November 9, 2009

Another Normal Year for U.S. Temperatures?

Filed under: Surface, Temperature History

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.


Figure 1. United States annual average temperature, 1895-1997 (data source: National Climate Data Center).

Then along came the 1998 El Niño, which raised both global and U.S. temperatures to record values, and our national temperatures remained elevated for 10 years thereafter (Figure 2). Instead of looking for some explanation of this unusual run of very warm years in the (naturally) changing patterns of atmospheric/ocean circulation in the Pacific Ocean, it was often chalked up to “global warming.”


Figure 2. United States annual average temperature, 1895-2007 (data source: National Climate Data Center).

But then something unexpected (by the global warming enthusiasts) happened in 2008—the U.S. annual average temperature returned to normal.

In reporting this in our World Climate Report article last January, we noted the drop in temperatures and wondered about the future:

But now, 2008 comes along and has broken this warm stranglehold. Perhaps this is an indication that the conditions responsible for the unusual string of warm years have broken down—and maybe they weren’t a sudden apparition of anthropogenic global warming after all.

Only time will tell for sure. But, at least for now, things seem like they have returned to a more “normal” state of being.

Now, 10 months have passed and we are starting to get a good idea of how 2009 is shaping up temperature-wise for the U.S. We may be jumping the gun a little here, because there are still two months (17%) of data still outstanding, and November has started out pretty warm across the West, but, in any case, Figure 3 shows the national temperature history for the first 10 months of the year.


Figure 3. United States January-October average temperature, 1895-2009 (data source: National Climate Data Center).

Thus far, 2009 is looking like another normal year—further indication that the warm period from 1998-2007 was an anomaly, rather than a step change to a new climate across the U.S. (be sure to check back in two months to see how the final 2009 numbers pan out).

No wonder the U.S. Senate is slow to get behind the need for restricting our fossil fuel-related energy supply in the name of climate change.




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