Reflecting Sunlight

Climate change is creating impacts that are widespread and severe for individuals, communities, economies, and ecosystems around the world. While efforts to reduce emissions and adapt to climate impacts are the first line of defense, researchers are exploring other options to reduce warming. Solar geoengineering strategies are 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, they could also introduce an array of unknown or negative consequences. This report concludes that a strategic investment in research is needed to enhance policymakers' understanding of climate response options. The United States should develop a transdisciplinary research program, in collaboration with other nations, to advance understanding of solar geoengineering's technical feasibility and effectiveness, possible impacts on society and the environment, and social dimensions such as public perceptions, political and economic dynamics, and ethical and equity considerations. The program should operate under robust research governance that includes such elements as a research code of conduct, a public registry for research, permitting systems for outdoor experiments, guidance on intellectual property, and inclusive public and stakeholder engagement processes. Table of Contents Front Matter Summary 1 Introduction 2 Assessment of the Current Solar Geoengineering Research and Research Governance Landscape 3 The Decision Space: Context and Key Considerations for Solar Geoengineering Research and Research Governance 4 A Solar Geoengineering Research Program: Goals and Approach 5 Solar Geoengineering Research Governance 6 An Integrated Agenda for Solar Geoengineering Research References Appendix A: Statement of Task Appendix B: Speakers from the Committee Meetings & Webinars Appendix C: Scenarios Developed By the Committee for the "Decision Maker Needs" Webinars Appendix D: Biographical Sketches of the Committee Members Appendix E: Acronyms and Abbreviations