The new normal is warmer.
That's the assessment of the nation's top weather agency, which releases data Friday that show the 30-year "normal" temperature in the United States.
"The climate of the 2000s is about 1.5 degree Fahrenheit warmer than the 1970s, so we would expect the updated 30-year normals to be warmer," said Thomas R. Karl, director of NOAA's National Climatic Data Center. That recent temperature trend was enough to drag the three-decade moving average, from 1981-2010, up by half a degree Fahrenheit from the 1971-2000 period, according to the report by the National Oceanic and Atmospheric Administration.
The 30-year baseline is used by scientists to understand climate conditions and trends, including climate change. Besides providing a perspective for daily weather records, the data are widely used by utilities to project energy use, by farmers to make decisions on crop selection and planting times, and by others whose livelihoods are dependent on weather.
Jim Hurrell, a senior scientist at the National Center for Atmospheric Research, said the rise in temperature is attributable to a buildup in greenhouse gases. "The climate is indeed warming and this is evidence for it," Hurrell said.
Because the 30-year moving averages overlap, the small change in temperature in the new data suggests the last decade was substantially warmer than the 1970s, said Kevin Trenberth, a senior scientist in the climate analysis section at the National Center for Atmospheric Research. "It means a lot of global warming is built into the new normals," Trenberth said.
Not all scientists consider normals to be a consistent yardstick. "The use of 30-year normals is misleading because the temperature pattern within each is different," said Tim Ball, chairman of the Natural Resources Stewardship Project, who is currently speaking at an international conference on climate change put on by the Heartland Institute, which is skeptical of global warming.
"A 0.5 F change is essentially insignificant," he wrote in an email.
NOAA said it has refined its methods for compiling the data, improving scientific quality control and statistical techniques. These new techniques also yield a more comprehensive set of statistics on precipitation, including snowfall, and give the agency the ability to provide hourly normals, according to NOAA.
A team of University of California, Berkeley, physicists and statisticians that set out to challenge the scientific consensus on global warming recently reported that its data-crunching effort produced results nearly identical to those underlying the prevailing view on climate change.
Berkeley physics professor Richard Muller, a longtime critic of government-led climate studies who launched the re-examination, told a congressional hearing in April that the work of the three principal groups that have analyzed temperature trends underlying climate science is "excellent. ... We see a global warming trend that is very similar to that previously reported by the other groups."
NOAA and its predecessor agencies have been providing updated 30-year normals once every decade since the 1921-1950 normals were released in 1956.
The recent report will be up on the NOAA website July 1.
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