Saturday, March 15, 2008

Chilling on the River

Our friends along that river in Egypt (dee Nile) are all hot and bothered about the imminent prospect of global cooling. The Winter of 2007-2008 has indeed been a cool one, and January of 2008 had the smallest global temperature anomaly since February of 1994. February of '08 was also chill - aside from 1/09, you need to journey through deep time all the way back to 2000 to find another month so relatively cold. The people who found the evidence of global warming to be wanting have been quick to sieze on this as proof of whatever alternative theories they like - sunspots, cosmic rays, aliens.

The more conventional climate scientists note that temperature statistics are noisy and that the 2007-2008 la Nina now appears to be quite strong, with the current value of the multivariate ENSO index the lowest since the 1980's. A look at the graphs of the Hadley monthly temperatures shows that the monthly data is indeed noisy and that while current temperature are low by the standards of the current decade, they are still rather high compared to the 160 year temperature record. Determining who is more correct may need to wait until after the current la Nina (or longer), but I know which way I am betting.