Estimates produced by the Metropolitan Washington Council of Governments show 65.6 million metric tons of carbon dioxide were emitted in the region in 2005 - more than in all of Hungary, Finland, Sweden, Denmark or Switzerland. And each of those countries have more people than the Washington area.

"It's not a surprise that we compete with entire countries in Scandinavia," said Mike Tidwell, who heads the Chesapeake Climate Action Network, an environmental group. "What this data does is point up just how huge America's contribution to climate change is . . . if our one capital region is emitting on par with other industrialized countries."

The study is one of the first to inventory pollution for an entire metropolitan area, rather than just looking at individual states and cities.

It has some surprising results for how carbon emissions are produced across political boundaries. The Maryland suburbs, often thought of as more liberal and environmentally friendly, produce more carbon dioxide than either the Virginia suburbs or the District of Columbia, according to the estimates.

Coal-burning power plants are among the biggest polluters, and nearby Maryland counties have three of them.