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How much global warming can the world’s glaciers take?

Writer: Time:2013-08-27
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The huge glaciers in the Himalayan mountain system are often called the “water towers of Asia”. These immense reservoirs feed the rivers that feed the world’s most populated continent.
But now there is a growing concern that melting of both glaciers and seasonal snow, due to climate change, will have severe effects on the food security of millions of people. But while the media is giving this subject a lot of attention, within the scientific community this prognosis remains controversial. There is not even a consensus on how much water glaciers and snow actually contribute to river flow.
Now, two new research reports from the International Water Management Institute (IWMI) aim to address this knowledge gap. The reports assess water storage properties and the hydrological role of glacier systems and seasonal snow coverage in six major Asian basins: namely Indus, Ganges, Brahmaputra, Mekong, Amu Darya and Syr Darya. The analysis is based on the data on the baseline (1961-1990) and current (2000-2010) states and the likely development of glaciers and snow under a changing climate.
IWMI’s Anna Deinhard spoke to the authors of the study, Oxana Savoskul and Vladimir Smakhtin:
How will climate change affect the river basins of Asia?
Over the last few decades glaciers and seasonal snow, the principal melt water resources for Asia’s river basins have been consistently losing their water storage capacity. The total reduction of glacier area from the 1960s to 2000s is within the 14-28% range, and ice volume loss is within the 11-40% range. The reduction of seasonal snow cover area over the same period is up to 5-15%, while the maximum water storage capacity of snow decreased by 9-27% depending on the basin.
Of the basins studied only the Syr Darya and Mekong Basins are likely to become glacier-free if the temperature by the end of the century increases by 4-5 oC. In the Indus, Ganges, Brahmaputra and Amu Darya basins, large and medium glaciers will survive the same warming, but total basin ice reserves may reduce by as much as three quarters. Seasonal snow is likely to play a more significant role in the regional water cycle only in the Indus and Amu Darya Basins.
Overall the amount of water in the basins will not change significantly due to the reduction of glacier and snow covered areas. Future changes in glaciers and seasonal snow due to climate change will mainly affect the seasonality of river flow and only marginally impact total amount of water in the basins.