Solar Radiation Modification Effects on Climate: a Meta-Analysis

As large-scale fossil fuel emissions continue and climate risks escalate, society has an urgent need for scientific information on the potential impacts of solar radiation modification (SRM). However, assessments and media coverage of SRM science mostly emphasizes uncertainty and lacks clear takeaways besides the need for more research. Wishing to clarify what we do and do not know about SRM climate impacts, we conduct the first structured meta-analysis of the SRM impacts literature. Following the “medical analogy” for climate intervention, we develop and apply novel metrics of “safety” and “efficacy” to assess SRM impacts across a wide range of scenarios, regions, and topics. We identify and discuss consistent results in the analyzed literature, including reduced temperature risks and risks to the polar oceans and cryosphere, and increased risks to stratospheric circulation from SAI. We consider how patterns in SRM impacts may illuminate fundamental aspects of how aerosol perturbations affect the climate system. We argue that there is higher confidence in how SAI would affect climate impacts than MCB, and discuss other salient topics for which little evidence is available.