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Carbon in the Court
The Supreme Court affirms the Environmental Protection Agency's authority to curb greenhouse gas emissions (again).

In a move that most observers see as a good sign for the Obama administration’s efforts to curb carbon pollution, the U.S. Supreme Court ruled this morning that the government has the right to require permits for greenhouse gas emissions from large, stationary pollution sources. That includes oil refineries, chemical factories, and—this one is key—power plants.

Why is it a good sign? Because earlier this month, President Obama and the Environmental Protection Agency announced a plan to limit carbon pollution from existing power plants. The administration is calling it the Clean Power Plan, and industry groups are already lining up to attack the new standards in court, once they become official after more than a year of public input and refinement.

Today’s case was about new power plants, not existing ones. But many are seeing it as a test of the EPA’s ability to regulate carbon pollution—a test that could indicate how the Supreme Court might rule on the Clean Power Plan, which seeks to cut 30 percent of carbon pollution from existing power plants (based on 2005 levels) by 2030.

The justices agreed 7-2 that if a new facility must obtain permits for “conventional pollutants" (the court's term) such as lead or mercury, it’s OK for the EPA to require those facilities to do the same for greenhouse gases such as CO2 and methane, which cause global warming. Fortunately, the country’s biggest carbon polluters would fall into this category.

The Washington Post said the decision “handed the Obama administration and environmentalists a big victory.” SCOTUSblog called it a “compromise ruling” that nevertheless gave the EPA the authority to require that power plants “use the best available technology also to control greenhouse gases.” And the New York Times said the court had “handed President Obama’s Environmental Protection Agency a victory in its efforts to regulate greenhouse gas emissions from stationary sources like power plants, even as it criticized what it called the agency’s overreaching.”

The case sprang from a decision dating back to 2007, in which the high court ruled that greenhouse gases do in fact count as air pollutants that endanger public health and welfare. That judgment gave the EPA the go-ahead for regulating the exhaust from new motor vehicles. The agency then sought to curb greenhouse gases from stationary pollution sources, and in 2011, the Supreme Court ruled it could do so for existing power plants. Now add new power plants to the list.

All in all, today’s ruling is a victory for the EPA, but at first glance, a few news outlets reported it as a loss. In the first part of the ruling, the justices held that the EPA can’t use the Clean Air Act to extend its permitting requirements to new, smaller emitters such as shopping malls, office buildings, schools, and churches. Such an extension, the justices ruled 5-4, would require Congressional approval. (That’s the part about the agency’s “overreaching,” as the Times described it.)

“EPA is getting almost everything it wanted in this case,” read Justice Antonin Scalia from the bench. “It sought to regulate sources it said were responsible for 86 percent of all the greenhouse gases emitted from stationary sources nationwide. Under our holdings, EPA will be able to regulate sources responsible for 83 percent of those emissions.”

When it comes to combating climate change, numbers like those deserve to be put in the win column.

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Melissa Mahony is's senior editor. She previously worked at Wildlife Conservation magazine, blogged about energy for SmartPlanet, and has written for many publications about science and the environment. MORE STORIES ➔