Washington: Black soot deposited on Tibetan
glaciers has contributed significantly to the retreat of the
world`s largest non-polar ice masses, a recent study led by
NASA scientists said.
According to the new research by scientists from NASA
and the Chinese Academy of Sciences, black carbon deposits on
Himalayas is probably responsible for as much as half of the
glacial melt, journal Proceedings of the National Academy of
Sciences reported.
The temperatures on the Tibetan Plateau -- sometimes
called earth`s "third pole" -- have warmed by 0.3 degrees
Celsius per decade over the past 30 years, about twice the
rate of observed global temperature increases.
New field research and ongoing quantitative modelling
suggests that soot`s warming influence on Tibetan glaciers
could rival that of greenhouse gases as the black carbon
absorbs incoming solar radiation and can speed glacial melting
when deposited on snow in sufficient quantities.
"Tibet`s glaciers are retreating at an alarming rate,"
said James Hansen, co-author of the study and director of
NASA`s Goddard Institute for Space Studies.
He said, "Black soot is probably responsible for as much
as half of the glacial melt, and greenhouse gases are
responsible for the rest."
While co-author Junji Cao from the Chinese Academy of
Sciences in Beijing said, "During the last 20 years, the black
soot concentration has increased two-to-three-fold relative to
its concentration in 1975".
"Fifty per cent of the glaciers were retreating from
1950 to 1980 in the Tibetan region; that rose to 95 per cent
in the early 21st century," said Tandong Yao, director of the
Chinese Academy`s Institute of Tibetan Plateau Research.
Some glaciers are retreating so quickly that they could
disappear by mid-century if current trends continue, the
researchers suggest.
Since melt water from Tibetan glaciers replenishes many
of Asia`s major rivers -- including the Indus, Ganges, Yellow,
and Brahmaputra -- such losses could have a profound impact on
the billion people who rely on the rivers for fresh water.
While rain and snow would still help replenish Asian
rivers in the absence of glaciers, the change could hamper
efforts to manage seasonal water resources by altering when
fresh water supplies are available in areas already prone to
water shortages.
Researchers led by Baiqing Xu analyzed five ice cores
from various locations across the Tibetan plateau, looking for
black carbon (a key component of soot) as well as organic
carbon.
The cores support the hypothesis that black soot amounts
in the Himalayan glaciers correlate with black carbon
emissions in Europe and South Asia.
At Zuoqiupu glacier -- a bellwether site on the southern
edge of the plateau and downwind from the Indian subcontinent
-- black soot deposition increased by 30 per cent between 1990
and 2003, they said.
The rise in soot levels at Zuoqiupu follows a dip that
followed the enacting of clean air regulations in Europe in
the 1970s.
Most soot in the region comes from diesel engines,
coal-fired power plants, and outdoor cooking stoves.
-PTI
