Sen. John W. Warner (R-Va.) is one of the sponsors of a bill that would create the first national mandate to reduce greenhouse gases. Some details of the legislation:
It would create a "cap and trade" system, in which the government would set limits for emissions and gradually reduce them over decades. Polluters that exceed their individual emissions limits would have to buy unused allowances from others.
By 2012, total emissions from major polluters would have to be reduced to their 2005 levels.
By 2050, those emissions would have to be reduced to 70 percent below the 2005 levels.
Some pollution credits would be given out for free, but others would be auctioned off by the government. Some of the proceeds would be used to fund renewable-energy research.