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PARIS: The haze of pollution that blankets southern Asia is
accelerating the loss of Himalayan glaciers, bequeathing an
incalculable bill to China, India and other countries whose rivers
flow from this source, scientists warned on Wednesday.
In a study released by the British journal
Nature, the investigators say the so-called Asian Brown Cloud is as
much to blame as greenhouse gases for the warming observed in the
Himalayas over the past half century.
Rapid melting among the 46,000 glaciers on the
Tibetan Plateau, the third-largest ice mass on the planet, is
already causing downstream flooding late summer. But long-term
worries focus more on the danger of drought, as the glaciers shrink.
The new report triggered an appeal from UN
Environment Program (UNEP) chief Achim Steiner, who urged the
international community “to ever greater action” on tackling
climate change.
Researchers led by Veerabhadran Ramanathan, a
professor of atmospheric sciences at Scripps Institution of
Oceanography in California, used an innovative technique to explore
the Asian Brown Cloud.
The plume sprawls across South Asia, parts of
Southeast Asia and the northern Indian Ocean, spewed from tailpipes,
factory chimneys and power plants, forests or fields that are being
burned for agriculture, and wood and dung which are burned for fuel.
Emissions of carbon gases are known to be the
big drivers of global warming, but the role of particulate
pollution, such as brown clouds, is unclear.
Particulates, also called aerosols, cool the
land or sea beneath them because they filter out sunlight, a process
known as global dimming.
But what they do to the air around them has been
poorly researched.
Some aerosols absorb sunlight and thus warm the
atmosphere locally, while others reflect and scatter the light.
Ramanathan’s team used three unmanned aircraft
of the type often used as for observation work by the military and
police, but this time fitted them with 15 instruments to monitor
temperature, clouds, humidity and aerosols.
Launched from the Maldives island of Hanimadhoo,
the remote-controlled craft carried out 18 missions in March 2006,
flying in a vertical stack over the Indian Ocean.
The planes flew simultaneously through the Brown
Cloud at heights of 500 meters (1,625 feet), 1,500 meters (4,875
feet) and 3,000 meters (9,750 feet).
They discovered that the cloud boosted the
effect of solar heating on the air around it by nearly 50 percent.
This was because its particles are soot, which is black and thus
absorbs sunlight.
The researchers then crunched data from
greenhouse gases and from the brown clouds in a US computer model
for climate change.
The simulation estimated that, since 1950, South
Asia’s atmosphere has warmed by 0.25 degrees Celsius (0.5 degrees
Fahrenheit) per decade at altitudes ranging from 2,000 to 5,000
meters (6,500 to 16,500 feet) above sea level, precisely the height
where thousands of Himalayan glaciers are located.
As much as half of this warming can be
attributed to the effects of brown clouds, Ramanathan told Agence
France-Presse by phone from the Himalayas, where he was setting up a
glacier monitoring station.
“It is frightening, but I also look at the
positive side, because it shows a way out of the conundrum,” said
Ramanathan.
Roughly 60 percent of the soot in South Asia
comes from biofuel cooking and biomass burning, which could be eased
by helping the rural poor get bottled gas or solar cookers, he
explained.
Ramanathan’s data has been validated with
measurements taken on the ground at Hanimadhoo and in space by the
NASA Earth-monitoring satellite CALIPSO.
UNEP’s Steiner said the Asian Brown Cloud and
greenhouse gases were linked by a common dependence on carbon fuels.
“The new findings should spur the
international community to ever greater action, in particular at the
next crucial climate change convention meeting in Indonesia this
December,” he said.
--AFP
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