Many glaciers, ice caps worldwide in retreat

Date:04/02/2010 URL: http://www.thehindu.com/thehindu/seta/2010/02/04/stories/2010020450051400.htm Back Sci Tech



Many glaciers, ice caps worldwide in retreat

90 per cent of the 612 glaciers across the High Asian region were retreating; this increased to 95 per cent from 1990 to 2005

— Photo: AFP





Core evidence: Ice cores collected in 2006 from the 6050 metre high Naimona’nyi Glacier lack the distinctive nuclear fallout footprints suggesting no net accumulation of ice since at least 1950s. This file picture shows the Khumbu Glacier in the Everest-Khumbu region.

Ice cores drilled from glaciers around the world generally contain elevated levels of beta radioactivity including chlorine-36 and tritium associated with thermonuclear bomb testing in the 1950s and 1960s (Kehrwald, Thompson and others, Geophysical Research Letters, Nov 22, 2008). These researchers found that the ice cores collected in 2006 from the 6050 metre high Naimona’nyi Glacier, in the Himalayas (Tibet), lack the distinctive nuclear fallout footprints suggesting no net accumulation of ice since at least 1950s .

Surprisingly, no one referred to these studies in the recent controversy over the Statement of the Intergovernmental Panel on Climate Change (IPCC) on the Himalayan Glaciers.

Professor Lonnie Thompson a leading glaciologist and a co-author of the paper made similar observations many months earlier (“Missing footprints of A-bomb fallout in Himalayan ice fields,” The Hindu, January 31, 2008).

Responding to my e-mail query, Prof. Thompson wrote that he conducted his research on glaciers across the Tibetan Plateau and on the Tibetan side of the Himalayas.

“From the Qilian Mountains on the northeast side of the Plateau, to the Kunlun Mountains in the west, to the northern slopes of the central and western Himalayas, all the glaciers and ice caps that I have studied are retreating,” he asserted.

He pointed out that all the glaciers he has studied in the Peruvian Andes are also shrinking. The glaciologists at the Institute of Tibetan Plateau Research in Beijing have found that from 1980 to 1990, 90 per cent of the 612 glaciers across the High Asian region were retreating, and from 1990 to 2005, this increased to 95 per cent.

Thompson admitted that meteorological records from the Tibetan Plateau and the Himalayas are scarce and of relatively short duration, most beginning in the mid-1950s to early 1960s; however those that do exist show that surface temperatures are rising, and rising faster at higher elevations than at lower elevations.

According to him, the Tibetan Plateau has been warming at a rate of 0.16 degrees centigrade per decade, with winter temperatures rising 0.32 degrees centigrade per decade.
GRACE data

“A recent paper by Matsuo and Heki in Earth and Planetary Science Letters (time-variable ice loss in Asian high mountains from satellite gravimetry) shows that from 2003 to 2009 the average ice loss from the Asian high ice fields, as measured by GRACE satellite observations, had accelerated twice as fast as the rate over four decades before, but the loss was not consistent over space and time”, he cautioned

He observed that ice retreat in the Himalayas slowed slightly, while loss in the mountains to the northwest increased markedly.

“So, between the surface temperature measurements, the satellite studies, the ground studies on glaciers, and ice core results, a case can be made that glacier retreat at high elevations is indeed occurring concomitantly with increasing temperatures, which is consistent with the IPCC model results which show not only low-latitude warming but an amplification of that warming at higher elevations where these glaciers are located,” he argued

Thompson stated that the rate at which glaciers respond to climate change depends on their size; larger a glacier, the longer it takes to retreat in response to a warmer/drier climate, or grow in response to a cooler/wetter climate.

“Thus, among the 15,000 glaciers in the Himalayas, the largest are currently reacting to changes that happened 100 years ago. However, some of the growing glaciers are in fact surging; that is, they are advancing because of dynamics of ice flow and not because of climate.
Temporal differences

On the short term, glaciers show rapid changes in response to changes in snowfall amounts as well as temperature, but over the long term temperature will dominate,” he clarified.

Prof. Thompson referred to their latest paper titled ‘Glacier loss on Kilimanjaro continues Unabated’ in the Proceedings of the National Academy of Sciences (November 2, 2009) which demonstrates that ice loss on Kilimanjaro is unfortunately right on track as predicted in their 2002 Science paper. New measurements completed on GEOEYE satellite images from July 17, 2009 shows that the loss of ice continues right along the project from their Science paper.

According to Anna Barnet, assistant editor and copy editor of Nature Reports Climate Change (July 9, 2009), Thompson has spent more time above 20,000 ft than any other human being. She noted that by collecting a vast library of ice samples from mountain peaks, he has developed a unique view of past and present-day climate change. Thompson had 7,000 metres of glacial ice in his collection (PNAS, 2006). He is eminently qualified to comment on the topic.

Prof. Thompson noted that the recent document by V.K. Raina, formerly Deputy Director General of the Geological Survey of India, has been catapulted into the fray over the Himalayan glacier retreat.

According to Prof. Thompson Mr. Raina states quite correctly in his report (before going on to present case studies of only 3 glaciers) that “a few glaciers cannot be taken as the representative of around 10,000 glaciers of various sizes that exist in the Indian part of the Himalayas.”

Prof. Thompson clarified that very few solid peer-reviewed papers exist on glacier retreat in this region of the world, and as Mr. Raina would evidently agree, nothing conclusive can be claimed based on studies of a handful of glaciers out of over 15,000 throughout the Himalayas, both on the Indian and the Tibet sides.

Poster child glaciers

Prof. Thompson stated that participants on both sides of the issue are drawing conclusions about what is happening in a very large and climatologically and topographically complex region based on the “behaviour” of a few glaciers that have been adopted collectively as the “poster child” for all the world’s bodies of ice.

He conceded that most glaciologists and climatologists, he included, do not believe that most of the Himalayas will be ice-free by as early as 2035.

‘The provenance of this statistic may not be scientific or peer-reviewed, and the authors and reviewers … may have erred by allowing it to slip past the fact-checking process while the report was being prepared, but it doesn’t invalidate the entire IPCC report.

If any of the report’s authors felt compelled for whatever reason to include such material, as apparently admitted by Murari Lal, one of the lead coordinating authors of the 2007 IPCC report’s chapter on Asia (US News and World Report, Jan 25), then that should be investigated and the current guidelines should be strengthened and more rigorously enforced to prevent future occurrences of non-peer reviewed material slipping through,” he suggested.

“Scientists hold the peer-review process as the “gold-standard” for publication, but as in all human endeavors mistakes are occasionally made.

“In the end, it is the total body of substantiated evidence on global climate change that is important, not occasional errors or miscommunications that provoke unbalanced and hyperbolic reactions,” Prof. Thompson clarified.

K.S. PARTHASARATHY

Raja Ramanna Fellow, Department of Atomic Energy

( ksparth@yahoo.co.uk )

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