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1998-35 FOR IMMEDIATE RELEASE: December 9, 1998

New NCAR Climate System Model Shows Earth's Surface Temperature to Rise .2 K per Decade

David Hosansky
UCAR Communications
P.O. Box 3000
Boulder, CO 80307-3000
Telephone: (303) 497-8611
Fax: (303) 497-8610
E-mail: hosansky@ucar.edu

BOULDER -- The earth's mean surface temperature is expected to rise nearly .2 Kelvin (one-third degree Fahrenheit) per decade over the next four decades, according to a new modeling study using the climate system model (CSM-1) developed at the National Center for Atmospheric Research (NCAR). NCAR scientists have just completed 170 years (1870-2040) of their two-century simulation of the earth's climate through 2100. NCAR's Byron Boville presented these results December 9 at the fall meeting of the American Geophysical Union in San Francisco. Other results expected by the end of the year will include climate changes related to precipitation, cloudiness, and basin-scale run-off. NCAR's primary sponsor, the National Science Foundation (NSF), funded the research, with additional computing time provided by the Electric Power Research Institute.

The CSM-1 is a physical climate model employing coupled atmosphere and ocean general-circulation models, a sea-ice model, and a land-biophysics and simple hydrology model. It is one of the few current climate models that maintain a stable surface climate over hundreds of years without the need for artificial corrections.

The climate simulations were driven by observed changes in atmospheric trace-gas concentrations for the period 1870-1990 and two projected trace-gas scenarios for the period 1990-2100. The greenhouse gases included in the model are carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons 11 and 12. Emissions of sulfur dioxide (SO2) resulting from human activity are also included, with projected increases over time. Natural SO2 emissions were assumed to be constant. SO2 is important because it is converted in the atmosphere into sulfate aerosol, which reflects some sunlight back into space and may slow or reverse global warming trends in certain regions.

NCAR is managed by the University Corporation for Atmospheric Research, a consortium of more than 60 universities offering Ph.D.s in atmospheric and related sciences.

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