Global warming might not be as severe in the central United States as it is in other parts of the country.

Even with the threat of global warming, the central states might be getting cooler, according to a recent study conducted at Iowa State.

“We expected to find that there would be a general warming over all of the U.S.,” said Gene Takle, professor of agronomy, geological and atmospheric sciences. “But what we found was that in the central part of the U.S., there’s a region where the warming is far less severe than in the rest of the country.”

The cooler area, or “warming hole,” is centered in eastern Kansas and includes portions of Iowa, Missouri, Nebraska and Oklahoma.

“That was surprising to us, because typically climate change studies have suggested that the middle of continents was going to warm more rapidly than surrounding oceans,” said Bill Gutowski, professor of geological and atmospheric sciences.

The study has received international attention, since no one noticed the warming hole before.

“As far as we know, we were the first people to notice this,” Gutowski said. “We need other people to come along and see if they can get the same results.”

Gutowski said the hole might have been missed because global climate models aren’t as sensitive as regional climate models, and a regional temperature change could have been easily overlooked.

“Global models that tell us a lot about climate change haven’t really shown this, or just shown hints of it at best,” Gutowski said. “And we think the reason is that we have finer resolution in our model. We don’t try to simulate the entire globe, we just try to simulate the U.S.”

The more sensitive a model is, the more information it can collect.

“We need to use fine-scale models if we want to understand the climate of any region, because there’s so much going on in the atmosphere that coarser models can’t include,” said Ray Arritt, professor of agronomy.

The central area is cooler than surrounding areas because of something known as the low-level jet phenomenon, Gutowski said.

The low-level jet is a stream of moist air that flows from the Gulf of Mexico into the south-central portion of the United States, bringing more moisture with it. In the summertime, the jet interacts with thunderstorms, resulting in more rain. The ground is wetter, so there is more water evaporation, which makes the area cooler.

“The effect is kind of like if you put water on your hand, and it evaporates off your hand, and it’s cooler,” Gutowski said.

The study was done using a computer model simulation to predict future climate patterns in the United States.

“We only have one model; we haven’t tried other models,” said Zaitao Pan, assistant professor of earth and atmospheric sciences at St. Louis University and lead author of the article published in Geophysical Research Letters. “It has some reliability but not absolute.”

Researchers also delved into the past to see if historical U.S. climate information was consistent with the predicted climate information found with the simulation.

They found that the central area had actually become cooler over a 25-year period, from 1975 to 2000, even though the surrounding areas had warmed up.

“There’s something going on in the real world that’s consistent with what the model is saying about the future,” Gutowski said.

Although global warming may not be as severe in the central United States, the cooling may cause problems such as more flooding, Gutowski said. The changes wouldn’t be immediately apparent, though, he said.

“If you just look at data from one year to the next, this may not show up,” Gutowski said. “Climate change is like a gradual trend superimposed on variations from one year to the next.”