The “new standard” in the United States is half a degree hotter than it was 20 years ago – fr

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The “new standard” in the United States is half a degree hotter than it was 20 years ago – fr


America’s new normal temperature is 0.5 C warmer than it was just two decades ago.
Scientists have long talked about climate change – warmer temperatures, changes in rain and snow, and more extreme weather – being the “new normal”. Data released Tuesday by the National Oceanic and Atmospheric Administration (NOAA) puts hard numbers on the picture.

The new normal in the United States is not only warmer, but more humid in the east and center of the country and considerably drier in the West than a decade earlier.

Meteorologists calculate climate normals based on 30 years of data to limit random fluctuations in daily weather. It is a standard set by the World Meteorological Organization. Every 10 years, NOAA updates the standard for the country as a whole, as well as for states and cities, by year, month, and season.

Environment Canada does the same for Canada, but its most recent published dataset is for 1981-2010. Dave Phillips, senior climatologist at Environment Canada, said the new data set will likely be released in the summer of 2022. However, Canada, especially the North, is warming faster than the rest of the world.

Annual temperatures in the United States in Fahrenheit relative to the 20th century average for each period of US climate normals from 1901-1930 (top left) to 1991-2020 (bottom right). Places where the normal annual temperature was 1.25 F (0.7 C) or cooler than the 20th century average are the darkest blue; places where the normal annual temperature was 1.25 F (0.7 C) or warmer than the 20th century average are the darkest red. (NOAA Climate.gov)

For the United States as a whole, the normal annual temperature is now 11.8 C based on weather station data from 1991 to 2020. Twenty years ago, the normal was 11.3 C on the basis of data from 1971 to 2000. The average temperature in the United States for the 20th century was 11.1 C.

The new annual normal temperature in the United States is 0.9 C higher than the first normal calculated for 1901 to 1930.

“Almost every location in the United States has gone from normal from 1981 to 2010 to normal from 1991 to 2020,” said Michael Palecki, NOAA’s standards project manager.

Fargo, ND, where the new normal is 0.05 ° C cooler than the old one, is an exception, but more than 90% of the United States has warmer normal temperatures than 10 years ago, a said Palecki.

In Chicago and Asheville, North Carolina, the new normal annual temperature has jumped 0.83 ° C in a decade. Seattle, Atlanta, Boston and Phoenix, Arizona have seen their normal annual temperatures rise by at least 0.28 ° C over the past decade.

Cities with the biggest changes

Charlottesville, Virginia experienced the largest increase in normal temperatures among 739 major weather stations. Other significant changes have taken place in California, Texas, Virginia, Indiana, Arizona, Oregon, Arkansas, Maryland, Florida, North Carolina and Alaska.

The normal news is warmer because the burning of fossil fuels has made the past decade “a much hotter period for much of the globe than previous decades,” said Natalie Mahowald, climatologist at Cornell University.

A large dust storm, or haboob, swept through downtown Phoenix, Arizona in 2012 amid a drought from Oklahoma to Utah. Normal annual precipitation in Phoenix has dropped 10%, to 18.2 centimeters, over the past 20 years. (Ross D. Franklin / The Associated Press)

For Phoenix, the biggest change from normal came in precipitation. The city’s normal annual precipitation fell 10 percent to 18.2 centimeters. Rainfall in Los Angeles fell 4.6%.

At the same time, Asheville experienced an almost 9% increase in precipitation, while precipitation in New York City increased by 6%. Normal in Seattle is five percent wetter than before.

Useful or misleading statistics?

Climatologists are divided on the usefulness or usefulness of new normals calculated in error.

Mahowald and University of Oklahoma meteorology professor Jason Furtado said updating normal calculations helps city planners and area planners prepare for floods and drought, farmers decide what and when to plant, energy companies to meet changing demand and doctors to tackle climate-related public health issues. change.

But Pennsylvania State University climate scientist Michael Mann said he prefers a constant baseline such as 1951 to 1980, which NASA uses. Adjusting normal every 10 years “perverts the meaning of” normal “and” normalizes “climate change,” he said in an email.

North Carolina state climatologist Kathie Dello said, “It seems strange to still call them normal because 1991-2020 was anything but climate normal. “

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