Earlier this week, we made an effort to answer a federal judge’s questions about climate science for readers who have asked similar questions. And on Wednesday, Judge William Alsup finally got his answers during a five-hour hearing.
The case was brought by the cities of San Francisco and Oakland against a handful of oil companies that they say should help offset the effects of sea level rise. This claim revolves around the idea that internal documents show that the companies knew that climate change was man-made, even though they campaigned publicly in the 1980s and 1990s.
Before the case gets underway, Judge Alsup wanted both sides to put their climate science cards on the table, to establish any disagreements about how our knowledge has evolved over time. He also wanted to answer a few questions of his own about why we are certain that humans are responsible for global warming.
Approach the bank
San Francisco and Oakland brought in a trio of climate scientists to do their presentation for them. The first was Myles Allen of Oxford, who tried to summarize more than a century of research into greenhouse gases and sources of CO2 emissions in one hour. As Allen walked through physics and history, the judge often came up with clarifying questions, seemingly taking up training.
Allen then passed it on to UC Santa Cruz researcher Gary Griggs, who focused on global sea level rise and its impact on California. Griggs placed the recent (accelerating) sea-level rise trend in the context of the past 20,000 years, and he emphasized the effect of short-term regional events that come on top of an ever-rising base sea level.
(We’ll come back to the third scientist.)
The defendants, on the other hand, let Chevron attorney Theodore Boutrous do the talking. (After Boutrous surprisingly stated that he would speak only on behalf of Chevron, the judge gave the other defendants two weeks to decide whether they agreed with everything presented.) As expected, Boutrous did not deny that humans caused climate change, but he did. try to portray climate science in the recent past as much more uncertain.
This probably forms the strategic basis for the case. Boutrous said Chevron accepted the conclusion of human responsibility in the Intergovernmental Panel on Climate Change’s last two reports (dating back to 2007), but the company tried to paint previous reports as fundamentally insecure.
To do this, the lawyer chose some of the cautious language about uncertainty dating back to the first report in 1990, which said we couldn’t yet calculate how much warming was caused by humans. But that report also clearly said that greenhouse gas emissions caused global warming and needed to be severely curtailed to avoid dangerous climate change and sea level rise. And as Plaintiff’s presentation pointed out, our estimate of how much warming is due to greenhouse gas emissions hasn’t really changed since a 1979 National Academy of Sciences report on the subject.
By adhering to the IPCC reports, the defendants seem to intend to argue that oil companies can be quite in disagreement about climate change as long as climate scientists say uncertain things. However, in order to do this, they should at least make a better effort to display the reports accurately.
Because this case focuses on the effects of sea level rise, Boutrous turned to uncertainties in those projections from the 2013 IPCC report, characterizing sea level rise as still unclear and difficult to quantify (without denying that some of it is due to the man is caused).
Finally, Boutrous argued that it is the use of fossil fuels – rather than their production and sale – that is causing climate change. He pointed out that the IPCC report covers population growth, land use and energy consumption, but not fossil fuels extraction. This is the obvious argument for the companies, despite the case explicitly targeting their behavior as sellers.
Boutrous said Chevron didn’t necessarily agree with everything in the paragraphs of the reporting on climate change impacts or mitigation, but he did call IPCC’s descriptions of climate change a global issue of collective action.
The rest of the story
When Boutrous was done, the prosecution had another presenter: Don Wuebbles of the University of Illinois. Wuebbles helped write the last two IPCC reports, as well as the 2017 US National Climate Assessment, so he had a few things to say about Boutrous’s comments.
Wuebbles stressed that climate science didn’t stop in 2012, when the last IPCC report was drafted. Specifically, research on sea level rise in recent years has led to clearer forecasts. That clearly includes possible scenarios of much higher sea level rise than the heavily reserved, conservative IPCC figures.
As the case progresses, the different version of the climate science certainty by the defendants will come into play over time. On the other hand, San Francisco and Oakland attorneys are likely to try to disprove that internal documents show that these companies were not confused by scientific uncertainty, but that they deliberately contested scientific certainty.