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How good are Climate-Prediction Models?

September 20, 2012; 5:18 PM

A new study based out of the University of Arizona shows that climate-prediction models are indeed good at forecasting long-term (over 30 years) climate patterns on a global scale, but deteriorate when applied to smaller, geographical regions and with time frames that are less than 30 years.

The research team evaluated 7 computer simulation models used to compile the reports that the IPCC issues every six years. The researchers fed historical climate records into the models and compared their results to the actual climate change observed between then and now, according to the story.

The team evaluated climate predictions from 1900 into the future, such as 10, 20, 30, 40 and 50 years. Then the same starting in 1901, 1902 and so forth, and applied statistics to the results.

The goal of the study was to bridge the communities of climate scientists and weather forecasters, who sometimes disagree with respect to climate change, according to Xubin Zeng, a professor in the University of Arizona department of atmospheric sciences.

Excerpts from the University of Arizona News story......

"Climate scientists are correct because we do show that on the continental scale, and for time scales of three decades or more, climate models indeed show predictive skills. But when it comes to predicting the climate for a certain area over the next 10 or 20 years, our models can't do it," said Zeng, who serves on the Board on Atmospheric Sciences and Climate of the National Academies and the Executive Committee of the American Meteorological Society.

The skill of a climate model depends on three criteria at a minimum, Zeng explained. The model has to use reliable data, its prediction must be better than a prediction based on chance, and its prediction must be closer to reality than a prediction that only considers the internal climate variability of the Earth system and ignores processes such as variations in solar activity, volcanic eruptions, greenhouse gas emissions from fossil fuel burning and land-use change, for example urbanization and deforestation.

"Our analysis confirmed what we expected from last IPCC report in 2007," said Koichi Sakaguchi. "Those climate models are believed to be of good skill on large scales, for example predicting temperature trends over several decades, and we confirmed that by showing that the models work well for time spans longer than 30 years and across geographical scales spanning 30 degrees or more."

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This research was published in the Journal of Geophysical Research-Atmospheres.

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