While the world has warmed in recent decades, parts of the eastern U.S. have actually been cooling since the 1960s, according to a recent study.
The study, led by Dartmouth College’s Trevor Partridge, examined thousands of weather and rain stations with data going back to 1901 and found clusters of seasonally-dependent cooling in the eastern U.S. starting in 1961.
Clusters of long-standing stations in the east showed monthly maximum and minimum temperatures decreasing “0.46°C and 0.83°C respectively” from 1961 to 2015, according to the study. Scientists have dubbed this phenomenon a “warming hole.”
The so-called “warming hole” is situated over the southeastern U.S. in the late winter and spring, but shifts to the midwest in the summer and fall.
“This paper is an excellent reminder that the Earth has not warmed uniformly and is not expected to during the 21st century regardless of anthropogenic global warming,” Ryan Maue, an atmospheric scientist with the libertarian Cato Institute, told The Daily Caller News Foundation.
“Scientists continue to highlight the importance of regional patterns of warming and cooling that are not accurately reproduced by global climate models,” said Maue, who was not involved in the Dartmouth study.
Starting in the 1960s, the eastern U.S. began to see cooler than average temperatures through 2015. Partridge’s study attributed the eastern cooling to a variety of influences, including ocean cycles, land-use changes and aerosols.
This is consistent with a recent Massachusetts Institute of Technology (MIT) study on summer cooling in the U.S. corn belt. That study attributed the cooling to increased atmospheric moisture from more intensive farming.
Partridge’s study found winter temperatures were “significantly correlated with the Meridional Circulation Index (MCI), North Atlantic Oscillation (NAO), and Pacific Decadal Oscillation (PDO)” — natural ocean cycles.
But ocean cycles alone can’t explain why eastern summers have been cooling, according to Partidge’s study.
The study also suggested land-use changes and aerosols are probably at work, but they hypothesize a shift in the jet stream in the late 1950s has resulted in cold Arctic air being driven to the U.S. southeast.
The “warming hole” appears in the eastern U.S. in the early 1960s and persists to this day, according to the study.
“Such regional changes in temperature are not unexpected since other factors such as land use change and agricultural irrigation are well known to affect local climate,” Maue said.
“This paper provides some nice diagnostics and cursory correlations with main atmosphere-ocean climate modes such as the PDO and NAO,” Maue said.
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