Friday, January 22, 2010

Climate and Himalayan Glaciers

The climate deniers are gloating again. Glaciergate! Glaciergate! they proclaim. Their outrage is directed against a single sentence in the 1000 page second report IPCC Fourth Assessment of 2007 which states that Himalayan glaciers could disappear by 2035. The claim is attributed to a 2005 WWF report - not a scientific research report. In mid December 2009 scientists were already questioning the inclusion of the statement.

The actual entry all the halabaloo is about states:

"Glaciers in the Himalaya are receding faster than in any other part of the world ... the likelihood of them disappearing by the year 2035 and perhaps sooner is very high if the Earth keeps warming at the current rate. Its total area will likely shrink from the present 500,000 to 100,000 km2by the year 2035 (WWF, 2005)."

Glaciologists in this mid December media background statement lead by Jeffrey S. Kargel from the University of Arizona - Satellite-era glacier changes in High Asia - have labelled it as a bad error. "It was a really bad paragraph, and poses a legitimate question about how to improve IPCC's review process. It was not a conspiracy. The error does not compromise the IPCC Fourth Assessment, which for the most part was well reviewed and is highly accurate."

Glaciers in the Himalayan region are complex, with many showing signs of retreat, some stagnant and a few showing signs of advancing. The presentation says:

"Many glaciers are rapidly retreating and in eastern Himalaya many glaciers will be much diminished in the next few decades, regardless of carbon emissions, aerosol emissions, and global warming trajectory. These glaciers are already out of equilibrium with existing climate due to late 20thCentury emissions. Further emissions increase disequilibrium."
"Some glaciers may undergo periods of comparative stabilization of length or even growth in mass. Long-term overall trends across South Asia indicate glacier retreat. Some may simultaneously retreat at low elevation and thicken at high elevation as more precipitation falls due to (1) increased evaporation of the warming sea, (2) shifting convergence of Indian monsoon and Westerlies, and (3) the Elevated Heat Pump. The EHP might shrink some glaciers, but might grow others in special topographic circum-stances. Influences of deposited soot/dust also appear important in shrinking glaciers."

"Too few observations of recent fluctuations constrain models of such a complex system, but the past 100 years suggests that the next 100 years will involve mainly retreat."


So how did the error occur?

It all started with a report on Himalayan Glaciology by Indian glaciologist Syed Hasnain of Jawaharlal Nehru University in Delhi in January 1999 that was to be presented in July 1999 to the International Commission on Snow and Ice (ICSI). Fred Pearce, a science reporter with New Scientist magazine wrote a story published 5 June 1999 titled Flooded Out. In the story he quotes Hasnain "All the glaciers in the middle Himalayas are retreating," and reports that "Hasnain's four-year study indicates that all the glaciers in the central and eastern Himalayas could disappear by 2035 at their present rate of decline."

According to Fred Pearce in New Scientist, 11 January, 2010 - Debate heats up over IPCC melting glaciers claim - Hasnain "has never repeated the prediction in a peer-reviewed journal. He now says the comment was 'speculative'."

WWF picked up the 1999 New Scientist report and included it in a 2005 report on Himalayan Glaciers.

So should this error in the 2007 IPCC report invalidate the whole report? On the contrary, the report was a conservative statement which in many areas - such as sea level rise and the dynamics of polar ice sheet collapse - has underestimated the changes ocurring.

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