The temperature trend, including data from 2010, shows the climate has warmed by approximately 0.36 F per decade since the late 1970s. "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 GISS. The analysis produced at GISS is compiled from weather data from more than 1000 meteorological stations around the world, satellite observations of sea surface temperature and Antarctic research station measurements.

A computer program uses the data to calculate temperature anomalies, the difference between surface temperature in a given month and the average temperature for the same period during 1951 to 1980. This three-decade period acts as a baseline for the analysis.  

The resulting temperature record closely matches others independently produced by the Met Office Hadley Centre in the United Kingdom and the National Oceanic and Atmospheric Administration's National Climatic Data Center. The record temperature in 2010 is particularly noteworthy, because the last half of the year was marked by a transition to strong La Nina conditions, which bring cool sea surface temperatures to the eastern tropical Pacific Ocean.

"Global temperature is rising as fast in the past decade as in the prior two decades, despite year-to-year fluctuations associated with the El Nino-La Nina cycle of tropical ocean temperature," Hansen and colleagues reported in the Dec. 14, 2010, issue of Reviews of Geophysics.  A chilly spell also struck this winter across northern Europe.