2010 Ties as Hottest Year on Record

BY Jenny Marder  January 20, 2011 at 6:06 PM EDT

Despite slight variations in data, a flurry of reports from different agencies has reached the same general conclusion: 2010 takes the prize as one of the hottest years ever recorded.

The World Meteorological Organization, which released its global temperature analysis on Thursday, has 2010 locked in a three-way tie with 2005 and 1998 for the warmest year on the books. Reports released by the National Oceanic and Atmospheric Administration and NASA’s Goddard Institute for Space Studies last week knocked 1998 out of the running, instead tying 2010 with 2005.

But the bottom line is clear, experts say: Temperatures continue to rise steadily. “The 2010 data confirm the Earth’s significant long-term warming trend,” according to WMO Secretary-General Michel Jarraud.

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The WMO marked 2010′s global average temperature at .95 degrees Fahrenheit above the 1961 to 1990 average, slightly lower than NOAA’s National Climatic Data Center average, which placed the year’s mean temperature at 1.12 degrees Fahrenheit higher than the 20th century average. NASA’s Goddard Institute for Space Studies said the year was 1.34 degrees warmer than average temperatures from 1951 to 1980.

And according to a statement released by NASA last week, 2009, the third warmest year, is statistically so close to 1998, 2002, 2003, 2006, and 2007, that those six years are also virtually tied.

These numbers are based on measurements collected from thousands of monitoring points around the globe, as well as satellite data and ships and buoys moored in the ocean.

The agencies used slightly different methods, which account for the varied results, says David Easterling, chief of the scientific division at the U.S. National Climatic Data Center.

For example, large swaths of the Arctic lack weather stations, making the area tricky to measure. NASA measurements fill that gap by using weather from the nearest monitoring stations; NOAA leaves much of the arctic out of its analysis. And whether 1998 was included or not, Easterling charecterizes the difference as marginal. “The difference from the long term average was just a few hundredths of a degree smaller than 2005 and 2010,” he said. “Part of it has to do with how many significant digits you go out.”

2010 stood out not only for its heat waves, but also hurricanes and severe flooding in Pakistan, Sri Lanka and Brazil. Africa and parts of Asia and the Arctic are warming the most. And 2001 to 2010 marks the hottest decade recorded since the beginning of climate records.

“I think the fact that all three of us found that 2010 was one of warmest years, if not the warmest year on record, just reinforces our analyses and shows how robust they are,” Easterling said.