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This weekend Leonardo DiCaprio’s latest movie will be released, but don't head to your local movie theater if you want to see it. The film, , is an environmental documentary that airs Sunday on the National Geographic Channel (and will also stream online for free). The Academy Award-winning actor plays a starring role—himself—as he tries to understand the extent of climate change and why so little is being done to stop it. His findings are simple: There are brilliant activists, scientists, writers, inventors, and community leaders working to slow the Earth's warming, repair the damage, and prepare for future threats. But there’s one thing blocking their way—politics.

The film opens with the 2014 United Nations Climate Summit in New York City, where the Academy Award-winning actor was honored as a Messenger of Peace for the Climate. “It all seems beyond our control,” he says in a voiceover. “If the U.N. knew how pessimistic I am about our future, they may have picked the wrong guy.”

Over the course of 96 minutes, DiCaprio takes viewers on a world tour of climate change conflicts. He travels to  (close to where he filmed his 2015 blockbuster The Revenant), exposing a gaping void in the boreal wilderness where crude oil extraction continues unabated. He ventures to the volatile Arctic, where icebergs careen around him as the glaciers melt. He journeys to Miami Beach and the South Pacific isles, each facing a sinking future as sea level rises. And he explores the palm jungles of Indonesia, a landscape scorched by the demands of the food industry. At each of these locations, DiCaprio interviews experts who amplify the same message: Climate change is happening now, and it’s gaining speed—but world powers aren’t doing enough to stop it.

One of the major offenders is the United States. “This country is the real starting point in the discussion point of climate change,” says Mark Monroe, the writer for Before the Flood and other environmental features such as Chasing Ice and The Cove. “We have the highest standard of living; we’ve had the biggest reward; we’re doing the most harm.” The United States emits nearly 18 percent of the world’s carbon emissions, second only to China among the world’s countries.

Yet whether the climate is changing remains a topic of debate in the U.S. government, even as unequivocal proof piles up. And more often than not, it’s ignored entirely. This continued disagreement is part of what fueled the documentary, Monroe says. “Hearing from the scientific community isn’t enough” to convince people, he says. “But physically seeing these threatened places and counting them as evidence should be.”

The movie also aims to communicate the gravity of climate change to younger generations; it will be screened at 200 schools across the United States in the upcoming weeks. “Films stay around for a long time,” Monroe says. “And every four years, millions of new people get to vote.” He believes that shifting public opinion is the best way to correct the political problem.

That is no small task. “Try to have a conversation with anybody, and the people just want to tune out,” DiCaprio says in the film. But just starting the conversation is also an issue: A found that people who think climate change is important rarely discuss it with family and friends. Even established green groups fail to address the world’s biggest environmental problem head-on. Just this month, a group of young environmentalists penned an open letter to the leaders of major conservation organizations, urging them to support the ratification of the first U.S. carbon tax in Washington State. “The silence is deafening,” they wrote. “Leaders of your stature belong on the field, not the sidelines.” (DiCaprio also for the tax earlier today.)

If the current state of inaction continues, models predict the damage will be irreparable. The seas are projected to rise by several feet by the end of the century. Hundreds of millions of people from their homes. More than 300 species of North American birds , along with countless other animals. These numbers are dizzying—so why aren’t they more persuasive?

At the end of the film, after President Obama and Pope Benedict both make appearances on screen, the scene cuts back to DiCaprio addressing the U.N. Climate Summit in 2014. “I’ve traveled all over the world in the last two years,” he says. “All that I’ve seen and learned on my journey has absolutely terrified me. No more talk; no more excuses; no more ten-year studies; no more allowing the fossil fuel companies to manipulate and dictate the science and policies that affect our future.”

Before the Flood—directed by Fisher Stevens and produced by DiCaprio—can be seen on the National Geographic Channel on Sunday, October 30 at 9 p.m. EST. It will also stream for free on YouTube, Hulu, iTunes, Amazon, Facebook, Twitter, and Google Play. It’s available in 171 nations and 45 languages. See here for , and watch the trailer below.