U.S. Experiences Wild Weather

The tornados that struck St. Louis this week are the latest in a record-breaking number of twisters that have swept across the country this month. That's in addition to historic droughts and fires in Texas, record low temperatures in Seattle, and snow and flooding in the Midwest. What's going on with the weather? Linda Wertheimer puts the question to John Christy, director of the Earth System Science Center at the University of Alabama in Huntsville.