If things had gone well, America would still be in the Paris Agreement on climate change, green energy would be spreading across the country and Al Gore wouldn’t have needed to make a sequel to An Inconvenient Truth. But it didn’t work out that way. With his new movie hitting theaters next week, Gore remains hopeful during these depressing times. “If somebody told me five years ago, marriage equality would be the law in all 50 states, I would have asked what they were smoking,” says the former vice president. “But it did happen, because it became a choice between right and wrong. That’s where the climate movement is now.” For the Spiel, why persuading doubters is so hard when it comes to climate change science.