There's a quote in my favorite film, Pennies from Heaven, when Steve Martin steps out of a theater and sighs, “Come out of the movies, the goddamn world has changed.” He’s miserable about the rain, but I think it sounds like hope. Every time the lights come up, especially at a festival like Sundance, there’s a chance that the audience will emerge different, with new ideas and faces and talents carved into their brains.

And then there are days like inauguration morning, when festival-goers sat down for their 9 a.m. screening and knew that in the next 90 minutes, the world would change. For everyone. Goddamn.

“We try to stay away from politics,” insisted Sundance founder Robert Redford at the opening press conference. But it didn't feel like a coincidence that during that 9 a.m. slot, the biggest theater in Park City screened former Vice-President Al Gore's An Inconvenient Sequel, the follow-up to his 2006 Oscar-winning documentary on global warming, An Inconvenient Truth. When Gore walked out in a blue sweater and green O-shaped pin — the symbol of the environmental revolution — the packed house gave him a standing ovation. Joked Gore, “It's an interesting day to watch this film, isn't it?”

In the decade since Truth, the weather has gotten worse. Gore's original slideshow included an animation of rising sea level flooding the World Trade Center memorial. Now he can show a video of the real thing, which happened in 2012 during Hurricane Sandy. In the last 15 years — 14 of which have been the hottest on record — the extreme air temperature has magnified hurricanes, droughts, and fires. “Every night on the news is like a walk through the Book of Revelations,” says Gore in the film, his voice thickening until he starts to shout like a general.

Which is fitting, because this is a war. It's being fought on three fronts: against the damage we've already done, against the damage we might yet do, and against the climate deniers like Florida governor Rick Scott, who ignore the chaos even when it's in their own state. In one sequence, Gore puts on galoshes to wade down the streets of Miami Beach. He clucks, “I just wonder how the governor can slosh through this and say, ‘I don't see anything.’” A billion civilians recognize the science, but Scott is one of the powerful thousands sticking their heads in the sand — not that they have much sand left. In 30 years, Mar-a-Lago will be a marsh.

Gore told the audience this slow-moving disaster sometimes feels like his own “personal failure.” While chunks of Greenland have melted from glacier white to rock brown, Gore's hair has turned as pale as snow. He learned earlier than the rest of us how stubbornly people resist facts. Sequel opens with Fox attacking Truth as fake news. "You don't go see Joseph Goebbels's films to see the truth about Nazi Germany," said an Exxon shill. "You don't want to go see Al Gore's film to see the truth about global warming."

There was an inauguration in Sequel, too, with Gore stoically watching George W. Bush ascend to the presidency and then immediately ground Gore's DSCOVR satellite, a climate monitor that the vice-president had commissioned while in office. Obama finally launched DSCOVR in 2013. During the hour and a half that the theater sat in the dark, a new president took power and immediately deleted all mentions of climate change from whitehouse.gov (though it's not clear how intentional that was).

So what now? In the film, Gore quotes Mike Tyson: “Everybody has a plan until they get punched in the mouth.” In person, Gore was more optimistic, but like his boss Bill Clinton, he felt the audience's pain. Despair, Gore cautioned, is “another form of denial.” Environmentalists can still win. Technology has advanced faster than he predicted, making renewable energy more cost-effective than oil and gas. While Gore waves off future election campaigns (“I'm a recovering politician,” he says, smiling), Sequel finds hope in an unexpected place: the heavily GOP area of Georgetown, Texas, where conservative mayor Dale Ross has already rewired his town to be 90 percent fueled by solar and wind. To Ross, ditching fossil fuels just makes sense. By the end of this year, Georgetown will be 100 percent green. And so, I came out of the movie inspired to do something I couldn't have imagined that morning: I went home and emailed a Trump voter a thank you letter.