Bill McKibben, a well known environmental author and activist, is the founder of 350.org, an international climate change campaign. 350.org is named for the safe level of Carbon Dioxide in the atmosphere, 350 parts per million. In 2011, McKibben helped lead the fight against the Keystone XL pipeline. The author of 13 best-selling books, McKibben been called "the world's best green journalist" by Time Magazine and "the nation's leading environmentalist" by the Boston Globe. He is a frequent contributor to newspapers and magazines including the New York Times, The Atlantic Monthly, Harper's, Orion Magazine, Mother Jones, The New York Review of Books, Granta and Rolling Stone.