2012 warmest year for U.S., officials say

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, the government announced Tuesday. That's a full degree warmer than the old record set in 1998.

Normally, temperature records are broken by a tenth of a degree or so.

Last year will go down as "a huge exclamation point at the end of a couple decades of warming," said Deke Arndt, head of climate monitoring at the National Climatic Data Center in Asheville, N.C.

The trend was matched on Long Island, which experienced its warmest year since records started being kept more than six decades ago, according to figures released last week. The mean temperature for the year in Upton was 54.22 degrees -- the highest mean temperature in the 63 years of weather data collection at Brookhaven National Laboratory.

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 Niña 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 fossil-fuel consumption, which sends heat-trapping gases, such as carbon dioxide, into the air, changing the climate, scientists say.

The U.S. temperatures are consistent with the long-term pattern of "big heat events that reach into new levels of intensity," Arndt said.

Last year was 3.2 degrees warmer than the average for the entire 20th century. U.S. temperature records go back to 1895 and the yearly average is based on reports from more than 1,200 weather stations across the Lower 48 states.