Q&A: the Climate Security Act

What would the legislation do?

Cap most emissions of greenhouse gases, beginning in 2012, and annually tighten the limits. The goal is to reduce total U.S. emissions by two-thirds by 2050. The bill focuses on the industries that emit nearly 90 percent of the nation's greenhouse gases. These include electric utilities, oil and gas firms, and the iron, steel, paper and chemical industries.

How would the limits be administered?

Via a so-called "cap-and-trade" system. Industries would be given carbon allowances that dictate how much carbon they can emit. Companies that reduce emissions below their limits could sell their excess allowances to other companies.

Foresters planting extra trees and farmers using practices that remove carbon dioxide from the atmosphere could earn carbon offsets, which they could sell to industries. Industries could use those offsets to satisfy up to 15 percent of their required annual reduction in emissions.

Does the bill do anything to reduce emissions outside the United States?

Companies could meet up to 15 percent of their required annual emission reductions by purchasing international allowances and by working on projects to preserve tropical rainforests. Destruction of those forests accounts for an estimated 20 percent of greenhouse gas emissions worldwide. The bill's supporters argue that such international projects would induce other nations to reduce their greenhouse gas emissions.

Would the cost of allowances be passed on to consumers in the form of higher energy prices?

Yes. The U.S. Energy Information Agency estimates that the additional annual cost of electricity could reach $325 per household by 2020.

The bill provides some relief, including $800 billion in tax breaks to consumers and a measure to offer more carbon allowances if the price gets too high.

Overall, studies predict that the bill would slightly slow but not halt growth in the nation's economy.

What are the major arguments for and against the legislation?

Proponents say global warming is a trigger for rising sea levels and catastrophic hurricanes that in coming decades could swamp coastal communities around the world. In other areas, warming could spawn droughts and famine. A cap-and-trade program to gradually lower emissions will curb warming while stimulating investments in clean, alternative energy sources, they say. All three presidential candidates support such a system.

Some environmentalists don't like the cap-and-trade method. They favor a tax on greenhouse gas emissions.

Other opponents question how much global warming is attributable to human activity and can be solved by human action. They argue that any solution must be international or else emerging nations such as China and India will simply gain an additional advantage over U.S. businesses. Some predict that already-high energy prices will skyrocket, triggering a worldwide economic crisis.