Jan. 16, 2009

Stephen Cole
Headquarters, Washington
202-358-0918
stephen.e.cole{at}nasa.gov

RELEASE: 09-009

REPORT CALLS AEROSOL RESEARCH KEY TO IMPROVING CLIMATE PREDICTIONS

WASHINGTON -- Scientists need a more detailed understanding of how
human-produced atmospheric particles, called aerosols, affect climate
in order to produce better predictions of Earth's future climate,
according to a NASA-led report issued by the U.S. Climate Change
Science Program on Friday.

"Atmospheric Aerosol Properties and Climate Impacts," is the latest
in
a series of Climate Change Science Program reports that addresses
various aspects of the country's highest priority climate research,
observation and decision-support needs. The study's authors include
scientists from NASA, the National Oceanic and Atmospheric
Administration and the Department of Energy.

"The influence of aerosols on climate is not yet adequately taken
into
account in our computer predictions of climate," said Mian Chin,
report coordinating lead author from NASA's Goddard Space Flight
Center in Greenbelt, Md. "An improved representation of aerosols in
climate models is essential to more accurately predict the climate
changes."

are visible as dust, smoke and haze. Aerosols come from a variety of
natural and human processes. On a global basis, the bulk of aerosols
originate from natural sources, mainly sea salt, dust and wildfires.
Human-produced aerosols arise primarily from a variety of combustion
sources. They can be the dominant form of aerosol in and downwind of
highly populated and industrialized regions, and in areas of intense
agricultural burning.

Although Earth's atmosphere consists primarily of gases, aerosols and
clouds play significant roles in shaping conditions at the surface
and in the lower atmosphere. Aerosols typically range in diameter
from a few nanometers to a few tens of micrometers. They exhibit a
wide range of compositions and shapes, but aerosols between 0.05 and
10 micrometers in diameter dominate aerosols' direct interaction with
sunlight. Aerosols also can produce changes in cloud properties and
precipitation, which, in turn, affect climate.

Current predictions of how much Earth's average surface temperature
will increase in the future fall in a wide range. If the amount of
carbon dioxide and other greenhouse gases double from the levels in
the atmosphere in 1990, the increase in temperature is expected to be
from 2.2 to 7.9 degrees Fahrenheit, according to the U.N.
Intergovernmental Panel on Climate Change. The role of greenhouse
gases in global warming is fairly well established, but the degree to
which the cooling effect of human-produced aerosols offsets the
warming is still inadequately understood. The report states that
scientists should strive to improve their understanding of aerosols'
climate influences with the goal of cutting that range of uncertainty
by nearly two-thirds.

The report states that to achieve the goal of reducing uncertainties
in aerosol impacts on climate, an advanced, multi-disciplinary
approach that integrates surface, aircraft, and space-based
measurements with models will have to be developed. Scientists have
made gains in modeling aerosol effects, but this capability has not
yet been fully incorporated into climate simulations, according to
the report.

The report advocates the development of new space-based, field, and
laboratory instruments and the incorporation of more realistic
simulations of aerosol, cloud, and atmospheric processes into climate
models. The United States faces the challenge of maintaining and
enhancing its existing aerosol monitoring capability from space.
Satellites have been providing global aerosol observations since the
late 1970s, with major improvements in accuracy since the late 1990s.
But some of these missions, such as NASA's suite of Earth Observing
System satellites, are reaching or exceeding their design lives, the
report notes.

The complete report is available at:

http://www.climatescience.gov/Library/sap/sap2-3/default.php

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