Baseline temperature averages issued by government scientists this week indicate that temperatures across the United States were half a degree warmer on average from 1981 to 2010 than they were from 1971 to 2000.

Every state’s annual maximum and minimum temperatures increased on average, the National Oceanic and Atmospheric Administration’s National Climatic Center said.

The 30-year averages, known as normals, are used to gain an understanding of how current climate conditions compare with those in recent history. Utilities use them to project energy consumption, and agribusinesses rely on them to assess crop yields and compare them with those in the recent past. The normals are updated every 10 years.

In another report released by the administration this week, a major global survey titled “State of the Climate in 2010,” the National Climatic Data Center said that 2010 tied with 2005 as the planet’s warmest year in recorded history.



Emissions of heat-trapping carbon dioxide increased more rapidly in 2010 than in 2009, and faster than they had on average over the last 30 years, the study showed. The report attributed the warmer temperatures both to a decades-long pattern of global warming and the El Niño climate pattern that prevailed in the first six months of the year.

The 261-page report devotes eight pages simply to listing the scientists who created it. “It’s 385 authors from 45 countries looking at 41 different climate variables,” said Justin Kenney, an agency spokesman. “And every single variable pointed toward a warming climate.”

Scientists have linked the warming trend to human activity like the burning of fossil fuels, in part by examining the composition of atmospheric carbon dioxide, the most rapidly increasing greenhouse gas. Man-made carbon dioxide and its naturally occurring counterpart tend to be made of different types of carbon atoms. The version associated with fossil fuel combustion is being found more frequently as the years go by, the report said.

“The current rate of increase in atmospheric CO2 is exceptional when compared to changes on geological time scales, as assessed from measurements of air trapped in ice cores,” the report said.

For Deke Arndt, who leads the climate monitoring branch at the agency’s National Climatic Data Center, one element of the findings in particular jumped out: an especially sharp increase in Arctic temperatures.

“What we’ve seen in Greenland is eye-opening,” Mr. Arndt, one of the report’s authors, said in an interview. Temperatures in Greenland and other Arctic regions, which he said could be an early indicator of significant climate change, increased at a much higher rate than in the rest of the world.

“The Greenland ice sheet lost a record amount of mass, as the melt rate was the highest since at least 1958, and the area and duration of the melting was greater than any year since at least 1978,” the report said.

With consistently warmer temperatures, Mr. Arndt said, the Arctic melting process feeds itself. When ice, an effective reflector of sun rays, melts away, it exposes more ocean surface area to the sun, further warming the water that melts the ice.