Rising Compound Low-Snow High-Temperature Events: Drivers, Ecosystem Responses, and Future Outlook

As global warming intensifies, high-latitude and mid-to-high-elevation watersheds are increasingly experiencing compound low-snow high-temperature events, posing serious challenges to water resources and ecosystem stability. However, the spatiotemporal characteristics of these events and their impacts on vegetation productivity and physiological processes remain insufficiently understood. In this study, drawing on multiple reanalysis datasets and hydrological models, we systematically evaluated the historical and future trajectories of low-snow high-temperature events across the Northern Hemisphere, including their potential lagged effects on ecosystems. By integrating diverse Gross Primary Productivity (GPP) datasets derived from observations, satellite products, and models—and employing an explainable causal machine learning framework—we identified key climatic and plant physiological drivers influencing GPP under these compound conditions. The findings highlight an increasingly frequent and persistent occurrence of low-snow high-temperature events, along with significant effects on vegetation functions, such as water-use efficiency, carbon uptake, and community structural adaptations. Overall, this research not only traces the upward trend of these compound events but also underscores their profound ecological implications, offering valuable insights for advancing global carbon cycle assessments and informing future climate adaptation strategies.