Geoengineering is not a silver bullet, and treating it as one could greatly increase already severe climate change risks,” they wrote to the committee. “While further research could help address questions about the proposed technologies’ efficacy, risks, and cost-effectiveness, we already know that geoengineering, including solar radiation management and carbon dioxide removal approaches, can at best be a supplement to reducing sources of greenhouse gas emissions and increasing our ability to cope with the effects of climate change.