Unprecedented ongoing shrinkage of European winters revealed by a six-century snow cover reconstruction

Snow cover shapes climate, ecosystems, water resources, and socio-economic activities, yet its long-term European variability remains poorly known due to short and fragmented observational records. Here, we present a continent-wide, 600-year reconstruction of monthly European snow cover extent at 2° spatial resolution, derived by combining reanalysis data through a machine learning technique. The record reveals an unprecedented seasonal reorganization at monthly scale since around 1850: December–January snow cover extent shrinks by up to 20%, while April–May snow cover extent declines by up to 30%, especially at latitudes higher than 50°N. February and March are comparatively stable. While snow cover exhibits the strongest sensitivity to rising temperatures, reduced precipitation still leaves a noticeable imprint, particularly in the Mediterranean basins and Scandinavia. These changes place recent loss of snow cover in a multi-centennial context and underline the urgent need to assess impacts on sensitive ecosystems, water resources, and socio-economic sectors. Our dataset provides a crucial baseline for adaptation planning and benchmarking climate model simulations. European snow-cover extent has undergone an unprecedented seasonal reorganization since around 1850, with monthly declines of up to 30%, according to a 600-year reconstruction combining reanalysis data and machine learning method.