Debate soon will intensify in the Senate on a bill that would cut industrial greenhouse gas emissions by 70% below 2005 levels by 2050. The proposal, introduced on Oct. 18 by global warming subcommittee Chairman Joseph Lieberman (I-Conn.)and John Warner (R-Va.), seeks to cut greenhouse gases from the power, transportation-fuel and industrial sectors through annual, incrementally tighter emission caps. Starting in 2012, these sectors would have to hold their greenhouse emissions to 2005 levels.

Lieberman’s subcommittee has slated a hearing on the measure for Oct. 24 and he says the panel could vote on it the following week. But the legislation’s path is likely to be bumpy.

Senate Environment and Public Works Committee Chairwoman Barbara Boxer (D-Calif.) has said she would put the measure before the full Senate by year’s end. But six Republicans on the committee are opposed to mandatory caps and want more hearings on the Lieberman-Warner bill. On the other hand, a few Democrats may back even stronger greenhouse-gas limits than called for in the Lieberman-Warner proposal. President Bush supports voluntary efforts on climate change.

The Lieberman-Warner bill sets up an emissions allowance trading system. It would be similar to the Clean Air Act program, which deals with electric utilities’ emissions that contribute to acid rain. Under the bill, emitting sources could buy and sell allowances to help meet the new restrictions until they are able boost their efficiency or install technologies to reduce their greenhouse-gas emissions.

The measure also would give away some allowances, about 20%, to the covered sectors but later ratchet them down until 2036, when there would be no free emission credits for utilities and the other emitting industries.

Coal-fired utilities argue that the bill would overburden their ratepayers. Some environmental groups contend that the free emission credits offer a windfall for industry.

Warner is confident the Senate will ultimately pass a climate-change bill but not without a fight. “We have caught the punt and we’re beginning to move down the field,” Warner says. “This is going to be a very long and contentious as it should be piece of legislation.”