Environmentalist and author Bill McKibben has shaped public perception–and public action–on climate change, alternative energy, and sustainability. He will give a talk (dubbed a Boston Globe Best Bet) on “350: The Most Important Number in the World” at Boston College on Oct. 24 at 7 p.m. in McGuinn Auditorium. After working as a journalist for the New Yorker, McKibben wrote The End of Nature, widely regarded as the first book on climate change for a general audience. His book Deep Economy: the Wealth of Communities and the Durable Future was a challenge to move beyond “growth” as the paramount economic ideal and to pursue prosperity in a more local direction — an idea that is the cornerstone of much of the sustainability discourse today. McKibben is the founder of 350.org, a grassroots climate change initiative that has coordinated thousands of rallies in nearly 200 countries. His latest book is Oil and Honey: The Education of an Unlikely Activist. Sponsors: Lowell Humanities Series and Winston Center for Leadership and Ethics.