Bill McKibben is cofounder of 350.org, which is "building a global grassroots movement to solve the climate crisis." The organization has coordinated more than 20,000 climate demonstrations in more than 188 countries and has led opposition to the Keystone XL pipeline, which would connect high-carbon tar-sand oil to Houston refineries.

As a bestselling author, McKibben has written books that have shaped public action on climate change, alternative energy and the need for more sustainable economies. The End of Nature (2006) is widely seen as the first book on climate change for a general audience. At his first appearance at The Progressive Forum, McKibben discussed his book, Deep Economy (2008), a bold challenge to move towards more localized, sustainable models.

McKibben is a contributor to The New York Times, The Atlantic Monthly, Harper's, Mother Jones, The New York Review of Books and Rolling Stone, among others.

He will sign books and greet fans at the end of the evening.