Intensifying Heatwave Extremes in the Northwest Himalayas, India: Trends, Teleconnections, Causal Drivers, and CMIP6 Projections

Global temperatures have been rising at an unprecedented rate, leading to recurrent heatwaves with far‐reaching environmental effects. The Northwest Himalayas (NWH) of India, characterised by extensive snow cover and glaciers, are particularly sensitive to temperature increases due to amplifying cryospheric and hydrological feedbacks. This study investigates spatio‐temporal variations and long‐term trends of heatwave indices and temperature extremes across the NWH and its three major basins from 1980 to 2022. Using spatial correlation analysis and the PCMCI+ causal discovery framework, we examine relationships between hot days (TX90p) and key atmospheric‐oceanic drivers, including geopotential height, outgoing longwave radiation (OLR), sea surface temperature (SST), land surface variables, and major teleconnection indices. Additionally, future projections of temperature extremes are derived from 13 bias‐corrected CMIP6 models under four SSP scenarios. Our results reveal statistically significant increasing trends in temperature extremes, particularly over higher‐elevation regions, with the Qura‐Qush basin exhibiting the strongest warming. Interdecadal analysis indicates that 2013–2022 experienced the highest heatwave frequency, number, and duration across all basins. Spatial correlation analysis revealed strong associations between TX90p and upper‐atmospheric circulation at both 200 and 500 hPa, while PCMCI+ causal analysis identified snow cover as the strongest direct driver through snow‐albedo feedback, followed by geopotential height at 200 hPa. Although no direct ENSO‐TX90p linkage was detected, indirect pathways were identified through ocean–atmosphere coupling, particularly via SST‐driven modulation of upper‐tropospheric circulation. Future projections indicate continued intensification under all SSP scenarios, with divergence becoming pronounced by mid‐century. By end‐century, warm nights (TN90p) are projected to reach 31.47% under SSP1‐2.6 to 75.72% under SSP5‐8.5, while hot days (TX90p) range from 29.27% to 70.22%. Warm nights consistently show stronger trends than hot days across all scenarios. These findings highlight the critical role of snow‐albedo feedback and upper‐atmospheric circulation in modulating heatwave occurrences, underscoring the region's growing susceptibility to extreme events.