ROCHESTER, NY (Dec. 11, 2007) A new study comparing the composite output of 22 leading global climate models with actual climate data finds that the models do an unsatisfactory job of mimicking climate change in key portions of the atmosphere.
This research, published on-line Wednesday in the Royal Meteorological Societys International Journal of Climatology*, raises new concerns about the reliability of models used to forecast global warming.
The usual discussion is whether the climate model forecasts of Earths climate 100 years or so into the future are realistic, said the lead author, Dr. David H. Douglass from the University of Rochester. Here we have something more fundamental: Can the models accurately explain the climate from the recent past? It seems that the answer is no.
Scientists from Rochester, the University of Alabama in Huntsville (UAH) and the University of Virginia compared the climate change forecasts from the 22 most widely-cited global circulation models with tropical temperature data collected by surface, satellite and balloon sensors. The models predicted that the lower atmosphere should warm significantly more than it actually did.
Models are very consistent in forecasting a significant difference between climate trends at the surface and in the troposphere, the layer of atmosphere between the surface and the stratosphere, said Dr. John Christy, director of UAH's Earth System Science Center. The models forecast that the troposphere should be warming more than the surface and that this trend should be especially pronounced in the tropics.
When we look at actual climate data, however, we do not see accelerated warming in the tropical troposphere. Instead, the lower and middle atmosphere are warming the same or less than the surface. For those layers of the atmosphere, the warming trend we see in the tropics is typically less than half of what the models forecast.
The 22 climate models
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