Sep 29, 2002 The “Asian Brown Cloud”, a vast haze of soot particle hovering over south Asia, is at least partly to blame for China’s recent climatic disasters drought in the north and floods in the south according a NASA study published this week in US journal Science.
Surabi Menon of NASA and Columbia University and James Hansen of NASA’s Goddard Institute said in the study there was a clear link between increased amounts of man-made soot and the kind of climate change witnessed in the south Asian region over the past few years.
Menon and Hansen conducted four computer simulations using scientific data from 46 ground stations in China to examine whether airborne soot affected China’s water cycle.
They found the soot particles affected the climate by absorbing sunlight, which then heated the air and made the atmosphere more unstable.
This created rising air that formed clouds and brought rainfall to heavily polluted southern China. It was balanced out by an increase of sinking air — which prevented clouds and rain from forming — in northern China, contributing to the droughts there.
The researchers took other factors into account, including ocean surface temperature and the presence of other greenhouse gases, in their computer models.
Soot is generated from industrial pollution, traffic, outdoor fires and household burning of coal and biomass fuels, such as cow dung and field residues. It occurs when the combustion of coal and other fuels is incomplete.
It continues to be produced in large amounts in Asia, especially in China and India, because cooking and heating are done using wood, coal and biomass fuels at low temperatures, which prevents complete combustion taking place.
Based on their simulations, the authors predicted soot-induced cooling over China, extended warming over northern Africa and cooling over the southern United States, amidst overall global warning.
The Asian Brown Cloud phenomenon has stirred controversy recently, as scientists across the globe warn of its radical consequences and regional scientists retort that it does not exist and is not specifically Asian.
In August the UN Environment Programme (UNEP) said the pollution haze was damaging agriculture, modifying rainfall patterns and endangering the population.