The U.S. Environmental Protection Agency formally declared that greenhouse gases like carbon dioxide are a significant threat to public health, opening the door to new government action on climate change.

The EPA reviewed possible health dangers from global warming caused by carbon dioxide and five other heat-trapping gases released by cars and trucks, power plants, and industrial sources.

The agency found, "In both magnitude and probability, climate change is an enormous problem. The greenhouse gases that are responsible for it endanger public health and welfare within the meaning of the Clean Air Act."

The Supreme Court ruled nearly two years ago that the Clean Air Act gives the EPA the authority it needs to act on global warming. The Bush administration strongly opposed such action.

President Obama and his new EPA administrator, Lisa Jackson, said they want Congress to create a new system to let industry cap and trade emissions.

But automakers and power generators have warned controls on emissions would mean severe economic damage.

The EPA has opened a 60-day public comment period before issuing a final ruling. Ultimately, the agency could issue its own regulations if Congress does not act.

"What makes this decision important is that, for the first time, the United States government is formally recognizing the impact that greenhouse gases have on our environment."- David Bookbinder, The Sierra Club

"These are emissions that take place throughout the world. And to cap emissions or to control emissions just in the United States puts American manufacturing at a competitive disadvantage." - Keith McCoy, National Association of Manufacturers

"Eighty percent of U.S. greenhouse gases come out of smokestacks and tailpipes. And EPA has been regulating other pollutants out of smokestacks and tailpipes successfully for four decades."- David Bookbinder, The Sierra Club

"You start to get into some of these regional issues in how energy is used, how it's consumed, and the potential cost for consumers and manufacturers. I think that's really where the rubber is going to hit the road"-Keith McCoy, National Association of Manufacturers

1. What is a greenhouse gas?

2. What does the EPA stand for?

1. What is the importance of the EPA ruling to you? To your community?

2. Mr. McCoy from the National Association of Manufacturers thinks that cap and trade barriers may put undue strain on U.S. manufacturing, what do you think? What should be done?

3. If a problem is both national and international, what is the best route to fixing the problem?

4. Explain how the EPA finding affects the legislative, judicial and executive branches of government.