Given the urgency of the risks posed by climate change, the U.S. should pursue a research program for solar geoengineering — in coordination with other nations, subject to governance, and alongside a robust portfolio of climate mitigation and adaptation policies, says a 2021 report from the National Academies of Sciences, Engineering, and Medicine. The report emphasizes that solar geoengineering is not a substitute for reducing greenhouse gas emissions.
 
Solar geoengineering refers to strategies designed to cool Earth either by adding small reflective particles to the upper atmosphere, by increasing reflective cloud cover in the lower atmosphere, or by thinning high-altitude clouds that can absorb heat. While such strategies have the potential to reduce global temperatures and thereby ameliorate some of the risks posed by climate change, they could also introduce an array of unknown or negative consequences…

Scientific understanding of many aspects of solar geoengineering technologies remains limited, including how they could affect weather extremes, agriculture, natural ecosystems, or human health. There currently is no coordinated national effort for solar geoengineering research. The report recommends a comprehensive plan for governing solar geoengineering research, designed to ensure it moves forward in a socially responsible manner. Researchers should follow a code of conduct, for example, and research should be catalogued in a public registry, be subject to regular program assessment and review, and allow for public engagement.

Deliberate outdoor experiments that involve releasing substances into the atmosphere should be considered only when they can provide critical observations that cannot be provided by laboratory study, modeling, or experiments of opportunity — such as volcanic eruptions. Outdoor experiments should be subject to appropriate governance including permitting and impact assessments, says the report…The report says the U.S. Global Change Research Program (USGCRP) should lead the effort to establish and coordinate a solar geoengineering research program across federal agencies and scientific disciplines, with funding in the range of $100 million-$200 million over the first five years. USGCRP would enable oversight and governance of research activities, including ensuring peer review, coordinating budget proposals and requests, periodically assessing progress, and defining program goals. Funding should be set aside specifically for implementation of governance and public engagement efforts.

Excerpts from New Report Says U.S. Should Cautiously Pursue Solar Geoengineering Research to Better Understand Options for Responding to Climate Change Risks, National Academies of Sciences, Engineering, and Medicine Press Release, Mar. 25, 2021