Mountains of Central Asia in the warmer world

Abstract:

This paper investigates the observed and projected changes in temperature and precipitation in the mountains of Central Asia and attempts to quantify the impacts on runoff supporting irrigated farming in the foothills and adjacent plains. Since the mid-20^th Century, mountains of Central Asia experienced significant climatic warming. Although there arefew continuous long-term records from high-altitude meteorological stations, those available indicate that climate has been warming at a rate of 0.02-0.03^oC a^-1 in summer when impacts of climatic warming are strongest as they affect melt of seasonal snow pack and glacier ice, availability of liquid precipitation and, therefore, runoff. Throughout the year, runoff generated by snow and glacier melt in the mountains, accounts for about 10-15% of the total in the foothills. However, in the summer growing season, it accounts for about 50% of the total and is crucial for irrigation. Assessments of glacier changes have shown that glaciers have lost between 5% and 40% of their area between the mid-20^th Century and early 21^st Century and in the areas generating runoff supporting agriculture, the recession was stronger at 15-40%. The share of glacier runoff in these regions, e.g. Zailiyskiy and Djungarsky Alatau, dropped from 60% and 40% of the summer total in 1955-1974 to 40% and 20% between 1955 and 2008 respectively in line with reduction of glacier area. However, quantification of the impacts of glacier recession is complicated by changes in snow accumulation, dates of snow melt and availability of liquid precipitation because it is melting of seasonal snow pack and liquid precipitation in summer that dominates runoff from the mountains accounting for about 70% of its total. In this paper, we use both observational data and regional climate model PRECIS to evaluate the recent past and future climatic changes and their impacts.