NASA, NOAA find 2012 among the hottest years on record
Last year was the ninth warmest year since 1880, and the average temperature during the year was 1.0 degrees warmer than the mid-20th century baseline, NASA announced Jan. 15.
NASA compares the average global temperature each year to the average from 1951-1980 to measure global warming. The last time the yearly average was cooler than that baseline was 1976.
2012 was also the warmest year on record for the continental United States.
Instances of unusually high temperatures have also become more common. A seemingly small uptick in the temperature can have major effects--as in 2012's persistent drought across the United States--noted James Hansen, director of NASA's Goddard Institute for Space Studies, during a Jan. 15 press call.
"This last year is a good teaching moment, because we can see how big an impact a summer-mean anomaly of two or three degrees can be," Hansen said.
The global temperature increase doesn't impact all parts of the globe the same way at the same time. But "eventually your turn comes, and when it does, the temperatures tend to be a lot warmer," added Thomas Karl, the director of the National Oceanic and Atmospheric Administration's National Climatic Data Center.
While there are many factors at play, Karl said greenhouse gas emissions were enough on their own to drive the temperature rise.
NOAA, which measures global temperatures separately from NASA, found 2012 to be the 10th warmest year on record instead of the ninth.
"Every approach has slightly different assumptions, and that's why we think it's so important that we've got independent groups going about it slightly differently," Karl said. "It's just too hard to say what is exactly the right approach."
NOAA's findings also show 2012 to be the warmest La Nina year on record. La Nina is associated with cooler-than-normal water temperatures in the equatorial Pacific Ocean.