Indian heatwaves in a future climate with varying hazard thresholds

Abstract

India has experienced remarkable changes in temperature extremes in recent decades due to rapid global warming leading to extreme heat events with disastrous societal impacts. In response to continuing global warming, this study investigates summertime (March–June) heatwave characteristics over India in the present and future climate. During 1951–2020, India Meteorological Department observational data show rising trends in heatwave characteristics such as frequency, intensity, duration, and season length, mainly over India’s northwest, central, and south peninsular regions. Further, the present study explores the changes in future heatwave characteristics using the state-of-the-art statistically downscaled bias-corrected climate models data from Coupled Model Intercomparison Project Phase 6 (CMIP6) of the Shared Socioeconomic Pathway scenario. This study uses varying hazard thresholds, namely fixed (time-invariant historical climatological threshold) and decadal moving thresholds (time-varying future climatological threshold), to define heatwaves and examine the future changes in heatwave characteristics over India. Results show a significant increase in mean summertime heatwaves defined using fixed thresholds in terms of their frequency, duration, number, amplitude, cumulative magnitude, and season length in the near future (NF) (2025–2054) and the far future (FF) (2065–2094) compared to the baseline period (1985–2014) over much of India, with the most substantial increases seen in the FF. However, heatwaves defined using the decadal moving thresholds show no significant changes in their characteristics during the NF but a substantial change in the FF over many parts of India. This work is the first attempt to use bias-corrected CMIP6 models data to project heatwave characteristics utilising the concept of the varying hazard thresholds across India. Overall, this study provides a comprehensive assessment of climate change’s impact on Indian heatwaves, which can help in planning better adaptation and mitigation strategies.

Keywords

• India
• heatwaves
• future projections
• CMIP6