Inside the Science of Climate Change

By now we've all heard that the climate is warming, but how do climate scientists study the problem and how do they know the current warming is unlike anything in the past? What tools do they use, and what can they tell us about how the planet is changing? To answer these questions we spend the hour with renowned professor Michael Mann, one of the foremost climate scientists in the world today, and author of the famous 'Hockey Stick' graph.