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The 30-year data set, to be released May 4, shows while some U.S. regions are growing warmer, others have cooler average temperatures.
The United States continues to grow warmer, though pockets of the country, particularly the Midwest, have seen average temperatures cool in the last three decades, scientists with the National Oceanic and Atmospheric Administration said this week.
“What we found is that the warming from the 1981-2010 to 1991-2020 normals is pretty widespread, but not ubiquitous,” Michael Palecki, normals project manager at NOAA’s National Centers for Environmental Information, said Tuesday on a call with reporters. “There are some areas that actually have cooler temperature normals, especially in the spring in the north-central U.S.”
NOAA is poised to release its new set of climate normals, a 30-year set of data updated once per decade that groups together observations from nearly 15,000 weather stations that record rain and snow, and 7,300 locations that record temperatures, according to Tuesday’s presentation. The current normals include data from 1981 through 2010, while the updated set, scheduled for release on May 4, will shift to 1991-2020.
Other countries will also update their climate normals this year, per a standing agreement with the World Meteorological Organization, an arm of the United Nations.
The normals “provide averages for climate variables like temperature and precipitation,” NOAA said, and are used most visibly in local weather forecasts, usually to frame whether a daily temperature is above or below normal.
But there are other uses as well, said Ray Wolf, a meteorologist with the National Weather Service. The data are used for drought assessment, agricultural planning, travel research, utility assessments and even budget and operational planning by local governments for things like snow removal.
They are also used to quantify the activity level of each year’s hurricane season. Beginning this year, the number of named storms in an “average” season will increase from 12 to 14, based on data in the forthcoming normals.
“What we’re trying to do with climate normals is to put today’s weather in a proper context so we understand whether we’re above normal or below normal,” Palecki said. “Also, we’re trying to understand today’s climate so people know what to expect and how to plan for both their personal activities and for various economic sectors.”
The new normals will show several important changes from the previous set, Palecki said, including widespread warming (with the exception of most of the Midwest, including Minnesota, Wisconsin, both Dakotas and Michigan), wetter seasons in the east and drier conditions in the west. In Asheville, North Carolina, for example, annual precipitation increased by 4.02 inches, while Hilo, Hawaii saw a 6.33-inch drop in precipitation, according to data from NOAA.
“There’s a huge difference in temperature over time as go from cooler climates in the early part of the 20th century to ubiquitously warmer climates here in the last two sets of normals,” he said. “We’re really seeing the fingerprints of climate change in the new normals.”
But the data also show that that change can seem inconsistent, he said, because patterns vary in different locations and from month to month.
“In the Southeast, it’s warm in October, cooler in November and warmer in December,” he said. “So not every month in every location is always warming, despite the fact that we, generally, are warming in our climate.”
Kate Elizabeth Queram is a senior reporter for Route Fifty and is based in Washington, D.C.