A critical water resource for almost 2 billion people in Asia, the Tibetan Plateau is facing severe threat from air pollution in South Asia, a recent study has concluded.
A study led by researchers from the Chinese Academy of Sciences’ Northwest Institute of Eco-Environment and Resources attributed an air pollutant known as black carbon as responsible for accelerating the shrinking of glaciers on the plateau.
The study warned that black carbon diposition could result in unprecedented melting of the plateau’s glaciers.
The findings have prompted call for cuts in black carbon emission in South Asia to preserve vital water balance on the Tibetan Plateau and avoid future water shortages and geological hazards.
The study found that increasing concentrations of black carbon in South Asia were causing reduced levels of summer precipitation over the Southern Tibetan Plateau. Black carbon when deposited on ice or snow reduces the glacial surface's ability to reflect sunlight, which in turn leads to heating of the surface and contributes to quicker glacial melting.
Black carbon emissions equally threaten ice covered regions like the Arctic, Antarctic and the Himalayas.
Black carbon is one of many particles and gases that are emitted when diesel, coal and other biomass are burned. It is part of fine particulate air pollution (PM2.5). Black carbon emissions absorb solar energy and heat the surroundings, thereby contributing to increasing global temperature.
South Asian countries are some of the world’s notorious air polluters and black carbon emissions from the region make it to Tibetan Plateau – resulting in worsening glacial melting. Researchers also called this phenomenon (black carbon from South Asia reaching the plateau) as “direct effect”.
The study published in the peer-reviewed journal Nature Communications on November 30 revealed that black carbon originating from South Asia impacted the glaciers by reducing the amount of precipitation in the Southern Tibetan Plateau.
As precipitation is reduced, the mass of the glacier does not get maintained
Researchers' analysis of precipitation data from 1961 to 2016 found that summer precipitation amounts over the Southern Tibetan Plateau began to decline in 2004 by an average of 4.4mm a year.
Summer precipitation accounts for more than 60 percent of the total annual precipitation over the plateau, so declines in the seasonal rains resulted in glacial shrinkage, the study said. And the problem has accelerated since 2000s.
Kang Shichang, one of the study’s corresponding authors and a researcher with the Chinese Academy of Sciences, said that black carbon produced in South Asia intensified atmospheric convection and cloud condensation – which resulted in more precipitation over South Asia but less water vapor over the Tibetan Plateau.
“Black carbon emissions are expected to increase in South Asia,” Kang said. “It is imperative to reduce emissions in South Asia to protect the Asian water tower,” he added.
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