Accumulation of atmospheric brown clouds caused by the buildup of greenhouse gases is significantly contributing to the melting of Himalayan glaciers, a recent study by scientists from the Scripps Institution of Oceanography at San Diego has revealed.
The team led by Prof V. Ramanathan, a 1965 Annamalai University engineering graduate, found that atmospheric brown clouds enhanced solar heating of the lower atmosphere by about 50 percent.
The findings, which appear in the Aug. 2 edition of the journal Nature, further said that the combined heating effect of greenhouse gases and the brown clouds, which contain soot, trace metals and other particles from a growing cadre of urban, industrial and agricultural sources, was enough to account for the retreat of Himalayan glaciers observed in the past half century.
"The rapid melting of these glaciers, the third-largest ice mass on the planet, if it becomes widespread and continues for several more decades, will have unprecedented downstream effects on southern and eastern Asia," said Prof. Ramanathan, who did his masters from the Indian Institute of Science, Bangalore.
The glaciers supply water to major Asian rivers including the Yangtze, Ganges and Indus. These rivers in turn comprise the chief water supply for billions of people in China, India and other south Asian countries.
"The main cause of climate change is the buildup of greenhouse gases from the burning of fossil fuels," said Achim Steiner, United Nations under-secretary general and executive director of the UN Environment Programme (UNEP), which helped support the research.
"But brown clouds, whose environmental and economic impacts are beginning to be unravelled by scientists, are complicating and in some cases aggravating their effects," he added.
"The conventional thinking is that brown clouds have masked as much as 50 percent of the global warming by greenhouse gases through the so-called global dimming. While this is true globally, this study reveals that over southern and eastern Asia, the soot particles in the brown clouds are intensifying the atmospheric warming trend caused by greenhouse gases by as much as 50 percent," said Prof Ramanathan.
A recent study by climatologists from the Chinese Academy of Sciences (CAS) had also found that the fast meltdown of the Tibetan and Xinjiang glaciers - the major source of Asia's biggest rivers - was seriously threatening the survival of major rivers, including the Yangtze, the Mekong, the Yellow River, the Indus and the Ganges.