Projected future changes in extreme precipitation over China under stratospheric aerosol intervention

Abstract. Extreme precipitation events are linked to severe economic losses and casualties in China every year; hence, exploring the potential mitigation strategies to minimize these events and their changes in frequency and intensity under global warming is of importance, particularly for the populous subregions. In addition to global warming scenarios, this study examines the effects of the potential deployment of stratospheric aerosol injection (SAI) on hydrological extremes in China based on the SAI simulations (G6sulfur) of the Geoengineering Model Intercomparison Project (GeoMIP) from UKESM1 (The UK Earth System Model) simulations. The simulated SAI deployment is compared with simulations of the future climate under two different emission scenarios (SSP5-8.5 and SSP2-4.5) and reduction in the solar constant (G6solar) to understand the effect of SAI on extreme precipitation patterns. The results show that, under future global warming scenarios, precipitation and extreme wet climate events are projected to increase by 2100 relative to the present day across all the subregions in China. Additionally, analyses of extreme drought events show a projected increase in southern China. The G6sulfur and G6solar experiments ameliorate the increases in extreme rainfall intensities, especially for the eastern subregions of China. The impacts of SAI in decreasing extreme precipitation events and in consecutive wet days are more pronounced than in G6solar. While the results from both G6sulfur and G6solar show encouraging abatement of many of the impacts on detrimental extreme events that are evident in SSP5-8.5 there are some exceptions. Both G6sulfur and G6solar show drying trendsat high latitudes within the region, which is consistent with our understanding of the spin-down of the hydrological cycle under SRM. For instance, the projected dry days increase for G6sulfur compared to SSP5-8.5. These side effects imply that a cautionary approach and further optimization may be required should any future SRM deployment be considered.