*WEEKLY SUMMARY (26 FEBRUARY - 03 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 PAPERS*Marine-cloud brightening: an airborne concept <https://iopscience.iop.org/article/10.1088/2515-7620/ad2f71> Claudel, C., Lockley, A. J., Hoffmann, F., & Xia, Y. (2023). Marine Cloud Brightening: an airborne concept. *Abstract* Marine Cloud Brightening (MCB) is a proposed Solar Radiation Modification (SRM) geoengineering technique to enhance Marine Boundary Layer (MBL) cloud albedo. Extant proposals consider 10,000-100,000 autonomous ships spraying seawater, generating and dispersing sea salt nanoparticles. Alternatively, this paper proposes industrially manufacturing NaCl nanoparticles using ethanol anti-solvent brine precipitation. With desiccation, size optimization and narrowed size distribution, aerosol mass flux reduces by 500x (17x for dry mass flux). This facilitates Unmanned Aerial Vehicle delivery (e.g. MQ-9 Reaper Unmanned Aerial Vehicle). Increased speed and wake turbulence improves areal coverage per vehicle vs. ships --- reducing fleet size. Utilizing extant airframe designs improves vehicle Technology Readiness Level (TRL) --– potentially improving system operational cost (est. $40B per year) and lead time. This approach further reduces energy requirements (5x less), technical risk and system complexity. Increased readiness amplifies proliferation risk --- particularly for inexpensive regional heatwave and hurricane suppression --- making governance more urgent. Implication of stratospheric aerosol geoengineering on compound precipitation and temperature extremes in Africa <https://www.pnnl.gov/publications/implication-stratospheric-aerosol-geoengineering-compound-precipitation-and> Obahoundje, S., Nguessan-Bi, V. H., Diedhiou, A., Kravitz, B., & Moore, J. C. (2023). Implication of stratospheric aerosol geoengineering on compound precipitation and temperature extremes in Africa. *Science of the Total Environment*, *863*, 160806. *Abstract* Three Coupled Model Intercomparison Project 5 (CMIP5) models that simulated the G4 experiment of the Geoengineering Model Intercomparison Project (GeoMIP) were used to investigate the impact of stratospheric aerosol injection (SAI) on combined temperature and precipitation extremes in Africa that can have greater negative impacts on human and the environment than individual rainfall or temperature extremes. The examined compound extremes included the dry (Rwarm?dry and Rcold?dry) and wet (Rwarm?wet and Rcold?wet) modes assessed during the injection (SAI, 2050–2069) and post-injection (postSAI, 2070–2089) periods compared with the historical period (1986–2005). We found a significant projected change in the occurrence of both wet and dry modes during SAI and postSAI related to the historical period. The magnitude and sign of this change depend on the season and the geographical location. During the SAI and postSAI, the wet (Rwarm?wet and Rcold?wet) modes are projected to be significantly lower while the dry modes are noted to increase in a large part of African continent depending on the season and the geographical location and may consequently leads to an increase of the droughts prone areas. The termination effect is noted to reduce the occurrence of dry modes, whichmay reduce the potential negative effects of the injection after halting. As the effect may vary fromone region to another and according to the season, it suggested assessing the key sector impacts of SAI. Thus, this change in drymodes due to SAI could affect all activitieswhich depend on water resources such as water supply, agriculture and food production, energy demand, and production with adverse effects on health, security, and sustainable development, but this needs to be assessed and quantified at regional scales. Identifying the regional emergence of climate patterns in the ARISE-SAI-1.5 simulations <https://iopscience.iop.org/article/10.1088/1748-9326/acc81a> Labe, Z. M., Barnes, E. A., & Hurrell, J. W. (2023). Identifying the regional emergence of climate patterns in the ARISE-SAI-1.5 simulations. *Environmental Research Letters*, *18*(4), 044031. *Abstract* Stratospheric aerosol injection is a proposed form of solar climate invention (SCI) that could potentially reduce the amount of future warming from externally-forced climate change. However, more research is needed, as there are significant uncertainties surrounding the possible impacts of SCI, including unforeseen effects on regional climate patterns. In this study, we consider a climate model simulation of the deployment of stratospheric aerosols to maintain the global mean surface temperature at 1.5 ∘C above pre-industrial levels (ARISE-SAI-1.5). Leveraging two different machine learning methods, we evaluate when the effects of SCI would be detectable at regional scales. Specifically, we train a logistic regression model to classify whether an annual mean map of near-surface temperature or total precipitation is from future climate change under the influence of SCI or not. We then design an artificial neural network to predict how many years it has been since the deployment of SCI by inputting the regional maps from the climate intervention scenario. In both detection methods, we use feature attribution methods to spatially understand the forced climate patterns that are important for the machine learning model predictions. The differences in regional temperature signals are detectable in under a decade for most regions in the SCI scenario compared to greenhouse gas warming. However, the influence of SCI on regional precipitation patterns is more difficult to distinguish due to the presence of internal climate variability. Towards a Non-Use Regime on Solar Geoengineering: Lessons from International Law and Governance <https://www.cambridge.org/core/journals/transnational-environmental-law/article/towards-a-nonuse-regime-on-solar-geoengineering-lessons-from-international-law-and-governance/83A71F8002DC88049D9575790743D3A1> Gupta, A., Biermann, F., van Driel, E., Bernaz, N., Jayaram, D., Kim, R. E., ... & Wewerinke-Singh, M. (2024). Towards a Non-Use Regime on Solar Geoengineering: Lessons from International Law and Governance. *Transnational Environmental Law*, 1-32. *Abstract* In recent years, some scientists have called for research into and potential development of ‘solar geoengineering’ technologies as an option to counter global warming. Solar geoengineering refers to a set of speculative techniques to reflect some incoming sunlight back into space, for example, by continuously spraying reflective sulphur aerosols into the stratosphere over several generations. Because of the significant ecological, social, and political risks posed by such technologies, many scholars and civil society organizations have urged governments to take action to prohibit the development and deployment of solar geoengineering techniques. In this article we take such calls for a prohibitory or a non-use regime on solar geoengineering as a starting point to examine existing international law and governance precedents that could guide the development of such a regime. The precedents we examine include international prohibitory and restrictive regimes that impose bans or restrictions on chemical weapons, biological weapons, weather modification technologies, anti-personnel landmines, substances that deplete the ozone layer, trade in hazardous wastes, deep seabed mining, and mining in Antarctica. We also assess emerging norms and soft law in anticipatory governance of novel technologies, such as human cloning and gene editing. While there is no blueprint for a solar geoengineering non-use regime in international law, our analysis points to numerous specific elements on which governments could draw to constrain or impose an outright prohibition on the development of technologies for solar geoengineering, should they opt to do so. Considering intentional stratospheric dehydration for climate benefits <https://www.science.org/doi/10.1126/sciadv.adk0593> Schwarz, J. P., Gao, R. S., Thornberry, T. D., Rollins, A. W., Rosenlof, K. H., Portmann, R. W., ... & Ray, E. A. (2024). Considering intentional stratospheric dehydration for climate benefits. *Science Advances*, *10*(9), eadk0593. *Abstract* We introduce a climate intervention strategy focused on decreasing water vapor (WV) concentrations near the tropopause and in the stratosphere to increase outbound longwave radiation. The mechanism is the targeted injection of ice-nucleating particles (INP) in air supersaturated with respect to ice at high altitudes in the tropical entryway to the stratosphere. Ice formation in this region is a critical control of stratospheric WV. Recent airborne in situ data indicate that targeting only a small fraction of air parcels in the region would be sufficient to achieve substantial removal of water. This “intentional stratospheric dehydration” (ISD) strategy would not counteract a large fraction of the forcing from carbon dioxide but may contribute to a portfolio of climate interventions by acting with different time and length scales of impact and risk than other interventions that are already under consideration. We outline the idea, its plausibility, technical hurdles, and side effects to be considered. <https://www.science.org/doi/10.1126/sciadv.adk0593> <https://iopscience.iop.org/article/10.1088/2515-7620/ad2f71> ------------------------------ FUNDING OPPORTUNITYResearch programme to model impact of solar radiation management <https://www.ukri.org/news/research-programme-to-model-impact-of-solar-radiation-management/> A new £10.5m, five-year research programme will deliver independent risk-risk analyses to inform policymakers in the area of solar radiation management (SRM). ------------------------------ WEB POSTSThe Degrees Initiative to host 2025 Global Forum on solar radiation modification <https://www.degrees.ngo/degrees-to-host-2025-global-forum-on-srm/> (The Degrees Initiative)Emergency atmospheric geoengineering wouldn't save the oceans <https://phys.org/news/2024-02-emergency-atmospheric-geoengineering-wouldnt-oceans.html> (Phys.org)*Safety fears stall U.N. bid to examine sun-blocking climate change tech <https://www.reuters.com/business/environment/safety-fears-stall-un-bid-examine-sun-blocking-climate-change-tech-2024-02-29/> (Reuters)*Climate Vulnerable Nations Reject US-led Push for Solar Geoengineering at UNEA-6 <https://www.ciel.org/news/ciel-response-to-geoengineering-srm-technology-rejection-unea-6/> (CIEL)Canada Bets Big on Bill Gates' Solar Geoengineering Initiative to Tame Global Warming <https://bnnbreaking.com/world/canada/canada-bets-big-on-bill-gates-solar-geoengineering-initiative-to-tame-global-warming> (BNN Breaking)Not such a bright idea: cooling the Earth by reflecting sunlight back to space is a dangerous distraction <https://theconversation.com/not-such-a-bright-idea-cooling-the-earth-by-reflecting-sunlight-back-to-space-is-a-dangerous-distraction-223353> (The Conservation)Dehydrate the stratosphere to curb global warming? Scientists float risky new strategy <https://www.science.org/content/article/dehydrate-stratosphere-curb-global-warming-scientists-float-risky-new-strategy> (Science) <https://theconversation.com/not-such-a-bright-idea-cooling-the-earth-by-reflecting-sunlight-back-to-space-is-a-dangerous-distraction-223353> ------------------------------ OPINIONSAerosols and land surface geoengineering <https://groups.google.com/g/geoengineering/c/MR10lmA5n14>UNEA6 fails to adopt SRM resolution <https://groups.google.com/g/geoengineering/c/5xGqaHPCX5E> ------------------------------ *PODCASTS*The Thorny Issue Of 1.5C | Outrage Optimism <https://www.outrageandoptimism.org/episodes/the-thorny-issue-of-15c?hsLang=en> “1.5C degrees is back in the news again as the recent Copernicus report reported that the world had exceeded this politically agreed temperature limit for the majority of 2023. But what does this mean? Do we abandon this target and set a new one? Is it still useful to use this as our north star in tackling the effects of man-made climate change? Is now the right time to start a serious conversation about geo-engineering? Join Christiana, Tom and Paul as they grapple with these difficult questions and their wider implications. Our guest this week is Dr. Michael E. Mann, Presidential Distinguished Professor of Earth & Environmental Science, and Director of the Penn Center for Science, Sustainability and the Media (PCSSM) at the University of Pennsylvania. He lends us his expertise to discuss the liabilities and implications of breaching the 1.5 degree ceiling, and what his latest legal victory means for the ‘war on science’.” Dimming the Sun | BBC Inside Science <https://www.bbc.co.uk/sounds/play/m001wqht> “Switzerland has submitted a proposal to create a United Nations expert group on solar geoengineering to inform governments and stakeholders. The idea was discussed at the UN Environment Assembly in Nairobi, Kenya, this week. Professor Aarti Gupta shares how, after tense negotiations, the different member states could not agree, and the proposal was withdrawn. Why is solar geoengineering a controversial issue? How would dimming the sun even work? And should we consider it a genuine option in our fight against climate change? Dr Pete Irvine and Professor Joanna Haigh join presenter Marnie Chesterton in the studio to discuss.” -- 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_AdN8rDWzDGQrVzpUW7kQf9LaHYtcRZ41wObyxE6ttvQ%40mail.gmail.com.
