WASHINGTON -- Sen. Max Baucus, D-Mont., announced Wednesday that he will support a climate change bill that would reduce greenhouse gas emissions by establishing a pollution credit trading system.

Baucus, a potential swing vote on the bill, decided to back a plan put forward by Sens. Joseph Lieberman, I-Conn., and John Warner, R-Va.

"We cannot be good stewards if we ignore the fact that climate change threatens to result in longer droughts, more severe wildfire seasons and no glaciers in Glacier Park," Baucus said at a hearing on the bill. "I believe it is a moral imperative to deal with climate change."

Baucus praised provisions that would encourage the use of technology to capture and store carbon dioxide.

"Stopping coal-fired power plans will not stop climate change; clean coal technology will stop climate change," he said.

But he said he still has some concerns about the bill, including its impact on rural electric cooperatives.

Lieberman said Baucus's support is a tremendous boost to get a real solution passed in this Congress.

Some environmental groups support the bill, while others say it should be tougher. Some business groups and Republican senators argue it would increase energy prices and cost jobs.

The bill would cover electric power, transportation and manufacturing sources that produce 75 percent of U.S. greenhouse gas emissions. Starting in 2012 it would cap emissions at 2005 levels and reduce the amount allowed each year so that by 2050 it would be 70 percent below the 2005 levels.

Companies would be allowed to buy, trade, save and borrow allowances to emit greenhouse gases, and to receive credits when they help noncovered businesses, farms and others to reduce their emissions. The money raised by auctioning such allowances would be used for improving technologies, addressing the impacts of global warming on wildlife, and helping low and middle income American with energy costs.

The bill would also strengthen energy efficiency standards for appliances and buildings.

The goal of the legislation is to keep the concentration of greenhouse gases in the atmosphere below 500 parts per million by the end of the century in hopes of avoiding the most severe impacts of global warming.

A Senate Environment and Public Works subcommittee is expected to pass the bill next week, after which it will go before the full committee.

Will Roehm, vice president of the Montana Grain Growers Association, testified in favor of the bill. Regulated companies and utilities could satisfy up to 15 percent of their allowance obligation by buying credits from American farmers and foresters who store carbon in soil through conservation practices.

Roehm praised the bill for allowing the agriculture industry to participate, but advocated for removing the 15 percent limit.

"The American farmer has long been a careful steward of the land and the environment, and contributing to the reduction of greenhouse gases is a logical extension of what we see as our stewardship responsibilities," he said.

Three other witnesses testified in support of the bill, although they all advocated specific changes to strengthen the bill. Only one witness opposed to the bill was called to testify.

Paul Cicio, executive director of Industrial Energy Consumers of America, noted that emission caps would be in place in just four years but argued there is not yet the needed technology or energy supply to allow the system to work.

Cicio said in trying to meet the emissions caps, the power industry would switch from coal to natural gas, which would cost the price of gas to skyrocket. He said Congress should not cap greenhouse gas emissions until there is an abundant, reliable supply of low-carbon energy available.

Sen. John Barrasso, R-Wyo., said change is coming to the energy market, with the need to reduce carbon emissions becoming widely recognized, and that Wyoming needs to be at the center of new technologies.

"The writing is on the wall regardless of where you stand on the issue of global climate change," he said.

But Barrasso said traditional energy sources cannot simply be shut off and that "rash policy decisions" should not be made based on uncertain future effects.

"We must also have a better understanding of what we're dealing with before rushing to pass legislation that may cost jobs, may raise gasoline prices," he said.

Tom France, director of the National Wildlife Federation's Northern Rockies Office in Missoula, praised Baucus for supporting the bill. He said there are pieces of it that could be improved but that it's the best bipartisan bill put together in the Senate so far and that his group strongly supports it.

"Sen. Baucus has been I think very careful in taking a position on global warming legislation and he has certainly been alert to watching out for issues from Montana," France said.