Hurricane science

Katrina and Rita seem to be threatening to break all records for a single hurricane season. A recent study says stronger storms -- Category 3, 4 and 5 hurricanes -- are becoming more frequent, though not all scientists agree. Guests: Kerry Emanuel, author of "Divine Wind: The History and Science of Hurricanes," and professor in the Department of Earth, Atmospheric and Planetary Sciences, MIT; Gerry Bell, lead forecaster for NOAA's seasonal hurricane outlook, of the Climate Prediction Center, National Weather Service; and Judy Curry, chairwoman of the School of Earth & Atmospheric Sciences, Georgia Tech.