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KNOXVILLE, Tenn. — This winter’s severe weather actually could be a sign of global warming, a University of Tennessee-Knoxville climatologist said Friday.

 Dr. Kenneth Orvis said record-low temperatures and other extreme weather around the world fit global warming and ozone depletion patterns anticipated by scientists.

 “People say there’s no global warming because the atmosphere is cooling. Well, it depends on which part of the atmosphere you’re looking at,” Orvis said.

 Weather changes in the lower atmosphere occur when rising temperatures, or global warming, cause the jet stream to move faster and with more energy, Orvis said.

 When the jet stream fluctuates this wildly, it causes cold arctic air to penetrate farther than it otherwise might, he said.

 “People think about global warming when there is a heat wave in the summertime,” said Orvis. “But there we were (in East Tennessee) in December, probably a good 20-30 degrees above normal. We don’t think about that as a heat wave because it’s pleasant.

 “It’s only when you start averaging temperatures all year long that you can (see the warming trend).”

 Global warming, also called the greenhouse effect, is predicted when excessive carbon dioxide in the atmosphere traps heat that would normally be radiated into space. The trapped heat causes temperatures to rise. Automobiles are responsible for most carbon dioxide emissions, Orvis said.

 Contact: Dr. Kenneth Orvis (423-974-2418)