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date: 24 April 2017

Elevation Dependent Climate Change in the Tibetan Plateau

This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Climate Science. Please check back later for the full article.

As the most unique and the highest gigantic plateau on earth, with an average elevation of more than 4,000 meters, the Tibetan Plateau (TP) is sensitive and vulnerable to climatic change, and its climatic tendencies can provide an early alarm for global climate change. Growing evidences suggest that the TP experienced more significant warming than its surrounding areas during the past decades, especially at elevations higher than 4,000 meters. The greater warming at higher elevations than at lower elevations has been widely accepted by scientists, and this interesting phenomenon is called the elevation-dependent climate change, or elevation-dependent warming (EDW).

At the beginning of 21st Century, Chinese scholars noticed that the TP had experienced significant warming since the mid-1950s, especially in winter, and the latest warming period in the TP occurred earlier than enhanced global warming since the 1970s. They also reported that warming rates increased with elevation in the TP and nearby, and the TP was one of the most sensitive areas in response to global climate change. Since then, increasing studies have shed light on the detailed characteristics of EDW in terms of mean and extreme indices, and at different seasons, using more and longer observations from meteorological stations and satellites. For example, the minimum temperature shows more evidence of EDW than the mean and maximum temperatures, and EDW is more significant in winter than in other seasons. The extreme temperature indices also keep increasing trends in the context of the EDW. Despite a global warming hiatus since the turn of the 21st century, the TP exhibits a persistent warming from 2001 to 2012.

Although consensus on the EDW phenomenon has grown, the underlying formation mechanisms are not entirely clear owing to sparse, discontinuous, and incomplete observations of climate change processes. Based on limited observations and model simulations, several factors including the snow-albedo feedback, cloud-radiation effects, water vapor and radiative fluxes, and aerosol forcing have been proposed as responsible for the EDW, all these factors working together to cause greater warming at higher elevations. At present, however, various mechanical explanations for the EDW are derived mainly from theoretical research and lack solid observational evidence. Therefore, a more extensive and multiple perspective climate monitoring system is urgently needed in the high altitude and complex terrain of the TP to comprehensively understand the mechanisms of the EDW.

Elevation-dependent climate change has resulted in a series of environmental consequences, such as vegetation changes, permafrost melting, and glacier shrinkage in the mountainous areas. In particular, the glacier retreat could alter the headwaters on the TP and the hydro-meteorological characteristics of several major rivers in Asia, threatening the water supply for hundreds of millions of people living in adjacent countries. Taking into account the climate models’ projection that the warming trend will continue over the TP in the coming decades, this region’s climate change and the relevant environmental consequences should be highly concerning.