Stronger evidence of global warming

With more recent data on the Himalayan glaciers from the Indian Remote Sensing (IRS) satellites, scientists of the Space Applications Centre (SAC) of the Indian Space Research Organisaation (ISRO) at Ahmedabad now have much stronger evidence of the finger print of global warming in the observed alarming retreat of these glaciers. The new results were presented at the ongoing National Space Science Symposium (NSSS-2008) here by Dr. Anil V. Kulkarni of SAC. In 2004 Dr. Kulkarni and his colleagues investigated the spatial extent of 466 glaciers in the basins of Chenab, Parbati and Baspa using remote sensed data and compared them with the 1962 topographic data of the Survey of India.They found an overall reduction of 21 per cent in the glacial surface area. They had also found that the process of deglaciation had led to the fragmentation of large glaciers resulting in the reduction in the mean surface area of glacial extent from 1 sq. km. to 0.32 sq. km. during 1962-2004.

The new data pertains to two additional basins of Warwan and Bhut comprising 253 and 189 glaciers respectively. Together with the earlier data on 466 glaciers, the cumulative area of these 908 Himalayan glaciers has been found to have reduced from 3391 sq. km. to 2721 sq. km., implying a total area reduction of 20 per cent. Another new finding is that the snow line — altitude above which there is no snowmelt had significantly increased in the Himalayan basins since 1970. Snow line essentially is the line of zero mass balance, where snow accumulation equals ablation or melting. For example, studying 30 glaciers in the Baspa basin, the scientists found that the snow line had increased from 4900 m in 1970 to 5300 m in 2006. More quantitatively, the scientists found that the percentage area of the 30 glaciers below the snow line was only 25 per cent between up to 1990. This means that only 25 per cent of the glacial area had negative mass balance. In 2006, this fraction increased to 70 per cent. The scientists predict that by 2050, this fraction would be a high 90 per cent.One of the significant changes due to warming that Dr. Kulkarni and his associates had seen even in the earlier work was that the winter run off had increased by as much as 75 per cent between 1966 and 1995. Now they have more quantitative glacier-wise data, which shows the snow accumulation having a wavelike pattern, instead of a flat profile of accumulated snow during peak winter.This shows that between snow storms or heavy snow falls the warming is resulting in significant melt. So, even the episodes of heavy snowfalls in the north during the most recent winter should not be taken to imply that warming has not significantly affected the Himalayan snow and glacier formation, Dr. Kulkarni said. Far less accumulation is occurring in glaciers today than before and this is a clear imprint of warming, he added.

The Hindu February 28, 2008