2009 Ends Warmest Decade on Record

Except for a leveling off between the 1940s and 1970s, Earth's surface temperatures have increased since 1880. The last decade has brought temperatures to the highest levels ever recorded, and the last year of the decade (2009) was tied for the second warmest year in the modern record, a new NASA analysis of global surface temperature shows. The analysis, conducted bythe Goddard Institute for Space Studies (GISS) in New York City, is based ontemperatures recorded at weather stations around the world and satellite dataover the oceans.

These maps illustrate just how much warmer temperatures were in 2009 (topimage) and the decade (2000-2009, lower image) compared to average temperaturesrecorded between 1951 and 1980 (a common reference period for climate studies).In the image, the most extreme warming, shown in red, was in the Arctic. Very few areas saw cooler than average temperatures, shown in blue in both timeperiods. Gray areas over Africa and parts of the Southern Ocean are places where temperatures were not recorded.

Although 2008 was the coolest year of the decade, dueto strong cooling of the tropical Pacific Ocean, 2009 saw a return tonear-record global temperatures, despite an unseasonablycool December in much of North America,Europe, and Asia. The year was only a fraction of a degree cooler than 2005, the warmest year on record, and tied with a cluster of other years-1998, 2002,2003, 2006 and 2007 1998 and 2007-as the second warmest year since modern record keeping began in 1880. In the Southern Hemisphere, 2009 was the warmestyear on record.

"There's always an interest in the annual temperature numbers and on agiven year's ranking, but usually that misses the point," said James Hansen,the director of GISS. "There's substantial year-to-year variability of global temperature caused by the tropical El Niño-La Niña cycle. But when we average temperature over five or ten years to minimize that variability, we find thatglobal warming is continuing unabated."

January 2000 to December 2009 was the warmest decade on record. Throughoutthe last three decades, the GISS surface temperature record shows an upwardtrend of about 0.2°C (0.36°F) per decade. Since 1880, the year that modern scientific instrumentation became available to monitor temperatures precisely, a clear warming trend is present. In total, average global temperatures have increased by about 0.8°C (1.5°F) since 1880.

Reference

Voiland, A. (2010, January 21). 2009: SecondWarmest Year on Record; End of Warmest Decade. NASAGoddard Institute for Space Studies. Accessed January 22, 2010.

Further Reading

NASA Climatologist Gavin Schmidt Discusses the Surface Temperature Record

Earth'sTemperature Tracker

GlobalWarming Factsheet

NASA images by Robert Simmon, based on data from the Goddard Institute for Space Studies. Caption by Adam Voilandand Holli Riebeek.

Instrument: 

In situ Measurement