The U.N. issued a report in May encouraging activists to use the courts to circumvent legislatures and company board rooms to push global warming policies.

The international body argued legal action “has arguably never been a more important tool to push policymakers and market participants.” Fast forward five months, and some local governments have taken the recommendation to heart.

Legal experts have taken notice.

“The global warming industry is increasingly turning to the courts to impose their agenda for the simple reason that it has failed through the proper democratic process,” Chris Horner, an attorney and senior fellow at the libertarian Competitive Enterprise Institute (CEI), told The Daily Caller News Foundation.

“These are not frivolous cases,” Michael Burger, executive director of the Sabin Center for Climate Change Law at Columbia Law School, told TheDCNF. “It remains to be seen whether more local governments will file similar suits, or whether they will wait to see how these ones play out in the early stages.”

Most recently, California local governments have filed suit against dozens of energy companies for damages allegedly caused by man-made global warming. That’s on top of a slew of lawsuits brought by environmental activists and Democratic state attorneys general.

San Francisco and Oakland filed suit against five oil companies looking for billions of dollars to pay for infrastructure upgrades they say are necessary because of global warming. Chevron and other oil companies named in the suit are partly responsible for rising sea levels, the cities argue.

“These fossil fuel companies profited handsomely for decades while knowing they were putting the fate of our cities at risk,” San Francisco City Attorney Dennis Herrera said in a statement.

In July, one California city and two counties filed suit against 37 energy companies they blame for global warming, including ExxonMobil and Royal Dutch Shell.

Imperial Beach, Marin County and San Mateo County argued these companies knew for decades “that greenhouse gas pollution from their fossil fuel products had a significant impact on the Earth’s climate and sea levels.”

“The preponderance of this activity taking place in the 9th Circuit might tell you a little about how they view their arguments’ appeal,” Horner said.

California local officials bringing suit against coal, oil and gas companies is only the latest salvo of global warming lawsuits. Environmentalists representing a group of kids have been trying to sue the government for years for not having strict enough climate policies.

Democratic attorneys general have brought legal action against Exxon, alleging the company misled investors and the public about the dangers of global warming. That legal battle is ongoing.

There are currently more than 770 global warming-related complaints making their way through U.S. courts, according to Sabin Center data.

However, Burger noted there are hurdles to bringing legal claims against companies for alleged damages from global warming, which scientists claim human activity is driving.

“But these are also not slam dunk cases,” Burger said. “There are significant legal hurdles plaintiffs will have to overcome.”

For starters, how does one prove greenhouse gas emissions from certain companies caused a particular amount of sea level rise? Scientists have developed models to help with such questions, but they are wrought with uncertainties and still can’t trace emissions back to their source.

There’s also the problem of federal law. Companies can argue the Clean Air Act usurps nuisance lawsuits since Congress gave the Environmental Protection Agency responsibility for regulating air quality — the courts have found EPA’s reach also applies to CO2.

Former Sierra Club attorney David Bookbinder seemed to agree cases brought against energy companies weren’t in the bag but added the suits brought by San Francisco and Oakland were more likely to succeed.

“Environmental harm is a classic case of public nuisance, and simply requires demonstrating that the defendant contributed to a condition that constitutes an unreasonable interference with public rights,” Bookbinder wrote.

“Unfortunately, the decision by San Mateo et al. to throw in the kitchen sink unthinkingly plays into the fossil fuel industry’s hands,” he wrote. “In fact, these well-intentioned cases may end up setting back legal efforts to hold fossil fuel companies liable for global warming injuries.”

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