National Climatic Data Center
24 April 2008
NOAA: 2007 a Top Ten Warm Year for U.S. and Globe
The year 2007 the 10th warmest year for the contiguous U.S., since national records began in 1895, according to preliminary data from NOAA's National Climatic Data Center in Asheville, N.C. The year was marked by exceptional drought in the U.S. Southeast and the West, which helped fuel another extremely active wildfire season. The year also brought outbreaks of cold air, and killer heat waves and floods. Meanwhile, the global surface temperature for 2007 was the fifth warmest since records began in 1880.U.S. Temperatures
The average U.S. temperature for 2007 was 54.2°F; 1.4°F warmer than the 20th century mean of 52.8°F. NCDC originally estimated in mid-December that 2007 would end as the eighth warmest on record, but below-average temperatures in areas of the country last month lowered the annual ranking. For Alaska, 2007 was the 15th warmest year since statewide records began in 1918.
Six of the 10 warmest years on record for the contiguous U.S. have occurred since 1998, part of a three decade period in which mean temperatures for the contiguous U.S. have risen at a rate near 0.6°F per decade.
The warmer-than-average conditions in 2007 influenced residential energy demand in opposing ways, as measured by the nation's Residential Energy Demand Temperature Index. Using this index, NOAA scientists determined that the U.S. residential energy demand was about three percent less during the winter and eight percent higher during the summer than what would have occurred under average climate conditions.
Exceptional warmth in late March was followed by a record cold outbreak from the central Plains to the Southeast in early April. The combination of premature growth from the March warmth and the record-breaking freeze behind it caused more than an estimated $1 billion in losses to crops (agricultural and horticultural).
A severe heat wave affected large parts of the central and southeastern U.S. in August, setting more than 2,500 new daily record highs.Global Temperatures
For 2007, the global land and ocean surface temperature was the fifth warmest on record. Separately, the global land surface temperature was warmest on record while the global ocean temperature was 9th warmest since records began in 1880. Some of the largest and most widespread warm anomalies occurred from eastern Europe to central Asia.
Including 2007, seven of the eight warmest years on record have occurred since 2001 and the 10 warmest years have all occurred since 1995. The global average surface temperature has risen between 0.6°C and 0.7°C since the start of the twentieth century, and the rate of increase since 1976 has been approximately three times faster than the century-scale trend.
The greatest warming has taken place in high latitude regions of the Northern Hemisphere. Anomalous warmth in 2007 contributed to the lowest Arctic sea ice extent since satellite records began in 1979, surpassing the previous record low set in 2005 by a remarkable 23 percent. According to the National Snow and Ice Data Center, this is part of a continuing trend in end-of-summer Arctic sea ice extent reductions of approximately 10 percent per decade since 1979.U.S. Precipitation and Drought Highlights
Severe to exceptional drought affected the Southeast and western U.S. More than three-quarters of the Southeast was in drought from mid-summer into December. Increased evaporation from usually warm temperatures, combined with a lack of precipitation, worsened drought conditions. Drought conditions also affected large parts of the Upper Midwest and areas of the Northeast.
Water conservation measures and drought disasters, or states of emergency, were declared by governors in five southeastern states, along with California, Oregon, Maryland, Connecticut, and Delaware at some point during the year.
A series of storms brought flooding, millions of dollars in damages and loss of life from Texas to Kansas and Missouri in June and July. Making matters worse were the remnants of Tropical Storm Erin, which produced heavy rainfall in the same region in August.
Drought and unusual warmth contributed to another extremely active wildfire season. Approximately nine million acres burned through early December, most of it in the contiguous U.S., according to preliminary estimates by the National Interagency Fire Center.
There were 15 named storms in the Atlantic Basin in 2007, four more than the long-term average. Six storms developed into hurricanes, including Hurricanes Dean and Felix, two category 5 storms that struck Mexico's Yucatan Peninsula and Nicaragua, respectively (the first recorded occurrence of two category 5 landfalls in the Atlantic Basin in the same year). No major hurricanes made landfall in the U.S., but three tropical storms and one Category 1 hurricane made landfall along the Southeast and Gulf coasts.
La Niña conditions developed during the latter half of 2007, and by the end of November, sea surface temperatures in the eastern equatorial Pacific were more than 3.6°F (2°C) below average. This La Niña event is likely to persist into early 2008, according to NOAA's Climate Prediction Center.