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NSF PR 95-74 - October 31, 1995
Media contact: |
Cheryl Dybas |
(703) 306-1070 |
Program contact: |
Jewel Prendeville |
(703) 306-1521 |
This material is available primarily for archival purposes. Telephone
numbers or other contact information may be out of date; please see current
contact information at media
contacts.
NSF Scientists to Study Airborne Particles that May
Be Cooling Earth
Scientists now suspect that increasing numbers of small
particles of sulfur compounds and other pollutants
floating in the atmosphere may affect so-called greenhouse
warming in heavily industrialized regions. By reflecting
sunlight back to space, these tiny airborne particles,
called aerosols, can cool the earth beneath. To learn
more about "background" aerosols -- the naturally
occurring counterparts to these pollutants - researchers
from eight universities and the National Science Foundation
(NSF)-supported National Center for Atmospheric Research
(NCAR) in Boulder, Colorado are flying to the remote
skies of Tasmania, with stops in Alaska, Hawaii, and
other sites along the way. Flight operations for detailed
studies of "clean" ocean air in the Southern Hemisphere
will be based at Hobart, Tasmania, and take place
from November 15 to December 14, 1995.
More than 100 scientists from 57 institutions representing
Australia, France, Germany, Italy, Japan, the Netherlands,
New Zealand, Sweden, the United Kingdom, and the United
States are participating in this major study of airborne
particles.
"Existing theories suggest that it should be very
hard to create new particles in the lower atmosphere,
yet they keep showing up," says researcher Barry Huebert
of the University of Hawaii at Honolulu. "We're deploying
stateof- the-art instruments to the remote marine
atmosphere for the first time to seek the source of
these new particles. This is the largest and most
comprehensive experiment on natural background aerosols
that we have ever done." Among the high- tech instrumentation
will be NCAR's dualwavelength airborne lidar, which
will map the vertical extent of aerosol layers in
the atmosphere. Experiments will be conducted from
a fully equipped C-130 research airplane owned by
NSF and operated by NCAR.
Researchers aboard the C-130 will spend as many flight
hours taking measurements during the two-week trip
from the north Alaska coast to south of New Zealand
as they will during the operations in Tasmania. In
Alaska, they will begin their research measurements
with a flight toward the North Pole and back. While
in Hawaii November 5 and 6, the C-130 will fly through
the Kilauea volcano plume to study how its particles
form and how much sunlight they reflect. After arrival
at Hobart, a flight toward the South Pole will complete
the study's nearly pole-to-pole measurements.
Called ACE-1, the study is the first of the Aerosol
Characterization Experiments, a series of international
field programs to help scientists understand the chemical,
physical, and optical properties of aerosols; how
they form and grow; and their effect on radiation
and climate.
Like carbon dioxide, sulfate aerosols are produced
by human activity, mainly the burning of fossil fuels.
They also exist naturally as sulfur emissions from
living organisms and volcanoes. By scattering incoming
solar energy back to space, both the natural and pollutant
aerosols directly affect the amount of radiation entering
the earth's atmosphere. They also serve as tiny sites
on which water vapor can condense, allowing more small
droplets to form within a cloud. This change in the
droplets' size distribution makes the cloud more reflective,
bouncing more solar radiation back to space and cooling
the earth below. In ACE-1, scientists will study the
natural marine system -distant from Northern Hemisphere
sulfate aerosols produced by human activity. ACE-2,
scheduled for 1997, will focus on the marine atmosphere
near European industrialized areas. As scientists
learn more about aerosols naturally occurring in the
undisturbed atmosphere, they can better assess the
growing influence of humanproduced sulfate aerosols
on climate.
"Until recently all climate models have supposed that
the only human activity driving climate change was
the production of carbon dioxide and other greenhouse
gases," explains scientist Tom Wigley of NCAR. "We
now believe that other factors, particularly sulfate
aerosols, may be as important as greenhouse gases."
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