*WEEKLY SUMMARY (11 MARCH - 17 MARCH 2024)* *Subscribe to our newsletter to receive monthly updates on Solar Geoengineering:* Solar Geoengineering Updates <https://solargeoengineeringupdates.substack.com?utm_source=substack&utm_campaign=publication_embed&utm_medium=email> Monthly news summaries about solar geoengineering. Links to scientific papers, news articles, jobs, podcasts, and videos. <https://solargeoengineeringupdates.substack.com?utm_source=substack&utm_campaign=publication_embed&utm_medium=email> By Andrew Lockley <https://solargeoengineeringupdates.substack.com?utm_source=substack&utm_campaign=publication_embed&utm_medium=email> ------------------------------ RESEARCH PAPERSThe El Niño response to tropical volcanic eruptions and geoengineering <https://meetingorganizer.copernicus.org/EGU24/EGU24-11374.html>
Kroll, C., & Wills, R. J. (2024). *The El Niño response to tropical volcanic eruptions and geoengineering* (No. EGU24-11374). Copernicus Meetings. *Abstract* Following tropical volcanic eruptions and in response to geoengineering efforts in climate models, the occurrence of El Niño is notably enhanced. However, the precise mechanisms leading to the preference of the El Niño state remain a subject of ongoing debate. In this study, we explore the El Niño response within the context of stratospheric aerosol injection experiments using the Community Earth System Model version 1, with the Whole Atmosphere Community Climate Model atmospheric component (CESM1 WACCM). Our investigation is centered around the Stratospheric Aerosol Geoengineering Large Ensemble Dataset encompassing three distinct scenarios: a simulation of the RCP8.5 scenario as baseline climate change scenario, a geoengineering scenario, in which surface temperature increases are completely compensated and a scenario focusing solely on the stratospheric heating derived from the geoengineering approach. Our analysis reveals that the El Niño response is primarily linked to the heating in the tropical tropopause layer and lower stratosphere, and notably, it occurs independently of tropospheric cooling effects. We explain the increased occurrence of El Niño after volcanic eruptions and simulated geoengineering interventions by a slow down of the tropical atmospheric circulation, which is caused by increases in gross moist stability due to aerosol heating in tropical tropopause layer. Impacts of ice-nucleating particles on cirrus clouds and radiation derived from global model simulations with MADE3 in EMAC <https://acp.copernicus.org/articles/24/3217/2024/> Beer, C. G., Hendricks, J., & Righi, M. (2023). Impacts of ice-nucleating particles on cirrus clouds and radiation derived from global model simulations with MADE3 in EMAC. *EGUsphere*, *2023*, 1-29. *Abstract* Atmospheric aerosols can act as ice-nucleating particles (INPs) and influence the formation and the microphysical properties of cirrus clouds, resulting in distinct climate effects. We employ a global aerosol–climate model, including a two-moment cloud microphysical scheme and a parameterization for aerosol-induced ice formation in cirrus clouds, to quantify the climate impact of INPs on cirrus clouds (simulated period 2001–2010). The model considers mineral dust, soot, crystalline ammonium sulfate, and glassy organics as INPs in the cirrus regime. Several sensitivity experiments are performed to analyse various aspects of the simulated INP–cirrus effect regarding (i) the ice-nucleating potential of the INPs, (ii) the inclusion of ammonium sulfate and organic particles as INPs in the model, and (iii) the model representations of vertical updraughts. The resulting global radiative forcing of the total INP–cirrus effect, considering all different INP types, assuming a smaller and a larger ice-nucleating potential of INPs, to explore the range of possible forcings due to uncertainties in the freezing properties of INPs, is simulated as −28 and −55 mW m−2, respectively. While the simulated impact of glassy organic INPs is mostly small and not statistically significant, ammonium sulfate INPs contribute a considerable radiative forcing, which is nearly as large as the combined effect of mineral dust and soot INPs. Additionally, the anthropogenic INP–cirrus effect is analysed considering the difference between present-day (2014) and pre-industrial conditions (1750) and amounts to −29 mW m−2, assuming a larger ice-nucleating potential of INPs. In a further sensitivity experiment we analyse the effect of highly efficient INPs proposed for cirrus cloud seeding as a means to reduce global warming by climate engineering. However, the results indicate that this approach risks an overseeding of cirrus clouds and often results in positive radiative forcings of up to 86 mW m−2 depending on number concentration of seeded INPs. Idealized experiments with prescribed vertical velocities highlight the crucial role of the model dynamics for the simulated INP–cirrus effects. For example, resulting forcings increase about 1 order of magnitude (−42 to −340 mW m−2) when increasing the prescribed vertical velocity (from 1 to 50 cm s−1). The large discrepancy in the magnitude of the simulated INP–cirrus effect between different model studies emphasizes the need for future detailed analyses and efforts to reduce this uncertainty and constrain the resulting climate impact of INPs. The role of sulfur injection strategy in determining atmospheric circulation and ozone response to solar geoengineering <https://gfzpublic.gfz-potsdam.de/pubman/faces/ViewItemFullPage.jsp?itemId=item_5018213_1> Bednarz, E., Visioni, D., Butler, A., Zhang, Y., MacMartin, D., & Kravitz, B. (2023). The role of sulfur injection strategy in determining atmospheric circulation and ozone response to solar geoengineering. In *XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)*. GFZ German Research Centre for Geosciences. *Abstract* Despite offsetting global mean surface temperature, various studies demonstrated that Stratospheric Aerosol Injection (SAI) could influence the recovery of stratospheric ozone and have important impacts on stratospheric and tropospheric circulation, thereby potentially playing an important role in modulating regional and seasonal climate variability. However, so far most of the assessments of such an approach have come from climate model simulations in which SO2 is injected only in a single location or a set of locations. Here we use CESM2-WACCM6 SAI simulations under a comprehensive set of SAI strategies achieving the same global mean surface temperature with different locations and/or timing of injections: an equatorial injection, an annual injection of equal amounts of SO2 at 15N and 15S, an annual injection of equal amounts of SO2 at 30N and 30S, and a polar strategy injecting SO2 at 60N and 60S only in spring in each hemisphere. We demonstrate that despite achieving the same global mean surface temperature, the different strategies result in contrastingly different impacts on stratospheric temperatures and circulation, thereby leading to different impacts on Northern Hemispheric polar vortex and, thus, winter mid- and high latitude surface climate, as well as leading to important differences in the future evolution of stratospheric ozone throughout the globe. Overall, the results contribute to an increased understanding of the underlying physical processes as well as lay ground for identifying an optimal SAI strategy that could form a basis of a future multi-model assessment. Exploring ship track spreading rates with a physics-informed Langevin particle parameterization <https://egusphere.copernicus.org/preprints/2024/egusphere-2024-235/> McMichael, L. A., Schmidt, M. J., Wood, R., Blossey, P. N., & Patel, L. (2024). Exploring ship track spreading rates with a physics-informed Langevin particle parameterization. *EGUsphere*, *2024*, 1-33. *Abstract* The rate at which aerosols spread from a point source injection, such as from a ship or other stationary pollution source, is critical for accurately representing subgrid plume spreading in a climate model. Such climate model results will guide future decisions regarding the feasibility and application of large-scale intentional marine cloud brightening (MCB). Prior modeling studies have shown that the rate at which ship plumes spread may be strongly dependent on meteorological conditions, such as precipitating versus non-precipitating boundary layers and shear. In this study, we apply a Lagrangian particle model (PM-ABL v1.0), governed by a Langevin stochastic differential equation, to create a simplified framework for predicting the rate of spreading from a ship-injected aerosol plume in sheared, precipitating, and non-precipitating boundary layers. The velocity and position of each stochastic particle is predicted with the acceleration of each particle being driven by the turbulent kinetic energy, dissipation rate, momentum variance, and mean wind. These inputs to the stochastic particle-velocity equation are derived from high-fidelity large-eddy simulations (LES) equipped with a prognostic aerosol-cloud microphysics scheme (UWSAM) to simulate an aerosol injection from a ship into a cloud-topped marine boundary layer. The resulting spreading rate from the reduced-order stochastic model is then compared to the spreading rate in the LES. The stochastic particle-velocity representation is shown to reasonably reproduce spreading rates in sheared, precipitating, and non-precipitating cases using domain-averaged turbulent statistics from the LES. ------------------------------ WEB POSTSHarvard has halted its long-planned atmospheric geoengineering experiment <https://www.technologyreview.com/2024/03/18/1089879/harvard-halts-its-long-planned-atmospheric-geoengineering-experiment/> (MIT Technology Review)How rerouting planes to produce fewer contrails could help cool the planet <https://www.technologyreview.com/2024/03/12/1089620/how-rerouting-planes-to-produce-fewer-contrails-could-help-cool-the-planet/> (MIT Technology Review)Degrees-funded scientists lead key discussions at Gordon Research Conference <https://www.degrees.ngo/degrees-funded-scientists-lead-key-discussions-at-gordon-research-conference/> (The Degrees Initiative)Can’t Solve a Problem — Take a Step Back and Share It <https://medium.com/@honegger.matthias/cant-solve-a-problem-take-a-step-back-and-share-it-1b7a9734ba44> (Medium)Effects of geoengineering must be urgently investigated, experts say <https://www.theguardian.com/environment/2024/mar/14/geoengineering-must-be-urgently-investigated-experts-say> (The Guardian)The Best Way to Find Out if We Can Cool the Planet <https://www.nytimes.com/2024/03/17/opinion/solar-geoengineering-risks-research.html> (The New York Times)Climate change: The 'insane' plan to save the Arctic's sea-ice <https://www.bbc.com/news/science-environment-68206309> (BBC) ------------------------------ REPORTStratospheric Controlled Perturbation Experiment (SCoPEx) Advisory Committee-Final Report <https://scopexac.com/finalreport/> <https://scopexac.com/finalreport/> ------------------------------ THESISAssessing the Potential of Cirrus Cloud Thinning through Cloud Chamber Experiments and Parcel Model Simulations <https://publikationen.bibliothek.kit.edu/1000168905> *Abstract* Cirrus cloud thinning (CCT) is a climate engineering approach to achieve regional cooling by reducing the coverage of effectively warming cirrus clouds. Seeding with ice-nucleating particles (INPs) would affect the natural cirrus cloud formation process and is expected to change the cloud properties to a thinner cloud with a shorter lifetime. With cirrus clouds having a warming effect (on average), diminishing these clouds could lead to a surface cooling. The Arctic could particularly benefit from such a intervention, due to regional feedback effects. In this work cloud chamber experiments and parcel model simulations on CCT are presented. These results contribute to a better understanding of the competition between heterogeneous and homogeneous freezing and will therefore support a more rigorous evaluation of CCT effectiveness. In our cloud chamber studies, CCT effectiveness is probed by investigating the competition between homogeneous freezing of sulfuric acid solution droplets and heterogeneous ice nucleation by three different seeding agents, i.e. fumed silica, quartz and calcium carbonate. These cloud chamber experiments show that CCT effectiveness (i.e. minimizing the total ice crystal number concentration) is dependent on the ambient temperature and the concentration of the seeding aerosol. The Lagrangian parcel model MAID (Model for Aerosol and Ice Dynamics) is validated against our experimental results and used to further analyze CCT effectiveness beyond the experimentally accessible parameter space. As part of this work, the model as improved and expanded by a new heterogeneous freezing scheme, internally calculated trajectories and the representation of gravity wave driven fluctuations. After validation we conduct atmospheric CCT simulations with smaller seeding concentrations and slower updraft velocities along adiabatic updraft trajectories. The results show regimes of optimal seeding conditions, as well as regimes with the opposite effect (overseeding). If the updraft trajectories are superimposed with gravity wave driven fluctuations, the characteristics of those regimes become less distinct and the effect of CCT is significantly reduced. Our results underline the complexity of CCT effectiveness and highlight the sensitivity with regard to variations of the seeding concentration, updraft velocity and gravity wave fluctuations. Due to the strong impact and statistical nature of gravity wave fluctuations a controlled application of CCT is challenging. Yet, a statistical analysis of stochastic updraft fluctuations shows thinned cirrus in 20 % to 30 % of the scenarios with low to moderate seeding. Our model simulations emphasize the importance of the competition between heterogeneous and homogeneous freezing, as well as gravity wave driven updraft fluctuations. ------------------------------ UPCOMING EVENTS(NEW) Solar Radiation Modification, Clouds, Aerosols, and their Impacts on the Biosphere and Earth System | EGU General Assembly <https://meetingorganizer.copernicus.org/EGU24/session/49142> | 18 April 2024 Solar Geoengineering Events Calendar <https://teamup.com/ks64mmvtit583eitxx> GUIDELINES:*Sync selected events to your default calendar in these simple steps:*1) Click on the event you want to sync.2) Tap the menu icon (three vertical lines) at the top left.3) Choose 'Share.'4) Pick your default calendar.5) Save the event.*Sync the entire Teamup Calendar to your default calendar with these simple steps:**1) Tap the menu icon (three vertical lines) at the top right.**2) Choose 'Preferences.'**3) Click 'iCalendar Feeds.'**4) Copy the URL shown for 'Solar Geoengineering Events / SRM Deadlines.'’**5) Paste the URL into your default calendar settings.**6) Click 'Subscribe' or 'Add Calendar.'**For more detailed instructions, visit: https://calendar.teamup.com/kb/subscribe-to-teamup-icalendar-feeds/ <https://calendar.teamup.com/kb/subscribe-to-teamup-icalendar-feeds/>* <https://teamup.com/ks64mmvtit583eitxx> ------------------------------ PODCASTSMCB with drones - Claudel | Reviewer 2 does geoengineering MCB with drones - Claudel Reviewer 2 does geoengineering 1:37:39 <https://podcasts.apple.com/us/podcast/mcb-with-drones-claudel/id1529459393?i=1000648967322&uo=4> “Christian Claudel comes on to explore the issues around using drones to distribute MCB particles. These are made by anti-solvent precipitation (much like diluting Ricard spirit). Despite @geoengineering1 being AN ACTUAL AUTHOR on the paper he still finds plenty of opportunities for nitpicking. Paper: Marine-cloud brightening: an airborne concept Christian Claudel, Andrew John Lockley, Fabian Hoffmann and Younan Xia DOI 10.1088/2515-7620/ad2f71” How to think about solar radiation management | Volts Volts How to think about solar radiation management <https://www.volts.wtf/p/how-to-think-about-solar-radiation?utm_source=substack&utm_campaign=post_embed&utm_medium=email> Even if greenhouse gas emissions halted entirely right now, we would continue to feel climate change effects for decades due to existing carbon dioxide in the atmosphere — and warming could accelerate, as we reduce the aerosol pollution that happens to be acting as a partial shield. In this episode, Kelly Wanser of nonprofit SilverLining makes the pitch… Listen now <https://www.volts.wtf/p/how-to-think-about-solar-radiation?utm_source=substack&utm_campaign=post_embed&utm_medium=email> a year ago · 31 likes · 8 comments · David Roberts “Even if greenhouse gas emissions halted entirely right now, we would continue to feel climate change effects for decades due to existing carbon dioxide in the atmosphere — and warming could accelerate, as we reduce the aerosol pollution that happens to be acting as a partial shield. In this episode, Kelly Wanser of nonprofit SilverLining makes the pitch for solar radiation management, the practice of adding our own shielding particles to the atmosphere to buy us some time while we step up our greenhouse gas reductions.” ------------------------------ YOUTUBE VIDEOS*We Need to Start Climate Engineering Soon, New Study Says | Sabine Hossenfelder* <https://www.youtube.com/watch?v=MZiEcx0F_CM> Climate engineering is the cheapest way to get us out of this unfolding climate disaster, but how do we do it? Two new papers have recently been released - one discussing the need to start stratospheric aerosol injections soon and the other introducing a new method of climate engineering. What are the pros and cons of stratospheric aerosol injections? What is this new method? Let’s have a look. Paper 1: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023GL106132 Paper 2: https://www.science.org/doi/10.1126/sciadv.adk0593 2023 2024 A New Era of Policy in Solar Geoengineering KCEP Digest 59 Solar Geoengineering | METERRORIST MEDIA <https://www.youtube.com/watch?v=aRVrYAm_e6w>2024 Towards a Non Use Regime on Solar Geoengineering Lessons from International Law and Governance | METERRORIST MEDIA <https://www.youtube.com/watch?v=eocYPYI4DH4>Solar Climate Intervention Virtual Symposium 9 (Daniel Hueholt & Prof David Keith) | Solar Climate Intervention Talks <https://www.youtube.com/watch?v=kJ1Kv-GlhsA> “Solar Climate Intervention Virtual Symposium 9 Daniel Hueholt (Colorado State University, USA): "Climate speeds help frame relative ecological risk in future climate change and stratospheric aerosol injection scenarios." Prof. David Keith (University of Chicago, USA): "Solar geoengineering could start soon if it is small." Solar Geoengineering/Sunlight Reflection Methods: Safe, Effective, Needed? w/ Doug MacMartin | Climate Chat <https://www.youtube.com/watch?v=_JBLMsXNmhs> “In this Climate Chat episode, we interview Cornell climate scientist Douglas MacMartin. Doug researches climate intervention techniques including Sunlight Reflection Methods (SRM, aka Solar Radiation Management or Solar Geoengineering). We will discuss how SRM can be achieved, how safe it is, how does SRM side effects compare with the side effects of not doing SRM, and why SRM may be needed very soon.” MEERTALK March 2024 - Tim Garrett | MEER SRM <https://www.youtube.com/watch?v=JvJ1VUsnlgY> “Clouds play a controlling role in the atmosphere, in large part because they cool it during daytime by reflecting sunlight to space. In recent decades clouds have been a primary target for climate modification because the addition of tiny aerosol particles to clouds can clearly be shown to make them brighter. However, clouds are highly dynamic creatures, and their overall response at the global scales that matter most to climate change is much harder to measure. and their overall response at the global scales that matter most to climate change is much harder to measure. Tim Garrett is a Professor of Atmospheric Sciences at the University of Utah. His research interests focus on the measurement and modeling of clouds and precipitation and their role in weather and climate.” ------------------------------ -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/geoengineering/CAHJsh9_Dmugk-dyxX34MvgiW2pX0icd%2BFR5u93zhxRGen88wSg%40mail.gmail.com.
