Tropical hydro-climatic responses to global warming and solar radiation modification in the Kelantan River Basin, Malaysia

Solar radiation modification (SRM) is a potential strategy to rapidly mitigate global warming by reflecting more sunlight into space. However, its impact on tropical hydrological cycles remains underexplored. This study investigates the potential effects of SRM on streamflow in the Kelantan River Basin (KRB) by incorporating climate projections from the Geoengineering Model Intercomparison Project Phase 6 (GeoMIP6) into the Soil and Water Assessment Tool plus (SWAT+) model. Results indicate that UKESM1-0-LL and MPI-ESM1-2-LR exhibit higher uncertainty in representing KRB's climate compared to CNRM-ESM2-1 and IPSL-CM6A-LR. Under SSP5-8.5, maximum and minimum temperatures are projected to increase by up to 3.52 °C by the late 21st century, while SRM scenarios may limit warming to 1.72-2.33 °C, similar to 1.96-2.22 °C under SSP2-4.5. The multi-model ensemble mean projected an inverse V-shaped trend in annual precipitation, with a peak in the mid-21st century before declining, except for G6sulfur, which exhibits a steady decrease. Increases in monthly precipitation from November to January during the 2045-2064 period under all evaluated scenarios may intensify flooding in the KRB. Meanwhile, decreases in streamflow during dry months are projected for the periods 2045-2064 and 2065-2085 under G6sulfur, particularly in the middle and upper basins.