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Science Forum Index » Environment Forum » SCIENTISTS "RECONSTRUCT" EARTH'S CLIMATE OVER PAST MILLENNIA
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| George |
 Posted: Wed Dec 17, 2003 12:32 am |
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http://www.gsfc.nasa.gov/topstory/2003/1211millenium.html
http://www.sciencedaily.com/releases/2003/12/031216075809.htm
Using the perspective of the last few centuries and millennia, speakers in a
press onference at the Fall Meeting of the American Geophysical Union in San
Francisco discussed the latest research involving climate reconstructions
and different climate models.
The press conference, held Thursday, December 11, featured Caspar Ammann of
the National Center for Atmospheric Research (NCAR), Boulder, Colo.; Drew
Shindell of NASA's Goddard Institute for Space Studies, New York; and Tom
Crowley of Duke University, Durham, N.C.
Changes in the sun's activity have been considered responsible for some part
of past climatic variations. Although useful measurements of solar energy
are limited to the last 25 years of satellite data, this record is not long
enough to confirm potential trends in solar energy changes over time.
Tentative connections between the measured solar activity, with sunspots or
the production of specific particles in the Earth's atmosphere (such as
carbon-14 and beryllium-10), have been used to estimate past solar energy.
Ammann discussed how he used a set of irradiance estimates with the NCAR
coupled Ocean-Atmosphere General Circulation computer model to show the
climate system contains a clearly detectable signal from the sun.
Ammann's work with the model also demonstrates that smaller, rather than
larger, background trends in the sun's emitted energy are in better
agreement with the long-term climate record, as obtained from proxy climate
records, such as tree-ring data.
Shindell discussed how he used a climate model that included solar radiation
changes, volcanic eruptions, and natural internal variability to arrive at a
more accurate look at Earth's changing climate today. Shindell said that
while solar radiation changes and volcanoes exert a similar influence on
global or hemispheric average-temperature changes, the solar component has
the biggest regional effect over time scales of decades to centuries, while
volcanoes cause the largest year-to-year changes.
Crowley discussed one of the goals of climate modeling, to test whether
moderately reliable predictions of regional climate change can be made under
globalwarming scenarios.
Using paleoclimate data, scientists can in some cases test computer
climate-model performance. This testing would occur for a time period in
which models accurately predict the larger (hemispheric-scale) response to
changes in the Earth's radiation balance.
NASA's Earth Science Enterprise is dedicated to understanding the Earth as
an integrated system and applying Earth System Science to improve prediction
of climate, weather and natural hazards using the unique vantage point of
space.
NCAR is a research laboratory operated by the University Corporation for
Atmospheric Research, a consortium of 67 universities offering doctoral
programs in the atmospheric and related sciences. NCAR's primary sponsor is
the National Science Foundation. |
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