New meta-study sheds doubt on reliability of climate models

From biopact

Even though there is an overwhelming scientific consensus on the fact that humans are responsible for climate change, there remains controversy and doubt over the reliability of climate models used to forecast future changes. 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.

The 22 climate models used in the study are the same models used by the UN Intergovernmental Panel on Climate Change (see the IPCC's own evaluation of climate models, in Chapter 8 of the Working Group I Report, 'The Physical Science Basis'). The usual discussion is whether the climate model forecasts of Earth's climate 100 years or so into the future are realistic, says lead author Dr. David H. Douglass from the University of Rochester. But the new study asks a more fundamental question: can these same 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 who publish their findings in the Royal Meteorological Society's International Journal of Climatology, 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.

But when the researchers looked at actual climate data, however, they did not see accelerated warming in the tropical troposphere. Instead, the lower and middle atmosphere was warming the same or less than the surface. In layers near 5 km, the modelled trend was 100 to 300% higher than observed, and, above 8 km, modelled and observed trends even have opposite signs. For those layers of the atmosphere, the warming trend they observed in the tropics is typically less than half of what the models forecast, shedding serious doubt on the reliability of the models.

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References:
David H. Douglass, John R. Christy, Benjamin D. Pearson, S. Fred Singer, "A comparison of tropical temperature trends with model predictions (p n/a)", International Journal of Climatology, Dec 5 2007, DOI: 10.1002/joc.1651

VIA Eurekalert: New study increases concerns about climate model reliability - December 11, 2007.