Further Reading

Tornadoes and climate change

Increases in carbon dioxide and other greenhouse gases are warming Earth, especially at ground level. They are also increasing humidity. Warmth and humidity fuel thunderstorms. So, will future storms unleash more tornadoes — or just more precipitation?

The answer may come down to another tornado ingredient: wind.

“Whether or not these storms become hail producers or tornado producers depends on how wind shear changes with changes in the concentrations of greenhouse gases,” says Jeff Trapp of Purdue University.

Harold Brooks, a research meteorologist at the National Severe Storms Laboratory in Norman, Okla., has been trying to forecast how wind shear might change for thunderstorms in a warmer climate. And that’s important, he explains, “because wind shear is the dominant factor in whether a severe storm produces wind, hail — or a tornado.” To do that, he and others have probed details of tornadoes from past decades. They’re looking for trends that might suggest under what conditions tornado frequency or intensity will change.

Unfortunately, Brooks points out, the numbers and intensities of tornadoes differ so much from year to year that finding any reliable trend about what to expect decades from now is almost impossible. Indeed, his computer analyses indicate it might take a century for such a trend to emerge.

So meteorologists, today look ahead to just next week, next month or, increasingly, next year. Indeed, one goal is to begin generating seasonal tornado forecasts, like those already common for hurricanes.

“Is there a way to say, in two weeks or six months from now, there is going to be a period when tornadoes will be very common — or not common?” asks Brooks. Such predictions remain a very tall order, he says, despite being very much in demand.

Frequently asked questions about tornadoes from the National Oceanic and Atmospheric Administration

As of December 2012, April 2011 was ranked the most active month for tornadoes in U.S. history, having spawned 758 twisters. Read more about 2011’s immense tornado activity.

E. Sohn. “Challenging the forces of nature.” Science News for Kids. Oct. 31, 2005.

S. Ornes. “Martian devil.” Science News for Kids. April 23, 2012.

E. Sohn. “The wind in the worlds.” Science News for Kids. April 24, 2007.

Teacher’s questions: Questions you can use in your classroom related to this article.