Hi Robert
All geoengineering options including SAI should presented not only with
the focus on the only one physical, chemical or biochemical focus as
done here by you: For instance, what happens exactly to the atmospheric
chemistry and to the oceans biology if the mentioned SAI scenarios would
happen. What would help the primary cooling if by a reduced atmospheric
oxidant cleaning the life time of greenhouse gases decrease by
SAI-reduced oxidation power? What would help the primary cooling if
geoengineering options of greenhouse gas depletion become reduced or
fail because of SAI-reduced sun radiation? As to compensate the
increased greenhouse warming by such a SAI induced rise of methane and
other greenhouse organics the needed TG-SO2 interventions/yr would need
a further decrease. According to the direct oxygen consumption of the
SO2 interventions also a massive decreasing influence of the oxydation
power of the stratospheric chemistry would happen. This would increase
also the life time of more or less oxidant resistant halogen methanes.
An SAI induced reduction of daylight would decrease the vertical size of
the photic zone. Also this might induce a lower phytoplankton productivity.
Hence all this physical cooling possible by SAI can done by much more
simple and cheeper cooling with cloud whitening and cloud generation,
additional possibly also by MEER.
Franz
Am 13.11.2022 um 11:00 schrieb 'Robert Tulip' via geoengineering:
This chart shows Stratospheric Aerosol Injection could deliver
*cooling of >2**°**C*by 2070 compared to the optimistic IPCC
projection of 4.5 w/m^2 without SAI.
That blows carbon-based cooling out of the water. Any time anyone
says 1.5°C is passed, just show them this. Geoengineering is urgent.
Source: D. G. MacMartin, D. Visioni , B. Kravitz, J.H. Richter, T.
Felgenhauer, W. R. Lee, D. R. Morrow, E. A. Parson, and M. Sugiyama,
/Scenarios for modeling solar radiation modification/, Proceedings of
the National Academy of Science, August 2022
*Fig. 3. *High-level results from simulations involving different
temperature targets: global mean temperature; SO2 injection rates;
land average precipitation
minus evaporation P-E; Arctic September sea-ice extent; total column
ozone in southern hemisphere (SH), 60 to 90 /◦/S in October (in Dobson
Units, DU); Global
Stratospheric Optical Depth; AMOC; and upper ocean heat content
(indicative of thermosteric sea-level rise).
*From:*[email protected]
<[email protected]> *On Behalf Of *Andrew Lockley
*Sent:* Wednesday, 9 November 2022 9:33 AM
*To:* geoengineering <[email protected]>
*Subject:* [geo] Scenarios for modeling solar radiation modification
Poster's note: not sure how this got missed.
Authors
D. G. MacMartin, D. Visioni B. Kravitz, and M. Sugiyama
https://www.pnas.org/doi/full/10.1073/pnas.2202230119
Significance
The benefits and risks of solar radiation modification (SRM; also
known as solar geoengineering) need to be evaluated in context with
the risks of climate change and will depend on choices such as the
amount of cooling. One challenge today is a degree of arbitrariness in
the scenarios used in current SRM simulations, making comparisons
difficult both between SRM and non-SRM cases and between different SRM
scenarios. We address this gap by 1) defining a set of plausible
scenarios capturing a range of choices and uncertainties, and 2)
providing simulations of these scenarios that can be broadly used for
comparative impact assessment. This is an essential precursor to any
international assessment by, e.g., the Intergovernmental Panel on
Climate Change.
Abstract
Making informed future decisions about solar radiation modification
(SRM; also known as solar geoengineering)—approaches such as
stratospheric aerosol injection (SAI) that would cool the climate by
reflecting sunlight—requires projections of the climate response and
associated human and ecosystem impacts. These projections, in turn,
will rely on simulations with global climate models. As with
climate-change projections, these simulations need to adequately span
a range of possible futures, describing different choices, such as
start date and temperature target, as well as risks, such as
termination or interruptions. SRM modeling simulations to date
typically consider only a single scenario, often with some unrealistic
or arbitrarily chosen elements (such as starting deployment in 2020),
and have often been chosen based on scientific rather than
policy-relevant considerations (e.g., choosing quite substantial
cooling specifically to achieve a bigger response). This limits the
ability to compare risks both between SRM and non-SRM scenarios and
between different SRM scenarios. To address this gap, we begin by
outlining some general considerations on scenario design for SRM. We
then describe a specific set of scenarios to capture a range of
possible policy choices and uncertainties and present corresponding
SAI simulations intended for broad community use.
Source: PNAS
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