Detection and attribution of extreme precipitation changes over India

Abstract Extreme precipitation events are intensifying across India, posing significant risks to its population and economy. While observations indicate widespread changes in rainfall extremes across the country, the role of different climate drivers remains poorly quantified, particularly at regional scales. This study provides the first comprehensive detection and attribution (D&A) of changes in extreme precipitation events across India’s homogeneous monsoon regions. Using the regularised optimal fingerprinting D&A framework, gridded daily rainfall observations from India Meteorological Department, and a 14-member multi-model ensemble from the Coupled Model Intercomparison Project Phase 6, we disentangle the contributions of greenhouse gases (GHGs), anthropogenic aerosols, and natural forcings to the observed changes in extreme precipitation. Observed extreme indices—Rx1day, Rx5day, R95p and R99p—were examined over India and found to exhibit contrasting trends across the homogeneous monsoon zones, with notable increases in the core monsoon region (West central (WC)), a weaker trend over the southern peninsula, and a marked decline over Northeast (NE) India in recent decades. D&A analysis was carried out for Annual and monsoon season extreme indices over homogeneous monsoon zones using decadal-average time series, and provides robust evidence that human activities have already altered India’s rainfall extremes with anthropogenic fingerprints detected across most regions and indices. GHG forcing emerges as the dominant driver of intensifying precipitation extremes, most consistently detected and attributed in the WC and Central NE regions, which make up the core monsoon zone, while anthropogenic aerosols exert a substantial counteracting influence, particularly since the mid-20th century. These results are consistent with previous findings of their effects on mean monsoon precipitation across global monsoon regions, and particularly the South Asian monsoon. Our findings suggest that the apparent absence of a strong increase in extreme precipitation does not indicate weak climate sensitivity, but highlight the competing effects of GHG-induced intensification and aerosol-driven suppression, with important implications for future risk as aerosol emissions decline.