So-called warming hole leading to cooler winters in the southeastern United States

Despite the long-term global warming trend, parts of the eastern United States are getting cooler, according to new research from Dartmouth College.

The research team, led by Jonathan M. Winter, an assistant professor of geography at Dartmouth, found a "warming hole" that moved around the eastern U.S. as the seasons changed over the past 60 years.

The study determined that the warming hole tended to be located over the southeastern U.S. during the winter/spring seasons as the Polar Vortex sends arctic air into the region from time to time.

The warming hole tended to shift northward into the midwestern U.S. by the summer.

A wavier jet stream pattern may be responsible for the warming hole in the winter. Rapid warming and melting sea ice in the Arctic region may play a role in wavier jet stream patterns during the winter, according to recent studies.

<img src="https://vortex.accuweather.com/adc2004/pub/includes/columns/climatewx/2018/590x554_02140425_screen-shot-2018-02-13-at-11.23.59-pm.png"/>

The Dartmouth research team found that the jet stream over the U.S. started to become wavier in the late 1950s, according to the <a href="https://www.eurekalert.org/pub_releases/2018-02/dc-pvd021318.php" target=n>Dartmouth report.</a>

During the summer months, the team concluded that the warming hole in the Midwest may actually be caused by intensified farming, increased irrigation and air pollution (increased aerosols reflect more of the sun's energy back to space).

The researchers utilized NOAA data from 1,407 temperature and 1,722 precipitation stations across the contiguous U.S. going back to 1901 to help reach their conclusion.

Daily temperatures in the warming hole cooled by an average of 1.2 degrees Fahrenheit since 1958, while the globe as a whole warmed about 1 degree during the same period.

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This study was recently published in the Geophysical Research Letters.

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