Climate Models Match Well With Current Observations

Future preductions are less certain.

Climate model of Earth
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More than a dozen centers around the world develop climate models to enhance our understanding of climate change and serve as the basis for policy decisions. But just how good are those models, and can they truly be relied upon? A new study by meteorologists at the University of Utah shows that current climate models are quite accurate and can be valuable tools for those seeking solutions to global warming trends.

"Coupled models are becoming increasingly reliable tools for understanding climate and climate change, and the best models are now capable of simulating present-day climate with accuracy approaching conventional atmospheric observations," said Thomas Reichler of Utah’s Department of Meteorology. "We can now place a much higher level of confidence in model-based projections of climate change than in the past."

Reichler and his colleague Junsu Kim compared the output of about 50 different national and international models against real, observed present climate. The simulations were developed over the past two decades at major climate research centers in China, Russia, Australia, Canada, France, Korea, Great Britain, Germany, and the United States and included those used for the 2007 report of the Intergovernmental Panel on Climate Change.

Most of those models project a global warming trend that amounts to about 7 degrees Fahrenheit over the next 100 years.

Coupled climate models factor in several physical characteristics that affect climate, such dynamics of the atmosphere, oceans, land surface, living things, sea ice, and energy from the Sun. Reichler and Kim chose 14 different variables to evaluate model performance, including atmospheric pressure at sea level, air temperature, wind, precipitation, snow cover and ocean salinity.

The most complex models are so elaborate they must be run on supercomputers. A commonly used model, known as the Community Climate System Model, is so complex it requires about 3 trillion computer calculations to simulate a single day of global climate. According to the researchers, improvements in modern-day models resulted from not only better computing power but more comprehensive data collection and a more sophisticated understanding of climate processes.

Although model-based projections of future climate are now more credible than ever, the study was designed to see how well the models stack up to current climate, which is reliably observed and recorded. The "underlying assumption," the scientists say, is that a model that accurately describes present climate will make a better projection of the future. Still, they admit there too many unknowns involved in the evolution of future climate, such as how much humans will curb their greenhouse gas emissions.

The study, "How Well do Coupled Models Simulate Today's Climate?," was published April 4, 2008, in the Bulletin of the American Meteorological Society.

This research was supported by the National Science Foundation and the National Oceanic and Atmospheric Administration.

—Leslie Fink/NSF

This report is provided by the National Science Foundation, an independent federal agency that supports fundamental research and education across all fields of science and engineering, in partnership with U.S. News and World Report.