aerosol modelling, which is evaluated against aerosol
extinction and optical depth measurements, necessitating a thorough
understanding of measurements of these quantities. MPL aerosol retrieval
showed extinction-to-backscatter ratios (0.031 on average) and
depolarization ratios (0.015 on average) consistent with clean, unpolluted
Southern hemispheric marine aerosol. The maximum depolarization ratio
tended to be above the layer of maximum MPL backscatter, which is
attributed to dried sea-salt layers above the boundary layer. MAX-DOAS and
MPL extinction profiles show aerosol layers extending beyond 2 km altitude
in the middle of the day, but predominantly below 1 km at other times. We
also compared aerosol optical depth measurements from integrating the
MAX-DOAS and MPL extinction profiles, with observations from a hand-held
Microtops sun photometer. Mean aerosol optical depth (AOD) values across
the campaign compare well, being 0.083 ± 0.002 for the Microtops, 0.090 ±
0.032 for the MAX-DOAS and 0.104 ± 0.028 for the MPL. However, AOD
observations at a given time, and the AOD diurnal cycle, often varied
between instruments. This likely indicates strong horizontal inhomogeneity
in aerosol in this environment, a factor which makes it challenging to
accurately compare AOD estimates from different viewing geometries, but
which is important for future aerosol modelling studies in this region to
consider.

*Source: EGU Sphere*

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[geo] SOLAR GEOENGINEERING WEEKLY SUMMARY (24 JUNE - 30 JUNE 2024)

[Geoengineering News]

*SOLAR GEOENGINEERING WEEKLY SUMMARY (24 JUNE - 30 JUNE 2024)*

Subscribe to our newsletter to receive monthly updates on Solar
Geoengineering:
Solar Geoengineering Updates

Monthly news summaries about solar geoengineering. Links to scientific
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By Andrew Lockley

--
DEADLINES*Call for Abstracts—AGU Conference | Submissions are open until 31
July 2024 *

*SRM Sessions at AGU2024:**GC009-Advances in Climate Engineering Science
**A081-Exploring
the Interplay of Weather Modification and Climate Intervention: Modeling,
Observations, and Field Campaigns
**GC004-Advancements
in Climate Intervention Research Technologies, Policies and Practices:
Opportunities and Issues
**GC048-Climate
Intervention, Mitigation, Adaptation, and Restoration: Assessing the Risks
and Benefits of Using Earth System Models for Guidance on Climate Action
*

*Call for Abstract—Cloud and precipitation responses to aerosol pollution,
weather modification and climate intervention
 | Deadline to apply: 15 August
2024*(NEW) Funding opportunity: Modelling environmental responses to solar
radiation management by Natural Environment Research Council (NERC) |
Deadline to apply: 08 October 2024

--
RESEARCH PAPERSAn assessment of the infrastructural and temporal barriers
constraining a near-term implementation of a global stratospheric aerosol
injection program


Smith, W. (2024). An assessment of the infrastructural and temporal
barriers constraining a near-term implementation of a global stratospheric
aerosol injection program. *Environmental Research Communications*.

*Abstract*

Models of stratospheric aerosol injection deployment scenarios have often
assumed that a global sunscreen could be applied to the Earth on relatively
short notice, perhaps in response to a climate emergency. This emergency
response framing confuses the timescales associated with the commencement
of such a program. Once deployed, stratospheric aerosols could cool the
Earth quite quickly, but the most commonly assumed deployment scenarios
would require aircraft and other infrastructure that does not currently
exist. Given the span required to develop and certify a novel aircraft
program and to subsequently build a fleet numbering in the hundreds,
scenario builders should assume a roughly two-decade interval between a
funded launch decision and the attainment of a target level of cooling.

Public perceptions on solar geoengineering from focus groups in 22 countries


Low, S., Fritz, L., Baum, C. M., & Sovacool, B. K. (2024). Public
perceptions on solar geoengineering from focus groups in 22 countries.
*Communications
Earth & Environment*, *5*(1), 1-19.

*Abstract*

Solar geoengineering maintains a vocal presence as a stop-gap measure in
assessments of climate and sustainability action. In this paper, we map
prospective benefits and risks, and corresponding governance approaches,
regarding three major proposals for solar geoengineering (stratospheric
aerosol injection, marine cloud brightening, and a space-based sunshield).
We do so by engaging with 44 focus groups conducted in 22 countries split
between the global North and South. We compare results against previous
research on the public perceptions of solar geoengineering as well as wider
activities in assessment, innovation, and decision-making. We find that
global South groups exhibit greater hope but an arguably richer range of
concerns for solar geoengineering, in the context of observable inequities
in climate action and potential geopolitical conflict. Meanwhile, a strong,
global preference for multilateral coordination and public engagement from
the conduct of research onwards is offset by skepticism of effective
multilateralism and public discourse.

Microphysical interactions determine the effectiveness of Solar Radiation
Modification via Stratospheric Solid Particle Injection


Sandro V., Sina K K., John A D., et al. Microphysical interactions
determine the eff

[geo] An assessment of the infrastructural and temporal barriers constraining a near-term implementation of a global stratospheric aerosol injection program

[Geoengineering News]

https://iopscience.iop.org/article/10.1088/2515-7620/ad4f5c/meta

*Authors*
Wake Smith

*Published 26 June 2024*

DOI 10.1088/2515-7620/ad4f5c

*Abstract*
Models of stratospheric aerosol injection deployment scenarios have often
assumed that a global sunscreen could be applied to the Earth on relatively
short notice, perhaps in response to a climate emergency. This emergency
response framing confuses the timescales associated with the commencement
of such a program. Once deployed, stratospheric aerosols could cool the
Earth quite quickly, but the most commonly assumed deployment scenarios
would require aircraft and other infrastructure that does not currently
exist. Given the span required to develop and certify a novel aircraft
program and to subsequently build a fleet numbering in the hundreds,
scenario builders should assume a roughly two-decade interval between a
funded launch decision and the attainment of a target level of cooling.

*Source: IOP SCIENCE *

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[geo] Public perceptions on solar geoengineering from focus groups in 22 countries

[Geoengineering News]

https://www.nature.com/articles/s43247-024-01518-0

*Authors*
Sean Low, Livia Fritz, Chad M. Baum & Benjamin K. *Sovacool *

*Citations: Low, S., Fritz, L., Baum*, C.M. et al. Public perceptions on
solar geoengineering from focus groups in 22 countries. Commun Earth
Environ 5, 352 (2024). https://doi.org/10.1038/s43247-024-01518-0

*27 June 2024*

*Abstract*
Solar geoengineering maintains a vocal presence as a stop-gap measure in
assessments of climate and sustainability action. In this paper, we map
prospective benefits and risks, and corresponding governance approaches,
regarding three major proposals for solar geoengineering (stratospheric
aerosol injection, marine cloud brightening, and a space-based sunshield).
We do so by engaging with 44 focus groups conducted in 22 countries split
between the global North and South. We compare results against previous
research on the public perceptions of solar geoengineering as well as wider
activities in assessment, innovation, and decision-making. We find that
global South groups exhibit greater hope but an arguably richer range of
concerns for solar geoengineering, in the context of observable inequities
in climate action and potential geopolitical conflict. Meanwhile, a strong,
global preference for multilateral coordination and public engagement from
the conduct of research onwards is offset by skepticism of effective
multilateralism and public discourse.

Complexes of hopes, concerns, and corresponding governance issues
associated with solar geoengineering.
[image: figure 1]


*Source: communications earth & environment *

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[geo] Microphysical interactions determine the effectiveness of Solar Radiation Modification via Stratospheric Solid Particle Injection

[Geoengineering News]

https://essopenarchive.org/doi/full/10.22541/essoar.171926549.92645374/v1

*Àuthors*
Sandro Vattioni,Sina K Käslin,John A Dykema,Luo Beiping,Timofei
Sukhodolov,Jan Sedlacek,Frank Keutsch,Thomas Peter,Gabriel Chiodo

*24 June 2024*

*Citations*: Sandro Vattioni, Sina K Käslin, John A Dykema, et al.
Microphysical interactions determine the effectiveness of Solar Radiation
Modification via Stratospheric Solid Particle Injection. ESS Open Archive .
June 24, 2024.
DOI: 10.22541/essoar.171926549.92645374/v1

*Abstract*
Recent studies have suggested that stratospheric aerosol injection (SAI) of
solid particles for climate intervention could reduce stratospheric warming
compared to injection of SO2.
However, interactions of microphysical processes, such as settling and
coagulation of solid particles, with stratospheric dynamics have not been
considered.
Using a global chemistry-climate model with interactive solid particle
microphysics, we show that agglomeration significantly reduces the
backscatter efficiency per unit of burden compared to mono-disperse
particles, partly due to faster settling of the agglomerates, but mainly
due to increased forward- over backscattering with increasing agglomerate
size.
Compared to injection of SO2, injection of 150\,nm radius diamond particles
still substantially reduces required injection rates as well as
perturbation of stratospheric winds, age of air and water vapor
concentrations due to the small stratospheric warming per radiative
forcing. Uncertainties remain as to whether stratospheric dispersion of
solid particles is feasible without formation of agglomerates.

*Source: ESS OPEN ARCHIVE *

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[geo] Stratospheric sulfate aerosols and their impact on climate: from volcanoes to proposed human interventions—Thesis

[Geoengineering News]

https://ricerca.univaq.it/bitstream/11697/208519/2/PhD_Thesis-5.pdf







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[geo] Different Strategies of Stratospheric Aerosol Injection Would Significantly Affect Climate Extreme Mitigation

[Geoengineering News]

https://www.osti.gov/pages/biblio/2370147

*Authors*
Jiang Jiu, Xia Yi, Cao Long, Kravitz Ben, MacMartin Douglas G, Fu Jianjie,
Jiang Guibin

https://doi.org/10.1029/2023EF004364

*04 June 2024*

*Abstract*
Abstract Stratospheric aerosol injection (SAI) has been proposed as a
potential supplement to mitigate some climate impacts of anthropogenic
warming. Using Community Earth System Model ensemble simulation results, we
analyze the response of temperature and precipitation extremes to two
different SAI strategies: one injects SO 2 at the equator to stabilize
global mean temperature and the other injects SO 2 at multiple locations to
stabilize global mean temperature as well as the interhemispheric and
equator‐to‐pole temperature gradients. Our analysis shows that in the late
21st century, compared with the present‐day climate, both equatorial and
multi‐location injection lead to reduced hot extremes in the tropics,
corresponding to overcooling of the mean climate state. In mid‐to‐high
latitude regions, in comparison to the present‐day climate, substantial
decreases in cold extremes are observed under both equatorial and
multi‐location injection, corresponding to residual winter warming of the
mean climate state. Both equatorial and multi‐location injection reduce
precipitation extremes in the tropics below the present‐day level,
associated with the decrease in mean precipitation. Overall, for most
regions, temperature and precipitation extremes show reduced change in
response to multi‐location injection than to equatorial injection,
corresponding to reduced mean climate change for multi‐location injection.
In comparison with equatorial injection, in response to multi‐location
injection, most land regions experience fewer years with significant change
in cold extremes from the present‐day level, and most tropical regions
experience fewer years with significant change in hot extremes. The design
of SAI strategies to mitigate anthropogenic climate extremes merits further
study.

*Source: U.S. Department of Energy*
*Office of Scientific and Technical Information*

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[geo] Targeted marine cloud brightening can dampen El Niño

[Geoengineering News]

https://arxiv.org/abs/2406.07853

*Authors*
Jessica S. Wan, John T. Fasullo, Nan Rosenbloom, Chih-Chieh Jack Chen,
Katharine Ricke

*12 June 2024*

*Abstract*
Many record-breaking climate extremes arise from both greenhouse
gas-induced warming and natural climate variability. Marine cloud
brightening, a solar geoengineering strategy originally proposed to reduce
long-term warming, could potentially mitigate extreme events by instead
targeting seasonal phenomena, such as El Niño-Southern Oscillation (ENSO).
By exploiting the 2019-2020 Australian wildfire experiment-of-opportunity,
we show that simulated marine cloud brightening in the southeast Pacific
reproduces observed cloud changes and induces La Niña-like responses. We
then explore how cloud brightening timing and duration modifies the
1997-1998 and 2015-2016 El Niño events. We find the earliest and longest
interventions effectively restore neutral ENSO conditions and dampen El
Niño's impacts. Solar geoengineering that targets climate variability could
complement tools such as ENSO forecasting and provide a pathway for climate
risk mitigation.

*Source: ArXiv*

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[geo] Diminished efficacy of regional marine cloud brightening in a warmer world

[Geoengineering News]

https://www.nature.com/articles/s41558-024-02046-7

*Authors*
Jessica S. Wan, Chih-Chieh Jack Chen, Simone Tilmes, Matthew T. Luongo,
Jadwiga H. Richter & Katharine Ricke
Nature Climate Change (2024)Cite this article

*21 June 2024*

*Citations*: Wan, J.S., Chen, CC.J., Tilmes, S. et al. Diminished efficacy
of regional marine cloud brightening in a warmer world. Nat. Clim. Chang.
(2024). https://doi.org/10.1038/s41558-024-02046-7

*Abstract*
Marine cloud brightening (MCB) is a geoengineering proposal to cool
atmospheric temperatures and reduce climate change impacts. As large-scale
approaches to stabilize global mean temperatures pose governance
challenges, regional interventions may be more attractive near term. Here
we investigate the efficacy of regional MCB in the North Pacific to
mitigate extreme heat in the Western United States. Under present-day
conditions, we find MCB in the remote mid-latitudes or proximate subtropics
reduces the relative risk of dangerous summer heat exposure by 55% and 16%,
respectively. However, the same interventions under mid-century warming
minimally reduce or even increase heat stress in the Western United States
and across the world. This loss of efficacy may arise from a
state-dependent response of the Atlantic Meridional Overturning Circulation
to both anthropogenic warming and regional MCB. Our result demonstrates a
risk in assuming that interventions effective under certain conditions will
remain effective as the climate continues to change.

*Source: Nature Climate Change *

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[geo] Solar Radiation Modification is projected to increase land carbon storage and to protect the Amazon rainforest

[Geoengineering News]

https://www.researchsquare.com/article/rs-4472495/v1

*Authors*
Isobel Parry, Paul Ritchie, Olivier Boucher, Peter Cox, Jim Haywood, Ulrike
Niemeier, Roland Séférian, Simone Tilmes, Daniele Visioni

*12 June 2024*

https://doi.org/10.21203/rs.3.rs-4472495/v1

*Abstract*
Solar radiation modification (SRM) aims to artificially cool the Earth,
counteracting warming from anthropogenic greenhouse gases by increasing the
reflection of incoming sunlight. One SRM strategy is stratospheric aerosol
injection (SAI), which mimics explosive volcanoes by injecting aerosols
into the stratosphere. There are concerns that SAI could suppress
vegetation productivity by reducing the amount of sunlight reaching the
Earth’s surface and by shifting rainfall patterns. Here we examine results
from five Earth System Models that use SAI to reduce the global mean
temperature from that of a high emissions world (SSP585), to that of a more
moderate global warming scenario (SSP245). Compared to SSP245, the SAI
simulations project higher global NPP values (+15.6%) and higher land
carbon storage (+5.9%), primarily because of increased CO2 fertilization.
The effects of SAI are most obvious in Amazonia where notable increases in
NPP (+13.8%) and land carbon storage (+8.6%) are projected compared to
SSP245, as well as compared to SSP585 (+10.8% and +7.1% respectively). Our
results therefore suggest that SAI could provide some protection against
the risk of climate change induced Amazon forest dieback, and may in fact
be a very effective method of atmospheric carbon sequestration.

*Source: ResearchSquare*

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[geo] Assessing Earth System Responses to Climate Mitigation and Intervention with Scenario-Based Simulations and Data-Driven Insight

[Geoengineering News]

https://www.researchsquare.com/article/rs-4469037/v1

*Authors*
Bradley Gay, Charles Miller, Kimberley Miner, Lukas Mandrake

https://doi.org/10.21203/rs.3.rs-4469037/v1

*posted 05 Jun, 2024*

*Abstract*
Given a world increasingly dominated by climate extremes, large-scale
geoengineering interventions to modify the Earth’s climate appears
inevitable. However, geoengineering faces a conundrum: accurately
forecasting the consequences of climate intervention in a system for which
we have incomplete observations and an imperfect understanding. We evaluate
the potential implications of mitigation and intervention strategies with a
set of experiments utilizing historical reanalysis data and scenario-based
model simulations to examine the global response to deploying these
strategies. Key findings included a global mean surface temperature and
total precipitation increases of 1.3740.481C and 0.0450.567 mm day−1
respectively over the observed period (i.e., 1950–2022). Mitigation and
intervention simulations reveal pronounced regional anomalies in surface
temperature and erratic interannual variability in total precipitation,
with surface temperatures up to 7.626C in Greenland, Northern Siberia, and
the Horn of Africa down to -2.378ºC in Central Africa and Eastern Brazil,
and total precipitation increases of 1.170 mm day−1 in Southern Alaska down
to -1.195 mm day− 1 in Colombia and East Africa. Furthermore, [CH4]
dynamics indicated the potential to alter global and regional climate
metrics but presented significant regional and global variability based on
scenario deployment. Collectively, intervention and mitigation simulations
tended to overestimate the variability and magnitude of surface temperature
and total precipitation, with substantial regional deviations and
scenario-dependent estimation heterogeneity for [CH4]. Furthermore, forward
projections indicate that both mitigation and intervention scenarios can
lead to varied climate responses, emphasizing the complexity and
uncertainty in predicting exact outcomes of different geoengineering
strategies. By constraining our investigation scope to include monthly
surface temperature, total precipitation, and atmospheric methane
concentration [CH4], we find these simulations were capable of accurately
capturing departures but unable to perfectly represent patterns of warming
and precipitation teleconnections clearly identified in the observational
record.

*Source: ResearchSquare*

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[geo] Fwd: SOLAR GEOENGINEERING WEEKLY SUMMARY (10 JUNE - 16 JUNE 2024)

[Geoengineering News]

*SOLAR GEOENGINEERING WEEKLY SUMMARY (10 JUNE - 16 JUNE 2024*

Subscribe to our newsletter to receive monthly updates on Solar
Geoengineering:
Solar Geoengineering Updates

Monthly news summaries about solar geoengineering. Links to scientific
papers, news articles, jobs, podcasts, and videos.

By Andrew Lockley

--
DEADLINES(NEW) Call for Abstract—Cloud and precipitation responses to
aerosol pollution, weather modification and climate intervention
 | Deadline to apply: 15 August
2024
--
RESEARCH PAPERSHow Does the Latitude of Stratospheric Aerosol Injection
Affect the Climate in UKESM1?


Henry, M., Bednarz, E. M., & Haywood, J. (2024). How Does the Latitude of
Stratospheric Aerosol Injection Affect the Climate in UKESM1?. *EGUsphere*,
*2024*, 1-23.

*Abstract*

Stratospheric Aerosol Injection (SAI) refers to a climate intervention
method by which aerosols are intentionally added to the lower stratosphere
to enhance sunlight reflection and offset some of the adverse effects of
global warming. The climate outcomes of SAI depend on the location, amount,
and timing of injection, as well as the material used. Here, we isolate the
role of the latitude of SO2 injection by comparing different scenarios
which have the same global-mean temperature target, altitude of injection,
and hemispherically symmetric injection rates. These are: injection at the
equator (EQ), and injection at 15° N and S (15N+15S), at 30° N and S
(30N+30S), and at 60° N and S (60N+60S). We show that injection at the
equator leads to many undesirable side effects, such as a residual Arctic
warming, significant reduction in tropical precipitation, reductions in
high-latitude ozone, tropical lower stratospheric heating, and
strengthening of the stratospheric jets in both hemispheres. Additionally,
we find that the most efficient injection locations are the subtropics (15
and 30° N and S), although the 60N+60S strategy only requires around 30 %
more SO2 injection for the same amount of cooling; the latter also leads to
much less stratospheric warming but only marginally increases high-latitude
surface cooling. Finally, while all the SAI strategies come with
trade-offs, we demonstrate that the 30N+30S strategy has, on balance, the
least negative side effects and is easier to implement than a
multi-latitude controller algorithm; thus it is a good candidate strategy
for an inter-model comparison.

The Wizards of Climate Change: How Can Technology Serve Hope and Justice?
An Ethical Framework for Climate Intervention Research: What It Is and Why
You Should Care 

Williams, B. M., Shimamoto, M. & Graumlich, L. J., (2024) “An Ethical
Framework for Climate Intervention Research: What It Is and Why You Should
Care”, Zygon: Journal of Religion and Science 59(1), 82–96.

*Abstract*

Climate change poses significant threats to ecosystems, human health, and
global stability. Despite international efforts to reduce greenhouse gas
emissions, the Earth’s climate continues to warm, leading to extreme
weather events, rising sea levels, and other detrimental impacts. In
response to this crisis, scientists have begun exploring various strategies
to mitigate climate change through geoengineering, which involves
deliberate interventions in the Earth’s climate system. This article
provides an overview of climate geoengineering research, focusing on key
techniques, challenges, and ethical considerations, including actions being
taken by the American Geophysical Union (AGU), a nonprofit professional
scientific society, to develop an ethical framework to help guide research
in this important area. AGU also is driving global engagement on this
topic, including with leaders and members of faith communities.

Changes in Shipping Emissions As a Natural Analogue for Climate
Intervention: Detecting and Attributing Changes Due to Specific Human
Activities As a Testbed for Future Controversies


Visioni, D., & Quaglia, I. (2024, January). Changes in shipping emissions
as a natural analogue for Climate Intervention: detecting and attributing
changes due to specific human activities as a testbed for future
controversies. In *104th AMS Annual Meeting*. AMS.

*Abstract*

In 2020, new regulations from the International Maritime Organization (IMO)
have resulted in a substantial reduction in the amount of SO2 emitted by
vessels crossing the oceans, particula

[geo] Natural Variability Can Mask Forced Permafrost Response to Stratospheric Aerosol Injection in the ARISE-SAI-1.5 Simulations

[Geoengineering News]

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023EF004191?af=R

*Authors*
A. L. Morrison, E. A. Barnes, J. W. Hurrell

*First published: 16 June 2024*

https://doi.org/10.1029/2023EF004191

*Abstract*
Stratospheric aerosol injection (SAI) has been proposed as a potential
method for mitigating risks and impacts associated with anthropogenic
climate change. One such risk is widespread permafrost thaw and associated
carbon release. While permafrost has been shown to stabilize under
different SAI scenarios, natural variability may mask this forced response
and make it difficult to detect if and when SAI is stabilizing permafrost.
Here we use the 10-member ensemble from the ARISE-SAI-1.5 simulations to
assess the spread in projected active layer depth and permafrost
temperature across boreal permafrost soils and specifically in four
peatland and Yedoma regions. The forced response in active layer depth and
permafrost temperature quickly diverges between an SAI and non-SAI world,
but individual ensemble members overlap for several years following SAI
deployment. We find that, due to projected permafrost variability, it may
take more than a decade of SAI deployment to detect the effects of SAI on
permafrost temperature and almost 30 years to detect its effects on active
layer depth. Not only does natural variability make it more difficult to
detect SAI's influence, it could also affect the likelihood of reaching a
permafrost tipping point. In some realizations, SAI fails to prevent a
local tipping point that is also reached in a non-SAI world. Our results
underscore the importance of accounting for natural variability in
assessments of SAI's potential influence on the climate system.

*Key Points*
Projected natural variability in permafrost fields in peatland and Yedoma
regions can mask forced response to stratospheric aerosol injection (SAI)

Effect of SAI on active layer and soil temperature is only detectable after
more than a decade of aerosol deployment

Natural variability affects likelihood of reaching precursor to permafrost
tipping point despite surface cooling effect of SAI

*Plain Language Summary*
Injecting highly reflective particles into the upper atmosphere, or
stratospheric aerosol injection (SAI), is a proposed climate intervention
method for deliberately stabilizing or cooling the Earth's temperature and
preventing undesirable impacts of human-caused climate change, such as
thawing permafrost. Permafrost can potentially release stored carbon into
the atmosphere as carbon dioxide and methane that contributes to the
greenhouse effect. Climate model simulations show that SAI could stabilize
permafrost and prevent it from thawing, but that natural fluctuations in
the Earth's climate may cause a wide range of outcomes for future
permafrost thaw depth and soil temperature. We show that, due to these
natural climate fluctuations, it may take 10–30 years of SAI to clearly see
its influence on permafrost thaw depth and temperature. Certain conditions
that lead to runaway thaw and soil carbon release (i.e., tipping points)
may also occur even if SAI successfully stabilizes the Earth's globally
averaged temperature. When weighing possible outcomes of proposed climate
intervention strategies, it is important to consider the effects of natural
climate fluctuations in assessing the pros and cons of different strategies.

*Source: AGU*

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[geo] Changes in Shipping Emissions As a Natural Analogue for Climate Intervention: Detecting and Attributing Changes Due to Specific Human Activities As a Testbed for Future Controversies

[Geoengineering News]

https://ams.confex.com/ams/104ANNUAL/meetingapp.cgi/Paper/431888


*Authors*
Daniele Visioni, Ilaria Quaglia

*2024*

*Abstract*
*In 2020*, new regulations from the International Maritime Organization
(IMO) have resulted in a substantial reduction in the amount of SO2 emitted
by vessels crossing the oceans, particularly over the Atlantic and Pacific
oceans (Watson-Parris et al., 2022). Studies published before the
regulations went into effect had already postulated that they would have an
effect on cloud formation and direct forcing from the lack of sulfate
aerosols produced, with an overall small but non-zero global impact (Jin et
al., 2018). In the meantime, greenhouse gases concentrations keep rising,
and there is a growing perception amongst the general public and the
climate community that the latest extreme events observed have grown over
the last few years: 2023 has a high likelihood of being the warmest year
ever on record, while there have been record fire seasons in both Canada
and Hawaii and many regions in the Northern Hemisphere have observed
anomalously high sea surface temperature (SSTs), coupled with (and
partially driven by) a strong positive phase of ENSO. Discussions in the
news about whether some particular factors have contributed to this extreme
year are growing, and many have focused on the reduction in
sunlight-reflecting aerosols as a potential culprit.

Such questions are strongly tied with those around the opportunity to study
Sunlight Reflection Methods (SRM) as a climate intervention strategy that
may ameliorate the effects of climate change by reducing incoming sunlight,
perhaps using a thin layer of aerosols in the stratosphere, where they last
longer and are not as harmful to people. There is robust agreement over the
cooling potential of aerosols in the climate system: at the same time,
there is similar agreement over the health benefits of reducing aerosol
concentrations near human centers to improve public health. SRM by means of
stratospheric aerosol injections (SAI) might be a proposal that ties both
considerations, but in order to consider it seriously far more research is
needed to reduce uncertainties and understand how the climate system would
respond.

In this study, we use both a range of observation spanning surface air
temperatures (SAT), sea surface temperatures (SST) and top-of-atmosphere
Earth Energy Imbalance (EEI) and a large ensemble of simulations performed
with the Community Earth System Model (CESM2) (Simpson et al., 2023).
Firstly, we will use the CESM2 LENS to understand the detection of the
global signal and to attribute specific changes in regional climate,
coupling available simulations with new ones where the aerosol emissions
from shipping are quickly removed, as the LENS uses the Shared
Socioeconomic Pathway (SSP) 3-7.0, where shipping emissions continue (Fig.
1). The comparison of the two scenarios will provide a needed
counterfactual that a simple analysis of observational datasets,
considering internal variability, does not allow. However, the comparison
of multiple observational datasets (such as the Berkeley temperature record
and various reanalysis products such as ERA5) will also allow for a
discussion of statistical significance of the detected signal based on
inherent uncertainties in our knowledge of the climate system and internal
climate variability.

Secondly, we will expand this by simulating similar scenarios, but in which
the aerosols are not removed completely but moved to the stratosphere in
order to understand the projected differences between tropospheric and
stratospheric aerosols in terms of regional climatic impacts. This will
allow us to make more generalized conclusion around the issue of Climate
Intervention (CI), in particular the combined health and climatic benefits
of both removing aerosols from the troposphere, but adding them in the
stratosphere so that they can cool without impacting negatively on surface
air quality. This way of thinking about climate intervention will highlight
the concept that CI should be thought of not as an addiction but as a
vertical re-distribution of a fraction of the tropospheric aerosols, so
that they can keep their benefit and reduce their negative impacts, and
will help the community gain a better understanding of the limits of
detectability for CI, which can better inform future governance discussions
around outdoor tests.



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[geo] New discovery reveals that ocean algae unexpectedly help cool the Earth

[Geoengineering News]

https://phys.org/news/2024-06-discovery-reveals-ocean-algae-unexpectedly.html

*By University of East Anglia*

*11 June 2024*

A common type of ocean algae plays a significant role in producing a
massively abundant compound that helps cool the Earth's climate, new
research has discovered.

The findings of the study by the University of East Anglia (UEA) and Ocean
University of China (OUC) could change our understanding of how these tiny
marine organisms impact our planet.

The work appears in Nature Microbiology.

The team identified the bloom-forming Pelagophyceae algae as potentially
abundant and important producers of a compound called
dimethylsulfoniopropionate, or DMSP.

Co-lead author Professor Jonathan Todd, of UEA's School of Biological
Sciences, said, "The Pelagophyceae are among the most abundant algae on
Earth, yet they were not previously known as important producers of DMSP.
This discovery is exciting because DMSP is an abundant antistress compound,
food source for other microorganisms and major source of climate-cooling
gases."

Dr. Jinyan Wang, OUC/UEA Ph.D. student and first author, said,
"Understanding the role of Pelagophyceae in DMSP production means we need
to rethink how much of this compound is being produced and how it impacts
our climate."

Every year, billions of tons of DMSP are produced in the Earth's oceans by
marine microorganisms, helping them to survive by protecting against
various stresses like changes in salinity, cold, high pressure, and
oxidative stress. Importantly, DMSP is the main source of a climate active
gas called dimethylsulfide (DMS), which is known as the smell of the
seaside.

This study suggests that DMSP production, and consequently DMS release, is
likely higher than previously predicted and emphasizes the key role of
microbes in regulating global climate. DMS also acts as a signaling
molecule, guiding marine organisms to their food and deterring predators.

When DMS is released into the atmosphere, DMS oxidation products help form
clouds which reflect sunlight away from the Earth, effectively cooling the
planet. This natural process  is
essential for regulating the Earth's climate and is also hugely important
for the global sulfur cycle, representing the main route by which sulfur
from the oceans is returned to land.

UEA and OUC established the Sino-UK Joint Research Centre to promote
cutting-edge research and teaching in marine and ocean science. UEA's Dr.
Andrew Curson was a key member of the team that identified the novel
enzymes responsible for the synthesis of DMSP in diverse bacteria,
photosynthetic cyanobacteria and algae. Dr. Curson said, "The identity of
these enzymes allowed our team to identify Pelagophyceae as potentially
abundant and important DMSP producers."

Co-lead author Professor Xiao-Hua Zhang, of OUC's College of Marine Life
Science, added, "By identifying the enzymes involved in DMSP production,
scientists can better understand and predict the behavior of these
ecosystem-disruptive, brown-tide-forming algae and their impact on global
climate change. This study has also raised questions about other
unidentified versions of the enzymes needed to make DMSP, or entirely
different pathways for making it that are currently unknown."

The researchers say further study of Pelagophyceae algae in their natural
environment is needed, as well as more detailed studies
 on other marine organisms. Better
measurements of environmental DMSP levels, production and breakdown rates,
and the abundance of the enzymes involved in making DMSP are also critical
to further advance the field.

The research was a collaboration between UEA and OUC, with contributions
from Qingdao Agricultural University, the University of Porto, Shandong
University and the Laoshan Laboratory in Qingdao, China.


*Source: Phys.Org*

*_*

*RESEARCH PAPER—Alternative dimethylsulfoniopropionate biosynthesis enzymes
in diverse and abundant microorganisms*

*Authors*

Jinyan Wang, Andrew R. J. Curson, Shun Zhou, Ornella Carrión, Ji Liu, Ana
R. Vieira, Keanu S. Walsham, Serena Monaco, Chun-Yang Li, Qing-Yu Dong, Yu
Wang, Peter Paolo L. Rivera, Xiao-Di Wang, Min Zhang, Libby Hanwell,
Matthew Wallace, Xiao-Yu Zhu, Pedro N. Leão, David J. Lea-Smith, Yu-Zhong
Zhang, Xiao-Hua Zhang & Jonathan D. Todd

*11 June 2024*

*Abstract*

Dimethylsulfoniopropionate (DMSP) is an abundant marine organosulfur
compound with roles in stress protection, chemotaxis, nutrient and sulfur
cycling and climate regulation. Here we report the discovery of a
bifunctional DMSP biosynthesis enzyme, DsyGD, in the transamination pathway
of the rhizobacterium Gynuella sunshinyii and some filamentous
cyanobacteria not previously known to produce DMSP. DsyGD produces DMSP
through its N-terminal DsyG methylthiohydroxybutyrate S-methyltransferase
and C-terminal DsyD dimethylsulfoniohydroxybutyrate deca

[geo] This London non-profit is now one of the biggest backers of geoengineering research — Plus, Simons, EDF and a new venture backed by Meta’s former CTO are poised to pour tens of millions more int

[Geoengineering News]

https://www.technologyreview.com/2024/06/14/1093778/foundations-are-lining-up-to-fund-geoengineering-research/

*By James Temple*

*14 June 2024*

A London-based nonprofit is poised to become one of the world’s largest
financial backers of solar geoengineering research. And it’s just one of a
growing number of foundations eager to support scientists exploring whether
the world could ease climate change by reflecting away more sunlight.

Quadrature Climate Foundation, established in 2019 and funded through the
proceeds of the investment fund Quadrature Capital, plans to provide $40
million for work in this field over the next three years, Greg De
Temmerman, the organization’s chief science officer, told *MIT Technology
Review*.
Advertisement

That’s a big number for this subject—double

what
all foundations and wealthy individuals provided from 2008 through
2018 and roughly
on par

with
what the US government

has
offered to date.

“We think we can have a very strong impact in accelerating research, making
sure it’s happening, and trying to unlock some public money at some point,”
De Temmerman says.

Other nonprofits are set to provide tens of millions of dollars’ worth of
additional grants to solar geoengineering research or related government
advocacy work in the coming months and years. The uptick in funding will
offer scientists in the controversial field far more support than they’ve
enjoyed in the past and allow them to pursue a wider array of lab work,
modeling, and potentially even outdoor experiments that could improve our
understanding of the benefits and risks of such interventions.

“It just feels like a new world, really different from last year,” says
David Keith, a prominent geoengineering researcher and founding faculty
director of the Climate Systems Engineering Initiative at the University of
Chicago.

Other nonprofits that have recently disclosed funding for solar
geoengineering research or government advocacy, or announced plans to
provide it, include the Simons Foundation
,
the Environmental
Defense Fund
,
and the Bernard and Anne Spitzer Charitable Trust.

In addition, Meta’s former chief technology officer, Mike Schroepfer, told *MIT
Technology Review* he is spinning out a new nonprofit, Outlier Projects. He
says it will provide funding to solar geoengineering research as well as to
work on ocean-based carbon removal

and
efforts to stabilize rapidly melting glaciers

.

Outlier has already issued grants for the first category to the
Environmental Defense Fund, Keith’s program at the University of Chicago,
and two groups working to support research and engagement on the subject in
the poorer, hotter parts of the world: the Degrees Initiative

 and the Alliance for Just Deliberation on Solar Geoengineering
.

Researchers say that the rising dangers of climate change, the lack of
progress on cutting emissions, and the relatively small amount of
government research funding to date are fueling the growing support for the
field.

“A lot of people are recognizing the obvious,” says Douglas MacMartin, a
senior research associate in mechanical and aerospace engineering at
Cornell, who focuses on geoengineering. “We’re not in a good position with
regard to mitigation—and we haven’t spent enough money on research to be
able to support good, wise decisions on solar geoengineering.”

Scientists are exploring a variety of potential methods of reflecting away
more sunlight, including injecting certain particles

into
the stratosphere to mimic the cooling effect of volcanic eruptions, spraying
salt

toward
marine clouds to make them brighter, or sprinkling fine dust-like material

into
the sky to break up heat-trapping cirrus clouds.

Critics contend that neither nonprofits nor scientists should support
studying any of these methods, argui

[geo] Simons Foundation Funds 14 Projects Exploring Earth-Cooling Techniques as Part of New International Research Program

[Geoengineering News]

https://www.simonsfoundation.org/2024/06/12/simons-foundation-funds-14-projects-exploring-earth-cooling-techniques-as-part-of-new-international-research-program/

*12 June 2024*

The funding will support researchers in advancing our scientific
understanding of solar radiation management strategies that might help cool
the planet.
Cirrus clouds such as these can prevent heat from escaping into space.
Scientists are investigating the viability of strategies to thin such
clouds to cool the planet. Dimitry B./Flickr

International efforts to reduce greenhouse gas emissions may not be enough
to prevent the worst effects of climate change over the coming decades and
meet the goals set by the 2015 Paris Agreement
. Indeed, the
rapid heating of the ocean over the past two years suggests that the
Earth’s temperature may rise even faster than some models predict.

“This is an all-hands-on-deck moment,” says Simons Foundation president
David Spergel. “We will likely need a wide set of tools to mitigate global
warming. While reduction in carbon emissions will be essential, recent
reports from the United Nations Environment Programme, the U.S. government,
the European Commission and the U.S. National Academy of Sciences have
recommended research on potential temporary interventions that could help
cool the planet as nations reduce their carbon emissions and develop ways
to remove existing carbon dioxide, methane and other greenhouse gases from
the atmosphere. Our goal is to support the basic science needed to
understand the risks and benefits of these potential interventions.”

With that goal in mind, the Simons Foundation and Simons Foundation
International have launched a new collaborative research program
 to
advance our scientific understanding of methods that aim to cool our planet
by increasing the reflection of sunlight away from the atmosphere or by
changing the properties of clouds. These solar radiation modification
techniques could help temporarily limit climate change, but assessments of
their safety and feasibility are inhibited by large uncertainties
surrounding their effectiveness, longevity and environmental impact.

The 14 research projects funded by the new program will pursue basic
research questions underlying these uncertainties, focusing specifically on
two different solar radiation management approaches.

The first investigates particles, known as aerosols, that could be injected
into the stratosphere to reflect sunlight away from Earth — an effect
already seen in nature when volcanoes erupt, ejecting sulfate particles
into the atmosphere.

The second approach explores modifying the properties of clouds. Several
projects will investigate various methods of thinning wispy high-altitude
cirrus clouds to allow more of the planet’s heat to escape into space. One
project will focus on a different cloud type and evaluate the influence of
pollution aerosols from the shipping industry on the reflectivity of
low-lying clouds over the ocean.

“The properties of different types of aerosols are not well understood,
leading to substantial uncertainty in how they would affect our climate on
a global and regional scale,” says program consultant Emily Carter, a
professor at Princeton University and associate laboratory director at the
Department of Energy’s Princeton Plasma Physics Laboratory. “The
fundamental measurements and modeling of such properties, supported by this
international collaborative, are urgently needed to increase understanding
before any such climate intervention strategy should ever be contemplated
for large-scale deployment.”

The solar radiation management science program — funded by the Simons
Foundation and Simons Foundation International and administered by the
Simons Foundation — will provide up to $10 million per year over the next
five years across all the projects.

Rajan Chakrabarty
 of
Washington University in St. Louis and his team will investigate the
optical properties of two prospective sunlight-reflecting aerosols —
calcite and aluminum oxide — and produce a database of their findings that
can be immediately implemented in new and existing climate models.

Zamin Kanji

of
ETH Zürich in Switzerland and his colleagues will use atmospheric
chemistry, physics and materials chemistry to study the formation of ice
crystals in the laboratory. Such crystals are involved in the formation of
cirrus clouds, the thinning of which can help to mitigate climate warming.

Frank Keutsch  of
Harvard University and his team will lead an effort to identify
alternatives to sulfuric acid for stratospheric aerosol injection. Sulfuric
acid is the most well-studied candidate

[geo] The Wizards of Climate Change: How Can Technology Serve Hope and Justice? An Ethical Framework for Climate Intervention Research: What It Is and Why You Should Care

[Geoengineering News]

https://www.zygonjournal.org/article/id/15389/

*Citations*: Williams, B. M., Shimamoto, M. & Graumlich, L. J., (2024) “An
Ethical Framework for Climate Intervention Research: What It Is and Why You
Should Care”, Zygon: Journal of Religion and Science 59(1), 82–96. doi:
https://doi.org/10.16995/zygon.15389

*Abstract*
Climate change poses significant threats to ecosystems, human health, and
global stability. Despite international efforts to reduce greenhouse gas
emissions, the Earth’s climate continues to warm, leading to extreme
weather events, rising sea levels, and other detrimental impacts. In
response to this crisis, scientists have begun exploring various strategies
to mitigate climate change through geoengineering, which involves
deliberate interventions in the Earth’s climate system. This article
provides an overview of climate geoengineering research, focusing on key
techniques, challenges, and ethical considerations, including actions being
taken by the American Geophysical Union (AGU), a nonprofit professional
scientific society, to develop an ethical framework to help guide research
in this important area. AGU also is driving global engagement on this
topic, including with leaders and members of faith communities.

The Case for Change

Our planet is at risk. The urgency and impact of global warming is bad and
is getting worse. Increasingly severe harmful impacts in many forms can be
seen across the globe, including human suffering, societal disruption, and
reduced ecological health. Impacts such as record-high global temperatures,
more severe storms, increased drought, a warming and rising ocean, more
health risks, increased poverty, and displacement are all reported in
authoritative reports by global climate scientists (United Nations, n.d.-a
).

One hope for reversing this trend was the 2016 Paris Agreement, a legally
binding international treaty on climate change. It was adopted by 196
parties (independent countries) at the Twenty-First Conference of the
Parties to the United Nations Framework Convention on Climate Change
(COP21) in Paris, France, in December 2015 and entered into force in
November 2016.

The overarching goal of the Paris Agreement was to “hold the increase in
the global average temperature to well below 2°C above pre-industrial
levels” and pursue efforts “to limit the temperature increase to 1.5°C
above pre-industrial levels” (United Nations, n.d.-b.
). However, in recent
years, world leaders have stressed the need to limit global warming to
1.5°C by the end of this century. That is because the United Nation’s
Intergovernmental Panel on Climate Change indicates that crossing the 1.5°C
threshold risks unleashing far more severe climate change impacts,
including more frequent and severe droughts, heatwaves, and rainfall. To
limit global warming to 1.5°C, greenhouse gas emissions must peak before
2025 at the latest, decline 43 percent by 2030, and target reaching
net-zero emissions by 2050. The agreement also called for each country to
establish and report goals for reducing its annual greenhouse gas emissions
(United Nations, n.d.-a 
).

The climate action urgency is this: emission-reduction goals are not being
met; in fact, global greenhouse gas emissions are actually increasing!
There is now general scientific agreement that dramatic reductions in
global CO2 emissions combined with the active removal of CO2 from the
atmosphere may be needed (IPCC 2023
). This consensus has
resulted in an expansion of climate intervention research. The likelihood
that global average temperatures will overshoot the targets agreed to by
the world’s nations (1.5–2.0 degrees Celsius) has led the Intergovernmental
Panel on Climate Change to consider climate intervention as a potential
pathway to reduce, remove, or offset some of the effects of climate change,
with risks and trade-offs that need to be better understood. In some cases,
limited outdoor testing is already underway and growing—attracting much
attention—but in many cases without ethical guidelines (National Academies
of Sciences, Engineering, and Medicine 2021
).
What Is Climate Intervention and Why the Concern?

Climate intervention and climate geoengineering are used interchangeably in
this article. Climate geoengineering refers to large-scale schemes for
intervention in the Earth’s oceans, soils, and atmosphere with the aim of
reducing the effects of climate change, usually temporarily (Grantham
Research Institute 2018 ).
While some argue that climate intervention should be a last resort, others
argue that Earth is rapidly approaching a climate emergency, requiring the
consideration of all options (Robock 2020

[geo] How Does the Latitude of Stratospheric Aerosol Injection Affect the Climate in UKESM1?

[Geoengineering News]

https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1565/

*Authors*
Matthew Henry, Ewa M. Bednarz, and Jim Haywood

*Citations*: Henry, M., Bednarz, E. M., and Haywood, J.: How Does the
Latitude of Stratospheric Aerosol Injection Affect the Climate in UKESM1?,
EGUsphere [preprint], https://doi.org/10.5194/egusphere-2024-1565, 2024.

*Received: 25 May 2024 – Discussion started: 10 Jun 2024*

*Abstract*
Stratospheric Aerosol Injection (SAI) refers to a climate intervention
method by which aerosols are intentionally added to the lower stratosphere
to enhance sunlight reflection and offset some of the adverse effects of
global warming. The climate outcomes of SAI depend on the location, amount,
and timing of injection, as well as the material used. Here, we isolate the
role of the latitude of SO2 injection by comparing different scenarios
which have the same global-mean temperature target, altitude of injection,
and hemispherically symmetric injection rates. These are: injection at the
equator (EQ), and injection at 15° N and S (15N+15S), at 30° N and S
(30N+30S), and at 60° N and S (60N+60S). We show that injection at the
equator leads to many undesirable side effects, such as a residual Arctic
warming, significant reduction in tropical precipitation, reductions in
high-latitude ozone, tropical lower stratospheric heating, and
strengthening of the stratospheric jets in both hemispheres. Additionally,
we find that the most efficient injection locations are the subtropics (15
and 30° N and S), although the 60N+60S strategy only requires around 30 %
more SO2 injection for the same amount of cooling; the latter also leads to
much less stratospheric warming but only marginally increases high-latitude
surface cooling. Finally, while all the SAI strategies come with
trade-offs, we demonstrate that the 30N+30S strategy has, on balance, the
least negative side effects and is easier to implement than a
multi-latitude controller algorithm; thus it is a good candidate strategy
for an inter-model comparison.

*Source: EGUsphere*

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[geo] Carbon Cycle Response to Stratospheric Aerosol Injection With Multiple Temperature Stabilization Targets and Strategies

[Geoengineering News]

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024EF004474

*Authors*
Mengying Zhao, Long Cao, Daniele Visioni, Douglas G. MacMartin

https://doi.org/10.1029/2024EF004474

*31 May 2024*

*Abstract*
We analyze the global carbon cycle response to a set of stratospheric
aerosol injection (SAI) simulations performed by the CESM2(WACCM6-MA)
model. The simulations are performed under the specified SSP2-4.5 CO2
concentration pathway. It is found that both the temperature stabilization
target and the SO2 injection strategy have important effects on the global
carbon sink. Relative to the SSP2-4.5 scenario, averaged over the last 20
years of our simulations (year 2050–2069), simultaneous multi-location SO2
injection causes an increase in cumulative land carbon uptake of 45 and 23
PgC, and an increase in cumulative ocean carbon uptake of 6 and 2 PgC for
temperature stabilization targets of 0.5°C and 1.5°C respectively. For a
temperature stabilization target of 1.0°C, SO2 injections increase land and
ocean carbon sinks by 22–42 PgC and 4–7 PgC, respectively, depending on the
strategies of SO2 injections (low latitude, mid-to-high latitude, and
multi-objective injection). Relative to SSP2-4.5, by year 2069, SAI
increases diagnosed cumulative CO2 emissions by 25–53 PgC (3%–6%), implying
a decrease in atmospheric CO2 if SO2 injections were performed under a
prescribed CO2 emission pathway. Stratospheric SO2 injections slow
permafrost thaw, but do not restore permafrost to the previous extent at
the same warming level for all injection strategies. An abrupt termination
of SO2 injection weakens both the ocean and land carbon sink, and causes a
rapid decline of permafrost extent. A gradual phaseout of SO2 injection
slows sharp decline of permafrost and delays the rebound of carbon sink.

*Key Points*
Both temperature stabilization goals and strategy for stratospheric aerosol
injection are important in affecting land and ocean CO2 uptake

Aerosol injections reduce CO2 concentrations, diagnosed here as a 3%–6%
increase in CO₂ emissions leading to specific CO2 concentrations

A gradual phaseout compared to an abrupt termination is shown to result in
a slower rebound of the carbon sink

*Plain Language Summary*
Stratospheric SO2 injections are proposed as a possible additional tool to
help counteract global warming. This method would affect aspects of the
climate system such as temperature, precipitation, and ocean circulation,
which would in turn alter the global carbon cycle. We use an Earth system
model to examine how SO2 injections would affect the ability of land and
ocean to absorb CO2. Under a moderate CO2 concentration increase scenario
(SSP2-4.5), SO2 is injected into the stratosphere to maintain global
temperature at the level of 0.5, 1.0 and 1.5°C above pre-industrial,
respectively. Compared to the background scenario, SO2 injections increase
the land and ocean CO2 sinks and reduce atmospheric CO2 (diagnosed here as
3%–6% increase in cumulative CO2 emissions that would lead to specific CO2
concentration). For the same 1°C target, the location of SO2 injections
(low-latitudes, high-latitudes, multi-latitudes) could produce a range of
response in land and ocean CO2 sinks that is as large as that caused by
different cooling targets. Both land and ocean CO2 sinks are weakened in
response to an abrupt or gradual termination of SO2 injection. SO2
injections slow permafrost thaw but do not entirely restore permafrost to
past extents at the same warming level.

*Source: AGU*

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[geo] Kicking the can down the road: understanding the effects of delaying the deployment of stratospheric aerosol injection

[Geoengineering News]

https://iopscience.iop.org/article/10.1088/2752-5295/ad53f3

*Authors*
Ezra Brod, Daniele Visioni, Ewa M Bednarz, Ben Kravitz, Douglas G
MacMartin, Jadwiga H Richter and Mari Rachel Tye

*Accepted Manuscript online 4 June 2024*

DOI 10.1088/2752-5295/ad53f3

*Abstract*
Climate change is a prevalent threat, and it is unlikely that current
mitigation efforts will be enough to avoid unwanted impacts. One potential
option to reduce climate change impacts is the use of stratospheric aerosol
injection (SAI). Even if SAI is ultimately deployed, it might be initiated
only after some temperature target is exceeded. The consequences of such a
delay are assessed herein. This study compares two cases, with the same
target global mean temperature of ~1.5°C above preindustrial, but start
dates of 2035 or a "delayed" start in 2045. We make use of simulations in
the Community Earth System Model version 2 with the Whole Atmosphere
Coupled Chemistry Model version 6 (CESM2-WACCM6), using SAI under the
SSP2-4.5 emissions pathway. We find that delaying the start of deployment
(relative to the target temperature) necessitates lower net radiative
forcing (-30%) and thus larger sulfur dioxide injection rates (+20%), even
after surface temperatures converge, to compensate for the extra energy
absorbed by the Earth system. Southern hemisphere ozone is higher from 2035
to 2050 in the delayed start scenario, but converges to the same value
later in the century. However, many of the surface climate differences
between the 2035 and 2045 start simulations appear to be small during the
10-25 years following the delayed SAI start, although longer simulations
would be needed to assess any longer-term impacts in this model. In
addition, irreversibilities and tipping points that might be triggered
during the period of increased warming may not be adequately represented in
the model but could change this conclusion in the real world.

*Source: IOP SCIENCE *

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[geo] Modeling 2020 regulatory changes in international shipping emissions helps explain 2023 anomalous warming

[Geoengineering News]

https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1417/

*Authors*
Ilaria Quaglia and Daniele Visioni

*How to cite*. Quaglia, I. and Visioni, D.: Modeling 2020 regulatory
changes in international shipping emissions helps explain 2023 anomalous
warming, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2024-1417,
2024.

*Received: 14 May 2024 – Discussion started: 05 Jun 2024*

*Abstract*
The summer of 2023 has seen an anomalous increase in temperatures even when
considering the ongoing greenhouse-gases driven warming trend. Here we
demonstrate that regulatory changes to sulfate emissions from international
shipping routes, which resulted in a significant reduction in sulfate
particulate released during international shipping starting on January 1
2020, have been a major contributing factor to the monthly surface
temperature anomalies during the last year. We do this by including in
Community Earth System Model (CESM2) simulations the appropriate changes to
emission databases developed for the Climate Model Intercomparison Project
version 6 (CMIP6). The aerosol termination effect simulated by the updated
CESM2 simulations is consistent with observations of both radiative forcing
and surface temperature, manifesting a similar delay as the one observed in
observational datasets between the implementation of the emission changes
and the anomalous increase in warming. Our findings highlight the
importance of considering realistic near-future changes in short-lived
climate forcers for future climate projections, such as for CMIP7, for an
improved understanding and communication of short-term climatic changes.

*Source: EGU sphere*

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[geo] California City Leaders End Cloud-Brightening Test, Overruling Staff

[Geoengineering News]

https://www.nytimes.com/2024/06/05/climate/alameda-cloud-brightening-geoengineering.html?unlocked_article_code=1.xk0.iaWh.YFC3BMPKYPzv&smid=nytcore-ios-share&referringSource=articleShare&sgrp=c-cb


The City Council in Alameda, Calif., voted to stop tests of a device that
could one day cool the Earth. Scientists and city staff had previously
concluded the tests posed no risk.

[image:
A side view of the spraying machine, looking something like a short cannon,
shooting a white mist skyward. The barrel is royal blue. A United States
flag waves on a short mast just behind, at the edge of the carrier’s flight
deck.]
The sprayer being tested at the end of March in advance of the experiment
on board the decommissioned U.S.S. Hornet in Alameda, Calif.

By Soumya Karlamangla 
and Christopher
Flavelle 

Soumya Karlamangla reported from the council meeting in Alameda, Calif.
Christopher Flavelle covered the start of the cloud brightening experiment
in April.
*June 5, 2024*

Elected leaders in Alameda, Calif., voted early on Wednesday to stop
scientists from testing a device that might one day be used to artificially
cool the planet, overruling city staff members who had found the experiment
posed no danger.

Despite assurances from experts that the experiment was safe for humans and
the environment, residents in the small city of 76,000 voiced the kinds of
fears that swirl around the idea of intervening with natural systems to
temporarily ease global warming.

The test involved spraying tiny sea-salt particles

across
the flight deck of a decommissioned aircraft carrier, the U.S.S. Hornet,
docked in Alameda in San Francisco Bay. Versions of that device could
eventually be used to spray the material skyward, making clouds brighter so
that they reflect more sunlight away from Earth. Scientists say that could
help to cool the planet and to fight the effects of global warming.

As humans continue to burn fossil fuels and pump increasing amounts of
carbon dioxide into the atmosphere, the goal of holding global warming to a
relatively safe level, 1.5 degrees Celsius compared with preindustrial
times, is slipping away. That has pushed the idea of deliberately
intervening in climate systems closer to reality.

Universities, foundations, private investors and the federal government
have started to fund a variety of efforts, from sucking carbon dioxide out
of the atmosphere

to
adding iron to the ocean in an effort to store carbon dioxide on the sea
floor.

The experiment in Alameda did not involve brightening clouds; it was only
testing the way sea-salt particles emitted through a spraying device behave
under different atmospheric conditions. It took researchers years to design
and build the spraying device and the experiment was expected to last for
months or even years at a cost of about $1 million a year.

But during a council meeting Tuesday that stretched past midnight,
Alameda’s five elected councilors, none of whom are scientists, said they
still weren’t sure the experiment off the deck of the U.S.S. Hornet was
harmless.

“I don’t think it’s appropriate for our community to be asked to bear that
risk,” councilor Trish Herrera Spencer said. “I don’t think this is the
right place.”

Mayor Marilyn Ezzy Ashcraft echoed those thoughts. “I don’t have a huge
desire to be on the cutting edge,” she said. “I just feel like this is not
the right time.”

Testing, conducted by researchers from the University of Washington, began
on April 2. It was temporarily halted by the city
,
after officials said they needed more time to assess its possible affect on
human health or the environment. Two weeks ago, Alameda released a report
from its city manager, which found no such risk

.

“The chemical components of the saltwater solution (which is similar to
seawater) being sprayed are naturally occurring in the environment,” the
report said. Staff recommended that the City Council allow the experiment
to continue, potentially with additional safeguards such as monitors to
measure air quality at the test site.

Sarah J. Doherty, director of the Marine Cloud Brightening Program at the
University of Washington, which is running the experiment, said in a
statement that she and her team “are disappointed by the decision from the
City of Alam

[geo] Chemical and Climatic Impacts of Solid Particles for Stratospheric Solar Climate Intervention

[Geoengineering News]

https://www.research-collection.ethz.ch/bitstream/handle/20.500.11850/675116/1/PhD_Thesis_Sandro_Vattioni_cp.pdf





*Source: ETH Zurich*

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[geo] Comparison of marine cloud brightening in large eddy simulations

[Geoengineering News]

https://meetingorganizer.copernicus.org/EGU24/EGU24-4102.html

*Authors*
William McFarlane Smith

*08 March 2024*

*How to cite: *Smith, W. M.: Comparison of marine cloud brightening in
large eddy simulations, EGU General Assembly 2024, Vienna, Austria, 14–19
Apr 2024, EGU24-4102, https://doi.org/10.5194/egusphere-egu24-4102, 2024.

*Abstract*
Modelling of marine cloud brightening (MCB), a form of solar radiation
modification, has thus far proven challenging due to the incongruous nature
of the scales required. The microphysics of the cloud droplets and aerosols
can only be resolved at really small scales, but just as important are the
large-scale impacts on circulation and radiation. Large eddy simulations
(LES) seem best placed to deal with this problem; they can resolve
circulation an turbulence, but also have small enough grid boxes that
useful parametrisation of microphysics can be made. When coupled to parcel
models their representation of microphysical processes can be improved even
further, although at a computational cost. There have been multiple studies
of MCB in LES so far, but with wide-ranging background conditions and
experimental designs. This leads to varying results that are challenging to
compare. The aim of this study is to directly compare the results of at
least two LES models, MONC and DALES, for an MCB experiment. They will
first be compared with a historic data set, before being configured to ran
the MCB experiment. It is hoped that MONC can also be coupled to a parcel
model to improve its representation of cloud microphysics.

*Source: EGUSPHERE *

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[geo] Changes in coastal upwelling in the northern Gulf of Guinea under Stratospheric Aerosol Injection

[Geoengineering News]

https://www.sciencedirect.com/science/article/pii/S2352485524002408

*Authors*
F.F.B.K. Ayissi, C.Y. Da-Allada, E. Baloïtcha, L.O. Worou, S. Tilmes

*29 May 2024*

https://doi.org/10.1016/j.rsma.2024.103607

*Highlights*
•Ekman transport and geostrophic flow are the main processes underlying the
seasonal coastal upwelling intensity in the NGoG.

•In Climate change, the major upwelling weakens due to geostrophic flow and
minor upwelling intensifies by Ekman transport.

•Under SAI, major coastal upwelling intensity decreases, but less so than
under climate change, as geostrophic effect weakens.

*Abstract*
This study aims to assess the impact of Stratospheric Aerosol Injection
(SAI) on the coastal upwelling in the northern Gulf of Guinea based, on
upwelling index computation and using the Community Earth System Model from
the Geoengineering Large Ensemble (GLENS) project. GLENS project targets
not only maintaining the global temperature but also the interhemispheric
and equator-to-pole temperature gradient at their 2020 values by preventing
part of the solar radiation from reaching the Earth’s surface under a
RCP8.5 scenario. The results show that along the coast of the northern Gulf
of Guinea main upwelling cells are to the east of Cape Palmas and Cape
Three Points, and that upwelling is most intense in the Ghana region
compared to Côte d’Ivoire region. It is also found that Ekman transport
associated with geostrophic flow can explain a large part of the intensity
of the coastal upwelling in the northern Gulf of Guinea. Geostrophic flow
towards the coast reduces upwelling intensity, especially in the Ghana
region. In the context of global warming, boreal summer upwelling intensity
decreases all along the coast by 6% (with 2% in the Côte d’Ivoire region
and a more significant decrease of 10% in the Ghana region). This decrease
in upwelling intensity is linked to the intensification of geostrophic flow
towards the coast. Under SAI, coastal upwelling intensity is still
decreased by 5% along the coast (with 3% in the Côte d’Ivoire region and 6%
in the Ghana region), but this decrease is relatively weak compared to
global warming. This increase in upwelling intensity compared with climate
change, especially in Ghana, is associated with a 50% reduction in the
effect of geostrophic flow limitation with respect to global warming.
During the minor upwelling season, the upwelling intensity increases, due
to Ekman transport, both under the climate change and SAI.

*Source: ScienceDirect *

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[geo] SOLAR GEOENGINEERING WEEKLY SUMMARY (27 MAY - 2 JUNE 2024)

[Geoengineering News]

*SOLAR GEOENGINEERING WEEKLY SUMMARY (27 MAY - 2 JUNE 2024)*

Subscribe to our newsletter to receive monthly updates on Solar
Geoengineering:
Solar Geoengineering Updates

Monthly news summaries about solar geoengineering. Links to scientific
papers, news articles, jobs, podcasts, and videos.

By Andrew Lockley

--
RESEARCH PAPERSStratospheric transport and tropospheric sink of solar
geoengineering aerosol: a Lagrangian analysis


Sun, H., Bourguet, S., Luan, L., & Keith, D. (2024). Stratospheric
transport and tropospheric sink of solar geoengineering aerosol: a
Lagrangian analysis. *npj Climate and Atmospheric Science*, *7*(1), 115.

*Abstract*

Stratospheric aerosol injection (SAI) aims to reflect solar radiation by
increasing the stratospheric aerosol burden. To understand how the
background circulation influences stratospheric transport of injected
particles, we use a Lagrangian trajectory model (lacking numerical
diffusion) to quantify particles’ number, flux, lifetime, and tropospheric
sinks from a SAI injection strategy under present-day conditions. While
particles are being injected, stratospheric particle number increases until
reaching a steady-state. During the steady-state, the time series of
particle number shows a dominant period of ~2 years (rather than a 1-year
cycle), suggesting modulation by the quasi-biannual oscillation. More than
half of particles, injected in the tropical lower stratosphere (15° S to
15° N, 65 hPa), undergo quasi-horizontal transport to the midlatitude. We
find a zonal asymmetry of particles’ tropospheric sinks that are co-located
with tropopause folding beneath the midlatitude jet stream, which can help
predict tropospheric impacts of SAI (e.g., cirrus cloud thinning).

Abrupt reduction in shipping emission as an inadvertent geoengineering
termination shock produces substantial radiative warming


Yuan, T., Song, H., Oreopoulos, L., Wood, R., Bian, H., Breen, K., ... &
Platnick, S. (2024). Abrupt reduction in shipping emission as an
inadvertent geoengineering termination shock produces substantial radiative
warming. *Communications Earth & Environment*, *5*(1), 281.

*Abstract*

Human activities affect the Earth’s climate through modifying the
composition of the atmosphere, which then creates radiative forcing that
drives climate change. The warming effect of anthropogenic greenhouse gases
has been partially balanced by the cooling effect of anthropogenic
aerosols. In 2020, fuel regulations abruptly reduced the emission of sulfur
dioxide from international shipping by about 80% and created an inadvertent
geoengineering termination shock with global impact. Here we estimate the
regulation leads to a radiative forcing of Wm−2 averaged over the global
ocean. The amount of radiative forcing could lead to a doubling (or more)
of the warming rate in the 2020 s compared with the rate since 1980 with
strong spatiotemporal heterogeneity. The warming effect is consistent with
the recent observed strong warming in 2023 and expected to make the 2020 s
anomalously warm. The forcing is equivalent in magnitude to 80% of the
measured increase in planetary heat uptake since 2020. The radiative
forcing also has strong hemispheric contrast, which has important
implications for precipitation pattern changes. Our result suggests marine
cloud brightening may be a viable geoengineering method in temporarily
cooling the climate that has its unique challenges due to inherent
spatiotemporal heterogeneity.

Response of the Southern Hemisphere extratropical cyclone climatology to
climate intervention with stratospheric aerosol injection


Reboita, M. S., Gabriel Martins Ribeiro, J., Machado Crespo, N., da Rocha,
R. P., Odoulami, R. C., Sawadogo, W., & Moore, J. C. (2024). Response of
the Southern Hemisphere extratropical cyclone climatology to climate
intervention with stratospheric aerosol injection. *Environmental Research:
Climate*.

*Abstract*

Little is known about how climate intervention through stratospheric
aerosol injection (SAI) may affect the climatology of the Southern
Hemisphere extratropical cyclones under warming scenarios. To address this
knowledge gap, we tracked extratropical cyclones from 2015 to 2099 in a set
of projections of three international projects: the Assessing Responses and
Impacts of Solar Climate Intervention on the Earth System with
Stratospheric Aerosol Injection (ARISE), the Stratospheric Aerosol
Geoengineering Large Ens

[geo] Stratospheric transport and tropospheric sink of solar geoengineering aerosol: a Lagrangian analysis

[Geoengineering News]

https://www.nature.com/articles/s41612-024-00664-8

*Authors*
Hongwei Sun, Stephen Bourguet, Lan Luan & David Keith

*30 May 2024*

*Citations*: Sun, H., Bourguet, S., Luan, L. et al. Stratospheric transport
and tropospheric sink of solar geoengineering aerosol: a Lagrangian
analysis. npj Clim Atmos Sci 7, 115 (2024).
https://doi.org/10.1038/s41612-024-00664-8

*Abstract*
Stratospheric aerosol injection (SAI) aims to reflect solar radiation by
increasing the stratospheric aerosol burden. To understand how the
background circulation influences stratospheric transport of injected
particles, we use a Lagrangian trajectory model (lacking numerical
diffusion) to quantify particles’ number, flux, lifetime, and tropospheric
sinks from a SAI injection strategy under present-day conditions. While
particles are being injected, stratospheric particle number increases until
reaching a steady-state. During the steady-state, the time series of
particle number shows a dominant period of ~2 years (rather than a 1-year
cycle), suggesting modulation by the quasi-biannual oscillation. More than
half of particles, injected in the tropical lower stratosphere (15° S to
15° N, 65 hPa), undergo quasi-horizontal transport to the midlatitude. We
find a zonal asymmetry of particles’ tropospheric sinks that are co-located
with tropopause folding beneath the midlatitude jet stream, which can help
predict tropospheric impacts of SAI (e.g., cirrus cloud thinning).

[image: figure 1]


Time series of the number of particles (black line) in the stratosphere,
with three stages divided by the red dashed lines.
Evaluations of particle distribution and transport in the stratosphere.
[image: figure 4]


a Spatial distribution (latitude vs. altitude) of zonally integrated
particle number concentration (with a unit of particles per square
meter). b Particle
number N (red values with the unit of particles), number flux *F* (blue
values with a unit of particles per year), and lifetime *L* (purple values
with a unit of years) in or between different regions (black boxes) during
the steady-state stage (2005.01–2010.01). The injection rate is scaled to
100 particles per year and all other values are scaled correspondingly.
*Source: Nature*

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[geo] Abrupt reduction in shipping emission as an inadvertent geoengineering termination shock produces substantial radiative warming

[Geoengineering News]

https://www.nature.com/articles/s43247-024-01442-3

*Authors*
Tianle Yuan, Hua Song, Lazaros Oreopoulos, Robert Wood, Huisheng Bian,
Katherine Breen, Mian Chin, Hongbin Yu, Donifan Barahona, Kerry Meyer &
Steven Platnick

*30 May 2024*

*Citations*: Yuan, T., Song, H., Oreopoulos, L. et al. Abrupt reduction in
shipping emission as an inadvertent geoengineering termination shock
produces substantial radiative warming. Commun Earth Environ 5, 281 (2024).
https://doi.org/10.1038/s43247-024-01442-3

*Abstract*
Human activities affect the Earth’s climate through modifying the
composition of the atmosphere, which then creates radiative forcing that
drives climate change. The warming effect of anthropogenic greenhouse gases
has been partially balanced by the cooling effect of anthropogenic
aerosols. In 2020, fuel regulations abruptly reduced the emission of sulfur
dioxide from international shipping by about 80% and created an inadvertent
geoengineering termination shock with global impact. Here we estimate the
regulation leads to a radiative forcing of
Wm−2 averaged over the global ocean. The amount of radiative forcing could
lead to a doubling (or more) of the warming rate in the 2020 s compared
with the rate since 1980 with strong spatiotemporal heterogeneity. The
warming effect is consistent with the recent observed strong warming in
2023 and expected to make the 2020 s anomalously warm. The forcing is
equivalent in magnitude to 80% of the measured increase in planetary heat
uptake since 2020. The radiative forcing also has strong hemispheric
contrast, which has important implications for precipitation pattern
changes. Our result suggests marine cloud brightening may be a viable
geoengineering method in temporarily cooling the climate that has its
unique challenges due to inherent spatiotemporal heterogeneity.

Simulated impact of IMO2020 on AOD and Nd.
[image: figure 1]


A simulated annual mean aerosol optical depth change induced by IMO2020
using NASA GOES-GOCART. B the ratio of aerosol optical depth changes
between that induced by IMO2020 and that between 1750 and 20052
. C map of
simulated annual mean Nd change due to IMO2020. D) same as B, but for Nd
 change.
Calculated IMO2020 forcing maps from different components.
[image: figure 2]


*Source: Nature *

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[geo] Response of the Southern Hemisphere extratropical cyclone climatology to climate intervention with stratospheric aerosol injection

[Geoengineering News]

https://iopscience.iop.org/article/10.1088/2752-5295/ad519e/meta

*Authors*
Michelle Simões Reboita, João Gabriel Martins Ribeiro, Natália Machado
Crespo, Rosmeri Portfírio da Rocha, Romaric C Odoulami, Windmanagda
Sawadogo and John C Moore

*Accepted Manuscript online 29 May 2024 *

*Abstract*
Little is known about how climate intervention through stratospheric
aerosol injection (SAI) may affect the climatology of the Southern
Hemisphere extratropical cyclones under warming scenarios. To address this
knowledge gap, we tracked extratropical cyclones from 2015 to 2099 in a set
of projections of three international projects: the Assessing Responses and
Impacts of Solar Climate Intervention on the Earth System with
Stratospheric Aerosol Injection (ARISE), the Stratospheric Aerosol
Geoengineering Large Ensemble (GLENS), and the Geoengineering Model
Intercomparison Project (GeoMIP/G6sulfur). Comparisons were performed
between no-SAI and SAI scenarios as well as between different timeslices
and their reference period (2015-2024). Among the findings, both no-SAI and
SAI project a decrease in cyclone frequency towards the end of the century
although weaker under SAI scenarios. On the other hand, cyclones tend to be
stronger under no-SAI scenarios while keeping their intensity more similar
to the reference period under SAI scenarios. This means that under SAI
scenarios the climatology of cyclones is less affected by global warming
than under no-SAI. Other features of these systems, such as travelling
distance, lifetime, and mean velocity show small differences between no-SAI
and SAI scenarios and between reference and future periods.

*Source: IOP SCIENCE*

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[geo] Toward an evidence-informed, responsible, and inclusive debate on solar geoengineering: A response to the proposed non-use agreement

[Geoengineering News]

https://wires.onlinelibrary.wiley.com/doi/10.1002/wcc.903

*Authors*
Edward A. Parson, Holly J. Buck, Sikina Jinnah, Juan Moreno-Cruz, Simon
Nicholson

*First published: 29 May 2024*

https://doi.org/10.1002/wcc.903

*Abstract*
A prominent recent perspective article in this journal and accompanying
open letter propose a broad international “non-use agreement” (NUA) on
activities related to solar geoengineering (SG). The NUA calls on
governments to renounce large-scale use of SG, and also to refuse to fund
SG research, ban outdoor experiments, decline to grant IP rights, and
reject discussions of SG in international organizations. We argue that such
pre-emptive rejection of public research and consultation would deprive
future policy-makers of knowledge and capability that would support
informed decisions to safely and equitably limit climate risk, sustain
human welfare, and protect threatened ecosystems. In contrast to the broad
prohibitions of the NUA, we propose an alternative near-term pathway with
five elements: assess SG risks and benefits in the context of related
climate risks and responses; distinguish the risks and governance needs of
SG research and deployment; pursue research that treats uncertainties and
divergent results even-handedly; harness normalization of SG as a path to
effective assessment and governance; and build a more globally inclusive
conversation on SG and its governance. These principles would support a
more informed, responsible, and inclusive approach to limiting climate
risks, including judgments on the potential role or rejection of SG, than
the prohibitory approach of the NUA.
Graphical Abstract

[image: Description unavailable]


Source: WIREs

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[geo] Chinese public’s perceptions and understanding of the potential roles of solar climate engineering for reducing climate change risks

[Geoengineering News]

https://link.springer.com/article/10.1007/s10668-024-05054-x

*Authors*
Zhihua Zhang, Donald Huisingh & M. James C. Crabbe

*Citations*: Zhang, Z., Huisingh, D. & Crabbe, M.J.C. Chinese public’s
perceptions and understanding of the potential roles of solar climate
engineering for reducing climate change risks. Environ Dev Sustain (2024).
https://doi.org/10.1007/s10668-024-05054-x

*24 May 2024*

*Abstract*
Limiting global temperature increases appear to be an exceedingly
challenging task due to great difficulty in advancing carbon reduction
emission negotiation. Solar climate engineering is emerging as an emergency
shield for climate risks. Except for its technical feasibility and
reasonable costs, public understanding is essential for future
implementation. Compared with wide studies in Europe and North America, our
study was the first large-scale survey to comprehensively investigate the
Chinese public’s attitude toward solar climate engineering. Moreover, our
study was the first to focus on combined solar climate engineering schemes
and investigate Public attitude toward international governance and
regulatory structures. Our survey revealed that: The surveyed Chinese
participants perceived a high level of its deployment costs and a middle
level of its effectiveness, technical readiness and side effects. A
majority of surveyed participants supported China’s active role in
international governance and regulatory structures for solar climate
engineering. About a half of the surveyed participants were willing to pay
taxes to support related research and possible future deployment. However,
when solar climate engineering was compared with seven mainstream climate
change mitigation schemes, Chinese participants favored less priority and
less funding for solar climate engineering. This means that Chinese
participants viewed it as only a backup option in climate strategies.

*Source: SpringerLink*

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[geo] Africa's Climate Response to Marine Cloud Brightening

[Geoengineering News]

https://meetingorganizer.copernicus.org/EGU24/EGU24-6419.html

*Authors*
Romaric C. Odoulami, Haruki Hirasawa, Kouakou Kouadio, Trisha D. Patel,
Kwesi A. Quagraine, Izidine Pinto, Temitope S. Egbebiyi, Babatunde J.
Abiodun, Christopher Lennard6, and Mark G.

*08 March 2024*

*How to cite:* Odoulami, R. C., Hirasawa, H., Kouadio, K., Patel, T. D.,
Quagraine, K. A., Pinto, I., Egbebiyi, T. S., Abiodun, B. J., Lennard, C.,
and New, M. G.: Africa's Climate Response to Marine Cloud Brightening, EGU
General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6419,
https://doi.org/10.5194/egusphere-egu24-6419, 2024.

*Abstract*
Climate intervention through solar radiation modification is one proposed
method for reducing climate risks from anthropogenic warming. Marine Cloud
Brightening (MCB), one such approach, proposes to inject sea salt aerosol
into a regional marine boundary layer to increase marine clouds'
reflectivity. This study assessed the potential influence of four MCB
experiments on the climate in Africa using simulations from the Community
Earth System Model (CESM2) with the Community Atmospheric Model (CAM6).
Four idealised MCB experiments were performed with the CESM2(CAM6) model
under a medium-range background forcing scenario (SSP2-4.5) by setting
cloud droplet number concentrations to 600 cm-3 over three subtropical
ocean regions: (a) Northeast Pacific (MCBNEP); (b) Southeast Pacific
(MCBSEP); (c) Southeast Atlantic (MCBSEA); and (d) the combination of these
three regions (MCBALL). The CESM2(CAM6) model reproduces the observed
spatial distribution and seasonal cycle of precipitation and minimum and
maximum temperatures over Africa and its climatic zones well. The results
suggest that MCBSEP would induce the strongest global cooling effect and
thus could be the most effective in decreasing (increasing) temperatures
(precipitation) and associated extremes across most parts of the continent,
especially over West Africa, in the future (2035-2054) while other regions
could remain warmer or dryer compared to the historical climate
(1995-2014). While the projected changes under MCBALL are similar to those
of MCBSEP, MCBNEP and MCBSEA could result in more warming and, in some
regions of Africa, create a warmer future than under SSP2-4.5. Also, all
MCB experiments are more effective in cooling maximum temperature and
related extremes than minimum temperature and related extremes. These
findings further suggest that the climate impacts of MCB in Africa are
highly sensitive to the deployment region.


*Source: EGU General Assembly *

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[geo] A Living Assessment of Different Materials for Stratospheric Aerosol Injection—Building Bridges Between Model World and the Messiness of Reality

[Geoengineering News]

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2024GL108314

*Authors*
Daniele Visioni, Ilaria Quaglia, Isabelle Steinke

*First published: 24 May 2024*

https://doi.org/10.1029/2024GL108314

*Abstract*
There are obstacles in better understanding the climate impacts associated
with new materials that could be used for Stratospheric Aerosol Injections
(SAI), like the lack of an integrated framework that combines climate
modeling across scales, laboratory studies and small-scale field
experiments. Vattioni et al. (2023, https://doi.org/10.1029/2023gl105889)
explored one aspect of using alternative, non-sulfate materials for SAI.
They investigated how uncertain the response of stratospheric ozone would
be to alumina injections for SAI. In their study, they quantify chlorine
activation rates in the presence of alumina, and then cascade these
uncertainties into estimates of ozone depletion, concluding that alumina
might have less detrimental impacts on stratospheric chemistry than
sulfate, but with large uncertainties. Their results provide a useful basis
upon which future research endeavors combining indoor and outdoor
experiments and modeling may be structured to produce robust assessments of
SAI impacts, benefits and uncertainties, together with clarifying what kind
of research needs to be prioritized.

*Key Points*
•Vattioni et al. (2023, https://doi.org/10.1029/2023gl105889) demonstrated
large uncertainties in the projected impacts of alumina particles in the
stratosphere

•We use the results to discuss more broadly how to better think about the
climate impacts and side effects of Stratospheric Aerosol Injection

•We propose the idea of a “living assessment” of Stratospheric Aerosol
Injections that can constantly integrate useful experimental results with
modeling work

*Plain Language Summary*
We could use tiny particles injected into the higher atmosphere to reflect
a small portion of incoming sunlight and thereby cool the planet. But doing
so comes with risks and uncertainties: for instance, one might wonder how
do we select which kind of particles to use. Sulfate is present in nature,
for instance during the aftermath of volcanic eruptions followed by an
observable surface cooling. However, we know that mimicking that effect
would come with some drawbacks, for example, it heats the upper layer of
the atmosphere and affects ozone. Alumina, supposedly, would impact
atmospheric chemistry less than sulfate and so might be considered
“preferable,” but not being naturally present in the atmosphere, there are
lots of things we don't know. For example, Vattioni et al. (2023,
https://doi.org/10.1029/2023gl105889) demonstrate that even potential
implications for atmospheric chemistry are highly uncertain when looking at
alumina particles as a candidate for Stratospheric Aerosol Injections
(SAI). Therefore, their study is a good opportunity to think more broadly
about intended SAI-associated climate impacts and unwanted side effects,
and how to better coordinate research activities in this space.


[image: Details are in the caption following the image]

Figure 1

(a) A simplified summary of the results in Vattioni et al. (2023
),
focusing on tropical ozone changes. For SO2 (red dot), an uncertainty bar
derived using multi-model results from Tilmes et al. (2022
)
has been added, even if the injection magnitude are higher in that case.
(b) Schematic of potential uncertainty ranges that would be associated with
sulfate or alumina (or other materials) in the case of SAI for both
effectiveness and environmental impacts. Due to the lack of natural
analogs, physical and environmental uncertainties might be larger for
alumina compared to sulfate, but with the potential for the central value
to be lower for a close to ideal material, as shown in panel (a). Some
uncertainties can be narrowed down with further observations, or with
direct tests. Scenario uncertainty, which depends on factors that might not
be related directly to chemistry or physics, such as the underlying
emission scenario of ozone depleting substances, or other sources that are
not within direct control, and that require more holistic assessments, are
also relevant to an overall assessment.

*Source: AGU*

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[geo] SOLAR GEOENGINEERING WEEKLY SUMMARY (20 MAY - 26 MAY 2024)

[Geoengineering News]

SOLAR GEOENGINEERING WEEKLY SUMMARY (20 MAY - 26 MAY 2024)

Subscribe to our newsletter to receive monthly updates on Solar
Geoengineering:
Solar Geoengineering Updates

Monthly news summaries about solar geoengineering. Links to scientific
papers, news articles, jobs, podcasts, and videos.

By Andrew Lockley

--
RESEARCH PAPERSA Living Assessment of Different Materials for Stratospheric
Aerosol Injection—Building Bridges Between Model World and the Messiness of
Reality


Visioni, D., Quaglia, I., & Steinke, I. (2024). A living assessment of
different materials for stratospheric aerosol injection—Building bridges
between model world and the messiness of reality. *Geophysical Research
Letters*, *51*(10), e2024GL108314.

*Abstract*

There are obstacles in better understanding the climate impacts associated
with new materials that could be used for Stratospheric Aerosol Injections
(SAI), like the lack of an integrated framework that combines climate
modeling across scales, laboratory studies and small-scale field
experiments. Vattioni et al. (2023, https://doi.org/10.1029/2023gl105889)
explored one aspect of using alternative, non-sulfate materials for SAI.
They investigated how uncertain the response of stratospheric ozone would
be to alumina injections for SAI. In their study, they quantify chlorine
activation rates in the presence of alumina, and then cascade these
uncertainties into estimates of ozone depletion, concluding that alumina
might have less detrimental impacts on stratospheric chemistry than
sulfate, but with large uncertainties. Their results provide a useful basis
upon which future research endeavors combining indoor and outdoor
experiments and modeling may be structured to produce robust assessments of
SAI impacts, benefits and uncertainties, together with clarifying what kind
of research needs to be prioritized.

Dependency of the impacts of geoengineering on the stratospheric sulfur
injection strategy – Part 2: How changes in the hydrological cycle depend
on the injection rate and model used


Laakso, A., Visioni, D., Niemeier, U., Tilmes, S., & Kokkola, H. (2024).
Dependency of the impacts of geoengineering on the stratospheric sulfur
injection strategy–Part 2: How changes in the hydrological cycle depend on
the injection rate and model used. *Earth System Dynamics*, *15*(2),
405-427.

*Abstract*

This is the second of two papers in which we study the dependency of the
impacts of stratospheric sulfur injections on the model and injection
strategy used. Here, aerosol optical properties from simulated
stratospheric aerosol injections using two aerosol models (modal scheme M7
and sectional scheme SALSA), as described in Part 1 (Laakso et al., 2022),
are implemented consistently into the EC-Earth, MPI-ESM and CESM Earth
system models (ESMs) to simulate the climate impacts of different injection
rates ranging from 2 to 100 Tg(S) yr−1. Two sets of simulations were run
with the three ESMs: (1) regression simulations, in which an abrupt change
in CO2 concentration or stratospheric aerosols over pre-industrial
conditions was applied to quantify global mean fast temperature-independent
climate responses and quasi-linear dependence on temperature, and (2)
equilibrium simulations, in which radiative forcing of aerosol injections
with various magnitudes compensated for the corresponding radiative forcing
of CO2 enhancement to study the dependence of precipitation on the
injection magnitude. The latter also allow one to explore the regional
climatic responses. Large differences in SALSA- and M7-simulated radiative
forcing in Part 1 translated into large differences in the estimated
surface temperature and precipitation changes in ESM simulations; for
example, an injection rate of 20 Tg(S) yr−1 in CESM using M7-simulated
aerosols led to only 2.2 K global mean cooling, while EC-Earth–SALSA
combination produced a 5.2 K change. In equilibrium simulations, where
aerosol injections were utilized to offset the radiative forcing caused by
an atmospheric CO2 concentration of 500 ppm, the decrease in global mean
precipitation varied among models, ranging from −0.7% to −2.4% compared
with the pre-industrial climate. These precipitation changes can be
explained by the fast precipitation response due to radiation changes
caused by the stratospheric aerosols and CO2, as the global mean fast
precipitation response is shown to be negatively correlated with global
mean atmospheric absorption. Our study shows 

[geo] Dependency of the impacts of geoengineering on the stratospheric sulfur injection strategy – Part 2: How changes in the hydrological cycle depend on the injection rate and model used

[Geoengineering News]

https://helda.helsinki.fi/items/b1ada402-ac01-413b-bc5b-80faac462218

*Author*
Laakso, Anton, Visioni, Daniele, Niemeier, Ulrike, Tilmes, Simone, Kokkola,
Harri

*2024*

*DOI*: https://doi.org/10.5194/esd-15-405-2024

*Abstract*
This is the second of two papers in which we study the dependency of the
impacts of stratospheric sulfur injections on the model and injection
strategy used. Here, aerosol optical properties from simulated
stratospheric aerosol injections using two aerosol models (modal scheme M7
and sectional scheme SALSA), as described in Part 1 (Laakso et al., 2022),
are implemented consistently into the EC-Earth, MPI-ESM and CESM Earth
system models (ESMs) to simulate the climate impacts of different injection
rates ranging from 2 to 100 Tg(S) yr−1. Two sets of simulations were run
with the three ESMs: (1) regression simulations, in which an abrupt change
in CO2 concentration or stratospheric aerosols over pre-industrial
conditions was applied to quantify global mean fast temperature-independent
climate responses and quasi-linear dependence on temperature, and (2)
equilibrium simulations, in which radiative forcing of aerosol injections
with various magnitudes compensated for the corresponding radiative forcing
of CO2 enhancement to study the dependence of precipitation on the
injection magnitude. The latter also allow one to explore the regional
climatic responses. Large differences in SALSA- and M7-simulated radiative
forcing in Part 1 translated into large differences in the estimated
surface temperature and precipitation changes in ESM simulations; for
example, an injection rate of 20 Tg(S) yr−1 in CESM using M7-simulated
aerosols led to only 2.2 K global mean cooling, while EC-Earth–SALSA
combination produced a 5.2 K change. In equilibrium simulations, where
aerosol injections were utilized to offset the radiative forcing caused by
an atmospheric CO2 concentration of 500 ppm, the decrease in global mean
precipitation varied among models, ranging from −0.7% to −2.4% compared
with the pre-industrial climate. These precipitation changes can be
explained by the fast precipitation response due to radiation changes
caused by the stratospheric aerosols and CO2, as the global mean fast
precipitation response is shown to be negatively correlated with global
mean atmospheric absorption. Our study shows that estimating the impact of
stratospheric aerosol injection on climate is not straightforward. This is
because the simulated capability of the sulfate layer to reflect solar
radiation and absorb long-wave radiation is sensitive to the injection rate
as well as the aerosol model used to simulate the aerosol field. These
findings emphasize the necessity for precise simulation of aerosol
microphysics to accurately estimate the climate impacts of stratospheric
sulfur intervention. This study also reveals gaps in our understanding and
uncertainties that still exist related to these controversial techniques.

*Source: University of Helsinki*

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[geo] A trial of cloud-brightening technology sparks controversy in a California city

[Geoengineering News]

https://www.nbcnews.com/science/environment/trial-cloud-brightening-controversy-california-rcna153092

Alameda, California, has found itself thrust into a debate about whether
and how to explore geoengineering projects to fight global warming.

*By Evan Bush*

*25 May 2024*

Scientists surprised the leaders of a Northern California city last month,
when they unveiled a project to study technology that could one day be used
to brighten clouds and mitigate global warming.

The experiment involved spraying saltwater along the deck of the USS Hornet
— an aircraft carrier docked in Alameda that serves as a museum — to test
devices that can create and measure plumes of aerosols. The team planned
three sprays per day, four days a week for 20 weeks.

The actions themselves were harmless — and, indeed, environmental
consultants the city hired to assess the project found no safety concerns,
according to a report published Thursday
.
But the work represents a first step toward understanding whether this type
of technology, at scale, could be used to make clouds reflect more sunlight
back to space and slow some global warming effects.

This possibility has thrust the city into the center of a larger debate
over whether and how the exploration of geoengineering technologies to
fight climate change ought to be explored — and who should have a say.

The project, led by a team from the University of Washington, represents
one of the first attempts to test marine cloud-brightening technology in
the United States.

City officials and constituents in Alameda said they only learned the full
details of it after The New York Times published a story

in
April. The Times said the researchers knew their testing might be
controversial to some, so they had “kept the details tightly held.”

Following the article’s publication, city leaders ordered the scientists to
halt the project, saying it was in violation of the lease with the USS
Hornet. The Alameda city council will decide the project’s fate in a June 4
meeting.

The idea behind cloud brightening concepts is to increase the number of
water droplets within low-level ocean clouds to boost their reflectivity
and potentially make the clouds last longer
. That process could
lead clouds to reflect more sunlight to space. It wouldn’t help with other
climate problems, like ocean acidification, and some researchers are
concerned that, at scale, it could shift atmospheric circulation with
unintended consequences

.

Scientists are far from even experimenting on that level. On the aircraft
carrier’s deck, the researchers were simply using a machine that looks like
a snowmaker to spray saltwater.

“The studies involve brief emissions of salt-water that evolves into a
plume of tiny salt particles whose number, size and path are measured by
instruments installed along the flight deck of the Hornet,” Rob Wood, a
professor of atmospheric sciences at the University of Washington and
project leader, said in a statement.

The researchers had planned to study how different-sized particles affect
the plume.

Wood said the studies are “basic science research” and not “designed to
alter clouds or any aspect of the local weather or climate.”
[image: Fog blankets the Golden Gate Bridge of San Francisco]The Golden
Gate Bridge during a foggy sunset in San Francisco in 2023.Tayfun Coskun /
Anadolu via Getty Images file

The safety assessment released Thursday identified no potential harms from
the work. “

We do not see this operation as a health risk to the surrounding
community,” consultant and engineer Andrew Romolo wrote in a letter to city
leaders. In a separate letter, a biological consultant said the plumes of
saltwater wouldn’t harm terns (a type of seabird) or any other sensitive
species.

Laura Fies, the executive director of the USS Hornet Museum, said her
initial conversations with the research team centered mostly on immediate
plans for the work, rather than its long-term implications. So the
resulting controversy was a surprise.

“We were like — we’re making some seafoam breeze, that’s cute, that’s fun,”
Fies said. “And you know, I fully admit, that the exciting, controversial
portion is like the most newsworthy. It’s also years away from what they’re
doing right now.”

Fies said the aircraft carrier has hosted events with pyrotechnics and
Jeeps driving around on deck.

“We do wilder things on the flight deck all the time,” Fies said. “What’s
being sprayed across the deck is saltwater, very clean saltwater. It didn’t
occur to us that the city would want to come inspect with a Hazmat team.”

Most geoe

[geo] High-resolution stratospheric volcanic SO2 injections in WACCM

[Geoengineering News]

https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1448/

*Authors*
Emma Axebrink, Moa K. Sporre, and Johan Friberg

*23 May 2024*

*How to cite. *Axebrink, E., Sporre, M. K., and Friberg, J.:
High-resolution stratospheric volcanic SO2 injections in WACCM, EGUsphere
[preprint], https://doi.org/10.5194/egusphere-2024-1448, 2024.

*Abstract*
Aerosols from volcanic eruptions impact our climate by influencing the
Earth’s radiative balance. The degree of their climate impact is determined
by the location and injection altitude of the volcanic SO2. To investigate
the importance of utilizing correct injection altitudes we ran climate
simulations of the June 2009 Sarychev eruptions with three SO2 datasets, in
the Community Earth System Model Version 2 (CESM2) Whole Atmosphere
Community Climate Model Version 6 (WACCM6). We have compared simulations
with WACCM’s default 1 km vertically resolved dataset M16 with our two 200
m vertically resolved datasets, S21-3D and S21-1D. The S21-3D is
distributed over a large area (30 latitudes and 120 longitudes), whereas
S21-1D releases all SO2 in one latitude and longitude grid-box, mimicking
the default dataset M16.

For S21-1D and S21-3D, 95 % of the SO2 was injected into the stratosphere,
whereas M16 injected only 75 % to the stratosphere. This difference is due
to the different vertical distribution and resolution of SO2 in the
datasets. The larger portion of SO2 injected into the stratosphere for the
S21 datasets leads to more than twice as high sulfate aerosol load in the
stratosphere for the S21-3D simulation compared to the M16 simulation
during more than 8 months. The temporal evolution in AOD from two of our
simulations, S21-3D and S21-1D, follows the observations from the
space-borne lidar instrument CALIOP closely, while the AOD in the M16
simulation is substantially lower. This indicates that the injection
altitude and vertical resolution of the injected volcanic SO2 substantially
impact the model’s ability to correctly simulate the climate impact from
volcanic eruptions.

The S21-3D dataset with the high vertical and horizontal resolution
resulted in global volcanic forcing of -0.24 W/m2 during the first year
after the eruptions, compared with only -0.11 W/m2 for M16. Hence, our
study high-lights the importance of using high-vertically resolved SO2 data
in simulations of volcanic climate impact, and calls for a re-evaluation of
further volcanic eruptions.

*Source: EGU Sphere*

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