Rapid regional aerosol reductions drive near future intensification of the South Asian Monsoon 

There is consensus that forcing due to Northern Hemispheric anthropogenic aerosols has played a significant role in the decline of South Asian monsoon precipitation since the mid-20th century. However, the future trajectory of regional aerosol emissions remains highly uncertain, particularly in light of potentially stricter air-quality regulations that could lead to reductions in aerosol loading across South and East Asia. Understanding how such changes may influence the near-term evolution of the monsoon is therefore critical. Here, we investigate the response of the South Asian summer monsoon to regional aerosol reductions using a suite of sensitivity experiments conducted with the IITM Earth System Model (IITM-ESMv2). Our simulations reveal a widespread intensification of monsoon precipitation over South and Southeast Asia following aerosol reductions. This response is driven by the combined effect of increasing greenhouse gas concentrations and declining absorbing aerosols over the subcontinent, which together enhance the land–sea thermal contrast. The strengthened thermal gradient promotes strengthened cross-equatorial low-level flow, leading to enhanced moisture transport and a sustained buildup of moisture across the monsoon region. The thermodynamic and dynamical changes favor widespread increases in precipitation. Our findings suggest that future air-pollution mitigation efforts across South and East Asia may play a critical role in shaping the near-future intensification of the monsoon, with important implications for regional hydroclimate over the coming decades.