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NASA and NOAA calculations differ mostly in the polar areas, where there are far less measurements.

A fourth group out of the University of Alabama at Huntsville looks at temperatures measured by satellites and only goes back to 1979, but is preferred by climate skeptics. That measurement ranked 2012 as the ninth warmest on record and notes that 11 of the 12 hottest years in their dataset have occurred since 2001.






Seth Borenstein can be followed at