The headline over Brenda Goodman's Wednesday story, "A Busy Year As Tornadoes Wreck Havoc ," was as ominous as a storm-warning: When would global warming be blamed for the increase in tornadoes in the Southern United States?
Goodman actually had sufficient self-control to get through over half the story without mentioning climate change, but closed with a non-scientist tornado victim that conveniently raised the issue herself.
The season probably got started earlier this year, Mr. Heim said, because of La Niña, a weather phenomenon that causes warmer winter temperatures in the Southeast. And it is likely that more tornadoes have been reported because meteorologists have gotten better at detecting them.
But several groups of researchers have begun to ask if the country is seeing more severe weather because of climate change.
"Our work suggests that the trend, the sign, is that conditions for severe weather will increase," said Robert J. Trapp, an associate professor of atmospheric science at Purdue University.
Dr. Trapp found that if human contributions to greenhouse gas emissions raised the global mean temperature by two to six degrees Celsius by the end of the century, the number of days with conditions that could create severe thunderstorms could double in cities in the South and along the Eastern Seaboard, including New York. His study was published in December in The Proceedings of the National Academy of Sciences.
Dr. Trapp warned that having the right conditions did not necessarily mean a thunderstorm or a tornado would form, and that his models could not predict when they would occur. So for now, Dr. Trapp and other experts agree, there is not enough good data to say if climate change is causing more tornadoes.
But in Arkansas, Mr. Hill's wife, Jackie, said she needed no more evidence about the cause of the twisters.
"I think people are just using too much of the resources," she said. "They're just messing with the ecosystem too much."