NewsJanuary 12, 2011

It's Official: 2010 in a Statistical Tie for Warmest Year On Record

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Heidi Cullen

By Heidi Cullen

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The race is over and the results are in: 2010 tied with 2005 for the title of the warmest year on record, according to separate reports by NOAA and NASA today.

According to NASA, 2010 and 2005 differed by less than 0.018°F — an amount smaller than the actual uncertainty in comparing the temperatures, putting them into a statistical tie. The NOAA analysis by the agency's National Climatic Data Center (NCDC) found 2010 to be approximately 1.12°F above the 20th century average, whereas the NASA analysis found 2010 approximately 1.34°F warmer than the average global surface temperature from 1951 to 1980. Although they track the same variable — average global surface temperatures — the two agencies use different methodologies.

Global surface temperature records began in 1880, and 2010 marks the 34th consecutive year with global temperatures above the 20th century average, and is consistent with the long-term warming trend inked, in part, to burning fossil fuels. The last year with temperatures below the 20th century average occurred in 1976, NOAA reported.

Surface temperature departures from average during 2010. Credit: NOAA.

“The climate is continuing to show the influence of greenhouse gases,” said David Easterling, chief of the Scientific Services Division at NCDC.

In the new NASA analysis, the next warmest years are 1998, 2002, 2003, 2006 and 2007, which are statistically tied for third-warmest year. “If the warming trend continues, as is expected, if greenhouse gases continue to increase, the 2010 record will not stand for long,” said James Hansen, the director of NASA’s Goddard Institute for Space Studies

Taken separately, the global land surface temperatures for 2010 were tied with 2005 for the second-warmest on record at 1.73°F above the 20th century average, while global ocean surface temperatures for 2010 tied with 2005 as the third-warmest on record, at 0.88°F above the 20th century average. Also, according to the Global Historical Climatology Network, 2010 was also the wettest year on record.

As for the U.S., 2010 marked the 14th consecutive year with an average annual temperature above the long-term average in the lower 48. Since 1895, the temperature across the nation has increased at an average rate of roughly 0.12°F per decade. Overall, the lower 48 recorded its 23rd warmest year on record in 2010.

Notable Extreme Events

La Niña conditions took hold by the end of 2010, marked by a broad area of below average sea surface temperatures, as seen in this NASA image from December.

The year will long be remembered for a number of extreme weather and climate events. A natural climate phenomenon known as the Arctic Oscillation, or AO, led to an unusual jet stream setup in January and February 2010 that helped push cold Arctic air into much of the Northern Hemisphere. Record cold temperatures and heavy accumulations of snow blanketed much of the eastern seaboard as well as Europe. The February AO index saw the largest negative anomaly since records began in 1950.

From mid-June to mid-August, a strong upper air pattern (five to six miles up) shifted north of western Russia and then bent south into Pakistan. The jet stream stayed locked in this pattern for weeks and helped usher in an unprecedented two-month heat wave to Russia. It also contributed to devastating monsoonal floods in Pakistan at the end of July.

The year also featured a split between a period with El Niño conditions, which features abnormally warm sea surface temperatures in the tropical Pacific Ocean, and La Ni

ña conditions, when cooler than average water temperatures can be found in the central and eastern equatorial Pacific. These two phases are part of a broader climate cycle known as the El Niño-Southern Oscillation, or ENSO, and can affect weather patterns worldwide.

By July 2010, the ongoing El Niño that had begun the year had fully transitioned into La Niña, which may have also contributed to the flooding in Pakistan. By November, the La Niña was moderate to strong and helped to simultaneously bring drier conditions across the U.S. Southwest and extremely wet conditions to Australia. Significant flooding in Queensland continued into early 2011.

La Niña tends to make it less likely that a record warm year will occur. “Based on history, La Niña tends to depress global temperatures slightly below the trend,” Easterling said. However, this year its presence was insufficient to knock 2010 out of record territory.

Andrew Freedman contributed reporting to this story.