Alaska’s Cooling Trend

  • Date: 18/02/13
  • Ned Rozell, Alaska Dispatch

Fairbanks isn’t the only chilly place in Alaska. Average temperatures at 19 of 20 long-term National Weather Service stations displayed a cooling trend from 2000 to 2010, according a recent study written up by Gerd Wendler, Blake Moore and Lian Chen of the Alaska Climate Research Center

The rest of the world has not been going Alaska’s way. For the 36th consecutive year, the yearly global temperature in 2012 was warmer than average. That temperature, calculated from satellite data by researchers with NASA’s Goddard Institute for Space Studies, was about 58.3 degrees Fahrenheit (Fairbanks’s was 24.1 degrees F).

Bucking the trend

During the first decade of the 2000s, Alaska bucked the global warming trend, though the temperature variations were so slight you might not have noticed — except during winter, when most of the cooling occurred. One example was the frigid January of 2012. How could you forget it in Bettles, where the average temperature was an all-time low of minus 35.6 degrees F? That’s a chilly month.

But January 2012 also featured record highs throughout the Lower 48. Almost everywhere outside of Alaska is warming (sic). So why has Alaska been an island of cool?

“This trend was caused by a change in sign of the Pacific Decadal Oscillation,” Wendler, Blake and Chen wrote in their paper, “The First Decade of the New Century: A Cooling Trend for Most of Alaska.”

The Pacific Decadal Oscillation is a pattern of sea-surface temperatures in the North Pacific Ocean that seems to flip-flop every 20-to-30 years. The PDO influences the intensity and location of the Aleutian Low, which spins just offshore of the Alaska Peninsula. When sea-surface temperatures are relatively high in the North Pacific, the Aleutian Low is strong, causing warmer weather patterns in Alaska. We were in that groove from about 1977 to about 2000. It seems the switch has flipped to cool again.

Despite our recent trend, Alaska has for the last century warmed at about twice the rate of the rest of the globe, “as expected by the increasing CO2 and other trace gases,” Wendler and his colleagues wrote. Regarding the effect of the Pacific Decadal Oscillation, they wrote that warming “is sometimes temporarily modified or even reversed by natural decadal variations.”

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