London, June 11 (ANI): Global warming will not shrink the Himalayan glaciers that feed Asia's five largest rivers by 2035, as was previously believed, according to the most detailed analysis yet of how climate change will affect key Asian glaciers.
In fact, only the glaciers that melt into the Ganges are shrinking, concluded the study.he Intergovernmental Panel on Climate Change's most recent report had previously predicted dire restrictions on water supplies in Asia.
But, the new study was aimed to determine how rising carbon dioxide levels will affect Asia's "water towers" - the glaciers whose meltwater supplies drinking and irrigation water to 1.4 billion people.
And although the glaciers are safe for now, the study warns of drought to come-the five rivers will be able to water crops for almost 60 million fewer mouths by 2050.
Walter Immerzeel of Utrecht University in the Netherlands used data from a pair of satellites known as GRACE to estimate changes in the thickness of the glaciers that supply the Indus, Brahmaputra, Ganges, Yangtze and Yellow rivers between 2001 and 2007.
He found that only the 100-metre-thick glaciers that feed the Ganges are thinning, at a rate of 22 centimetres per year.
The glaciers that sit at the head of the Indus grew at a rate of 19 centimetres per year on average, while those that melt into the other rivers in the study were unchanged.
"It is unlikely that the Himalayan glaciers will have disappeared completely by 2035, as the IPCC's latest report claimed. The real date is further off," New Scientist quoted Immerzeel as saying.
In a controversial statement that was debunked earlier this year, the IPCC's 2007 Fourth Assessment Report found that "glaciers in the Himalaya are receding faster than in any other part of the world and, if the present rate continues, the likelihood of them disappearing by the year 2035 and perhaps sooner is very high if the Earth keeps warming at the current rate".
"Immerzeel's study is a very useful first attempt in setting the numbers to a right order of magnitude," said Georg Kaser at the Institute for Geography in Innsbruck, Austria.
Until now, it has been unclear how much Asia's rivers rely on melting glaciers.
Immerzeel fed his GRACE data on ice cover, as well as temperature and rainfall data gathered between 2001 and 2007, into a standard model of river flow.
The model shows that the Indus and the Brahmaputra rely most on glaciers-meltwater accounts for 60 per cent of water carried by the Indus and 20 per cent of that in the Brahmaputra, but less than 10 per cent of the Ganges, Yangtze and Yellow rivers comes from melted ice. Rainfall makes up the rest.
The results would suggest that the Indus and Brahmaputra will be hardest hit by climate change - but taking into account changes in rainfall patterns with climate change causes a different pattern to emerge, said Immerzeel.
To make up for this, he fed temperature, rainfall and snow projections into his model.
He found that by 2050, the upstream flow of the Brahmaputra and Indus could shrink by 19.6 per cent and 8.4 per cent respectively, despite 25 per cent more rain.
The Ganges, Indus and Yangtze could see declines of 17.6, 8.4 and 5.2 per cent respectively.
This means that by 2050, 60 million fewer people - 4.5 per cent of the world's population - will be able to feed themselves using water from the Brahmaputra, Ganges, Yangtze and Indus, which supports the world's largest irrigation system.
The Yellow river is the only winner in a warmer world- with meltwater accounting for just 8 per cent of its flow, and rainfall predicted to rise by 14 per cent, it will be able to feed 3 million extra mouths by 2050. (ANI)