Conference 7.286::space

881.0. "NASA develops model of the earth "breathing"" by PRAGMA::GRIFFIN (Dave Griffin) Tue Dec 21 1993 09:29

Brian Dunbar

December 20, 1993
Headquarters, Washington, D.C.

Diane Farrar
Ames Research Center, Mountain View, Calif.

RELEASE:  93-223

        Scientists at NASA's Ames Research Center, Mountain View, Calif., have
created the first geographically precise image of the Earth
"breathing"--removing and releasing carbon dioxide into the atmosphere.

        The dynamic computer model shows monthly changes for carbon dioxide
released into the atmosphere as microbes decompose plant debris in the Earth's
soil.

        "The carbon stored in soils is the sleeping giant of global warming,"
said Dr. Christopher Potter, an ecologist at Ames.

        Carbon dioxide is a potent greenhouse gas, trapping heat close to the
Earth that would otherwise radiate into space.  Many scientists think that
increased amounts of carbon dioxide and other greenhouse gases, produced as
byproducts of human activities, are trapping enough heat to eventually warm the
Earth's atmosphere.

        Using recently assembled satellite images of the global land surface,
Potter and Steven Klooster, another Ames scientist, modeled how decaying plant
matter responds to changes in temperature and precipitation.

        "Remote-sensing satellites give us a new, unique view of the Earth as a
living, breathing system," Klooster said. "Before, we had only 'snapshots' or
static pictures from space.  Continuous satellite coverage now shows us
seasonal changes and helps us understand how carbon is distributed between the
tropics and high latitudes and how that distribution changes from month to
month."

        Potter said scientists are concerned that even a small degree of
greenhouse warming from the burning of fossil fuels and deforestation could
release increased carbon dioxide from the soil, setting up a chain reaction.  A
slight warming of the Earth's surface could cause temperature-sensitive
microbes to decompose carbon more rapidly, releasing increasing amounts of
carbon dioxide into the atmosphere.  This increased carbon dioxide could then
feed back into the climate system, raising temperatures further and beginning
the cycle again.

        The Ames research is among the first uses of satellite data from the
National Oceanic and Atmospheric Administration's NOAA-9 satellite to help
estimate the amount of carbon dioxide emitted from Earth's soil.  Scientists
from the Carnegie Institution of Washington and Stanford University
collaborated with Potter and Klooster.

        Understanding the links between large environmental systems, in this
case land surfaces, atmospheric chemistry and climate, is a fundamental goal of
NASA's Mission to Planet Earth (MTPE).  Using satellite data, other
measurements and analytical research MTPE is dedicated to understanding how the
Earth's global environment is changing, and to distinguishing natural changes
from human-induced changes.  The Ames research is part of MTPE's primary focus
on climate change.

        The Carnegie Ames Stanford Approach (CASA) Biosphere model shows annual
production of carbon dioxide from soils is 10 times that produced by fossil
fuel emissions.  The model shows that plants, however, absorb carbon dioxide in
amounts equal to that produced by the soils, balancing the output.

        The model also shows 60 percent of the carbon dioxide is produced and
absorbed at tropical latitudes.

        Monthly observations of climate, solar radiation and satellite data at
a one-degree latitude/longitude resolution for the entire globe drive the
model.

        Soil and vegetation types are also included because different types of
plant material decompose at different rates, Potter said.  Green, leafy matter
decomposes easily; woody, stem debris takes longer.  The CASA model shows that
the slowly decomposing soil carbon is predominant in most ecosystems.  It is
especially abundant in colder northern latitudes.

         Recent warming trends in the Arctic tundra, other research indicates,
may have produced an increased release of carbon dioxide from the large amounts
of carbon stored in high latitudes.

        The CASA model is also one of the first to simulate global soil
emissions of nitrous oxide, another important greenhouse gas.

        Potter said human activity is rapidly changing the nitrogen cycle.  A
significant part of the nitrogen used in agricultural fertilizer ends up in the
air, dramatically changing atmospheric concentrations of nitrous oxide.  When
it finds its way into the stratosphere, it also aids ozone depleting reactions,
he said.

        The CASA model can be used to study how tropical deforestation and
changes in land use effect emissions of atmospheric trace gases.  It can bring
a better understanding of the role of forests and land- use change in global
biochemical cycles.

        Models like the CASA approach, which are verified by independent
observations and continually refined, are an important element of NASA's
Mission to Planet Earth (MTPE).  MTPE focuses on the interactions of
large-scale environmental systems, such as Earth's plant life and the
atmosphere and climate.  The goal of MTPE is to collect, analyze and distribute
data that ultimately will allow humans to make informed policy decisions about
how their actions are affecting the global environment.

         This research is conducted by the Earth System Science Division at
Ames. It is funded by NASA Headquarter's Office of Mission to Planet Earth.