Eco-warrior and United Nations peace ambassador Leonardo DiCaprio has been one of the most visible faces trying to raise awareness about climate change for years, and he teamed up with filmmaker Fisher Stevens to further that campaign with a new documentary, Before the Flood. Stevens won an Oscar in 2010 for taking on ecological devastation with The Cove, and his latest effort, which recently made its world premiere at the Toronto International Film Festival, now has its first trailer. There are stunning flyover shots of melting glaciers, burning oil fires, and flooded landscapes, laced together with DiCaprio asking politicians, scientists, and religious figures if we’ve gone past the global-warming event horizon or if there is still a way back from the brink.