A changing climate for climate modeling

Is the Earth's climate changing, and to what degree are these changes due to human actions? These are the key questions that must be answered before ratification of the Kyoto Protocol. Measurements must be used to evaluate the credibility of supercomputer models of the atmospheric, oceanic, and biotic systems that determine the world's climate. Unlike weather models, climate models deal with the entire atmosphere, ocean, and ice/land-surface system for decades or even centuries. One limiting factor on the use of these models is the availability of computer power to perform the simulations. The adequacy of computer resources and appropriateness of institutional arrangements for climate modeling in the United States was the subject of a National Research Council (NRC) report. Because climate models are not as strongly parallel as many fluid dynamics models, researchers have tended to use vector computers. Researchers are now working to optimize climate models to run on massively parallel computers such as the Cray T3E. Coordination among the federal agencies funding climate modeling has improved greatly. There will not be one national model, but each agency is supporting a few modeling groups and the modeling groups are exchanging modules between the models. Such interchange will allow researchers to choose the best component for each computational approach for each physical component contributing to a model.