South Asian Black Carbon Aerosols

According to a study, published in Nature Communications, found that since the 21st century, South Asian black carbon aerosols have indirectly affected the mass gain of the Tibetan Plateau glaciers by changing long-range water vapour transport from the South Asian monsoon region.

What is Black Carbon? 

• Black carbon results from the incomplete combustion of fossil fuels and biomass.
• The fine particles absorb light and about a million times more energy than carbon dioxide.
• It is said to be the second largest contributor to climate change after CO2.
• Unlike CO2, which can stay in the atmosphere for years together, black carbon is short-lived and remains in the atmosphere only for days to weeks before it descends as rain or snow.
• The concentration varied from a minimum of 0.01μg/cubic metre in winter to 4.62μg/cubic metre during summer.

About Black Carbon Aerosols –

• Black carbon aerosols are produced by the incomplete combustion of fossil fuels and biomass, and are characterised by strong light absorption.
• The South Asia region adjacent to the Tibetan Plateau has among the highest levels of black carbon emission in the world.
• Many studies have emphasised black carbon aerosols from South Asia can be transported across the Himalayas to the inland region of the Tibetan Plateau.
• Black carbon deposition in snow reduces the albedo of surfaces — a measure of how much of Sun’s radiations are reflected — which may accelerate the melting of glaciers and snow cover, thus changing the hydrological process and water resources in the region.
• Black carbon aerosols in South Asia heat up the middle and upper atmosphere, thus increasing the North­–South temperature gradient.
• Accordingly, the convective activity in South Asia is enhanced, which causes convergence of water vapour in South Asia. Meanwhile, black carbon also increases the number of cloud condensation nuclei in the atmosphere.
• These changes in meteorological conditions caused by black carbon aerosols make more water vapour form precipitation in South Asia, and the northward transport to the Tibetan Plateau was weakened.
• As a result, precipitation in the central and the southern Tibetan Plateau decreases during the monsoon, especially in the southern Tibetan Plateau.
• The decrease in precipitation further leads to a decrease of mass gain of glaciers.
• From 2007 to 2016, the reduced mass gain by precipitation decrease accounted for 11% of the average glacier mass loss on the Tibetan Plateau and 22.1% in the Himalayas.