The oil industry used climate data from the latest IPCC assessment for a judge's hearing on Wednesday.The oil industry used data from the latest IPCC assessment in Wednesday's climate tutorial, but played up the science's "uncertainty." Photo credit: IPCC, via Flickr

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By Amy Westervelt

In a climate science tutorial in San Francisco on Wednesday, U.S. District Court Judge William Alsup pushed both defendants and plaintiffs in the San Francisco and Oakland climate liability cases to answer dozens of questions about the state of climate science. But the five-hour hearing all boiled down to one fundamental question: At what point was it clear man-made CO2 emissions were putting the climate on a path toward destruction?

It was the concept of scientific certainty, more so than the science itself, that Alsup seemed to be probing. He asked questions ranging from why various ice ages happened to which are the best renewable energy sources to whether we should have chosen to rely more on nuclear energy back in the 1950s.

Predictably, the defendants argued that the science on the causes and impacts of climate change has been too uncertain to lay the blame at their feet. The plaintiffs relied on three scientific experts who described the data from the UN’s Intergovernmental Panel on Climate Change (IPCC) and even more recent science and how climate models from as far back as the 1950s mapped out impacts the world is seeing today.

Alsup had ordered the tutorial to inform him of the scientific issues at hand in the case. The cities of San Francisco and Oakland are suing five major oil companies for public nuisance, saying the companies have known for decades their products contributed to global warming and not only did nothing to mitigate the harm, but also impeded action on climate change.

The judge did chastise four of the defendants for refusing to present arguments at the tutorial. Only Chevron chose to speak, relying on attorney Ted Boutrous to explain its views on the science, while attorneys from ExxonMobil, ConocoPhillips, BP and Shell sat in the courtroom but did not make a presentation. Alsup gave those four companies two weeks to to provide a statement in writing either agreeing with or refuting each point made in Boutrous’ presentation. “You can’t get away with sitting there in silence and then saying later, ‘Oh, he [Boutrous] doesn’t speak for us,'” Alsup said.

The plaintiffs called on Myles Allen, head of the Climate Dynamics group at the University of Oxford, whom Alsup would call “a genius” by the end of the hearing; Gary Griggs, distinguished professor of Earth and planetary sciences at the University of California at Santa Cruz; and Dr. Don Wuebbles, professor of atmospheric science at the University of Illinois and lead author of the IPCC’s fourth scientific assessment report and a member of the team who compiled the 2014 U.S. National Climate Assessment.

After announcing the acceptance of all amicus briefs (including a controversial brief backed by the conservative Heartland Institute), and noting that the U.S. government has been given until April 20 to provide one, Alsup turned the floor over to the plaintiffs. Allen started by walking through the history of climate science, including the work of Nobel Prize-winning Swedish physicist and chemist Svante August Arrhenius, who first theorized that CO2 emissions would trigger atmospheric warming. He also described Charles Keeling’s observations in Hawaii, now known as the Keeling Curve, which showed that the planet’s rising CO2 levels couldn’t just be attributed to human respiration.

Stopped frequently by Alsup to explain a chart or a bit of jargon, Allen made the case that science has successfully identified the sources and impacts of carbon dioxide in the atmosphere for a very long time and that scientific consensus emerged as early as the 1950s. On this point, even Chevron’s Boutrous agreed, despite spending the majority of his two hours making the case that the science around anthropogenic climate change and its impacts has been uncertain up until the early 2000s. He agreed with Alsup that despite some disagreements on Arrhenius’s work in the 1930s and 1940s, by the early 1950s, there was consensus around the warming effect of CO2. Boutrous said, “That’s the theory that still holds today,” a statement that seemed to contradict his earlier statements that there had been no consensus around warming until 2000.

Griggs presented his findings on sea level rise, the science most relevant to the case because most of the damages claimed by the communities stem from seal level rise. Griggs discussed his work on sea level rise, how the rate is increasing and related attribution science.

Boutrous tried to counter his testimony by showing sea level rise projection charts from the fifth IPCC assessment, calculated five or more years ago. By leaving out the past five years, when global warming has produced record-breaking global temperature records and accelerated sea level rise, he attempted to leave the impression of continued uncertainty in the science.

Wuebbles, however, mentioned the science around sea level rise in particular has progressed since the last IPCC report, but did not specifically point out the misleading nature of the defendants’ choice of data and dates.

Asked why none of the experts explicitly discussed attribution science—including the Carbon Majors report that attributes more than 70 percent of global emissions to 100 companies, for example, or Allen’s work connecting extreme weather events to climate change—San Francisco city attorney Dennis Herrera said the time for that would come. “This was just a tutorial on the state of science and the history—how long it’s been known and what people knew about it for how long. In terms of attribution, that will be proven throughout the case,” Herrera said.

Boutrous, meanwhile, continually hit  three key points: the history of uncertainty in climate science, the global nature of emissions and climate change and the role that individuals and economies play in generating emissions.

Despite opening with a warning from Alsup “not to get political,” the tutorial ended on a political note. Boutrous referenced a paragraph in the plaintiffs’ complaint that accuses the defendants of colluding to suppress public information about climate change. “From what I’ve seen—and feel free to send me other documentation—but all I’ve seen so far is that someone went to the IPCC conference and took notes,” Alsup said. “That’s not a conspiracy.”

The defendants indicated they plan to file a motion to dismiss the case, while the plaintiffs said they will not appeal Alsup’s ruling that the case should stay in federal court, despite them having filed it initially in California state court.

After the tutorial, Boutrous told reporters that he thought the presentation had gone well, and restated his company’s commitment to using the IPCC assessments as a guide to dealing with climate change.

Three other California climate liability suits, filed by the counties of San Marin and San Mateo and the city of Imperial Beach, meanwhile, have been sent back to state court by a different U.S. District Court judge, where the communities believe they have a stronger chance of success under state law.