WASHINGTON - America set an off-the-charts heat record in 2012.
A brutal combination of a widespread drought and a mostly absent winter pushed the average annual U.S. temperature last year up to 55.32 degrees Fahrenheit, the government announced Tuesday. That's a full degree warmer than the old record set in 1998.
Breaking temperature records by an entire degree is unprecedented, scientists say. Normally, records are broken by a tenth of a degree or so.
"It was off the chart," said Deke Arndt, head of climate monitoring at the National Climatic Data Center in Asheville, N.C., which calculated the temperature records.
Last year, he said, will go down as "a huge exclamation point at the end of a couple decades of warming."
The data center's figures for the entire world won't come out until next week, but through the first 11 months of 2012, the world was on pace to have its eighth warmest year on record.
Scientists say the U.S. heat is part global warming in action and natural weather variations. The drought that struck almost two-thirds of the nation and a La Nina weather event helped push temperatures higher, along with climate change from man-made greenhouse gas emissions, said Katharine Hayhoe, director of the Climate Science Center at Texas Tech University. She said temperature increases are happening faster than scientists predicted.
"These records do not occur like this in an unchanging climate," said Kevin Trenberth, head of climate analysis at the National Center for Atmospheric Research in Boulder, Colo. "And they are costing many billions of dollars."
Global warming is caused by the burning of fossil fuels - coal, oil and natural gas - which sends heat-trapping gases, such as carbon dioxide, into the air, changing the climate, scientists say.
What's happening with temperatures in the United States is consistent with the long-term pattern of "big heat events that reach into new levels of intensity," Arndt said.