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

January 23, 2008

2007 Ranks Among the Warmest Years on Record

2007 was either the second-warmest or fifth-warmest year on record for the globe, depending on which group of researchers you listen to. The Goddard Institute of Space Studies (GISS), a part of the National Aeronautics and Space Administration, claims that 2007 ties with 1998 as the second-warmest year on record, but the National Climatic Data Center, a part of the National Oceanic and Atmospheric Administration (NOAA), puts 2007 in fifth place. And to muddle things further, the two agencies use different baselines for comparison: GISS says 2007 was 1.026 degrees Fahrenheit above the mean temperature for 1951-1980, while NOAA says 2007 was 0.99 degrees Fahrenheit above the average temperature for the entire 20th century.

Regardless of the rankings, the two agencies agree that the eight warmest years on record have all occurred since 1998, making the past decade a clear record-breaker. And as GISS notes, the warmth in 2007 occurred despite solar irradiance (the amount of energy Earth receives from the sun) reaching a minimum and a strong La Niña episode (a cooling in the equatorial region of the Pacific Ocean) developing late in the year, both factors that would tend to push down global temperatures. 2007 started with a warming boost from an El Niño event, which is a warming in the equatorial region of the Pacific Ocean, but that phenomenon faded quickly, confounding some predictions for 2007 to be a record-breaking year. See the press releases from GISS and NOAA and the analyses from GISS and NOAA.

Both GISS and the United Kingdom's Met Office ("Met" being short for "Meteorological") agree on a separate matter: that 2008 will probably be cooler than 2007, but will still be among the warmest years on record. Both agencies expect the continuing La Niña to hold down global temperatures, while GISS also notes that solar irradiance will still be near its minimum. The Met Office expects 2008 to be the coolest year since 2000, but it uses yet another temperature baseline for comparison, so we won't even mention its exact forecast. See the Met Office press release.