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Kai Ryssdal: The climate change spotlight for the next couple of weeks is going to be firmly on Copenhagen, Denmark. And when President Obama shows up at the big UN meeting in about 10 days or so, he is not going to have an American domestic climate-change bill to brag about. But today the Environmental Protection Agency gave him something he can at least point to: A formal finding that global warming gases endanger human health. From the Marketplace Sustainability Desk, Sarah Gardner reports.

LISA JACKSON: Today, I’m proud to announce that EPA has finalized its endangerment finding on greenhouse gas pollution and is now authorized and obligated to make reasonable efforts to reduce greenhouse pollutants under the Clean Air Act.

That’s EPA chief Lisa Jackson. Her message is simple. If Congress isn’t going to pass legislation to control global warming, her agency will regulate. That means limiting emissions from heat-trapping gases like carbon dioxide. But also methane, nitrous oxide, and a few trace gases you didn’t learn in Chem 101 like “sulphur hexafluoride.”

BRENDA EKWURZEL: Some of them have heat-trapping capacity that are thousands of times more than carbon dioxide.

Brenda Ekwurzel at the Union of Concerned Scientists says greenhouse gases come from dozens of sources. Power plants, steel mills, trucks, refrigerators, even cow poop.

But David Bookbinder, chief climate counsel for the Sierra Club, says the EPA will target only the biggest polluters. He expects the first thing the EPA will do is tighten tailpipe standards for automobiles. Later, he says the agency may even require coal-fired power plants to switch to a more climate friendly fossil fuel.

DAVID BOOKBINDER: Will EPA talk about natural gas as a control technology for CO2? And that is a very big question that EPA is wrestling with right now.

Of course, we may not get the answer anytime soon. Already some opponents of regulation say they’ll file suit to stop the EPA.

I’m Sarah Gardner for Marketplace.