It’s been six years since cities in California started the trend of taking Big Oil to court for deceiving the public about the consequences of burning fossil fuels. The move followed investigations showing that Exxon and other companies had known about the dangers of skyrocketing carbon emissions for decades, but publicly downplayed the threat. Today, around 30 lawsuits have been filed around the country as cities, states, and Indigenous tribes seek to make the industry pay for the costs of climate change.

Until recently, most of these cases had been stuck in limbo. Oil companies were trying to move them from the state courts in which they were filed to federal courts, a more business-friendly setting. But just in the past year, the Supreme Court declined to hear their arguments to relocate these cases on three separate occasions, most recently clearing the way for Minnesota’s case to proceed in state court. That means executives from Exxon Mobil, BP, and other oil giants may soon have to defend their actions in front of a jury.

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“Last year was a really pivotal year in terms of getting past the industry’s big push and their delay tactics,” said Alyssa Johl, vice president for the legal program at the Center for Climate Integrity, an environmental advocacy organization that provides support for these cases. “That issue and that effort has been put to rest, and now they have to face the music.”

The long delays might have strengthened the legal arguments against fossil fuel companies. Researchers have uncovered more details about what oil companies knew about climate change and when, and the science connecting fossil fuel emissions to climate disasters has matured, arming cities and states with more evidence. All the while, the effects of climate change — the heat waves, the blazes, the wildfire smoke — have only grown more obvious, and more costly. Last year, the U.S. recorded a billion-dollar disaster every two weeks.

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“With each month and with each year that these cases are stalled, the impacts for communities just grow,” said Delta Merner, the lead scientist for the Union of Concerned Scientists’ litigation hub. “I think that’s important context for understanding these cases, and for understanding the additional cases that have been filed over the last six years.”

That might explain the spread of lawsuits from coastal cities and states to inland areas like Minnesota, Colorado, and most recently, Chicago. With the third-largest city in the country suing BP, Chevron, Exxon Mobil, and other oil titans for lying about climate change, a quarter of Americans now live in cities and states that are taking fossil fuel companies to court, according to the Center for Climate Integrity.

One of the cases that’s furthest along, filed by Massachusetts against Exxon Mobil in 2019, is already in the process of “discovery,” the last major step before a trial. In this stage, both sides try to uncover evidence that could help their case in court. The discovery process could unearth further details of oil companies’ deception, such as what individual CEOs or other company executives did with the information they learned about climate change, Johl said. 

“It’s really what the industry fears the most,” Johl said. “They don’t want anyone digging through their archives and divulging their innermost thoughts and secrets.” Much of what the public learned about the tobacco industry’s effort to cover up the link between lung cancer and smoking, for example, came out of the discovery process, made public as part of a major settlement in 1998, when Philip Morris, R.J. Reynolds, and other tobacco giants agreed to pay states $206 billion over the next 25 years. 

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The discovery phase of the Massachusetts case is expected to wrap up later this year, and it could head to trial as early as 2025, Johl said.

Oil companies have plans to fight back, though. In response to the new lawsuit from Chicago, industry representatives characterized the lawsuits as a “waste of taxpayer resources” and contended that climate change should be addressed by Congress, not the courts. “They’re going to raise issues every step of the way and raise defenses every step of the way,” Johl said. 

Photo of a car splashing through a flooded road
A pickup truck plows through a flooded street in Honolulu, Hawaiʻi, in December 2021, the morning after a powerful winter tropical storm hit with heavy rain and high winds, causing widespread flooding and power outages across the state. Eugene Tanner / AFP via Getty Images

Another case that’s at the front of the pack is Honolulu’s suit seeking damages from Exxon Mobil, Chevron, and Sunoco, among others. In October, the Hawaiʻi Supreme Court dismissed the companies’ appeal to throw out the suit, clearing the way for a trial. Last week, the companies asked the Supreme Court to toss that ruling.

The industry’s current line of argument in the Honolulu case (and others) is that these lawsuits are about the broader issue of emissions and pollution, and that the federal Clean Air Act preempts any claim brought by cities and states. So far, this approach has seen some modest success. In January, Delaware’s Superior Court denied oil companies’ motion to dismiss the state’s case against them while granting a few concessions, including that out-of-state emissions were the territory of the Clean Air Act, beyond the limits of state law. Emissions that originated in Delaware, however, were fair game.

As these climate cases have slowly begun to proceed, recent months have brought lawsuits from California, cities, and tribes. Last September, the state of California demanded that oil companies fund efforts to recover from extreme weather. In December, the Makah and Shoalwater Bay tribes along the coast of Washington state became the first Native American tribes to take oil companies to court over the costs of responding to climate-related risks from rising seas, flooding, and ocean acidification. Meanwhile, Hoboken, New Jersey, and a collection of cities in Puerto Rico have added racketeering lawsuits to the mix, alleging that oil companies engaged in a conspiracy of deception.

New research has made it harder for oil giants to say they couldn’t have known the outcome of burning so much fossil fuel. A study published in the journal Science last year found that Exxon’s scientists predicted the effects of climate change with startling accuracy in the 1980s. Exxon’s models nearly matched actual temperature changes over the past several decades.

Then there’s the blooming area of scientific inquiry that connects climate change to extreme weather events. Researchers are now able to quantify how corporate emissions have fueled climate disasters, a critical development for these cases, Merner said. “This is the cutting edge where the science is moving towards — to be able to look not just at these global averages, but to see what is happening regionally.”

A study Merner coauthored last year found that 37 percent of the forests burned in the Western United States since 1986 can be linked to carbon pollution from a group of 88 of the world’s largest fossil fuel producers and cement manufacturers. Last June, Multnomah County — home to Portland — cited the research in its lawsuit against oil companies over their contributions to a deadly heat wave that hit the Pacific Northwest in 2021. In newer cases, like Multnomah’s and the ones filed by Indigenous tribes, the oil industry is sticking to its strategy of trying to move the case to federal courts, according to Margaret Barry, who maintains a climate litigation database at Columbia Law School’s Sabin Center.

The new and improved science linking climate change to weather disasters has been a game changer for all of these cases, Merner said. “We can’t sit back and argue whether or not climate change played a role in extreme weather or public health problems that we’re facing today, because attribution science shows that it does and can calculate what that role was.”