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A plume of exhaust extends from the Mitchell Power Station, a coal-fired power plant built along the Monongahela River, 20 miles southwest of Pittsburgh, in 2013 in New Eagle, Pennsylvania. The Evironmental Protection Agency (EPA) and the Obama administration will announce new regulations to reduce carbon emissions by existing coal-burning plants. - 

Expect to hear a lot about carbon dioxide in the next week. It's the main gas that's collecting in the atmosphere and contributing to global warming. Next Monday, for the first time, the Environmental Protection Agency will propose rules limiting the carbon dioxide emitted by the power plants that produce most of our electricity. If the U.S. is going to play a role in the global reduction of greenhouse gases, the regulations the EPA is preparing are the most likely way that will happen any time soon.

Previous EPA rules have hit existing coal-burning plants by focusing on pollutants, like mercury and sulphur dioxide, that older coal plants produce. Pending rules would limit carbon dioxide pollution from new power plants and factories.

“The rule the EPA will introduce next week is the first step that’s specifically aimed at the power sector— reducing greenhouse-gas emissions from the power sector,” says Jonas Monast, director of climate and energy programs at Duke University’s Nicholas Institute for Environmental Policy Solutions.

The administration will create carbon-reduction targets for states and allow each state to make a plan for hitting its target. One of the most efficient ways to hit a target: Shut down older, heavily-polluting coal-burning plants.

This isn’t exactly war on coal. “The real war on coal is not being waged by the Obama administration. It’s being waged by cheap natural gas,” says Ted Nordhaus, chairman of the Breakthrough Institute, an energy and environmental think tank.

Coal’s biggest advantage as a power source has been that it’s cheap. Low natural gas prices have eaten away much of that advantage. Utilities have been shutting down older coal plants and opening up new gas plants that also pollute less.

Regulations can lock in that shift and extend it, says Kevin Book, with ClearView Energy Partners. Adding next week’s proposals to what’s already been proposed could mean the U.S. ends up getting about a third less energy from coal than it did a few years ago. How much carbon emissions get reduced will depend on the targets EPA sets.

“This is the crown jewel of the Obama’s administration’s climate policy,” says Book. The rules could enable U.S. policy to have a global impact. In effect, they could put a price on carbon emissions. 

Follow Dan Weissmann at @danweissmann