Contrasting elevation-dependent warming and snowfall changes in the Karakoram and Central Himalaya

Raj Pritam Gupta , Pankaj Kumar 

High Mountain Asia shows strong regional differences in climate and glacier change, yet how future warming and precipitation responses vary with elevation remains unclear. Here, we examine elevation-dependent changes in near-surface temperature, snowfall fraction, snowfall amount and rain–snow transition elevations across glacier-containing grid cells of the Karakoram–Himalaya. We analyse a future simulation with the dynamically coupled regional glacier–climate model REMOglacier under RCP4.5, comparing 2021–2050 with 1980–2005 across 500-m elevation bands, with emphasis on the Karakoram and Central Himalaya. REMOglacier reproduces the main precipitation seasonality and captures part of the interannual variability in the reference datasets, while annual spatial-mean 2-m temperature agrees more closely with ERA5 than standalone REMO. During June–September, warming increases with elevation in the Karakoram (+0.23 ± 0.04 °C km-1) but decreases slightly with elevation in the Central Himalaya (−0.05 ± 0.02 °C km-1). Snowfall fraction decreases by 2.4% and 21.5%, respectively; however, snowfall increases across all analysed Karakoram elevations (+1.3% to +41.7%) but decreases across the Central Himalaya (−11.0% to −32.4%). Freezing-level and rain–snow transition elevations generally shift upward, with the Central Himalayan summer transition frequently moving above the modelled terrain. Random Forest diagnostics identify downward longwave radiation as the variable most strongly associated with the contrasting summer warming gradients. These results show that future mountain snowfall depends on the vertical structure of warming, precipitation phase and moisture supply, rather than warming magnitude alone.