High-impact and low-likelihood compound hot and dry extremes in India

Compound hot and dry extremes (CHDEs) in India have lasting impacts on agriculture, water resources, and energy sectors, which are likely to increase under the warming climate. However, the occurrence and implications of high-impact and low-likelihood (HILL) CHDEs under the observed and projected future climate remain underexplored. We identified that India witnessed HILL-CHDEs in 1987 and 2015 during the summer monsoon (June-September) and non-monsoon (October-May) seasons, respectively, between 1979 and 2024. The two CHDEs during the observed climate had high impacts, as these severely affected agriculture and water availability and covered about half of the country. Using 100 ensemble simulations from the Community Earth System Model (CESM2-LENS2), we find that HILL-CHDEs are projected to rise significantly in frequency, duration, spatial extent, and intensity, especially during the summer monsoon. This increase is primarily driven by climate warming and further intensified by El Niño events. The growing occurrence of HILL-CHDEs may severely impact food production, water supplies, groundwater use, and hydropower generation in the future.