Energetic constraints on tropical precipitation changes under stratospheric aerosol geoengineering: a topical review

Abstract Since Crutzen’s (2006 Clim. Change 77 211–20) call for research into stratospheric aerosol geoengineering (SAG), a form of solar radiation modification, the field of SAG research has witnessed substantial growth. This paper reviews the existing literature on the impacts of SAG on tropical precipitation. It is structured around two key constraints based on planetary energetics that strongly influence tropical precipitation: (a) a global energy budget constraint based on the fast adjustment and slow responses framework, and (b) a constraint based on interhemispheric changes in energy budget that influences the position of the intertropical convergence zone. The impact of stratospheric heating, characteristic to SAG using sulfate aerosols, on the changes in precipitation is also discussed under the first constraint. The combined effects of these two energetic constraints can explain most of the large-scale tropical precipitation changes as demonstrated by a recent study. By synthesizing key results from literature, this review provides a sound scientific basis and simple framework for understanding the changes in tropical precipitation based on planetary energy budget constraints. Finally, from the perspective of these two energetic constraints, we also discuss the design of SAG strategies that could avoid the detrimental effects on tropical precipitation, a suite of model simulations that address these issues and research areas that need further investigation.