By Juliet Eilperin
Washington Post Staff Writer
Wednesday, January 12, 2011; 7:32 PM
Last year has tied 2005 as the warmest year on record, the National Oceanic and Atmospheric Administration and NASA's Goddard Institute for Space Studies announced Wednesday.
That conclusion, drawn from analyses of global surface temperatures, means that the decade that just ended included nine of the 10 hottest years on record.
Derek Arndt, who heads the climate monitoring branch at NOAA's National Climatic Data Center in Asheville, N.C., said the new data should be viewed in the context of the record retreat of snow cover in the Northern Hemisphere at the end of the melt season and a near-record retreat of Arctic sea ice.
"Together across the board, it was an unusual year, and a year that in many ways was a culmination of what we've been seeing for the past several years," Arndt said.
NASA's Goddard Institute conducted an analysis separate from NOAA's but reached the same conclusion Wednesday. Later this month both the Hadley Center, part of Britain's national weather service, and the U.N. World Meteorological Organization will report their assessments of last year's temperatures.
Global temperatures have been above the 20th-century average for 34 consecutive years. In 2010, the combined land and ocean annual surface temperature was 1.12 degrees above average. Scientists have been keeping records since 1880.
Last year was also the wettest on record in terms of global average precipitation, according to the Global Historical Climatology Network, which collects data from meterological organizations around the world.
But the rate of precipitation, like the temperature, varied widely depending on the region: The 2010 Pacific hurricane season had only seven named storms and three hurricanes, the fewest since researchers started using satellite tracking in the 1960s.
Meanwhile, an unusual jet stream brought a two-month heat wave to Russia last summer and helped spur severe flooding in Pakistan at the end of July.
The United States started off 2010 with extremely low winter temperatures and snowfall that broke records in several locations, including Washington and Baltimore, and prompted lawmakers such as Sen. James M. Inhofe (R-Okla.) to question whether climate change was happening. But the overall average annual temperature for the contiguous United States in 2010 was above normal, resulting in the 23rd-warmest year on record.
Jim Hurrell, a senior research scientist at the National Center for Atmospheric Research in Boulder, Colo., noted that 2010 managed to be a record-warm year despite the fact that two natural factors - less solar activity and the onset of La Nina, an irregular cycle that brings cooler temperatures to the Pacific Ocean - would have exerted a cooling effect.
"Despite year-to-year variability, this continues to illustrate we're still in an extremely warm period of Earth's history," Hurrell said, adding that human-generated fossil-fuel emissions were contributing to climate change.
Although lawmakers show little interest in imposing a national cap on such emissions, environmentalists said they hoped the latest temperature analyses would shift political attitudes on the issue.
"Hopefully, this new data will finally convince congressional climate-science deniers that global warming is real and that action is urgent," said Daniel J. Weiss, who directs climate strategy for the Center for American Progress, a liberal think tank. "To reject this latest evidence is like ignoring strange spots on a chest X-ray and continuing to smoke."