In a federal court in San Francisco on Wednesday, major oil companies concurred with the “scientific consensus,” saying it was “extremely likely” that human activity has been driving global warming since the middle of the 20th century. They just don’t think they can be sued for it.

“Chevron accepts what the IPCC [Intergovernmental Panel on Climate Change] has reached consensus on concerning science and climate change,” said Theodore Boutrous, who represents Chevron and is heading up the assorted legal team for the five oil companies that are defendants in this lawsuit. But, he said, that didn’t mean that a civil lawsuit was the right way to address climate change. “It’s a global issue that requires global action,” he said.

Over the course of two hours, Boutrous ran through the findings of the most recent IPCC report (released in 2013), acknowledging that global temperatures were rising due to carbon dioxide caused by human activity, that other factors were negligible, and that as a result, sea levels were rising. No time was given to any denials of climate science, with Boutrous sticking closely to the substance of the IPCC report. Even his attempt at implying that his client was not at fault was framed within the substance of the IPCC report; he said that the report never said “extraction or production” of oil was the cause of carbon dioxide emissions, but rather the “economic activity” that burned fossil fuels.

Major oil companies went on the record to say that human-caused climate change is real

Judge William Alsup, who is presiding over the lawsuit, is giving the other oil companies — ExxonMobil, ConocoPhillips, Royal Dutch Shell, and BP — a week to quibble with anything Boutrous said in court about climate change. “Chevron welcomes meaningful efforts to address the issue of climate change, but litigation is not an appropriate tool for accomplishing that objective,” Sean Comey, a spokesperson for Chevron, said in an emailed statement to The Verge. “Chevron provided a neutral assessment of the science based on the most recent comprehensive scientific assessment.” The other companies did not immediately respond to requests for comment.

Wednesday’s session was not a trial, or really even a hearing in the typical sense of the word. It was, in Judge Alsup’s terminology, a “tutorial” — a session in which the legal teams for both sides present background facts for his edification. It’s not discovery, it’s not evidence, and just because it was presented Wednesday, it’s not necessarily admissible for a jury in the future should this case go to trial. Nonetheless, the hearing marked a moment in which major oil companies went on the record to say that human-caused climate change is real. At this point, the science is so undeniable that it no longer makes sense for oil companies to try and refute it.

“Rhetorical claims don’t cut the mustard.”

This is the first time Judge Alsup — or any judge, really — has held a climate change tutorial. These types of sessions are not typical in the legal system, but Alsup has requested tutorials in other cases in the past, including tutorials on immigration for a DACA case and LIDAR for the Waymo v. Uber case. Alsup’s approach to science has not gone unappreciated in this case. Myles Allen, a climate scientist from the University of Oxford, who presented before the judge on Wednesday, says, “The court is evidently taking our science as seriously as they’re taking the science involved in patent law cases, where the court really does have to understand the technicalities and where rhetorical claims don’t cut the mustard.”

At the start of the tutorial, Alsup warned the press, “You will probably find this boring,” reiterating that this was all so “the poor judge can learn some science.” (Judge Alsup was previously an engineering major at Mississippi State, ultimately graduating with a math degree.) Although Alsup promised that “if you get bored, you can just leave,” the throng of observers that packed the gallery and an additional overflow room barely thinned through a five-hour session that started early in the morning.

Lawyers for the cities of San Francisco and Oakland were largely silent at the tutorial, with Steve Berman, representing the San Francisco city attorney’s office, stepping up to the podium only to introduce climate scientist after climate scientist.

Only Boutrous spoke on the defendants’ side, not bothering to bring on any scientists to speak for the oil companies. Boutrous appeared to have studied the IPCC’s 2013 AR5 report from start to finish, and he stuck closely to what he characterized as the scientific consensus. (When it was his turn, Don Weubbles of the University of Illinois sniped at the limited scope of Boutrous’ presentation, saying pointedly that “science did not stop” after 2013.)

It became swiftly apparent that the judge was taking the opportunity to satisfy his curiosity on absolutely anything that had occurred to him, prompting Allen at one point to spread his arms out in a wobbling motion to describe the motion of carbon dioxide molecules when they absorb infrared radiation. At another point, Judge Alsup and Allen went on a long, wandering detour about whether the relationship between two variables was logarithmic or linear.

The wide range of questions put Boutrous at a disadvantage. At one point, the judge interrupted him with a question about undersea lava flows and ocean temperatures, citing an interesting “geology show” he had seen on television a few weeks ago. Because this fell far outside the scope of any of the presentations or the IPCC report, his question went unanswered.

The unnamed geology show wasn’t the only kind of preparation that Alsup had made. He also mentioned that he had rewatched An Inconvenient Truth, and acknowledged that he had been reading several books on climate science and its history, even challenging Boutrous at one point about a scientist that he had left out in his rundown of the history of climate science.

“You jumped over 1938. Who was in 1938?” he asked the lawyer.

“... 1938?” Boutrous asked.

“There was a guy named Callendar,” Alsup prompted. “The Callendar effect is named after him.”

The science experts didn’t seem used to lecturing to a single student who is completely unabashed about asking any question that pops into his head. They occasionally had trouble indulging or recovering from tangential lines of questions, but still, they had a wider range of knowledge to draw from when put on the spot. Although Boutrous — a noted Supreme Court litigator — couldn’t answer questions about undersea lava flows or why the rise of sea water is inconsistent across the planet, he was at least at ease with a judicial style of questioning, and his strategy was clear: if the oil companies were going to go on the record with a vocal acceptance of climate science, they would take the opportunity to have a professional rhetorician sow doubt about where oil companies fit into the blame game.

The thrust of Boutrous’ presentation wasn’t that climate science was wrong — he, too, took a turn running through graphs showing the precipitous rise in global temperatures and sea levels — but he also took care to show the rate of emissions in China and India, lingering particularly on a graph that said that China’s emissions currently exceed the United States. He said that this was largely due to the burning of coal, which is being reduced in the US. In fact, Boutrous even credited hydraulic fracking with reducing carbon dioxide emissions in the US.

Boutrous seemed to say that fossil fuel companies aren’t responsible for how people use their products. “IPCC doesn’t say that the extraction or production of fossil fuels leads to emissions,” Boutrous said. “It’s energy use, the economic activity, that drives the demand for fuel that leads to emissions.”

“We’re just making the cigarettes, people are choosing to smoke.”

It’s an argument we’ve heard before from tobacco companies, says Peter Frumhoff, chief climate scientist at the Union of Concerned Scientists. “Tobacco companies for years said that ‘We’re just making the cigarettes; people are choosing to smoke,’” Frumhoff says. And for years, courts sided with the companies, he says — until public opinion began to change. “It was the consequence of their efforts to disinform that led juries and judges — who are members of the public — to say, ‘Wait a minute,’” Frumhoff says. The lawsuit itself says bluntly that the defendants “borrowed the Big Tobacco playbook in order to promote their products.” The complaint accuses the oil companies of “promoting massive use of fossil fuels by misleading the public about global warming by emphasizing the uncertainties of climate science.”

In response, Boutrous’ presentation on the history of climate science focused on the controversy around the theory that climate change was caused by humans. Chevron may be willing to say now that climate change was caused by humans, but surely it wasn’t wrong to say otherwise then. For example, both Boutrous and Allen mentioned Swedish chemist Svante Arrhenius who, at the turn of the 20th century, grew increasingly concerned that anthropogenic carbon emissions could increase global temperatures.

But Boutrous took time to emphasize that, until about the 1960s, most scientists didn’t believe him. This isn’t strictly wrong — although Judge Alsup himself noted that in 1938, Guy Callendar linked climate change to anthropogenic carbon dioxide emissions. Even NASA’s Earth Observatory agrees that Arrhenius was largely disregarded until the second half of the century. “It’s trial and error. Scientists debating each other,” Boutrous said in court. “Questioning other scientists’ views is part of the scientific process.” (Boutrous did not call any scientific experts on behalf of the oil companies to speak before Judge Alsup Wednesday about how the scientific process is conducted or anything else.)

“What’s actually said is not nearly as important as what the evidence is to support it.”

Boutrous drew quotes from IPCC reports across the years, showing the increasingly strong language that was used to characterize its conclusions about climate change. In 1995, the IPCC said that “the balance of evidence suggests” human-caused climate change, the 2007 report goes with the phrase “very likely,” and by 2013, it becomes “extremely likely.” In other words, the oil companies are emphasizing that it’s taken time for scientists to reach a consensus on climate change. It’s a strategy that climate law expert Jessica Wentz at Columbia Law School was expecting. “Not directly attacking the science, but undermining it by emphasizing uncertainty,” she says.

The legalistic reading of the IPCC’s statements was frustrating to Allen, he said in an interview with The Verge after the tutorial concluded, because to scientists, the evidence and context are more important than the language. “The question of whether somebody writing a scientific paper uses the word ‘likely’ or ‘very likely’ is kind of neither here nor there,” Allen says. “What’s actually said is not nearly as important as what the evidence is to support it.”

Still, on the basic facts, the two sides agreed more than they disagreed — which kept arguments over whether or not climate change was real from derailing the hearing. This wasn’t for lack of trying on the part of the deniers: academics William Happer, Richard S. Lindzen, and Steven E. Koonin requested leave to file their own scientific presentation, which questions anthropogenic climate change. Happer and Lindzen are climate deniers; Koonin claims climate science is “not settled.” Another group of deniers, led by a British viscount with a degree in classical architecture, asked to file an amicus brief in the case. Neither group has yet received permission to contribute to the case, but the judge has asked both to disclose their funding sources and any links to either of the parties in the case. Notably, Koonin disclosed that he had “some money vested in a BP pension plan arising from his employment that ended nine years ago.” (He was chief scientist at BP for five years, according to his NYU bio.)

The judge wore his “science tie”

Alsup insisted that this tutorial was a purely educational opportunity, and his enjoyment of the session was obvious. (For the special occasion, he wore his “science tie” under his robes, printed with a graphic of the Solar System.) But the hearing could have impacts beyond the judge’s personal edification, Wentz says. “It’s a matter of public record, so you certainly could refer to it in a court of public opinion, or the court of law in the future,” she says. Now, Wentz says, there’s a formal declaration in the public record from a Chevron lawyer, stating once and for all: “It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.”