You may know Leonardo DiCaprio from the movies, but he also wants you to know him as a United Nations Messenger of Peace.
Fisher Stevens’s documentary “Before the Flood” features DiCaprio, a longtime environmental advocate, in the Canadian tar sands of Alberta and in pollution-choked Beijing. He is granted an audience with Pope Francis and has a bromantic confab with President Obama. He speaks at the climate change conference in Paris. It should all resemble a vanity project except for one thing: The film lays out the case for reform with steadfast rigor. Grade: B (Unrated.)