PNNL

Abstract

Solar geoengineering is rapidly emerging at the forefront of climate policy discussions. To support future decisions, society will need to know the best estimate of impacts and how uncertain these estimates are, as well as the limits of what can be known about solar geoengineering prior to deployment. Because solar geoengineering via stratospheric aerosols has never been deployed in the real world, most conclusions about its climatic effects are obtained through models and, to a limited degree, natural analogues. This raises questions about how confident the research community is in its conclusions about solar geoengineering, the basis for that confidence, and how to improve confidence. Here we review the state of knowledge around solar geoengineering via stratospheric aerosols with a focus on uncertainty and risk: what is the basis for confidence in the present state of knowledge, and how can uncertainties be prioritized so that a mission-driven research agenda can be designed? Included is a discussion of how to address uncertainties, as well as the importance of a design perspective in bounding which uncertainties are relevant for a given scenario or strategy. We conclude with an assessment of future needs, including a framework for prioritizing future research efforts.