If politics is the art of the possible, have Sens. Jeff Bingaman, D-N.M., and Arlen Specter, R-Pa., sculpted climate legislation that can actually be passed this Congress and signed by the president?

Backed by unions and some big electrical utilities, the lawmakers are to roll out on Wednesday a new global warming proposal.

Their news release says the bill is the product of a "vigorous and open" process, reflecting revisions to a draft first circulated in January. The revisions followed hearings, analyses and "extensive input" from stakeholders and congressional staff, they say.

The bill would set a target emissions cap for 2020 at 2006 levels and for 2030 at 1990 levels. Like other cap-and-trade proposals, it would allow companies to buy and sell the right to emit carbon dioxide.

Supporters say the proposal offers many new ideas endorsed by important players in the debate and presents the best chance of getting some form of carbon control system enacted by the end of next year. It was written in conjunction with the National Commission on Energy Policy, a privately funded group formed in 2002 to try to find a bipartisan solution to climate change.

"The goal was to put forward a proposal that takes into account the current science and encourages the technology that will be needed to address this problem," Bingaman says. "We also think this proposal can get broad enough bipartisan support that we can actually enact it in this Congress."

The proposal would grant permits to all emitting industries. Cars, trucks and airplanes are not covered, but owners would face significantly higher fuel prices passed on by oil and gas firms.

Additional emissions permits could be bought at $12 a metric ton of carbon dioxide emissions in the first year, rising by 5 percent above the rate of inflation annually after that. The revenue from the permits would finance research into clean energy, mitigation of the effects of global warming, compensation for farmers for higher fuel costs and aid to help low-income families pay their heating and gasoline bills. Under the bill, the United States would market green technology to China, India, Brazil and other developing countries whose economies are growing, to help them bring their carbon emissions under control. It also would impose tariff-like fees on imports of carbon-intensive products such as steel and automobiles from those nations if the president deemed their cleanup efforts inadequate.

To win the endorsement of Alaska's two Republican senators, the bill would authorize billions of dollars to help their state cope with the effects of climate change on roads, bridges and coastal areas.

Environmentalists' reactions are mixed. Dan Becker, global warming director at the Sierra Club, says it's worse than nothing. David Doniger, climate policy director for the Natural Resources Defense Council, says the bill is evidence that Congress has gotten the message on global warming.