Leonardo DiCaprio is a veteran climate crusader who has used his celebrity and media power to raise awareness about one of the greatest issues facing humanity And the Oscar-winning actor's new documentary, Before the Flood, is both a visual delight and a stirring call to action.

In the film, DiCaprio travels to Alberta, Miami Beach, Beijing and Indonesia. He observes toxic tar sands, flooded streets, smoggy cities and the wreckage of forest fires. Witnessing the sudden cleaving of a massive glacier in the Arctic, DiCaprio exclaims, "Oh my god, look at how violent that is!"

While the drama of climate change unfolds in sometimes extraordinarily powerful ways across the globe, he acknowledges the difficulty in getting people to join the discussion and push for action. "Try to have a conversation with anyone about climate change, people just tune out," DiCaprio says in the film.

Thankfully, he's joined by a number of high-profile figures to help sound the alarm and get the public more involved, including Tesla CEO and inventor Elon Musk, meteorologist and astronaut Piers Sellers, activist and environmentalist Sunita Narain, and even President Barack Obama.

"Looking forward to sharing this documentary with everyone as we continue to act on #climatechange together," DiCaprio tweeted.

Looking forward to sharing this documentary with everyone as we continue to act on #climatechange together. https://t.co/oSTXwCHtDf — Leonardo DiCaprio (@LeoDiCaprio) September 9, 2016

Before the Flood premiered at the Toronto International Film Festival on September 9 and hits theaters nationally October 21.

While filming #BeforeTheFlood, @LeoDiCaprio sees – and hears – Arctic narwhals. Screen the film today at #TIFF16. pic.twitter.com/IkHijLoTSk — Nat Geo Channel (@NatGeoChannel) September 9, 2016

Watch the trailer for Before the Flood: