BOULDER--The earth's mean surface temperature is expected to rise nearly 0.2 Kelvin (one-third degree Fahrenheit) per decade over the next fourdecades, according to a new modeling study using the climate systemmodel (CSM-1) developed at the National Center for Atmospheric Research(NCAR). NCAR scientists have just completed 170 years (1870-2040) oftheir two-century simulation of the earth's climate through 2100. NCAR'sByron Boville presented these results December 9 at the fall meeting ofthe American Geophysical Union in San Francisco. Other results expectedby the end of the year will include climate changes related toprecipitation, cloudiness, and basin-scale run-off. NCAR's primarysponsor, the National Science Foundation (NSF), funded the research,with additional computing time provided by the Electric Power ResearchInstitute.
The CSM-1 is a physical climate model employing coupled atmosphere andocean general-circulation models, a sea-ice model, and a land-biophysicsand simple hydrology model. It is one of the few current climate modelsthat maintain a stable surface climate over hundreds of years withoutthe need for artificial corrections.
The climate simulations were driven by observed changes in atmospherictrace-gas concentrations for the period 1870-1990 and two projectedtrace-gas scenarios for the period 1990-2100. The greenhouse gasesincluded in the model are carbon dioxide, methane, nitrous oxide, andchlorofluorocarbons 11 and 12. Emissions of sulfur dioxide (SO2)resulting from human activity are also included, with projectedincreases over time. Natural SO2 emissions were assumed to be constant.SO2 is important because it is converted in the atmosphere into sulfateaerosol, which reflects some sunlight back into space and may slow orreverse 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 atmosphericand related sciences.
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