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Snowfall is a critical part of the hydrological system in high-altitude regions and strongly impacted by climate change. This study uses a threshold temperature method to estimate spatial and temporal variations of snowfall at 71 stations across the Tibetan Plateau from 1960 to 2014. Regional air temperature and precipitation have increased by 0.039 degrees C/yr, and 1.43 mm/yr, respectively. While warming rates have been fairly uniform across the plateau, spatial variations in snowfall trends are large, with decreases in the eastern and northeastern areas but increases at higher elevations in the center and west. Region-wide snowfall increased during 1961-1990 and 1971-2000 but decreased in 1981-2010 and 1991-2014. Wintertime snowfall has increased, but summer snowfall has decreased. These divergent trends can be explained because maximum snowfall is recorded at temperatures between 1 and 2 degrees C. Above/below this threshold snowfall usually decreases/increases with increased warming. Although maximum snowfall temperature is a key factor to understand future snowfall changes, concurrent influences such as changing moisture sources and atmospheric circulation patterns require further research.

Plain Language Summary The Tibetan Plateau is warming as a result of climate change. This is decreasing the amount of snow and ice in general. However, the biggest snowfalls occur when the temperatures are near freezing because warmer air can hold more moisture. We examine the trends in snowfall amounts using 71 stations for the last 45-50 similar to years. Early in the period the snow tended to increase, but since 1981 there has been a rapid decline in snowfall over most of the plateau, especially in the east and at moderate elevations around 2000 similar to m above sea-level. Above 3000 similar to m, however, most areas have shown an increase in snowfall. Even though the snowline is therefore moving up the mountain, at the highest elevations (where it is still cold and below freezing) there is still plenty of snowfall, at least over the recent past. This is because where it is very cold increasing temperatures can bring more snow. Where it is already around freezing increasing temperatures will mean snow will change to rain and there will be a rapid decrease. This also means that there is a difference between the seasons with winter showing more snowfall, in general, and summer and autumn much less.