Elevation-dependent climate change in mountain environments

Mountain regions show rapid environmental changes under anthropogenic warming. The rates of these changes are often stratified by elevation, leading to elevation-dependent climate change (EDCC). In this Review, we examine evidence of systematic change in the elevation profiles of air temperature and precipitation (including snow). On a global scale, differences between mountain and lowland trends for temperature, precipitation and snowfall are 0.21 °C century^–1 (enhanced mountain warming), –11.5 mm century^–1 (enhanced mountain drying) and –25.6 mm century^–1 (enhanced mountain snow loss), respectively, for 1980–2020, based on averaging available gridded datasets. Regional analyses sometimes show opposite trend patterns. This EDCC is primarily driven by changes in surface albedo, specific humidity and atmospheric aerosol concentrations. Throughout the twenty-first century, most models predict that enhanced warming in mountain regions will continue (at 0.13 °C century^–1), but precipitation changes are less certain. Superimposed upon these global trends, EDCC patterns can vary substantially between mountain regions. Patterns in the Rockies and the Tibetan Plateau are more consistent with the global mean than other regions. In situ mountain observations are skewed towards low elevations, and understanding of EDCC is biased towards mid-latitudes. Efforts to address this uneven data distribution and to increase the spatial and temporal resolution of models of mountain processes are urgently needed to understand the impacts of EDCC on ecological and hydrological systems.