Monday, April 22, is Earth Day, an annual day of demonstrations, actions, and workshops to raise public awareness about the environment, first observed in 1970. Have nearly 50 years of Earth Days helped move the needle when it comes to public concern about the environment? The existential crisis posed by climate change -- the warming of the earth's atmosphere caused by the world's addiction to fossil fuels -- is the subject of the new book by environmentalist Bill McKibben. It's a book that widens our lens to include not just the climate crisis but also the amazingly rapid advances in artificial intelligence and human genetic engineering that pose equally profound threats to humanity. McKibben, who serves as the Schumann Distinguished Scholar in Environmental Studies at Middelbury College in his home state of Vermont, is also the co-founder of one of the world’s largest climate action groups, 350.org. In his 1989 best-seller, The End of Nature, McKibben was one of the first writers to warn of the dangers of global warming. With his new book, thirty years later, he issues an even more dire warning about the threats humanity is facing, and offers hopeful ideas for surviving them. The book is called Falter: Has the Human Game Begun to Play Itself Out?Bill McKibben joins us from the studios of NPR in Washington.