New information about the effect airplanes have on the atmosphere is coming to light.

David Travis, a professor from the University of Wisconsin-Whitewater, will give a speech titled “Jet Contails and Climate: Information Gained from the Grounding of U.S. Airplanes Following the Sept. 11, 2001, Terrorist Attacks.” Contails are white vapor trails from jet exhaust.

After the Sept. 11 attacks, the United States grounded all commercial flights for three days, giving meteorologists and climatologists a rare opportunity to study the atmosphere without them, said Wei Luo, an assistant professor of geography at NIU.

Travis worked on a post-Sept. 11 climate study with geography graduate student Ryan Lauritsen, who is a former student of the University of Wisconsin-Whitewater. Together, they looked at the temperature ranges during the three days without flights. Travis and Lauritsen compared the ranges to the temperature ranges of the three days preceding and following the attacks and to the average temperature range for the 30 years prior.

During the hour-long presentation, Travis will speak about how he and Lauritsen discovered an increased temperature range about just over one degree Celsius during the three days. The days were slightly warmer and the nights slightly cooler.

“This may seem like a small increase, but in terms of climate studies, it’s very significant,” Lauritsen said.

Jet contails normally help block incoming solar radiation during the day, and help block outgoing radiation during the night.

The discovery could have an effect on some of the global warming arguments, and a few scientists even have proposed purposely flying planes over major cities to help regulate temperatures.

“But, that is an extreme idea, and I doubt that it would happen,” Lauritsen said.

Travis’ speech, co-sponsored by the Graduate Colloquium Committee and the NIU Department of Geography, is free and open to the public.