This is an excerpt from EERE Network News, a weekly electronic newsletter.

January 19, 2011

NOAA, NASA: 2010 Tied for Warmest Year on Record for the Globe

Independent analyses performed by the National Oceanic and Atmospheric Administration (NOAA) and the National Aeronautics and Space Administration (NASA) have found that 2010 is tied with 2005 as the warmest year in the 131-year instrumental record of global surface temperatures. NOAA's National Climatic Data Center (NCDC) found that the annual average for the combined global land and ocean surface temperatures was 1.12°F (0.62°C) above the 20th century average. While 2010 was the warmest year on record for the Northern Hemisphere, it was the sixth warmest year on record for the Southern Hemisphere. The record temperatures were aided by high ocean surface temperatures from January through April that were due to a strong El Niño, but a shift into a cold La Niña phase late in the year helped to lower the average ocean temperatures for the year. As a result, the global ocean surface temperature for 2010 tied with 2005 as the third warmest on record, while the global land surface temperature also tied with 2005 as the second warmest on record. See the NOAA press release and the NCDC report.

NASA's Goddard Institute for Space Studies (GISS) confirmed NOAA's findings, also placing 2010 in a tie with 2005 as the warmest year on record. GISS found that six recent years are statistically tied for third place—1998, 2002, 2003, 2006, 2007, and 2009—and that the Earth's climate has warmed by about 0.36°F per decade since the late 1970s. These decadal temperature trends are far more important than any particular year's ranking, according to GISS. The institute also noted that each independent agency handles the global temperature records in slightly different ways, sometimes causing minor differences in annual rankings, although they all agree on the overall warming trend. Most importantly, NASA, NOAA, and the U.K.'s Met Office Hadley Center all agree that the last decade (2000–2009) was the warmest on record. See the NASA press release on average global temperatures and the GISS press release on the differences in temperatures reported by the independent agencies.

Taking a longer view, researchers at the National Center for Atmospheric Research (NCAR) projected greenhouse gas emissions through the end of this century and found that if current trends continue unabated, atmospheric concentrations of greenhouse gases will reach levels that last existed 30–100 million years ago. At that time, global temperatures averaged about 29°F (16°C) above the average temperature recorded during relatively recent pre-industrial years. The study suggests that the warming effect of greenhouse gases may be double the effect that current models suggest. The authors speculate that current models, focused on short-term trends, fail to account for processes that will amplify the warming effect, such as the loss of ice sheets. See the NCAR press release.