By Avery Palmer, CQ Staff

The chairman of the Senate Environment Committee has made a number of changes to a global warming bill that could help build support in advance of a committee markup next week.

The bill (S 2191) narrowly won subcommittee approval Nov. 1. Most Republicans on the full committee are likely to vote against it, while several Democrats have flagged concerns they want addressed in order to ensure their support.

The legislation, sponsored by Joseph I. Lieberman , I-Conn., and John W. Warner , R-Va., would cap emissions of greenhouse gases and set up a market-based trading system for polluting industries. It is a top priority for Environment and Public Works Chairwoman Barbara Boxer , D-Calif, and it could move to the floor early next year.

Boxer has prepared a chairman’s mark of the legislation that makes several changes to the bill approved in subcommittee.

One legislative aide said supporters are “guardedly optimistic” the changes will secure a majority for the bill at the full committee markup scheduled for Dec. 5.

One key change is to increase the percentage of emission allowances to be auctioned to industry, rather than given away, in the early years of the program.

Environmentalists strongly favor the auction approach, maintaining that free allowances would lead to windfall profits for businesses. The government would use some of the revenue from the auctions for technology deployment and to help low-income energy consumers.

The bill would begin by auctioning around one-fourth of the allowances in 2012, gradually ramping up to slightly more than 70 percent in 2031. The previous version of the bill would auction fewer allowances at the outset and plateau at 73 percent in 2036.

“A lot of people looked at these allocated allowances as tantamount to a windfall and it made sense to try to curb that amount a little bit,” the aide said.

Committee members such as Frank R. Lautenberg , D-N.J.; Bernard Sanders , I-Vt, and others pushed for increasing the amount of auctioned allowances under the bill. Sanders voted against the bill in subcommittee, while Lautenberg voted for it.

The revised version also would expand the scope of facilities required to comply with the emissions cap. During the subcommittee markup, Lautenberg successfully offered an amendment to expand the coverage to natural gas emissions from residential and commercial uses, rather than just industrial uses.

The new language specifies that natural gas processing plants, which separate gas liquids from natural gas before the product goes to consumers, would have to comply with the bill. It also would cover producers of natural gas in Alaska and any importer of natural gas, including in liquid form.

Thomas R. Carper , D-Del., has pushed for the bill to regulate several air pollutants from power plants unrelated to global warming. The new version of the bill would not control these pollutants, but it would require EPA reports to Congress on the latest scientific information on the health effects of mercury pollution. The EPA also would report on how limits on greenhouse gases indirectly help states meet clean air standards for ozone and particulate matter.

Another adjustment to the bill changes the requirements for hydrofluorocarbons, used as substitutes for other chemicals that were phased out because of their ozone-depleting potential. They are among the greenhouse gases regulated under the bill.

The chairman’s mark would allow hydrofluorocarbon producers to trade emission allowances with each other, but not with facilities producing other greenhouse gases such as carbon dioxide. Because hydrofluorocarbons are much more potent than other greenhouse gases, some have feared producers would simply sell allowances and move offshore.

Despite the changes, the markup next week is certain to be contentious. Given the number of amendments possible, Boxer said she was prepared for the markup to last more than one day.

Many Republicans on the committee have objected that they do not know enough about how the bill would affect the economy. Lieberman and Warner have asked the EPA and the Energy Information Administration to analyze the economic impacts of the bill, but the analyses are not expected to be ready before the markup.