Advocates of forceful action on climate change have long held a trump card. The primary source of greenhouse gas emissions in the U.S. is coal plants, and — since the Supreme Court has determined that those emissions are a pollutant — the EPA is mandated to regulate them. At some point, then, whether whatever president likes it or not, the agency had to make a rule limiting carbon dioxide emissions.
But, what the court giveth, the court can rescind in a tightly contested vote. And with a barrage of petitions raining down on a conservative-leaning Supreme Court, it's possible that the EPA's pollution-control mandate could be eradicated well before the threat of climate change is.
Among large, developed countries, only Australia emits more carbon dioxide per person than the United States. China emits the most overall, of course, but as greenhouse gas polluters, we're still in the top tier. For decades, environmentalists have pushed to cut the country's overall emissions levels, winning a significant victory in 2007 when the Supreme Court ruled in Massachusetts vs. EPA that carbon dioxide was an air pollutant. Under the Clean Air Act, that required that the EPA take action. So far, it hasn't.