NCPA - National Center for Policy Analysis


July 6, 2004

The National Center for Atmospheric Research in Boulder, Colo., released the latest version of its Community Climate System Model -- CCSM3. Its predecessors were among several mathematical models run on supercomputers to study climate.

CCSM3 exemplifies the promise and problems that face those who try to predict the Earth's climate:

  • A single day's worth of global climate simulation requires 3 trillion calculations; the new CCSM3 is fast enough to calculate four years of climate in a day.
  • The CCSM3 has been able to calculate the extent of Artic sea ice, a feature that previous models had been unable to do.
  • Even more importantly, the model replicates clouds whose impact on the weather is significant, either in heating the planet by creating a "blanket" to trap warm air, or in cooling the planet by preventing the sun's heat from reaching the surface.

The down side to the new model, says scientist Philip Merilees, is that "the clouds are too thick, too thin or not in the right places."

The new model predicts that global average temperatures will warm by 4.7 degrees Fahrenheit if carbon dioxide output is doubled, which is a greater warming than the previously used CCSM2 model predicted. The new CCSM3's prediction, however, should be viewed with caution, since the model still has inconsistencies.

Furthermore, while models can provide predictions about general climate change, people are more interested in how their local area will be affected by climate change. The challenge for large-scale climate models is how they will interact with local climate events.

Source: Dan Whipple, "Climate: Cloudy Days in Climate Modeling," Washington Times, June 28, 2004; and William O'Keefe and Jeff Keuter, "Climate Models: A Primer," George C. Marshall Institute.

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