January
30, 2007
NASA PROBES
THE
SOURCES OF THE WORLD'S TINY POLLUTANTS
Pinpointing
pollutant sources is an important part of the ongoing battle to improve
air
quality and to understand its impact on climate. Scientists using NASA
data
recently tracked the path and distribution of aerosols -- tiny
particles
suspended in the air -- to link their region of origin and source type
with
their tendencies to warm or cool the atmosphere.
By altering the
amount of solar energy that reaches
the Earth's surface, aerosols influence both regional and global
climate, but
their impact is difficult to quantify because most only stay airborne
for about
a week, while greenhouse gases can persist in the atmosphere for
decades. In a
study published Jan. 24 in the American Geophysical Union's Journal of Geophysical Research-Atmospheres,
researchers investigated the sources of aerosols and how different
types of
aerosols influence climate.
"This
study offers details on the aerosol source
regions and emission source types that policy makers could target to
most
effectively combat climate change," said Dorothy Koch, lead author and
atmospheric scientist at Columbia University and NASA's Goddard
Institute for
Space Studies (GISS), New York.
Using
a GISS computer model that includes a variety
of data gathered by NASA and other U.S.
satellites, the researchers
simulated realistic aerosol concentrations of important aerosol types
in the
atmosphere and studied the amount of light and heat they absorb and
reflect
over several regions around the globe.
Each area has a
unique mix of natural and pollutant aerosol sources that produces
different
types of aerosols and causes complex climate effects. The industry and
power sectors
are particularly important in North America and Europe and produce
large
amounts of sulfur dioxide, while Asia
has
higher emissions from residential sources, which produce relatively
more
carbon-containing aerosols.
"Computer
model simulations showed that black
carbon in the Arctic,
a potentially important
driver in climate change, derives its largest portion from Southeast
Asian
residential sources," said Koch. "According to current model
estimates, the residential sector appears to have a substantial
potential to
cause climate warming and therefore, could potentially be targeted to
counter
the effects of global warming."
Black carbon,
commonly called soot, is generated
from motor vehicles and industrial pollution, in addition to outdoor
fires and
household burning of coal and bio-fuels. Soot is produced by incomplete
combustion, especially of diesel fuels, coal and wood. Residential soot
emissions are largest in areas where cooking and heating are done with
wood,
field residue, animal dung and coal.
Black carbon absorbs
sunlight, warming the
atmosphere just as dark pavement absorbs more sunlight and becomes
hotter than
light pavement. It has a large influence on global climate because
winds
transport approximately half of the black carbon aerosols produced in
important
aerosol source regions like Asia and South Africa
to other parts of the
world. When lofted above precipitating clouds, these aerosols can
remain
airborne for relatively longer periods. Some of these aerosols are
carried to
polar regions where they settle on the surface of ice or snow and
absorb
sunlight and boost melting.
Most particles,
especially sulfates produced from the sulfur dioxide emissions of
factories and
power plants, are light-colored and tend to cool the atmosphere by
reflecting
sunlight or making clouds more reflective. Computer model simulations
suggest
this effect is especially heightened over parts of the Northern
Hemisphere,
including the central United States.
The study found, however, that
sulfur dioxide emissions in Southeast Asia and Europe
have a smaller impact on climate because atmospheric conditions in
those areas
are not as efficient at turning the emissions into sulfate particles.
The study also
showed large amounts of aerosols
containing organic carbon -- which also tend to cool the atmosphere and
partially offset the warming from greenhouse gas emissions -- are
produced by
biomass (vegetation) burning. Most of the world’s biomass
burning emissions
appear to come from Africa and secondarily, from South America.
However, precipitation removes a greater proportion of biomass-burning
aerosols
from the atmosphere over Africa than over South
America.
As a result, more than one-half of the biomass-burning aerosols in the
Southern
Hemisphere can be traced back to South
America.
"This research is
only the first step in
considering the impacts of aerosols from different sectors on climate,"
said Koch. "Aerosols have other effects, like altering cloud
characteristics that influence precipitation and climate." In a related
paper accepted for publication in Geophysical
Research Letters, the researchers examine how anticipated
advances in
technology will impact the amount of aerosols emitted from each sector
in the
future, so that specific regions and types of aerosols can be targeted.
For
more
information and images, visit:
http://www.nasa.gov/centers/goddard/news/topstory/2007/tiny_pollutants.html
For more
information
about NASA's Global Aerosol Climatology Project, visit:
http://gacp.giss.nasa.gov/
Feature
story on soot and the changing arctic environment:
http://earthobservatory.nasa.gov/Newsroom/NasaNews/2005/2005032318608.html
Feature
story on aerosols and climate change:
http://earthobservatory.nasa.gov/Library/Aerosols/aerosol.html
Writer: Mike Bettwy,
NASA
Goddard Space Flight Center
##
Contact:
Lynn Chandler
NASA Goddard Space Flight Center
301-286-2806
Lynn.Chandler-1@nasa.gov
This text is
derived from:
http://www.nasa.gov/centers/goddard/news/topstory/2007/tiny_pollutants.html
Recommend this Article to a Friend
Back to: News |