The current status, recent and potential future changes of glacier systems and seasonal snow cover in the Indus, Ganges, Brahmaputra, Amu Darya, Syr Darya and Mekong river basins are for the first time systematically analyzed at the basin scale. The baseline (1961-1990) status of each basin’s glacier system is evaluated using a comprehensive meta-database for the 48,607 glaciers, which represents a new data product in its own right compiled specifically for this study. The data gaps in existing glacier inventories are identified and filled with expert estimates. It is illustrated that structural diversity of a glacier system determines how it responds to climate change. Recent changes in glacier systems are characterised using estimated annual rates of areal reduction and ice loss derived from data published by the World Glacier Monitoring Service (WGMS) and a compilation of sources based on remote sensing extending from 1960s to 2000s.

Glacier sensitivity to climate change (CC) is examined in terms of the critical warming signal, which would be required for the complete disappearance of glaciers in a basin under the assumption of 3% changes in precipitation per degree of global air temperature rise. It is shown that Syr Darya and Mekong basins are likely to become almost glacier-free under the projected warming temperature of 4-5 degrees celcius by the end of the twenty-first century. In Indus, Ganges, Brahmaputra and Amu Darya river basins, glaciers belonging to the large and medium size classes are expected to survive the warming of 4-5 degrees celcius, with total basin ice reserves reduced to 20-50% of the baseline 1961-1990.