[Illustrations, footnotes and references available in PDF version]
Early last January, when the final 2008 numbers were in for the U.S. annual average temperature, we ran an article titled “U.S. Temperatures 2008: Back to the Future?” in which we noted that “The temperature in 2008 dropped back down to the range that characterized most of the 20th century.”
2009 seems to be following in 2008’s footsteps.
The national average temperature had been elevated ever since the big 1998 El Niño, which was leading some folks to clamor that global warming was finally showing up in the U.S. temperature record. “Finally,” because prior to 1998, there was little sign that anything unusual was going on with U.S. average temperatures (Figure 1). The end of the record was hardly any different than any other portion of the record. The slight overall trend arose from a couple of cool decades at the start of the 20th century rather than any unusual warmth towards the end.