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