We've heard Greta Thunberg's angry, apocalyptic warnings about the problems arising from climate change. Now economist Paul Krugman says she's closer to the economics than her critics are. What's the right way to think about all this? Sponsor: This election season, trust C-SPAN to give you an unfiltered look at politics and the candidates. Follow Campaign 2020 on the C-SPAN television networks, on the C-SPAN app, or online at .