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RESEARCH PAPERSSong, 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.
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.
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 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.
Dove, Z., Jinnah, S., & Talati, S. (2024). Building capacity to govern emerging climate intervention technologies. Elementa: Science of the Anthropocene, 12(1). 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.
Boselius, L., Duffey, A., & Irvine, P. J. (2024). Peak Shaving with Solar Radiation Management Would Shorten Global Temperature Overshoot. Authorea Preprints. 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.
WEB POSTS
UPCOMING EVENTSDiscovery workshop focussing on atmospheric science (SRM) | 18 October 2024 | Online Integrative synthesis workshop focusing on identifying gaps in current governance & ethics | 18 November 2024 | Online
Solar Geoengineering Events Calendar
JOB OPPORTUNITY"The Degrees Initiative is a UK-based NGO that builds the capacity of developing countries to evaluate solar radiation management geoengineering (SRM), a controversial proposal for reducing some impacts of climate change by reflecting sunlight away from the Earth. Degrees is neutral on whether SRM should ever be used, but we believe that developing countries should be empowered to conduct their own research and to play a central role in SRM discussions. The initiative has been working in different forms for over a decade and our work receives worldwide coverage and widespread acclaim. We are confident that Degrees can continue to grow, including by expanding and diversifying its funding base."
YOUTUBE VIDEOSWebinar on Science of SRM: Research Implications for Pakistan | SDTV Episode 621 Oceans and Spray | ToSaveTheWorld "Jessica Wan models climate processes. She explains to Patricia Quinn and Robert Tulip that the effects of marine cloud brightening may be beneficial today, but not by mid-century, when the climate will be warmer. Such an intervention done locally will have global effects that are hard to predict, so it is important to do research now about these processes."
MEERTALK August - Jessica Wan | MEER SRM "Jessica Wan's work demonstrates that regional marine cloud brightening in the North Pacific can be effective at reducing the risk of extreme summer heat exposure over the Western United States under present-day climate, but the same interventions become ineffective and even counterproductive under mid-century warming. Jessica Wan is a climate sciences PhD candidate in Dr. Kate Ricke's lab at Scripps Institution of Oceanography at the University of California San Diego studying how climate geoengineering proposals, particularly marine cloud brightening, might alleviate regional climate change impacts. She is also a National Defense Science and Engineering Graduate (NDSEG) fellow and an Achievement Rewards for College Scientists (ARCS) scholar."
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