2012 was hottest year in U.S. history

It's official: 2012 marked the warmest year on record for the USA, scientists from the National Climatic Data Center in Asheville, N.C., announced Tuesday. The past year smashed the previous record for the warmest year, which was 1998.

The average temperature for 2012 was 55.3 degrees, 3.2 degrees above the 20th-century average, and 1 degree above 1998.

U.S. weather records date to 1895.

"We had the warmest spring on record, the warmest July on record, and the third-warmest summer on record," said Deke Arndt, chief of the climate monitoring branch of the climate center, late last year.

Every state had a warmer-than-average year. A total of 19 states, stretching from Utah to Massachusetts, had record warmth in 2012 and an additional 26 states had a Top 10 warm year.

"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."

"What was truly astonishing," added Weather Underground weather historian Christopher Burt, "was the ratio of heat records vs. cold records that were established over the course of the year." Burt says that in 2012, there were 362 all-time record-high temperatures set across the nation, and zero all-time record lows.

The climate center also reported that 2012 was the driest year for the nation since 1988. Two states, Nebraska and Wyoming, had their driest years on record. Eight additional states had annual precipitation totals ranking among the bottom 10.

The large area of dry conditions in 2012 resulted in a very large footprint of drought conditions, which peaked in July with about 61% of the continental U.S. in moderate-to-exceptional drought, according to the climate report. "The footprint of drought during 2012 roughly equaled the drought of the 1950s, which peaked at approximately 60%."

The U.S. Climate Extremes Index also showed that 2012 was the second-most extreme year on record for the nation. The index, which evaluates extremes in temperature and precipitation, as well as tropical storms and hurricanes that make landfall, was nearly twice the average value and second only to 1998.

The past year had 11 disasters that reached the $1 billion threshold in losses, including Superstorm Sandy, Hurricane Isaac, and tornado outbreaks in the Great Plains, Texas and Southeast/Ohio Valley.

"A picture is emerging of a world with more extreme heat," said Andrew Dessler, a Texas A&M University climate scientist. "Not every year will be hot, but when heat waves do occur, the heat will be more extreme. People need to begin to prepare for that future."

Global data will be released next week by the climate center. Through November, the Earth was seeing its eighth-warmest year on record.