Sensitivity of projected Afro-Asian monsoon precipitation to solar radiation management

We assess the impact of two solar radiation management (SRM) approaches, stratospheric aerosol injection (G6Sulfur) and solar radiation dimming (G6Solar), on SSP5-8.5-projected changes in summer monsoon precipitation across Afro-Asia for the mid-future (2040-2069) and far-future (2070-2099) periods, using Geoengineering Model Intercomparison Project (GeoMIP) experiments under CMIP6. Relative to SSP5-8.5, both SRM methods increase consecutive wet days (CWD), largely due to an enhanced increase in light-to-moderate precipitation rates (0.1-10 mm/day). Heavy precipitation (>10 mm/day) decreases across all three monsoon regions, leading to widespread reductions in mean precipitation, precipitation variability, and very heavy precipitation extremes (RX5day, R95pTOT), with far-future decreases nearly twice as large as those in the mid-future. Moisture budget diagnostics show that SRM-induced reductions in mean precipitation are driven primarily by a weakened vertical thermodynamic term, linked to reduced specific humidity resulting from SRM-induced cooling. Furthermore, SRM modifies projected precipitation seasonality. In the mid-future, precipitation onset is delayed by ∼3 days over most regions, while heterogeneous shifts in cessation result in little net change in season length. By contrast, in the far-future, earlier onset and later cessation lead to an extension of the precipitation season by up to ∼5 days. Urban and rural population exposure to wet and dry extremes decreases substantially under both SRM methods, except over South Asia and West Africa, where exposure to CWD increases. Overall, both G6Solar and G6Sulfur show potential to reduce the SSP5-8.5-induced intensification of Afro-Asian monsoon precipitation, while producing notable spatial and temporal heterogeneity in the monsoon response.