Impacts of solar radiation modification on temperature extremes and heatwaves in Southeast Asia

Solar Radiation Modification (SRM) has been proposed as a rapid solution to mitigate temperature rise, but its effects on regional temperature extremes and heatwaves remain underexplored. Southeast Asia, a region highly vulnerable to climate change due to its unique environmental and socio-economic conditions, necessitates detailed assessments of SRM impacts. This study evaluates the effects of SRM using two scenarios, G6Solar and G6Sulfur, alongside traditional emissions pathways (SSP245 and SSP585). Downscaled and bias-corrected GeoMIP6 datasets are analyzed for selected temperature and heatwave indices across 20 Southeast Asian sub-regions from 2020 to 2099. Under SSP585, annual maximum temperatures (TXx) by 2099 are projected to increase by 4–6 °C relative to the baseline, with heatwave characteristics intensifying substantially. Heatwave duration (HWD) could rise by 40–180 days, while occurrences (HWN) may increase 3–5 times, and intensity (HWA) could escalate by 5–6 °C. In contrast, SRM scenarios effectively moderate these impacts, aligning closer to the moderate SSP245 scenario. Between the two SRM approaches, G6Sulfur proves slightly more effective than G6Solar in reducing temperature extremes particularly in continental regions. Under SRM, heatwave frequency, duration, and intensity are less severe compared to SSP585, though spatial variability in effectiveness is observed and with minimal differences in mainland Southeast Asia. This study presents a comprehensive assessment of SRM's impacts on temperature extremes and heatwaves in Southeast Asia, utilizing a multi-model ensemble across multiple SRM and SSP scenarios. By focusing on a region often underrepresented in SRM research, this work offers critical insights for policymakers considering SRM as a climate mitigation strategy.