The Limits of Climate Change Litigation

Aerial view of the village of Kivalina on a spit of land in the Chukchi Sea.

Joe Raedle/Getty Images

Kivalina, an Iñupiat village on the Chukchi Sea threatened by sea level rise, Alaska, September 10, 2019.

When Myles Allen first proposed suing fossil fuel companies in 2003, the outlook for climate action in the political sphere was bleak. The United States, responsible for a quarter of the world’s greenhouse gas emissions, still had no major carbon regulations in place. Two years into the Bush administration and its oil-industry cronyism, any meaningful policy shifts in the near future seemed unlikely. Although in 2001 the Intergovernmental Panel on Climate Change (IPCC) had issued its clearest statement yet that global warming was caused by human activities, Bush declined to join the Kyoto Protocol and abandoned his campaign pledge to cap carbon emissions, instead issuing a record number of oil drilling permits on public and tribal lands.

Taking Big Oil to court for climate-related damages was only a thought experiment at that point. But Allen, a climate scientist at Oxford University, believed a suit would be relatively straightforward. As he wrote in a 2003 Nature commentary, it was simply a matter of reconstructing a chain of events that began with the carbon emissions produced by a given fossil fuel company and ended with the role of those emissions in climate-related harms.

The field of research that emerged in service of these aims, known as climate change attribution science, quantifies the influence of anthropogenic greenhouse gases in observed changes in natural systems, like rising sea levels, and extreme weather events, like heat waves and hurricanes. Rather than draw causal connections between emissions and events, attribution science deals in risks and probabilities: scientists have recently found, for example, that climate change increased the risk of the severe flooding in Western Europe this past summer by at least 20 percent. The hope is that such data will provide lawyers with the hard evidence to hold fossil fuel companies accountable for climate change. It is a technical solution to the problem of apportioning blame.

It’s also an attractive one for anybody who has ever felt enraged that they’re forced to live in a world run on fossil fuels, having to foot the bill for damages that oil companies knew for decades their products would cause. Yet, to date, no case against the fossil fuel industry has made it to trial. Instead, while climate scientists now have persuasive methods for holding industry to account, lawyers have come up against the limits of US tort law, as time and again the courts have ruled that climate change is too politicized, too international, too entangled in policy—too big, in short, to litigate.


In January 2003, after several months of exceptionally heavy rainfall, the river Thames flooded its banks, temporarily submerging much of England’s central Thames valley. The river level had climbed to a degree not seen since the 1940s, leaving motorists stranded, rail lines underwater, and schools shuttered for several days. Hundreds of local residents, the vast majority of whom had never experienced flooding in the region before, reported that water overtook the basements and ground floors of their homes.

Climate scientists understood that, in a warming world, extreme events like the Thames flooding would occur with increasing frequency. But the extent to which climate change had caused this event in particular was generally believed impossible to determine.

Watching the flood waters creep toward his home in south Oxford, Allen thought otherwise. Scientists were already using computer models to isolate the effects of human activities on the climate system. Allen believed a similar method could be used in the context of weather events. In this case, scientists would compare two simulations: one that modeled the risk of an extreme event like a flood in the world with its current levels of greenhouse gases, and one that modeled the risk of the event in a world with anthropogenic emissions removed. The difference in the two risk values would be the portion of the event that could be attributed to humans. Theoretically, then, science could quantify the degree to which climate change had “loaded the dice” in favor of the event. Allen was optimistic that scientists could pull it off. “We are not yet in the position to produce such figures for the contribution of greenhouse-gas emissions to the increased risk of flooding in south Oxford,” he wrote. “But the point is, if we get the science right, we could be.”

As proof of concept, the following year, Allen, working with Oxford colleague Daíthí Stone and Peter Stott of the Met Office (the UK’s national weather service), published the world’s first event-attribution study. They calculated that global warming had doubled the risk of Europe’s 2003 heat wave, in which over 30,000 people died. Since then, scientists have produced attribution studies of weather events ranging from droughts and wildfires to hurricanes and typhoons. Attribution science’s methods are widely accepted as sound, and have received endorsements from the National Academy of Sciences and the IPCC.


All the while, Allen and colleagues in Britain and the US reached out to the legal community, writing essays for law review journals and attempting to educate lawyers in attribution science, in hopes that the research would one day form the basis of lawsuits. Allen believed it was especially important to develop something like an “industry standard” for attribution studies, in order to avoid an overreliance on expert witnesses in court.

Scientists like Allen were primarily concerned with what’s known as event attribution science, which links extreme weather events with the increased concentrations of greenhouse gases in the atmosphere. But to be useful in fossil fuel litigation, lawyers would also need to be able to causally connect those events with the historical emissions of a specific company—a branch of research known as climate change source attribution.

Here help came from Richard Heede, a consultant who specializes in producing greenhouse gas inventories for cities and organizations looking to quantify their carbon impact. Heede first began working on the source attribution question in 2005, after Greenpeace International commissioned him to produce a study of the total greenhouse gas emissions of ExxonMobil. The results were startling: Exxon and its subsidiaries were responsible for 20.3 billion metric tons of carbon dioxide emissions—an amount that added up to about 5 percent of the world’s total anthropogenic emissions since the late nineteenth century. Impressed by this finding, Greenpeace commissioned a second study, this time to quantify the total emissions contributions of every fossil fuel corporation since the 1850s. It was painstaking work that involved tracking down annual reports, SEC filings, and obscure court documents, and tallying up each company’s annual production numbers across convoluted corporate mergers and acquisitions histories.

The results, which Heede published in 2014, showed that about two thirds of the world’s greenhouse gas emissions came from just ninety companies, a group he described as the “carbon majors.” Equally important, Heede found that that of those emissions, about half had occurred after 1988—the conventional benchmark for when the scientific community arrived at a consensus on global warming. In other words, a significant portion of the world’s total emissions had occurred during a period when it would be difficult for companies to plausibly argue that they were unaware of the risk their products posed to the climate.

Heede’s work provided researchers with the data they needed to connect fossil fuel producers’ emissions with climate impacts. In 2017, it enabled a group of scientists led by Brenda Ekwurzel of the Union of Concerned Scientists to show that emissions from the carbon majors were responsible for about 30 percent of total greenhouse gas–related sea level rise since 1880. Two years later, another Ekwurzel group traced about 50 percent of all ocean acidification back to carbon majors’ emissions. It appeared that attribution science had advanced to a point where scientists could precisely pinpoint a given company’s share of the responsibility for climate change—exactly as Myles Allen had first envisioned.  


Meanwhile, climate litigation efforts had gotten underway in earnest. The same year that Allen published his Nature commentary, the environmental lawyer David Grossman independently outlined what it would take to sue fossil fuel companies under US tort law. Like Allen, Grossman believed it could be done, but he anticipated at least two major challenges in bringing these suits before a jury. Given the runaway success of industry’s campaign to cast doubt on the certainties of climate science, Grossman thought it likely that fossil fuel companies would “challenge everything” about the science during a trial, even at the level of seemingly basic issues like the causal relationship between greenhouse gases and climate change.

But before a case could make it to this point, plaintiffs would need to contend with a relatively obscure legal concept known as the political question doctrine. The political question derives from the constitutional principle of separation of powers. It refers to issues that judges deem outside the scope of their authority and better left to other branches of governments to resolve; to rule in such a case would be to effectively legislate from the bench. (The Supreme Court’s 2019 ruling that gerrymandering is “beyond the reach of the federal courts” turned on the political question doctrine.) The doctrine says nothing about matters of justice: judges might acknowledge that the matter at hand involves clear wrongdoing even as they claim their hands are tied by the Constitution to do anything about it. Grossman suspected that judges might refuse to hear climate suits under the political question doctrine: “the major issues of causation, multiple defendants and plaintiffs, and the variety of remedies, and present and future harms all suggest a more comprehensive approach to climate change that might be better taken by a legislature or agency.” But with a payoff potentially so enormous, Grossman believed the tort approach was worth a try.  


One of the first cases against the fossil fuel industry was brought in 2005. In a class action suit, Comer v. Murphy Oil, Mississippi property owners sued a group of oil and refining companies for damages incurred during Hurricane Katrina, arguing that global warming had made Katrina a storm of “unprecedented strength and destruction.” Pointing to the political question doctrine, a district court dismissed the case. In 2009, a panel of judges on the Fifth Circuit Court of Appeals partially reversed the lower court’s dismissal, but in a later hearing before the full appeals court, the judges failed to achieve a quorum because so many had recused themselves (presumably because they held stock in fossil fuel corporations), so the original district court’s decision was left to stand.

The case was the first indication that the political question doctrine would pose a major hurdle in bringing cases to trial, just as Grossman anticipated. Another soon arose after residents of Kivalina, a small Iñupiat village located on a barrier peninsula off the coast of Alaska, sued two dozen oil, gas, and energy companies in 2008. Sea level rise was rendering Kivalina increasingly uninhabitable, and the community wanted the fossil fuel industry to cover the cost of relocating the town to the tune of $400 million. Here, again, a judge dismissed the case on the grounds of the political question doctrine, ruling that “the allocation of fault—and cost—of global warming is a matter appropriately left for determination by the executive or legislative branch.”

Litigators received another blow from the Supreme Court’s 2007 decision in Massachusetts v. EPA, which determined that the EPA had the authority to regulate carbon dioxide emissions under the Clean Air Act. (The agency had previously argued that it could not regulate greenhouse gases because they were not technically pollutants.) The ruling led the agency to issue more stringent emissions rules for automobiles and power plants, but it reaffirmed judges’ arguments that climate change was a political issue by designating greenhouse gases the domain of the EPA—and, by extension, the legislative and executive branches—rather than the courts.


More than a decade after Myles Allen wrote his commentary, attribution science had yet to see the inside of a court room. This changed in 2018. As part of a case brought by the cities of Oakland and San Francisco against five major oil companies, the presiding judge, William Alsup, requested that each side provide the court with a two-hour tutorial on the history of climate science and the current state of scientific knowledge—the first time such a presentation had ever been requested. As Allen recently told me, the event created an entirely novel way for plaintiffs to “smoke out” the oil industry’s defense strategy when it came to contesting the climate science.

Allen was one of three scientists to present evidence for the plaintiffs. To a packed courtroom, he and American climate scientists Don Wuebbles and Gary Griggs methodically walked the court through the scientific evidence that showed the changes happening in the earth’s natural systems, the extent to which these events could be attributed to carbon emissions, and the projections for future changes to come.

To the surprise of many court observers, the presentation for the defense was not so dissimilar from that of the plaintiffs. From the very first slide, which quoted the IPCC’s 2013 conclusion that “it is extremely likely that human influence has been the dominant cause” of global warming, it was evident that the oil companies did not plan to contest the science. To be sure, at various points the presenting lawyer fell back on the industry’s penchant for doubt-mongering, overstating the uncertainty of some parts of climate science and quibbling with the extent to which fossil fuels alone were responsible for global warming. But the significance was clear: despite years of publicly refusing to accept the scientific consensus on climate change, the fossil fuel industry was willing to admit in a court of law that global warming was real and was caused—at least in part—by its products. For a brief and shining moment, climate science seemed to have won the day.

Yet, three months after the tutorial spectacle, Judge Alsup dismissed the case, invoking a now-familiar refrain: climate change, he argued, is an issue for Congress, not the courts.

Three years on, despite the ever-increasing frequency of extreme weather events, fossil fuel litigation remains at a discouraging juncture. Attribution science has evolved and sharpened to the extent that scientists can now determine precisely how much the fossil fuel industry is responsible for a given portion of the effects of global warming. It can tell us, for example, that between 2015 and 2020, oil and gas production in Belgium added 49.6 million tons of carbon dioxide to the atmosphere, or 0.15 percent of the world’s total emissions during that period. But tort law, designed as it is to redress discrete and defined harms, still hews to legal doctrines unsuited for the distinctly modern problem of climate change—in which the environmental harms at stake are diffuse, uncoupled from any single emissions source, and largely invisible. (This is why Yale law professor Douglas Kysar describes climate change as the “paradigmatic anti-tort.”)

It is also a problem that lends itself to naive arguments about who truly is to blame. “Everyone has contributed to the problem of global warming,” as Judge Alsup put it in his ruling, “and everyone will suffer the consequences.” In Alsup’s telling, climate change is simply the price we all must pay for the advantages of modern life:

[O]ur industrial revolution and the development of our modern world has literally been fueled by oil and coal. Without those fuels, virtually all of our monumental progress would have been impossible. All of us have benefitted. Having reaped the benefit of that historic progress, would it really be fair to now ignore our own responsibility in the use of fossil fuels and place the blame for global warming on those who supplied what we demanded?

Even an attribution science with pinpoint precision is useless in a system of justice willing to believe that culpability for climate change is a universal condition. This, of course, is also what fossil fuel companies have been leading us to believe for decades, with their “we’re all in this together” rhetoric and their efforts to lay blame on individual consumption with tools like the “personal carbon footprint calculator,” a concept introduced to the public by a British Petroleum marketing campaign in 2004.


It’s now been over thirty years since climate scientist James Hansen famously testified before lawmakers to warn them about global warming. In the meantime, nothing much has changed. In recent years private citizens have begun suing the government over its continued refusal to regulate the oil and gas industry. In cases like Aji P. v. State of Washington and Funk v. Wolf, groups of young people have accused the government of failing to uphold its duty to preserve the climate under the public trust doctrine, the idea that the government has a responsibility to protect certain shared natural resources. The suits are long shots—many have also been dismissed under the political question doctrine—but they speak to the extent to which the government’s inaction has become pathological. In one of the most well-known of these cases, Juliana v. United States, the presiding district judge recently directed lawyers for the plaintiffs and the Department of Justice to begin settlement negotiations, but whether the two sides will reach an agreement is far from certain.  

Yet there is reason to be optimistic—if cautiously so. In international judicial settings, cases that rely on attribution science have seen promising results. In 2015, a group of nongovernmental organizations in the Philippines asked the nation’s Commission on Human Rights to determine whether the carbon majors had committed human rights violations by damaging the climate. Heede’s studies formed the scientific basis for their petition. After convening public hearings that included testimony from individual Filipinos whose livelihoods were threatened by climate change, the Commission found that fossil fuel companies could in fact be held liable. The decision opened the door for other litigants to bring suit against the companies under Philippine civil law. And last May, a district court in the Hague ruled that, under the Dutch human rights principle of “duty to care,” Royal Dutch Shell must cut its emissions 45 percent by 2030 to prevent further harming the climate. Shell is currently appealing the decision.

As for the United States, 2017 saw a new wave of litigation against fossil fuel companies, this time brought by state attorneys general, targeting the industry’s long-waged campaigns of disinformation and deception. These suits represent a shift in strategy: rather than take the tort approach and address the present and future harms of climate change, they accuse fossil fuel companies of suppressing internal climate research and publicly spreading doubt. More than a dozen such cases are pending. Courts have again dismissed several of these cases, but at least one—Massachusetts v. Exxon, which accuses the oil company of misleading its investors about the threat that climate change poses to its business—inched closer to a trial this past June after a judge denied a motion to dismiss.

Attribution science will play a more limited role in these cases, as their outcomes will largely turn on the plaintiffs’ ability to prove what individuals inside the companies knew and when they knew it. For this, they can draw upon decades of work by investigative journalists, social scientists, and historians to assemble a cache of documents that lays out a comprehensive timeline of industry’s deceptions. The history of Big Tobacco litigation is instructive here, and more cause for optimism: after a series of failed attempts in the 1980s to sue cigarette manufacturers for lung cancer–related damages, the tide turned in the 1990s when documents came to light showing that, despite publicly arguing that the dangers of smoking remained unproven, companies were in fact well aware of the relationship between nicotine and addiction and between smoking and lung cancer. The documents paved the way for the largest civil litigation settlement in US history, in which the country’s four largest cigarette producers agreed to pay billions annually to states to cover health care costs related to smoking.

And last week, as climate activists staged a hunger strike outside the White House to protest the Biden administration’s elimination of a landmark clean electricity program from the Build Back Better spending plan (an indication that Biden might prove as weak-kneed on climate legislation as his predecessors), CEOs from six major oil companies and industry trade groups testified during a House Oversight Committee hearing on climate change disinformation. The event was largely an exercise in question-dodging. Pressed to reconcile Exxon’s public statements in the 1990s that the scientific evidence of global warming was “inconclusive” with an internal 1982 memo that reported “unanimous agreement” among scientists about the relationship between fossil fuels and climate change, current Exxon CEO Darren Woods insisted that his company’s position “has always been consistent with the science.” In response to a question from Representative Ro Khanna, Democrat of California, about whether Exxon would commit to decreasing its oil and gas production, Woods countered with a commitment to reduce emissions. When Khanna pointed out Chevron’s plans to increase its production 3.5 percent annually, CEO Mike Wirth responded, “I’m very proud of our company and what we do.”

Evasions aside, the hearing may be an indication that the federal government is finally willing to start the process of holding the fossil fuel industry to account—just as the courts have been asking it to do all along. Near the end of the hearing, New York Representative Carolyn Maloney announced that she intended to subpoena the companies for additional documents related to their work with public relations firms and “shadow groups.”

As Myles Allen pointed out to me, if attribution science didn’t exist as an airtight field of research, then perhaps industry would have invested more aggressively in climate denialism as a legal strategy. But in his view, lawyers still bringing civil suits against fossil fuel companies are fighting “yesterday’s war.” For attribution science to ever take down Big Oil, cases will need to brought under a branch of the law that can avoid the tort-law trap of collective culpability and instead do the work of holding power to account. Even then, making industry pay for climate damages is just one small piece of the climate-justice puzzle. A successful lawsuit might win relief funds for a city after a hurricane, but will do nothing to hurt companies’ bottom lines. Until the government implements meaningful decarbonization measures, we’ll still be left cleaning up after the industry’s messes. The fact remains: oil and gas companies knowingly inflicted harm on the world. Will we continue to let them get away with it?

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