South Asian Summer Monsoon under Stratospheric Aerosol Intervention

Abstract The South Asian summer monsoon (SAM) bears significant importance for agriculture, water resources, economy, and environmental aspects of the region for more than 1.5 billion people. To minimize the adverse impacts of global warming, Stratospheric Aerosol Intervention (SAI) has been proposed to lower surface temperatures by reflecting a portion of solar radiation back into space. However, the effects of SAI on SAM are still very uncertain and demand more research. We investigate this using the Stratospheric Aerosol Geoengineering Large Ensemble datasets. Our study reveals a reduction in the mean and extreme summer monsoon precipitation under SAI in this scenario, driven by a combination of the SAI-induced lower stratospheric warming and the associated weakening of the northern hemispheric subtropical jet, changes in the upper-tropospheric wave activities, geopotential height anomalies, and the strength of the Asian Summer Monsoon Anticyclone. Local dust changes that can otherwise be important for SAM rainfall variability under climate change also contribute to changes under SAI. As the interest in SAI research grows, our results demonstrate the urgent need to understand SAM variability under different SAI scenarios, which is essential for sustainable development and disaster preparedness in South Asia.