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Glacier estimate is on thin ice

IPCC may modify its Himalayan melting forecasts.

When might the majestic Himalaya glaciers disappear for good? Credit: G. Wiltsie/National Geographic

Hundreds of millions of people rely on water from the Himalayas' mighty glaciers, which experts agree are shrinking as a result of rising global temperatures. But a claim that all of the ice could be gone by 2035 — enshrined in the most recent report from the Intergovernmental Panel on Climate Change (IPCC) — has come under fire from, among others, a coordinating lead author of the IPCC chapter that uses the questionable figure.

The dispute highlights the fact that the panel sometimes relies on 'grey' or unrefereed literature. IPCC chairman Rajendra Pachauri says that the panel is investigating whether its report needs to be modified — which, if it were to happen, would be highly unusual.

A hasty retreat

At issue is a statement in the portion of the 2007 IPCC report1 compiled by its working group on impacts, adaptation and vulnerability. It says 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". The source cited was a 2005 overview from the conservation group WWF's Nepal Program2, which, in turn, refers to non-refereed findings by glaciologist Syed Iqbal Hasnain, a senior fellow at The Energy and Resources Institute in New Delhi.

Hasnain recently told the magazine New Scientist that his initial conclusions, contained in a 1999 report by the Working Group on Himalayan Glaciology of the International Commission on Snow and Ice, were "speculative". Nature could not reach him for comment.

Satellite observations and in situ measurements do suggest that many of the more than 45,000 glaciers in the Himalayan and Tibetan region are losing mass. But given the observed rate of decline so far, many experts doubt that even small glaciers will melt completely before the end of the century.

"The IPCC's statement is wrong and misleading," says Andreas Schild, director-general of the International Centre for Integrated Mountain Development in Kathmandu, Nepal. "It was pretty clear early on that this was an error awaiting correction," adds Michael Zemp, a glaciologist with the World Glacier Monitoring Service in Zurich, Switzerland.

The next IPCC report should accurately characterize the risks of water insecurity and glacial lake outburst flooding. ,

The loudest charges, however, have come from Murari Lal, director of the Climate, Energy and Sustainable Development Analysis Centre in Ghaziabad, who served as coordinating lead author for the Asia chapter in the working group report. He says that his team followed proper IPCC procedures for using non-refereed studies, which require chapter teams to review the quality of such sources before citing results. The WWF report seemed credible, he says, but he admits that the team should have looked more carefully at the secondary sources to which it refers.

Even so, Lal argues that Hasnain, rather than the IPCC reviewers, is to blame, for coming up with and continuing to talk about a speculative date. "The findings would have been of major significance to the whole region," Lal says.

IPCC representatives say that the bottom line of the Asia chapter remains the same. "There is no scientific doubt on the rapid melting of the glaciers in the Himalayas," says Pachauri, although they are very unlikely to disappear during the next few decades.

The section also includes other, smaller errors that are drawing less attention. The chapter attributes to the WWF report, for instance, a related but less drastic estimate that the total area of the Himalayan glaciers could shrink from the present 500,000 square kilometres to 100,000 square kilometres by 2035. The WWF publication gives no such number.

Christopher Field, who is overseeing the impacts working group for the next full IPCC assessment report, says that the team will carefully consider the "extremely important" future of the Himalayan glaciers. By 2014, when the next working group report is due, it should be possible to assess Himalayan glacier retreat "in a way that accurately characterizes the risks of water insecurity and glacial lake outburst flooding", says Field, of the Carnegie Institution for Science in Stanford, California.

The IPCC will continue to use a combination of peer-reviewed studies and carefully selected grey literature for its next full report. But Field says the incident shows that the IPCC has an extra responsibility to thoroughly assess the quality of the underlying work.

Meanwhile, lingering uncertainty over glacier retreat has prompted India and other countries to put more emphasis on glaciological research. India's environment minister, Jairam Ramesh, has called the shrinking Himalayan ice a matter of national security — even though a report he commissioned last year found little evidence of drastic retreat due to climate change3. Pachauri has challenged that finding as "unsubstantiated".

Settling the issue of glacier retreat gained urgency last year with the publication of several papers4,5 based on data from the GRACE gravity-sensing satellites, which highlighted the problem of groundwater depletion in India. As they shrink, the glaciers are expected to add melt water to Himalayan rivers. But if the glaciers disappear altogether, run-off to the headwaters of ten major rivers, including the Indus and the Ganges, will drop markedly.

Still, it is unclear whether or when this may happen. Himalayan glaciers, says glaciologist Michael Bishop of the University of Nebraska in Omaha, behave very differently in different places. "Sweeping conclusions," he says, "just don't hold water."


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  2. WWF Nepal Program An Overview of Glaciers, Glacier Retreat, and Subsequent Impacts in Nepal, India and China (2005); available at

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Schiermeier, Q. Glacier estimate is on thin ice. Nature 463, 276 (2010).

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