Bill McKibben: 350: The Most Important Number on Earth

Bill McKibben is the author of a dozen books on environment, including The End of Nature, the first book about climate change. A former staff writer for the New Yorker, he helped organize 2,000 demonstrations across the United States last year to call for action on global warming. Now he is organizing the first global grassroots effort on the problem, at 350.org. His most recent books are Deep Economy and The Bill McKibben Reader