Emerging global risks of extreme rain-on-snow events under climate warming

Global warming is profoundly altering precipitation regimes and snow cover dynamics, thereby reshaping both the frequency and intensity of rain-on-snow (ROS) events worldwide. Yet the future global risks and driving mechanisms of ROS events under climate warming scenarios remain insufficiently understood. Here, using ERA5-Land and a CMIP6 multi-model ensemble, we establish a global ROS event database covering the period 1950–2100 and characterize its spatiotemporal variability, driving mechanisms, and high-risk regions. We find that, relative to the historical period (1950–2023), future ROS events (2024–2100) will exhibit a contraction in spatial extent but an increase in occurrence frequency, with the most pronounced intensification occurring in mid- to high-elevation regions across the mid- to high-latitude Northern Hemisphere. A conditional probability analysis further reveals a synergistic mechanism among temperature, precipitation, and snow depth: when temperatures approach the 0 °C threshold, rainfall intensifies, and persistent snow cover is present, the likelihood of ROS events increases markedly. The projected rise in ROS events across mid- to high-latitude mountainous regions designates the Tibetan Plateau, the margins of Greenland, eastern and western North America, eastern Asia, and eastern Europe as global hotspots of extreme ROS events risk. These events peak in April and exhibit stronger intensities and higher recurrence under warmer climate scenarios. This study provides new insights into the future evolution of global ROS events in the context of ongoing climate warming.