Global warming: January update

Globally, last month was among the cooler Januaries of the last 20 years but still ended up as the 17th warmest January in the period of record dating to 1880, according to the National Climate Data Center.

The combined land-sea surface temperature finished 0.68 degrees Fahrenheit above the 20th Century average, the center reports.

That places it at No. 14 among Januaries of the last 20 years, which dominate the top spots in the January warming derby.

Last month also was about 0.4 degrees Fahrenheit cooler than January 2010, and that probably has a lot to do with the state of the tropical Pacific.

In the winter of 2009-10, an El Nino warming dominated millions of square miles of Pacific sea-surface. This year, it has been a La Nina cooling.

Arctic sea ice was at its smallest January extent since record-keeping began in 1979, the center said.

Snow cover in the Northern Hemisphere was above average for the fourth consecutive January.