A recurrent motif of the climate scam is that the melting of glaciers in certain regions of the world will shortly cut off the water supply of otherwise dry downstream areas that draw their water supplies from the runoff of the glaciers.
The most famous example of this motif appeared in the IPCC's Fourth Assessment Report that came out in 2007. Here is the section of that Report relating to the Himalayan Glaciers. Excerpt:
Himalayan glaciers cover about three million hectares or 17% of the mountain area as compared to 2.2% in the Swiss Alps. They form the largest body of ice outside the polar caps and are the source of water for the innumerable rivers that flow across the Indo-Gangetic plains. Himalayan glacial snowfields store about 12,000 km3 of freshwater. About 15,000 Himalayan glaciers form a unique reservoir which supports perennial rivers such as the Indus, Ganga and Brahmaputra which, in turn, are the lifeline of millions of people in South Asian countries (Pakistan, Nepal, Bhutan, India and Bangladesh). . . . Glaciers in the Himalaya are receding faster than in any other part of the world (see Table 10.9) 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.
Got that? The Himalayan glaciers are a "lifeline" for well over a billion people! Without the glaciers to supply the water, the billion people are toast!
When I first read this, I thought it was completely ridiculous. Kindly think about this for one minute. The runoff from the glaciers in any given year is equal to whatever precipitation falls on them plus any net melting. Suppose there is no net melting and the glaciers are perfectly stable at their current size. Then the amount that runs off from the glaciers in a year is exactly equal to the amount added by new precipitation. Now suppose that the glaciers have completely melted away and the temperature has gotten so warm that no snow and ice any longer accumulate; all precipitation runs off within the year. Then the amount that runs off from the previously-glaciated area in a year is exactly equal to the amount added by new precipitation. So stable glaciers and no glaciers lead to exactly the same result: runoff equal to precipitation. Then why is the melting of the glaciers a problem for water supply in downstream areas? It never made any sense, and it still doesn't.
But it turned out that the IPCC Himalayan glacier story of 2007 fell apart for an entirely different reason. In early 2010, various independent researchers did some checking on the IPCC claim, and found both the claim and its source to be highly dubious. The actual melt rate of the Himalayan glaciers did not remotely support the claim that they would be gone, or even significantly diminished, by 2035. The 2035 prediction proved to be based on a non-peer reviewed WWF pamphlet from 2005. Here is a report from early 2010 from climateaudit blogger Steve McIntyre on how the IPCC story fell apart. Similar reports appeared at the time on other blogs, including Watts Up With That here. But as far as I can find, nobody questioned the underlying premise that it would make any difference to the water supply of downstream areas whether the glaciers were there or not.
The disintegration of the IPCC's 2007 melting glacier story caused the organization a good deal of embarrassment, and led to calls for the resignation of its then-head, Rajendra Pachauri. But the way in which the glacier melting scare had imploded left it open for the IPCC to come back in its next big assessment with another claim that melting glaciers were somehow going to leave masses of people without drinking water. The IPCC's Fifth Assessment Report came out in 2013. Sure enough, Mr. Pachauri was still around, and still peddling ridiculous stories that melting glaciers were going to leave the masses waterless. Here is an article from the Financial Times from September 2013, reporting on an interview with Mr. Pachauri at the time of the release of the IPCC's Fifth Assessment Report. Excerpt:
The glaciers of the Himalayas are melting so fast they will affect the water supplies of a population twice that of the US within 22 years, the head of the world’s leading authority on climate change has warned. . . . [T]he UN’s Intergovernmental Panel on Climate Change, . . . this week starts releasing its first extensive report in six years on how the global climate is changing. . . . This is the panel’s first big study since it was mired in controversy four years ago over a mistaken suggestion in its last assessment in 2007 that the Himalayan glaciers could disappear as early as 2035, a date it admitted was “poorly substantiated”. . . . While the glaciers may not vanish by 2035, [Pachauri] added, the pace at which they are melting is bound to affect vast numbers of people depending on them for water. “Even before 2035 it’s going to start showing up in terms of changes in water flows, which affect, as we had estimated, 500m people in south Asia and 250m people in China,” he said.
Needless to say, the FT reporter nowhere questions Mr. Pachauri as to whether his premise makes any sense whatsoever.
And finally, I bring up this history today because the melting glaciers scare is back, this time in an article in Nature Geoscience published Monday August 17. The next day the Wall Street Journal covered the story, in a piece titled "Asian Glaciers Melting Faster." This time it's the Tien Shan mountains of Central Asia, rather than the Himalayas:
The glaciers of Central Asia’s Tien Shan mountain range have lost a quarter of their ice mass over the past five decades, largely because of increased melting linked to a rise in summer temperatures, according to new research.
So why again is this a problem?
Both glacial melting and snow are vital sources of water for people living in semiarid parts of Kazakhstan, Kyrgyzstan, Uzbekistan, Turkmenistan and China. The worry is that continual glacial shrinkage could affect the water cycle and reduce the water supply in coming decades.
Now I don't know whether the glaciers in the Tien Shan mountains -- or for that matter the Himalayas -- are actually experiencing net melting at all, let alone rapidly disappearing. What I do know is that if these glaciers completely disappeared tomorrow, then the annual runoff going forward would be exactly the same as it would be if the glaciers were totally stable at today's size, namely that annual runoff would be equal to annual precipitation in both cases.