Global Warming--More Evidence?

New research from the U.N. adds evidence to the theory that burning oil, gas, and coal is causing the earth's temperature to rise. But some climatologists say it's still too early to tell if warming trends are due to humans or regular cycles of the planet. Steve's guests are
NH State Climatologist Barry Keim with the University of New Hampshire (www.unh.edu/geography/climate.html) and Adam Markham, Executive Director of Clean Air-Cool Planet (www.cleanair-coolplanet.org).