GeoengineeringResponding to Climate Change: U.S. Should Cautiously Pursue Solar Geoengineering

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 new 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, says Reflecting Sunlight: Recommendations for Solar Geoengineering Research and Research Governance.

A U.S. solar geoengineering research program should aim to enhance policymakers’ understanding of climate response options.  The research should work to better understand solar geoengineering’s technical feasibility, possible impacts on society and the environment, public perceptions, and potential social responses — but it should not be designed to advance future deployment of these interventions. 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.