An abnormally warm decade is part of the new ‘normal’

It turns out that, even when you're talking about the weather, "normal” is a relative term. On July 1, normal temperatures all across the United States became slightly warmer. That's because the 30-year averages used to determine "normal” changed, dropping the decade of the 1970s and adding the decade of 2001 through 2010. - "Definitely on a national scale and globally, 2001 through 2010 was the warmest decade in history. On a regional basis, it gets a little thornier to say it's the warmest, but it is up there,” said Karin Bumbaco, a University of Washington research scientist with the Joint Institute for the Study of the Atmosphere and Ocean in the College of the Environment. Normal weather conditions are revisited at the end of each decade, when the National Climatic Data Center , an arm of the National Oceanic and Atmospheric Administration , adds the figures for the most recent decade and eliminates those from the decade that ended 30 years earlier. In the past the process didn't make much of a splash because it had little practical effect.