EXCERPT:
GATES: “There are days when it looks very hard. If people think it's easy, they're wrong. If people think it's impossible they're wrong."
COOPER: "It's possible."
GATES: "It's possible. But it'll be the most amazing thing mankind has ever done."
COOPER: "That's what it has to be?"
GATES: "Yeah. It's an all-out effort, you know, like a world war, but it's us against greenhouse gases."