CLIMATE predictions for many regions of the world may have to be rethought, following the discovery that global warming may have a bigger effect on air pressure than anyone thought.
Nathan Gillett at the University of East Anglia, UK, compared observed changes in air pressure in the northern hemisphere over the past 50 years with simulations from nine modern climate models. The models only simulated around 10 per cent of the pressure changes actually observed. Even when Gillett factored in external influences such as ozone depletion, the changes were underestimated (Nature, vol 437, p 496).
The models may underestimate the effect of greenhouse gases on pressure, Gillett suggests. 鈥淎nother possibility is that the variations are natural, and that the natural variability in air pressure is underestimated by all the models.鈥�
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Recent pressure changes are thought to have caused milder, wetter winters in northern Europe, drought in southern Europe and warmer, windier winters in the north-western US. If climate models cannot predict such changes, they will not accurately forecast changes in regional weather patterns, Gillett says.
