Litigation about climate change took off in the early 2000s. Its focus has varied with the occupant of the White House. Under George W. Bush, most suits were brought by environmental groups and blue states, frustrated by the lack of federal action, seeking to push regulations or impede fossil fuel projects. Under Barack Obama, climate litigation was mostly industry and red states seeking to block regulations. And now under Donald Trump, it is largely about environmental groups and blue states trying to preserve the rules adopted under President Obama, and to seek novel remedies to get around federal hostility to action on climate change.

More than 100 lawsuits were filed in the United States in 2017 raising claims concerning either the impacts of climate change or reducing greenhouse gas emissions; 82 of them were specifically about federal deregulation. These suits are all tracked on a website we maintain, www.climatecasechart.com.

Challenging Obama-Era Regulations

The Clean Power Plan, the Obama Administration's premier climate rule, was aimed chiefly at reducing the burning of coal to generate electricity. The Supreme Court stayed the rule in February 2016 pending the final conclusion of legal challenges. The U.S. Court of Appeals for the District of Columbia Circuit heard argument en banc in September 2016. But President Trump campaigned on a pledge to repeal the rule, the Environmental Protection Agency (EPA) has begun the necessary rulemaking process to do so, and meanwhile the D.C. Circuit is holding the case in abeyance.

Industry has filed several lawsuits challenging standards for energy efficiency, refrigeration, vehicular emissions, and renewable fuels. One notable case was Mexichem Fluor v. EPA, a challenge to an EPA rule prohibiting certain uses of hydroflourocarbons (a group of chemicals that are powerful greenhouse gases). In August 2017, the D.C. Circuit partially vacated the rule on the grounds that it exceeded EPA's statutory authority. 866 F.3d 451 (D.C. Cir. 2017). In January 2018, the court denied reconsideration and rehearing, which had been sought by several manufacturers of substitute chemicals, and by environmental groups.