U.S. government weather forecasters say 2006 was the warmest year on record in the United States.
The National Oceanic and Atmospheric Administration (NOAA) said Tuesday that based on preliminary data, the average temperature in the U.S. last year was 12.7 degrees Celsius. Forecasters say this was 1.2 degrees warmer than average.
The forecasters attributed the warming trend in part to El Nino, an abnormal warming of water in the tropical Pacific Ocean that occurs every few years and can bring warmer temperatures to the U.S.
Additionally, they said a contributing factor was a long-term warming trend linked to increases in greenhouse gases. But, they said it was not clear how much of the recent warmth was due to greenhouse gases and how much was due to El Nino.
The previous warmest year on record was 1998.
Some information for this report was provided by AP and Reuters.