16 December,2009 10:00 AM IST | | IANS
Soot and dust contribute as much to a temperature rise in the Himalayas as greenhouse gases do, according to a new study by the US space agency NASA.
Most of the soot goes from the thousands of wood and dung-burning cooking stoves in use all over South Asia, says the study led by William Lau, head of atmospheric sciences at NASA's Goddard Space Flight Centre in Greenbelt, Maryland.
The study, which looked at soot and dust concentrations in South Asia between 2000 and 2007 as well as air circulation patterns during that period, was made available at the December 7-18 climate summit here.
It says much of the soot - as well as dust - travels along air currents from southern Asia to the Tibetan plateau, where it accumulates. It also accumulates along the southern slopes of the Himalayas.
With a detailed numerical model, the study reinforces what Veerabhadran Ramanathan of the Scripps Institution of Oceanography in San Diego, California, has been saying - the soot and dust contribute as much to warming in the Himalayas as other greenhouse gases.
This is because the black soot and grey dust accumulate on the white snow and ice of the Himalayas and reduce the extent to which the surface reflects the sun's heat back into the atmosphere. Dark colours reflect less heat.
Lau points out that this warming adds to the faster melting of glaciers and threatens water supply to 1.3 billion people dependent on the rivers flowing down the Himalayas.
The NASA scientists found that the most rapid melting of ice and snow takes place at the western end of the Tibetan plateau between April and September each year, coinciding with the time soot and dust concentrations are highest in the atmosphere in northern India and Nepal.
It forms a dirty blanket that has been called the Asian Brown Cloud.
The Himalayas are often called the Third Pole because this area holds the largest store of fresh water in the world after the Antarctic and the Arctic. But the area covered by the Himalayan glaciers has declined by over 20 percent since the early 1960s.
An estimated 1.3 billion people depend on the waters flowing down the Himalayas through rivers such as the Ganga, Indus, Brahmaputra and their tributaries in South Asia, Yellow and Yangtze in China, Salween and Mekong in Southeast Asia.
Soot is formed due to incomplete burning of fossil fuels. Inefficient cooking stoves using wood and dung are the worst culprits.
India's leading glaciologist Syed Iqbal Hasnain, who has also been warning about the impact of soot on warming in the Himalayas, is now doing on-ground studies to determine how much soot and dust is accumulating on two of the glaciers in the southern slopes of the world's tallest mountain range.
