Southwest leads nation in warming

Posted: Jun 13, 2012

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Warming in the US

The Southwest is the fastest-warming region in the United States, with Arizona experiencing the most rapid temperature change, according to a report released today by Climate Central.

The continental United States warmed about 1.3 degrees Fahrenheit on average over the past century, the analysis by the nonprofit research and journalism organization found. But Claudia Tebaldi, a senior scientist at Climate Central, and her colleagues highlighted the significant differences among regions and states.

Between 1912 and 2011, the top 10 fastest-warming states heated up 60 times faster than the 10 slowest-warming states, according to the report "The Heat Is On: U.S. Temperature Trends."

Arizona topped the list, followed by Michigan, Minnesota, Wisconsin, Vermont, New Mexico, Utah, Maine, Texas and Massachusetts.

"The Southwest and North Central and Northeastern states are clearly warming faster than the rest of the country," Tebaldi said in a statement.

Tebaldi, who is also a visiting scientist at the National Center for Atmospheric Research, used recorded daily maximum and minimum temperatures from the National Climatic Data Center for the analysis.

States that experienced the least amount of warming include those in the Southeast like Florida and South Carolina, and parts of the central Midwest, like Iowa and Nebraska. There was no warming in three states -- Alabama, Arkansas and Georgia -- over most of the century.

However, the analysis found the pace of warming noticeably accelerated nationwide starting in the 1970s, including in the states that had not experienced warming.

An interactive map shows how much each state warmed from 1970 to 2011, compared with warming since 1912. The past 40 years are mostly orange and red, showing that temperature increases more than tripled across the lower 48 states.

"We want people to be drawn in and be interested in finding out about their states," Tebaldi said. "We also invite them to explore what is happening elsewhere and have a larger perspective on this issue."

The report authors note that scientists have long recognized that warming varies across the globe and over time. While it is difficult to attribute what is happening at a state level to global warming, the 1970s acceleration is consistent with global trends that have been attributed to a variety of factors, most notably greenhouse gases, Tebaldi said in an interview.

Richard Seager, a climate scientist at Columbia University's Lamont-Doherty Earth Observatory, said the analysis is not surprising, but more research is needed to explain the variation across regions.

"The warming in the southwest has already been implicated in making droughts worse than they otherwise would be because the reduction in precipitation is augmented by increased evaporation from the surface," Seager said in an email. "However I don't think we know why the southwestern states are amongst the fastest warming ones or why there has been so little warming in the southeastern states."

The New Jersey-based Climate Central says its mission is to "communicate the science and effects of climate change to the public and decision-makers, and inspire Americans to support action to stabilize the climate and prepare for a hotter world."

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