Rising compound heatwave exposure in India: insights from CMIP6 climate model projections

Abstract This study analyses the variability of daytime-only, nighttime-only, and compound heat waves (HWs) and their impact on population exposure across India using shared socioeconomic pathways (SSPs) scenarios (SSP126, SSP245, SSP370, and SSP585) from the Coupled Model Intercomparison Project Phase 6 experiment. The research questions addressed are: (1) what effects might compound heatwaves have under climate change scenarios? (2) How are compound heatwaves expected to impact the population in the future? The outcomes indicate that the compound HWs may increase by 4.6 events annually in Northwest India (NWI) under the SSP585 scenario. In contrast, daytime-only HWs are expected to decline after 2060, except in the Himalayan region, possibly due to changes in monsoon patterns and increased evaporative cooling. It is anticipated that nighttime-only heatwaves will uniformly increase across all regions and scenarios, with the most substantial rises observed in the Central Northeast India (CNI) and NWI. Under the SSP370 scenario during 2061–2100, the population exposure to compound heatwaves and nighttime-only heatwaves is projected to increase substantially across all regions. Specifically, exposure to compound heatwaves is anticipated to exceed historical levels by more than 30 times in most regions. Both the CNI and NWI regions show the highest rise in compound and nighttime-only heatwave extremes. The outcomes provide a substantial scientific foundation for policymakers to inform and enhance heat action plans at the national, state, and local levels.