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This item was posted on December 10, 2010, and it was categorized as Arctic Oscillation, Climate Change, El Nino/La Nina.
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Despite a strong La Niña, the past “meteorological year” was the warmest on record. With one month to go in 2010, the calendar year may well enter the record books too.

UPDATE 12/10/10 2:45 p.m.: ScienceNow and the Washington Post are now reporting the same thing. And they point out something I missed with my earlier post this morning: the December through November period is considered the “meteorological year” by scientists. So the fact that Dec. 2009 through Nov. 2010 comprised the warmest such period on record was even more of a distinction than I indicated. (Also, thanks to Climate Central for cross-posting my article.)

This morning’s original post starts here:

The table above shows the Land-Ocean Temperature Index, or LOTI, for each month over the past 10 years, through this past November. Published by NASA’s Goddard Institute for Space Studies, it is a measure of how much global temperature has departed from the 1951 to 1980 base period.

I’ve copied the data just for the past 10 years, but the entire chart shows that this past November was not only the warmest over the past decade, but also the warmest since record keeping began in 1880. This is despite current strong La Niña conditions, which tend to hold temperatures down. (Keep reading for information on La Niña’s impact on the United States . . .)

The column at the extreme right of the chart shows that the last 12 months (Dec. 2009 through Nov. 2010) comprised the warmest such period on record.

UPDATE 12/10/10 12:15 p.m.: NASA has just released it’s November temperature anomaly maps. Here’s how temperatures varied from the 1951-1980 base period around the globe that month:

The current strong La Niña is evident in this map as the bluish — meaning cool — surface water in the equatorial Pacific. Meanwhile, major parts of the Arctic and Russia, as well as the Antarctic Peninsula, were unusually warm.

The picture was different for the United States during November.

According to the National Climatic Data Center, November temperatures averaged across the country were near-normal.

That said, autumn in the United States, meaning the Sept-Oct.-Nov. period, was warmer than normal — thanks mostly to high temperatures in September and October. (My home state, Colorado, was much warmer than normal.) Since 1895, only 13 autumns have been warmer.

November temperatures in the United States were strongly influenced by two large-scale climatic patterns: La Niña and a strongly negative Arctic Oscillation. (Click on the links for more information about these phenomena.)

“The opposing temperature influences of these two atmospheric patterns contributed to a national temperature rank near the middle of the historical distribution,” according to the NCDC’s most recent report.

The current La Niña episode is the third strongest on record, using a scale called the Multivariate ENSO Index, or MEI. During a La Niña year, winter conditions in the United States tend to be warmer and drier than normal in the Southeast, and cooler and wetter than normal in the Northwest.

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This thing has 2 Comments

  1. spyder
    Posted December 10, 2010 at 5:03 pm | Permalink

    Judging by our winter so far, the cooler wetter prediction is slightly off for the NW. It may be due to the rather extreme warming of the Arctic regions to our own northwest, where the mix of cooler-wetter water in the atmosphere from la Nina is mixing with the much warmer than normal Arctic air spilling down with the jet stream. We are currently in a prolonged very wet period, warmer than normal, with snow levels well above the norm (mountain highway passes are still clear).

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