Caused by the burning of fossil
fuels, wood and plants, the brown
clouds also play a significant role
in exacerbating the effects of
greenhouse gases in warming up the
earth's atmosphere, the report said.
"Imagine for a moment a
3-kilometer-thick band of soot,
particles, a cocktail of chemicals
that stretches from the Arabic
Peninsula to Asia," said Achim
Steiner, U.N. undersecretary general
and executive director of the U.N.
environment program.
"All of this points to an even
greater and urgent need to look at
emissions across the planet because
this is where the stories are linked
in terms of greenhouse emissions and
particle emissions and the impact
that they're having on our global
climate," he said.
Glaciers
melting
Some particles within the
pollution cloud, such as soot,
absorb sunlight and heat the air.
That has led to a steady melting of
the Himalayan glaciers, which are
the source of most of the major
rivers on the continent, the report
said.
The Chinese Academy of Sciences
estimates the glaciers have shrunk
by 5 percent since the 1950s. At the
current rate of retreat, glaciers
could shrink by as much as 75
percent by the year 2050, posing a
major risk to the region's water
security.
The pollution clouds also have
helped to reduce the monsoon season
in India. The weather extremes may
have also played a part in reduced
production of key crops such as
rice, wheat and soybean, the report
said.
At the same time, the brown clouds
have also masked the full impact of
global warming by helping to cool
the earth's surface and tamp down
rising temperatures by between 20 to
80 percent, the study said. That's
because some of the particles that
make up the clouds reflect sunlight
and cool down the air.
The latest findings, conducted by an
international collaboration of
scientists over seven-plus years,
are the most detailed to date on the
brown cloud phenomenon, which is not
unique to Asia. Other hotspots are
seen in North America, Europe, South
Africa and South America.
In
everyone's backyard
The enormous cloud masses can move
across continents within three to
four days, illustrating the fact
that the phenomenon is not just a
regional urban issue but a global
one, said lead scientist
Veerabhadran Ramanathan, with the
Scripps Institution of Oceanography
at the University of California in
San Diego.
"The main message is that it's a
global problem. This is not a
problem where we point fingers at
our neighbors. Everyone is in
someone else's backyard," said
Ramanathan.
The report also noted that health
problems associated with particulate
pollution, which include
cardiovascular and respiratory
diseases, are linked to nearly
350,000 premature deaths in China
and India every year, said Henning
Rohde, a University of Stockholm
scientist who worked on the study.
The value of the study is that
scientists looked at the effect of
the brown clouds on multiple levels,
said Ankur Desai, assistant
professor of atmospheric and oceanic
sciences at the University of
Wisconsin-Madison.
"Quantifying the impact on people,
ice, agriculture, etc., is certainly
going to be useful," he said. "The
study also brings together
scientists who don't traditionally
work together into thinking together
about the impact, mitigation and
fundamental science on how this
works."
