NE - 'Brown clouds' contribute to Himalayan Glacier Melt

[Guest guest]

* " Brown Clouds " Contribute to Himalaya Glacier Melt*

**

http://news.nationalgeographic.com/news/2007/08/070801-brown-clouds.html

 

Anne Casselman

for National Geographic News

August 1, 2007

 

Soot-filled " brown clouds " over the Indian subcontinent warm the lower

atmosphere just as much as greenhouse gases do, a recent study reports.

 

Such clouds contain aerosols—tiny particles suspended in the air that are

known to create a general cooling effect that could mitigate global warming.

 

 

 

But the latest study suggests that aerosols can be responsible for regional

warming. Specifically, the clouds of aerosols over India enhance atmospheric

warming there by 50 percent.

 

" We found this brown cloud can cover the entire North Indian Ocean, an area

the size of the continental United States, " said lead author Veerabhadran

Ramanathan, a climate scientist at Scripps Institution of Oceanography at

the University of California, San Diego.

 

The haze of brown clouds over the region can be up to two miles (three

kilometers) thick, Ramanathan said.

 

And the haze touches the lower parts of the glaciers in the Himalaya

mountain range, said study co-author David Winker, principal investigator of

the CALIPSO satellite at NASA's Langley Research Center.

 

This suggests that the brown clouds may be contributing to glacial melting

in the Himalaya.

 

(Related: " Mountain Glaciers Melting Faster Than Ever, Expert Says "

[February 16, 2007].)

 

*How Now Brown Cloud?

*

Brown clouds contain dark aerosols such as soot that are released into the

atmosphere by burning organic matter.

 

These particles absorb solar energy and then release it to the surrounding

air as heat.

 

Natural forces such as forest fires can create soot, but so can human

actions such as burning fossil fuels. Ramanathan credits the clouds'

formation to a combination of the area's tropical meteorology, outdated

technology use, and rapid industrialization.

 

These dark particles, especially near urban and industrial regions, may add

significantly to heating in the atmosphere, cautions Scripps' Craig

Corrigan, a study co-author.

 

" When we introduce a little more of our own pollution—especially when it's

dark black soot—there's a more dramatic effect on warming, " Corrigan said.

 

In contrast, lighter-colored aerosols don't absorb solar energy the way

darker particles do.

 

These nonabsorbant particles act like a parasol over Earth, reflecting

energy back into space (read " Extreme Global Warming Fix Proposed: Fill the

Skies With Sulfur " [August 4, 2006]).

 

" If you go into a parking lot, the white sidewalk is cooler than the black

asphalt, " Corrigan explained.

 

But unlike greenhouse gases, light and dark aerosols are not distributed

uniformly throughout the globe, said Peter Pilewskie, an atmospheric

scientist at the University of Colorado at Boulder who was not involved in

the study.

 

Averaging the effects of aerosols worldwide masks regional processes that

" we need to truly understand when we put all the pieces of the planet

together, " Pilewskie said.

 

* " Lawn Mower With Wings " *

 

To better understand the brown clouds, the researchers sent three unmanned

aerial vehicles into the haze.

 

Each flyer was " the size of a small lawn mower with wings, " Corrigan said.

 

The three vehicles simultaneously flew above, through, and below segments of

the brown clouds lingering over the Maldives, an island country in the

Indian Ocean.

 

During 18 missions in March 2006 the vehicles mapped the clouds' makeup and

measured the solar energy they soaked up.

 

" It just so happened NASA launched this CALIPSO satellite, which gave us a

precise measurement of the thickness of the cloud, " Ramanathan said.

 

The combined data are detailed in tomorrow's issue of the journal Nature.

 

In 2008 NASA is planning to launch a satellite called Glory that will carry

a new sensor to determine how much energy aerosols absorb from the sun.

 

" Our understanding of how air pollution and these brown clouds are

influencing climate change is evolving, " Ramanathan said.

 

--