Sen. Barbara Boxer on Thursday promised major policy shifts on global warming, air quality and toxic-waste cleanup as she prepares to lead the U.S. Senate's environmental committee.

"Time is running out, and we need to move forward on this," Boxer said of global warming during a conference call with reporters. "The states are beginning to take steps, and we need to take steps as well."

Boxer's elevation to chairwoman of the Senate Environmental Public Works Committee comes as Democrats return to power in the Senate. It also marks a dramatic shift in ideology for the panel.

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The California Democrat is one of the Senate's most liberal members and replaces one of its most conservative, Republican James Inhofe of Oklahoma.

Inhofe had blocked bills seeking to cut the greenhouse gases contributing to global warming, calling the issue "the greatest hoax perpetrated on the American people."

Environmentalists were overjoyed at the change.

"That's like a tsunami hit the committee," said Karen Steuer, who heads government affairs at the National Environmental Trust, a nonprofit based in Washington, D.C. "You can't find two members or people more ideologically different."

As chairman, Inhofe tried to overhaul the Endangered Species Act and supported the Bush administration's 2002 rules to roll back provisions in the Clean Air Act.

He also promoted legislation that would have allowed the government to suspend air and water quality rules in response to Hurricane Katrina.

Boxer said she intends to introduce legislation to curb greenhouse gases, strengthen environmental laws regarding public health and hold oversight hearings on federal plans to clean up Superfund hazardous waste sites across the country.

On global warming, Boxer said she would model federal legislation after a new California law that imposed the first statewide limit on greenhouse gases and seeks to cut California's emissions by 25 percent, dropping them to 1990 levels by 2020.

"Some of the practical solutions are in the California approach," Boxer said.

A top environmental aide at the White House signaled Thursday that the administration would work with her.

George Banks, the associate director for international affairs at the Council for Environmental Quality, has requested a meeting to discuss global warming, Boxer said.

President Bush has opposed a federal mandate to limit greenhouse gas emissions from industry and automobiles, saying such steps should be voluntary.

"We look forward to working with Congress in bipartisanship on all issues," said Kristen Hellmer, a spokeswoman for the Council on Environmental Quality. She declined to discuss specifics related to the upcoming global warming discussion.

Some environmentalists said major changes in policy won't occur before 2008.

"On the issue of global warming in particular, we're going to need a new president before we see major progress," said Eric Antebi, spokesman for the San Francisco-based Sierra Club. "But this Congress can really lay the groundwork for that and make incremental changes."