Abstract
Solar Radiation Modification (SRM) has been proposed to reduce global temperatures by reflecting more solar radiation into space, but its
effects on precipitation extremes across Southeast Asia remain uncertain. This study evaluates the impacts of two SRM strategies on precip-
itation extremes in Southeast Asia, using the multi-model ensemble mean from five climate models in the Geoengineering Model Intercom-
parison Project Phase 6 (GeoMIP6). Under a high-emission scenario (SSP585), two SRM approaches are tested: injecting sulfur dioxide
(G6sulfur) into the stratosphere and reducing the solar constant (G6solar) to maintain radiative forcing at the level of a moderate-emission
scenario (SSP245). Bilinear interpolation and linear scaling were used to downscale and bias-correct daily precipitation data before calcu-
lating precipitation extreme indices, respectively. The results show that G6sulfur causes more regional variation in annual total and mean wet day
precipitation, the average daily precipitation on days with 1 mm rainfall, compared to G6solar. In areas like central Borneo, northern mainland
Southeast Asia, and eastern Indonesia, the annual maximum 1-d precipitation per year is projected to increase by 30%e50% under SSP585
relative to the historical 1995e2014 baseline period but this rise could be reduced to around 20% by SSP245, G6sulfur, or G6solar. G6sulfur has
less influence on continuous wet and dry spells than G6solar, yielding results closer to SSP585. Both SRM strategies lower the projected increase
in heavy precipitation days, except in areas like East Coast Peninsular Malaysia, Nusantara Indonesia, and East Timor. In conclusion, SRM may
effectively mitigate increases in extreme precipitation events in most of Southeast Asia, but G6solar provides a more consistent reduction, while
G6sulfur shows more complex spatial responses.
