For the first time in decades, it's hard to ignore the threat of nuclear war. But as long as you're far from the blast, you're safe, right? Wrong. In this sobering talk, atmospheric scientist Brian Toon explains how even a small nuclear war could destroy all life on earth -- and what we can do to prevent it. A professor in the Department of Atmospheric and Oceanic Sciences at the University of Colorado-Boulder, Brian Toon investigates the causes of the ozone hole, how volcanic eruptions alter the climate, how ancient Mars had flowing rivers, and the environmental impacts of nuclear...