What will a historian in the 22nd century learn about our country, our age, by unearthing video of CNN’s town hall on the climate crisis? She will learn that candidates for our highest office, centuries after the Enlightenment, still had to declare publicly that they believe in science. She will learn that these candidates also believe that climate change is a paramount threat that must be confronted immediately, but in an incremental way. She will learn that the “global war on terror” unleashed 1.2 billion metric tons of greenhouse gases, that a senator named Cory Booker was a Trekkie and that a businessman named Andrew Yang wanted to dole out “democracy dollars,” and that a cable news network — for all its turbulence and theatrics — devoted a workday’s worth of its programming, on a Wednesday in September, to the issue that shaped her reality.

It was an exercise in perspective, in relativity, in epochal concerns scrunched into a sliver of prime time that seemed to go on forever. It was an “unprecedented” televised discussion about an “existential” threat, but it often collapsed into quips about lightbulbs and cheeseburgers.

When she pulls up the video, it will start like this:

“This is an important evening for all of us,” Wolf Blitzer said at 5:02 p.m., after connecting climate change to Hurricane Dorian, which provided CNN with a convenient real-world catastrophe to liven up a string of 40-minute Q&As with 10 candidates.

Behind Blitzer was a panorama of Earth, that hot blue dot with a thin haze of atmosphere — our protector, our smotherer — arcing across the stage. The audience was made of Democrats and independents. Many of the questions came from college students pursuing climate-related degrees and young activists from the Sunrise Movement, whose pressure on the media and politicians precipitated this town hall. But it was a retired teacher who asked the first deadly serious question: Is it fair to expect our children to reproduce, given the climate chaos that awaits them?

Julián Castro, the first candidate up, emitted a sigh. “Right now, if we don’t act, we’re passing off to our grandchildren” a problem that we can solve now, said the former secretary of housing and urban development, who proposed “new civil rights legislation” to rectify environmental racism.

Next, Yang bemoaned “the almighty dollar” that clouds our rectitude and recommended that we reconfigure GDP so that it measures health and sustainability, not just economic output and growth.

“Will we have to drive electric cars?” Blitzer asked him, as if there could be no worse thing.

“There will still be some legacy gas guzzlers on the road for quite some time,” Yang assured him.

CNN anchors fixated on carbon-heavy American lifestyles, because we are nothing more than gaping mouths and spread-eagled wallets.

“We all love our cars and trucks,” Anderson Cooper said at one point.

“We all like our Amazon Prime,” Erin Burnett said at another. (Amazon CEO Jeff Bezos owns The Washington Post.)

“They’re saying you want me to eat less beef?” Chris Cuomo said, pretending to be a theoretical voter from middle America.

“First of all, I’m from Indiana,” South Bend Mayor Pete Buttigieg replied. “And second of all, I like cheeseburgers.”

“I am hopeful that we’re going to be able to do this in a way where we can continue to have hamburgers and cheese,” said Sen. Amy Klobuchar (Minn.).

“I love a cheeseburger from time to time,” confirmed Sen. Kamala D. Harris (Calif.). (Her appearance was followed by a commercial featuring Golden Corral’s “endless sirloin” option.)

“It just hit me: The burger obsession comes from Fox News coverage of the Green New Deal,” wrote climate reporter Rebecca Leber of Mother Jones, on Twitter, “aka ‘they’re coming after your favorite things.’ ”

Meanwhile, over on Fox News, the planet was spinning on a different axis. Tucker Carlson was ribbing Walmart for ending the sale of handgun ammunition, Sean Hannity was reminding viewers that the Hillary Clinton campaign hired Fusion GPS to dig up Russian dirt on Donald Trump, and Laura Ingraham was exposing the Democrats’ plan to “radically transform America” by taking away everyone’s guns. If a 22nd-century historian watches this archive instead, she might wonder if humans knew about climate change at all.

Back on CNN:

“Do you ban plastic straws?” Erin Burnett asked Harris.

“I’m going to be honest,” Harris said. “It is difficult to drink out of a paper straw.”

“Do you think that the government should be in the business of telling you what kind of lightbulb you could have?” Cuomo asked Sen. Elizabeth Warren (Mass.).

“Oh, come on, give me a break,” Warren said, attempting to stomp out the whole government-in-my-pantry discussion sometime during Hour 5. The fossil-fuel industry, she said, is counting on people to fight over the small stuff. “They want to be able to stir up a lot of controversy around lightbulbs, around your straws, and around your cheeseburgers — when 70 percent of the pollution, of the carbon we’re throwing into the air, comes from three industries.”

And what about fossil-fuels companies and their sway? During Joe Biden’s turn onstage, in prime time, a Bernie bro popped the former vice president for planning to attend a fundraiser hosted by Andrew Goldman, the co-founder of a natural-gas company (as reported by the Intercept’s Akela Lacy).

“He’s not a fossil-fuel executive, I’m told,” Biden replied. Within minutes a metaphor would inflame Biden’s left eye, in the form of an apparent subconjunctival hemorrhage.

The seven-hour town hall on the “climate crisis” lasted only two-millionths of a second — if you plot it on Carl Sagan’s cosmic calendar, which plunks the 13.8 billion years since the Big Bang into a single calendar year — but it felt like a butt-numbing eternity when measured by the attention span of Homo sapiens. Between each candidate’s session, CNN updated its viewers on Dorian, a whirl of black and red on its radar. It was almost a Category 3, meteorologist Jennifer Gray said during multiple breaks. Almost a Category 3. Almost a Category 3.

“Scientists says that humans only have 11 more years to avoid the catastrophic consequences of this crisis,” said CNN’s Don Lemon around 11:20 p.m.

The historian from the 22nd century will also hear plenty of lofty rhetoric and ambitious policy: Harris arguing that food labels should include a measure of environmental impact; Klobuchar equating confronting climate change with landing on the moon or passing civil rights legislation; former Texas congressman Beto O’Rourke saying he would ban offshore drilling but not implement a carbon tax; Booker saying he wants zero-emission electricity by 2030 and a carbon-neutral country by 2045.

“There’s not a damn thing we can’t do,” Biden said.

“There will be a transition,” said Sen. Bernie Sanders, acknowledging that personal sacrifice will be required to meet the challenge. “And there will be some pain there.”

“This isn’t just saving the planet,” said Buttigieg, at 37 the youngest candidate to take the stage. “This is saving the future for specific people who are alive right now.”

The town hall was exhausting but not exhaustive, and an admission that the topic deserves more airtime but won’t get it during the Democratic debates. (The general-election debates in autumn of 2020 will feature even less climate talk than the primaries: perhaps a few minutes on the topic, with a Republican saying there’s no problem and a Democrat saying there’s a huge problem.) But there was praise on Twitter for CNN and the candidates.

“Overall, I think the #ClimateTownHall was a great success!” tweeted climate researcher Leah Stokes.

“Groundbreaking night,” tweeted Katharine Wilkinson, vice president of communication and engagement at Project Drawdown. “Candidates are quite climate literate!”

“The Democratic climate change discussion represents a sea change,” tweeted climate and water scientist Peter Gleick. “We’ve moved from ‘is it real’ to ‘what do we do about it.’ ”

And if the historian from the 22nd century keeps watching past the end of the town hall, she will see Anderson Cooper start his program at midnight by announcing that Hurricane Dorian had finally strengthened to a Category 3.