Global patterns of rain-on-snow and its impacts on runoff from past to future projections

Global warming has induced rain-on-snow (ROS) in cold regions leading to significant consequences on ecosystems and socioeconomic development. However, a global analysis of ROS under historical conditions and future projections following different emissions scenarios, essential for management strategies, is currently lacking. Here, we examine ROS changes and their impacts on the water available for runoff, analyzing historical conditions since 1950 and projecting future trends under SSP245 and SSP585 until 2100. By the end of the century, ROS will predominantly occur in high-latitude and altitude regions such as High Mountain Asia, the Alps, Northern Eurasia, and America with rates up to three times higher than those of the historical conditions. Nonetheless, the increasing rainfall will reduce by more than half the contribution of ROS to the water available for runoff despite its rise. Although regions like the Western United States have historically experienced significant ROS, warming will diminish ROS impacts as they become twice lower due to decreasing snowpack and intensified rainfall.