Serge Dedina, the mayor of Imperial Beach, said his community was already dealing with coastal flooding and increasingly heavy rains, and sees more to come as the sea level rises.
“How do we make sure those responsible pay the costs so that residents of communities like mine don’t have to pay the costs?” he asked.
The supervisor for District 3 of Marin County, Kathrin Sears, said, “It’s time to hold these oil, gas and coal companies accountable for the damage they knew their products would cause.”
Vic Sher, the lawyer whose firm developed the California cases, said the earlier unsuccessful climate cases had relied on federal common law, which the courts decided could not be applied because common law on these issues was displaced by the Clean Air Act. His case, he noted, is grounded instead in state common law, which was unaffected by the prior rulings.
And California, he said, might only be the beginning of this litigation: “Filing these cases has led to a lot of interest in other communities.”
Kent Robertson, a spokesman for Chevron, one of the targets of the case, said that the company recognized the threat of climate change, but that the new lawsuits were not the proper way to address the problem. “Chevron welcomes serious attempts to address the issue of climate change, but these suits do not do that,” he said.
Chevron opposes the United States’ withdrawal from the Paris climate agreement, as do most major fossil-fuel companies. Fighting climate change is a “global issue,” Mr. Robertson said, but suits filed by counties and cities “will only serve special interests at the expense of broader policy, regulatory and economic priorities.”
The case brought on behalf of young people by the group Our Children’s Trust has broader goals than the California cases: to force the federal government to fight climate change aggressively.
“These children’s lives and their security are threatened by what the government is doing,” said Julia Olson, one of the lead lawyers in the case.
The case began under the Obama administration, which the plaintiffs argue had not taken sufficient steps to avoid the effects of global warming.
“Even the minimal steps that were taken by, for example, the Obama administration are now being reversed by the Trump administration,” Ms. Olson said.
The case has so far survived efforts by the Obama and Trump administrations to have it dismissed, and the lawsuit’s progress led industry groups that had added themselves to the case, in order to oppose the children’s group, to quietly withdraw.
The United States Court of Appeals for the Ninth Circuit, however, has now asked for new briefs from the parties after the Trump administration asked the court to step in and review decisions by the Federal District Court judge, Ann Aiken. Legal experts said that Judge Aiken’s 2016 decision to let the case move forward had been unexpected and that it was not surprising that the appeals court wanted to take a closer look.
One of the plaintiffs, 17-year-old Xiuhtezcatl Martinez, said, “I’m still confident it will make it to court in February.” The case, he added, “has a lot of opportunity and ability to create some tangible and long-lasting change.”
Michael Burger, the executive director of the Sabin Center for Climate Change Law at Columbia University, said of the California and Oregon cases: “They are both bold and ambitious litigation strategies that at first blush will raise eyebrows, and will encounter a certain degree of skepticism. But they both have a chance.”
The pressure of litigation could also lead companies to alter their practices or work with lawmakers on a deal, as the tobacco companies did to resolve their litigation.
Perhaps the most effective litigators in the fight against climate change could turn out to be state attorneys general. During the Obama administration, conservative attorneys general like Oklahoma’s Scott Pruitt, who had a particularly close relationship with fossil fuel interests, fought environmental initiatives and often had private-sector players as fellow plaintiffs.
Now Mr. Pruitt heads the Environmental Protection Agency, and progressive attorneys general, especially New York’s Eric T. Schneiderman, are suing just as enthusiastically, along with environmental groups, to counter the administration’s efforts to roll back climate change regulations. Mr. Schneiderman and Massachusetts’s attorney general, Maura Healey, are also spearheading an investigation of Exxon Mobil’s research and actions on climate change.
Their pushback could already be having an effect. Last week, the Environmental Protection Agency reversed itself on a one-year delay it had announced on enforcing a rule regarding ozone — one day after attorneys general filed a lawsuit challenging the delay.