Regional air pollution brightening reverses the greenhouse gases induced warming-elevation relationship

Mountain waters, glaciers, hazards, and biodiversity are vulnerable to the impacts of global warming. Warming is projected to amplify over mountains by global climate models, yet meteorological records do not show a uniform acceleration of warming with elevation. Here we explore warming-elevation relationships using records from 2660 meteorological stations and determine that the vertical gradient of warming rate varies with location. The warming is faster at higher altitudes in Asia and western North America, but the opposite is observed over Central Europe and eastern North America which have received more short-wave radiation (brightening) associated with a decrease of aerosols and clouds since the 1980s. We found that altitudinal differences in air pollution (brightening), with observations showing more short-wave radiation received at low altitudes than at mountains, modulate the warming-elevation relationships. The advance in understanding of the drivers of regional climate change will contribute to the formulation of strategies for climate change mitigation at high elevations.