Capping two years of research, a nationwide group of over
100 scientists has created a powerful new computer model of the Earth’s
climate. The model surpasses previous efforts by successfully incorporating
the impact of such variables as ocean currents and changes in land-surface
temperatures.

Researchers will use the model, called CCSM-2 (Community Climate System
Model, version 2) to probe how our climate works and to experiment with
“what-if” scenarios to predict what our climate may be like
in the future. The model will also look at past climate. For example,
researchers plan to perform an extended, multicentury simulation of past
shifts in the climate’s equilibrium.

The model’s increased capabilities will permit new types of studies, such
as the “Flying Leap Experiment,” which will track fossil fuel
carbon emissions as they are dissolved in the oceans and subsequently
released back into the atmosphere.

Jeffrey Kiehl, a key leader in development of the model at the National
Center for Atmospheric Research, expects the CCSM-2 to play an integral
role in the next climate assessment by the Intergovernmental Panel on
Climate Change, the international organization that issues periodic assessments
of global climate change.

Based at NCAR, the model is funded by the National Science Foundation
and the Department of Energy.

“The model is better [than its earlier version] at simulating phenomena
with worldwide climate implications, such as El Niño,” says
Kiehl. “The new version has higher spatial resolution in both oceans
and sea ice, and the atmosphere is represented by a larger number of vertical
layers."

To achieve the extensive modifications in the latest version, which was
released last month, scientists applied the model to specific problems.
For example, they weighed the climatic impacts of past volcanic eruptions,
fluctuations in ocean salinity, changes in land vegetation, and the thickness
of sea ice. The resulting model has far more data than the earlier version,
allowing scientists to make more detailed climate projections.

“A coordinated community activity on this scale is rare in the climate
sciences," says Kiehl. The contributors worked in groups on land,
ocean, sea ice, and other components of the model toward the single, common
goal of capturing the Earth’s climate system. It was truly a collaborative
effort.”

Since 1983, NCAR scientists have been refining global climate models that
are freely available to researchers worldwide. CCSM-2, which supercedes
the first CCSM created in 1998, will be used to produce improved simulations
of average climate and climate variability.

Richard Anthes, president of the University Corporation for Atmospheric
Research (wh3manages and operates NCAR) says: “The CCSM effort
is a great example of the trend towards increasing collaboration among
research institutions on complex and important scientific problems.”

NCAR’s primary sponsor is the National Science Foundation. •
David Hosansky