The mean snow-water equivalent in the Northern and Western Tien Shan has remained relatively stable over the past few decades, but several studies have concluded that the glacial systems of the Central Asian mountains are decreasing in size and volume. The number of days of high air temperature (>40 °C) has increased from the 1950s to 2000s. The number of days with low temperatures (below either -15 °C or -20 ®C) has decreased, for example, in Tashkent since the late 1870s.