WACO, Texas, Jan. 31 (UPI) -- U.S. scientists have created the first historic temperature record of the North American Great Plains -- an area stretching from Canada to north Texas.
Baylor University geology Professor Lee Nordt, along with Professor Joseph von Fisher of Colorado State University and Larry Tieszen of the U.S. Geological Survey, produced the 12,000-year temperature record by studying the stable isotopic composition of buried soils.
"The results really surprised us, especially between 12,000 and 7,000 years ago," Nordt said. "Earth temperatures should have been getting warmer during that time, but they weren't. We concluded it was caused by negative feedback from the melting glaciers. The ocean water temperature was colder because the glaciers were melting. That, in turn, caused temperatures to drop."
Nordt said the sun's intensity on the Earth is the main reason why temperatures generally increased during the last 12,000 years. That intensity is decreasing but temperatures are not.
"Is this caused by global warming or are temperatures just lagging behind?" Nordt asked. "We don't know."
The research is detailed in the February issue of the journal Geology.
