Observational uncertainties in snow mass have made the detection and attribution of human-forced snow losses elusive. This study shows that human-caused warming has caused declines in Northern Hemisphere-scale March snowpack over 1981–2020. Using an ensemble of snowpack reconstructions, robust snow trends were identified in 82 out of 169 major Northern Hemisphere river basins, 31 of which are confidently attributed to human influence. A highly nonlinear temperature sensitivity of snowpack was revealed, where snow becomes more sensitive to warming above -8°C. This nonlinearity explains the lack of widespread snow loss and augurs sharper declines and water security risks in populous basins. Human-forced snow losses and their water consequences are attributable and will accelerate with near-term warming, posing risks to water resources.

Alexander R. Gottlieb, Justin S. Mankin