What's the Latest Development?

Only three weeks after an unprecedented series of twisters wrought destruction across the Southeast, residents of Joplin, Missouri, are still digging out from the destruction of a tornado. It is shaping up to be an unusually active year: "Over the last couple of decades, an average of about 1,200 tornadoes touched down each year in the continental United States. This year, about 1,076 had been counted even before this week's activity in Missouri and elsewhere." Experts say America's history of urban sprawl makes larger areas of land susceptible to tornadoes. 

What's the Big Idea?

What can explain this increase in tornado frequency and strength? "The Gulf of Mexico is warmer than normal, sending more moist air over the South. The jet stream has also been moving somewhat farther south than usual, bringing it into contact with that excess moisture and triggering the large storms. ... It is impossible to link specific storms and weather events to climate change. But one of the predictions of the climate change models is that we'll be in for more intense storms as average global temperatures climb. That is what appears to be happening, both in summer and in winter."