The science of climate change was on trial on Wednesday when leading experts testified about the threats of global warming in a US court while a fossil fuel industry lawyer fighting a high-profile lawsuit sought to deflect blame for rising sea levels.



The hearing was part of a courtroom showdown between liberal California cities and powerful oil corporations, including Chevron, ExxonMobil, Shell and BP. San Francisco and Oakland have sued the world’s biggest fossil fuel companies, arguing that they are responsible for damages related to global warming.

While climate change-related cases have entered courtrooms throughout the US, the judge in the California case, William Alsup, took the unusual step of convening a formal “tutorial” on the subject “so that the poor judge can learn some science”, allowing renowned experts and some of the biggest oil companies to answer key questions.

“From Chevron’s perspective, there’s no debate about climate science,” said Theodore Boutrous Jr, the attorney for the US oil giant, which chose not to have scientists or experts testify on its behalf. While he repeatedly referred to the Intergovernmental Panel on Climate Change (IPCC) conclusion that it is “extremely likely” humans have been the dominant cause of warming since the mid-20th century, he also worked to paint the problem as an international one for which individual corporations are not liable.

“Climate change is a global issue that requires global engagement and global action,” he said, later saying “production and extraction” are not responsible for increases in emissions, but rather “economic and population growth” are, adding: “It’s the way people are living their lives.”

The attorney spoke for hours in a packed San Francisco courtroom of attorneys, journalists and activists who lined up early in the dark of morning to get a seat, with dozens forced into a crowded overflow room and many live-tweeting fact-checks and commentary.

The communities in California, known as a leader in climate activism, have argued that greenhouse gas emissions from the companies’ activities over time will cause billions of dollars’ worth of damage, have locked in significant rises in sea level, and are endangering lives. The defendants are accused of long knowing the environmental impact of their emissions and working to deny and conceal this knowledge.

The Chevron attorney also presented a graph showing that China is burning more coal than the US, saying: “It really goes to the global nature of this.”

Environmentalists, however, pointed out that the assessment ignored cumulative emissions and that the US is the biggest carbon polluter in history.

Don Wuebbles, who helped lead the 2013 IPCC assessment of climate science and 2014 US National Climate Assessment, testified for the cities and noted that Chevron was relying on outdated reports: “The science does not stop at 2012 … There’s a lot we have learned over the last five years.”

Chevron sought to paint climate change as a product of ‘the way people are living their lives’, not the fault individual corporations. Photograph: Lucy Nicholson/Reuters

He talked about severe weather incidents becoming more intense and noted that 2014 was “the warmest year on record”, adding: “2015 was warmer. 2016 was warmer yet.” Seventeen of the last 18 years were the warmest on record, he said.

Chevron did not present any science from climate deniers, but climate change contrarians with ties to Donald Trump’s administration have also gotten involved in the litigation, offering to contribute a presentation.

William Happer, a Princeton University physicist, rumored last year to be a frontrunner for Trump’s science adviser, co-authored a recent motion in the case that said: “It is not possible to tell how much of the modest recent warming can be ascribed to human influences.” He has previously described climate scientists as “a glassy-eyed cult”.

Alsup, known as an unorthodox judge, who memorably learned to code for a Silicon Valley intellectual property lawsuit, said he had read headlines comparing his hearing to the famous Scopes “monkey trial” on evolution in the US and urged reporters in the room not to blow the event out of proportion.

“If you get bored, you can just leave,” said Alsup, who said he wore his “science tie” with a solar system in honor of the hearing.

Although there was no meaningful cross-examination, the five-hour hearing offered a window into how the oil corporations can attempt to simultaneously acknowledge human-caused climate change while trying to fight off this type of litigation. Courts across the globe have increasingly become the new frontline for climate action, and the San Francisco case could also build a factual foundation that could be cited in future suits.

At one point, Boutrous clarified that he was not speaking for the other companies, and Alsup at the end of the hearing ordered the other defendants to file motions saying whether they agreed with the Chevron attorney: “You can’t get away with sitting here in silence.”