Brief Communications

Nature 437, 496 (22 September 2005) | doi:10.1038/437496a; Published online 21 September 2005

Climate modelling: Northern Hemisphere circulation

Nathan P. Gillett1

Air pressure at sea level during winter has decreased over the Arctic and increased in the Northern Hemisphere subtropics in recent decades, a change that has been associated with 50% of the Eurasian winter warming observed over the past 30 years, with 60% of the rainfall increase in Scotland and with 60% of the rainfall decrease in Spain1. This trend is inconsistent with the simulated response to greenhouse-gas and sulphate-aerosol changes2, 3, but it has been proposed that other climate influences — such as ozone depletion — could account for the discrepancy3. Here I compare observed Northern Hemisphere sea-level pressure trends with those simulated in response to all the major human and natural climate influences in nine state-of-the-art coupled climate models over the past 50 years. I find that these models all underestimate the circulation trend. This inconsistency suggests that we cannot yet simulate changes in this important property of the climate system or accurately predict regional climate changes.

  1. Climatic Research Unit, School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK

Correspondence to: Nathan P. Gillett1 Email:


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