TORONTO: Leonardo DiCaprio has unveiled his climate change documentary 'Before the Flood' at the Toronto International Film Festival, saying the film is intended to 'give the scientific community a voice.' The film was directed by Fisher Stevens. It chronicles DiCaprio's exploits around the globe to raise awareness about climate change. DiCaprio is a United Nations Ambassador of Peace. He was greeted by fans outside the film's premiere Friday. The Academy Award-winning actor says, 'We are truly at a turning point in history.' He says this issue 'depends on the education of the public and the evolution of our species to combat what is the largest crisis we've ever faced.' Stevens says the film's release is intentionally timed to the US presidential election. The film will air October 31 on National Geographic.