This piece was first published in Forbes on June 26, 2019. It is reprinted with their permission.
The last few years have seen a remarkable chipping away at the defenses that the fossil fuel industry has long used to deny accountability for its role in climate change. Earlier this year, the U.S. Supreme Court denied a request from ExxonMobil to review a Massachusetts court decision that allowed the state’s attorney general to seek internal company documents. Those documents related to ExxonMobil’s knowledge of the threat of climate change, and its efforts to publicly discredit climate science and downplay climate risk. Massachusetts’ legal action, and similar litigation from New York, are rooted in a 2015 investigation that found that Exxon’s leadership clearly understood climate risk as far back as 1977.
The revelations have helped fuel a wave of legal challenges—none yet successful—from municipalities that contend that the oil industry should be held liable for damages resulting from climate change. In one surreal episode, representatives of Chevron led a climate change education session for the federal judge hearing San Francisco and Oakland’s challenge to fossil fuel companies (the oil companies played the climate science straight). Clearly, the industry has learned to publicly accommodate climate science even as it struggles to deflect efforts to hold it culpable for warming.
A rapidly developing scientific discipline could make efforts to deny accountability more difficult. The discipline, climate attribution science, has drawn public attention for its ability to make connections between increasingly frequent extreme weather events, such as a recent California heat wave and unprecedented Midwest flooding, and the warming of Earth’s climate that make such events all the more likely. While this domain of attribution science, known as extreme event attribution, has captured media attention, potentially more damning may be a related branch of science that has the power to quantify the contribution of individual companies to climate change.
That discipline, source attribution, has been substantially developed through the work of geographer Richard Heede, who spent years compiling a database of historic greenhouse emissions. The result was a 2014 report that traced two-thirds of industrial carbon dioxide emissions, and 43% of total atmospheric carbon increase, to just 90 companies.
Heede calculated that the top two investor-owned emitters, Chevron and ExxonMobil, and two leading state-owned companies, Saudi Aramco and Gazprom, contributed 10% of total greenhouse emissions for the period 1880 to 2010. Of the 90 companies, 83 were fossil fuel producers and 7 were cement makers.
In 2017, a group of researchers including Peter Frumhoff, chief climate scientist at the Union of Concerned Scientists, took Heede’s research to its logical next step by translating those 90 companies’ emissions into real environmental impacts. The scientists found that the companies’ emissions drove 3 inches of sea level rise, nearly half of the 7 inches of total sea level rise during the 130 year span.
Potential climate litigants are now anxious to understand the extent to which source attribution can provide evidence in cases that seek reparations for climate damage.
“In a sense, attribution does provide legal evidence that wasn’t there before,” says Michael Burger, executive director of the Sabin Center for Climate Change Law at Columbia University.
“If some of the current cases do move to trial and to an evidentiary phase, then I expect that these studies and other ones will come forward. And there will ultimately be something of a battle between the plaintiff’s experts and the defendant’s experts over the best methodologies, and over how much blame really can be assigned to particular defendants.”
To understand how attribution science might be used in the courtroom, it helps to understand its limits. Experts are quick to point out that climate attribution is a probabilistic discipline, not a deterministic one.
In other words, scientists can show how climate change may have created conditions that make a given flood or drought more likely, just like the medical profession draws connections between cigarette smoking and an increased probability of lung cancer among smokers. In both cases, however, scientists stop short of saying emissions (or smoking) were the definite cause of a specific instance of extreme weather (or lung disease).
“Yet, we can conclude in a societally significant way that smoking increases the risk of lung cancer, says Frumhoff, of the Union of Concerned Scientists. “And we therefore have held tobacco companies accountable for their contributions to that problem.”
The same line of reasoning might someday succeed in holding industries, and nations, responsible for the climate damage rooted in their actions. Although the complexity of our climate, and the large number of actors that have contributed to climate change over centuries, means that plaintiffs aiming to hold companies legally accountable for climate damages face an uphill battle.
A company might find itself more vulnerable if it can be shown that it fully understood the climate danger posed by its business, yet elected to engage in harmful activity anyway. This is why Massachusetts and New York’s efforts to access Exxon’s internal records are so fraught, and why the company has pushed back as hard as it has to keep the records hidden.
To this point, Heede’s 2014 research offers data that could make fossil fuel companies more nervous. His emissions database showed that more than half of total cumulative emissions from the top 90 polluting companies came after 1986, well into the era in which the oil industry, and Exxon in particular, understood the impact of oil, gas, and coal emissions.
“There’s a strong case that companies should be held responsible for the emissions of the products that they marketed while knowing, since the mid-1960s, of the climate risks of their products,” says Frumhoff. “Should these cases come to court, we might see a ramp up of that sort of narrative.”
Today, plaintiffs in Juliana v. the United States, the youth-led challenge that accuses the U.S. government of causing dangerous carbon dioxide concentrations, are similarly arguing that the government’s knowledge of the danger of greenhouse emissions, and simultaneous lack of action to stop those emissions, are particularly incriminatory.
It’s too early to tell if attribution science will provide the equivalent of a smoking gun in cases aiming at extracting damages and climate action from big emitters. But it does appear that industry is working to alter its defense by spreading the blame for climate damage all around. For example, a fuel refinery might argue that it may be responsible for emissions from operations, but not for the greater tailpipe emissions of cars that burn its fuel. Fossil fuel companies would rather that responsibility be passed to consumers.