New Scientist: Some regional warming trends are natural and not caused by anthropogenic climate change, according to a recent report published in the Proceedings of the National Academy of Sciences. In the US Pacific Northwest, temperatures have risen by about 0.8 °C since 1900. To try to understand why, James Johnstone and Nathan Mantua of the University of Washington in Seattle compared the air pressure at sea level with sea-surface and air temperatures over the past century. They noticed a strong correlation between changes in sea-surface temperature and changes in atmospheric circulation. "The most straightforward explanation is that changes in the wind have forced the changes in the temperature," says Johnstone. Although they don’t know what causes the winds to shift, they could find no obvious link to global warming.
