At the turn of the 16th century, a pre-Renaissance artist named Jheronimus van Aken, a.k.a., Hieronymus Bosch, began producing a series of artworks that channeled the aesthetic of a world unhinged. His paintings, about 25 in all, are rife with dyspeptic monsters, fallen angels, and burning horizons. In the most famous of these, such as The Garden of Earthly Delights, Bosch took categories of the familiar world and inverted them to produce scenes of elaborate dysfunction: a pack of dogs feasting on a knight balancing on a butcher knife; giant musical instruments with human figures impaled on the strings; a globe made of glass, half-full with water, in which a landscape inside is being consumed by the Flood. In this upside-down ecosystem of contradiction and mirth, all that makes us human—our joy and sorrow, our reason and madness—rotates on an axis of one all-too-human truth: Our passions will be our undoing. 

So begins the story of Before the Flood, the new climate change documentary starring Leonardo DiCaprio and directed by Fisher Stevens. The Garden of Earthly Delights forms a kind of narrative frame for what amounts to, on the one hand, the film’s tenacious argument about the extent to which the planet is changing, and on the other, DiCaprio’s skepticism that anything can be done about it. This is very much a story about the fall from innocence—but it is not without its moment of hope, and a way forward. 

George DiCaprio, an underground American comic distributor, placed on the ceiling above his son Leonardo’s crib a reproduction of Bosch’s most famous work: a triptych in which the Garden of Eden in the first panel gradually declines into a hellish dystopia by the third. “I would stare at it every night before I went to bed,” DiCaprio tells us at the beginning of the film. “If you look at these panels long enough, they start to tell a story.” 

That story, of a paradise devolving into a “twisted, decayed, burnt landscape,” haunts us for the next 90 minutes as we watch DiCaprio breathlessly travel to five continents, methodically building the case that weather patterns are changing, habitats are dying, and entire ecosystems are being decimated. We’re on a planet brimming with wild beauty, now careening over the tipping point of catastrophic climate change. “We’re knowingly doing this,” DiCaprio says. “It’s just on a much larger scale.” 

Of the eco-activist films focused on the perils of a warming planet—An Inconvenient Truth and Chasing Ice most notable among them—few sound the alarm with such ferocity as Before the Flood. In place of the meditative deep breath with which Al Gore begins his classroom presentation of pedagogical charts and graphs, Before the Flood delivers a five-alarm bell meant to wake us back up to reality: Climate change is real, it’s happening right now, and we’ve passed the point where buying hybrids or changing lightbulbs is going to solve it. 

The fossil-fuel industries on which most of our economy is based play an outsize role, Sierra Club’s executive director Michael Brune explains in the film—such as mountain-top removal for coal, fracking for natural gas, and offshore drilling for oil. “There is no such thing as clean fossil fuel,” he says. Take the carbon dioxide these industries are dumping into the atmosphere, add in the methane-producing beef industry and rampant deforestation for palm oil plantations, and you’ve got a perfect recipe for global warming. 

But this isn’t a film about what a warming climate could do 50 years from now. Before the Flood is about what’s happening right now, before our very eyes, should we have the wherewithal to open them and look. DiCaprio visits climate change hotspots worldwide in a bid to witness what’s happening. In the United States, he documents “sunny day flooding” in Miami Beach that now regularly backflows seawater into the streets. In Indonesia, he examines how Sumatran rainforests are being burned for palm oil plantations. During a trip to India, he learns about one community that received half a year’s rainfall in five hours, destroying its crops.

 
Leonardo DiCaprio diving with Jeremy Jackson and discussing the oceans.

He also takes a trip to the Alberta tar sands and sees the oily sand dunes that have replaced the boreal forest. “It kind of looks like Mordor,” DiCaprio observes while peering out from a helicopter. 

Later, we follow him to the middle of Baffin Island in the high Canadian Arctic. While crooning narwhals pop and roll from the dappled water nearby, a local fisherman describes to DiCaprio and the National Geographic Society’s Dr. Enric Sala how the ice all around them used to be a hard kind of blue, whereas now it has the consistency of ice cream slush. Without the Arctic, which serves as “the air conditioning for the Northern Hemisphere,” weather patterns and ocean currents will change, leading to more catastrophic floods and droughts.

The visual impact of these scenes, courtesy of cinematographer Antonio Rossi, is matched in affect and intensity by the film’s sonic musical score, the product of a unique collaboration between Trent Reznor, Atticus Ross, Gustavo Santaolalla, and Mogwai. The music has its own narrative arc, alternating between beating, chthonic rhythms to isolated strums of acoustic guitar, to the quiet denouement on which the film finally lands: Reznor, with piano, singing in fragile keys. The song, "A Minute to Breathe," co-written with Atticus Ross, recalls some of the best and most vulnerable music from Nine Inch Nails, such as Pretty Hate Machine’s “Something I Can Never Have,” Downward Spiral’s “Hurt,” and The Fragile’s “La Mer.” 

Reznor told Sierra that the collaborators were seeking a cohesive musical vision for the film that channels the realities of climate change, without being overly pessimistic. “We want you to leave the theater feeling concerned, but with a sense of hope,” Reznor says. “This isn’t about the end of the world.” (Check out Sierra's complete interview with Trent Reznor.)

 
Leonardo DiCaprio, Enric Sala (National Geographic explorer-in-residence), and Jake Awa (Arctic guide, Pond Inlet).

There has been an orchestrated campaign to discredit the science around climate change, and the film identifies some of those key players, such as the Koch brothers and Oklahoma senator James Inhofe. But in an interesting play to undermine the most common argument we hear from such climate deniers—that global warming is the cockamamie fantasy of a few nerdy scientists and their celebrity hangers-on—the film produces evidence that experts have been aware of climate change for more than half a century. 

Before the Flood doesn’t dwell much on climate deniers. Skepticism when it comes to climate change, however, does have a role in this film—not about whether climate change is real, but whether there’s still time to do anything about it. That skepticism surprisingly comes from the film’s own narrator, United Nations Messenger of Peace Leonardo DiCaprio. His dejection as he travels around the world witnessing dead corral reefs, burning cloud forests, and melting glaciers is palpable. 

At one point DiCaprio confesses, “If the UN really knew how I feel, how pessimistic I am about our future? I mean, to be honest? They may have picked the wrong guy.” 

DiCaprio is strikingly honest about how naïve he was in his early days as a global warming activist. We see clips of him talking with leaders and giving speeches, and appearing on television touting individual actions such as changing lightbulbs. “It seemed like a positive thing at the time, you know?” he says. “Changing your lightbulb. But it’s pretty clear that we’re way beyond that point now. Things have taken a massive turn for the worse.”   

The film does try to remain upbeat and profiles nations making the transition to renewable fuels, such as China’s push toward wind and solar, and Sweden’s recent pledge to become the world’s first fossil-fuel-free nation. Advances in battery technology like those pioneered at Tesla Motors show how private industry can play its part. The film also gives a nod to policy, and examines how a carbon tax can help push down demand for fossil fuels by forcing us to take account of the full costs of climate change.   

The filmmakers also insist that there are individual actions we can take to do our part. We can choose to not support some of the industries most responsible for polluting the planet, such as the corporate beef industry. Cows produce methane, a powerful greenhouse gas. About 10 to 12 percent of total U.S. emissions are due to corporate beef industry practices such as CAFO (concentrated animal factory operations) farming. So a change in your diet can make a difference. 

Yet DiCaprio still spends much of the film seemingly unconvinced that humanity will make its way through this crisis. He continues seeking answers from scientists, government leaders, and industry experts, talking with everyone from UN Secretary-General Ban Ki-moon, to Secretary of State John Kerry, to Elon Musk and President Obama—even meeting at one point with Pope Francis, during which DiCaprio presents him with a book on Hieronymus Bosch. 

 
Leonardo DiCaprio with President Barack Obama.

DiCaprio does finally get the answer he’s looking for—but not necessarily from charts or treaties, or meetings with presidents, or the pope. In one of the most moving scenes of Before the Flood, NASA astronaut and climate scientist Piers Sellers sits with DiCaprio before a giant digital display of Earth. Sellers, who has terminal stage-four pancreatic cancer, walks him through what it’s like to see Earth from space, to see the “astonishingly fragile” film of the atmosphere with your own eyes, the cities at night, the sun coming up over the rim of the horizon. Sellers puts on the display representations of the facts of climate change, from melting and drought trends to weather patterns, and then explains the knowable solutions for what to do about it. 

In the end, it’s a dying Sellers who delivers the message DiCaprio has been seeking: There’s still time. If we do the right things, we can still avert catastrophic climate change. 

“I have faith in people,” Sellers tells him. “Once people come out of the fog of confusion on an issue, or uncertainty about an issue, and realistically appreciate on some level the threat, and they are informed on what the best action is to deal with it, they got on and did it. And what seemed like almost impossible to deal with became possible.” 

Director Fisher Stevens told Sierra that he was eager to pivot off of DiCaprio’s personal story of discovery while making use of his mega-celebrity to bring the issue of climate change to a mainstream audience. He points out that for DiCaprio, the experience of being on camera without scripted lines, focusing on an issue he cares passionately about, made him much more vulnerable than he is used to being. 

“The thing about Leo is that he’s never been in a film where he was just himself and had no lines,” Stevens says. “This is Leo being Leo, and he was very vulnerable and nervous. But he really cares about this issue. He was constantly discovering, so I wanted Leo to kind of represent everybody. That’s his role: to be you and me and everybody else, just finally realizing, ‘Oh wow. Climate change is real. It’s really happening, and it’s happening now.’” 

Stevens had his own journey of discovery while making the film. Much of what he learned about efforts now underway to combat climate change gave him hope. He points to China’s embrace of renewable energy as one example. “China is moving a lot faster on this issue than I had thought until I got there,” Stevens told Sierra. “They have to, because you can’t breathe the air there in a lot of their cities.” 

And something Stevens discovered that made him more pessimistic? “To see the ice melting firsthand in Greenland was beyond terrifying. To see what Miami is going through to raise their roads, because they really are sinking . . . a community in India that got five months of rainfall in five hours, and what it did to the crops. . . . Yeah, there were a lot of things that just shocked me."

 
Fisher Stevens and Leonardo DiCaprio.

Before the Flood is the latest in what has become a new career for Stevens as a vanguard eco-activist filmmaker. The Chicago native was recognizable in the 1980s for buddy roles in films such as The Flamingo Kid and Short Circuit. Over time, he took on a wide range of roles, both in film (Reversal of Fortune, Hackers), on television (Early Edition, Lost), and on and off Broadway. He’s since produced The Cove (2009), a collaboration with underwater photographer Louis Psihoyos, for which he won an Academy Award, and directed the Emmy Award-winning Mission Blue (2014) about Sylvia Earle’s work to protect marine sanctuaries. In 2015, he teamed up again with Psihoyos, producing Racing Extinction to document the plight of endangered species.

Stevens and DiCaprio became friends over occasional bouts of pick-up basketball. Aside from a love for the game, they also bonded early about being raised by politically active parents. Stevens’s mother, Sally Fisher, is a longtime outspoken activist on issues ranging from HIV/AIDS to violence against women. From an early age, she modeled activism for her son. She was arrested in 1968 while protesting the Vietnam War. Later on, they protested the Iraq War together. Stevens says she was a huge influence on his life. “She infused in me a need to use my voice, as an actor, as someone in this business, to try to make change.” 

Is there one thing Stevens would have people go do immediately after watching Before the Flood? “Write your representative and your senator that you want a carbon tax,” he says. “And don’t eat so much beef.” 

Like the works of Hieronymus Bosch, Before the Flood holds up a mirror to the present age and puts on display all its beauty and grace—while, at the same time, invoking the possibilities of a new and nightmarish world order convulsing into existence. 

Before the Flood is one of the most compelling examinations to date of the realities we face from climate change. It is both a cautionary tale and a call to action—one that still rings with hope.

Before the Flood will be in theaters in New York City and Los Angeles starting October 21 and will air globally in 171 countries and 45 languages on the National Geographic Channel on October 30.