Washington ? Democratic California Sen. Barbara Boxer refereed a blistering verbal assault on Al Gore by the leading Republican skeptic on global warming Wednesday as the former vice president returned to Capitol Hill to call for immediate congressional action to save the planet.

Gore, whose documentary film “An Inconvenient Truth” recently won an Academy Award, had a heated exchange with Sen. James Inhofe, R-Okla., who tried to paint the Tennessee Democrat as an overzealous hypocrite when Gore ducked a question about whether he would sign a pledge to have his household cut greenhouse gas emissions.

With boxes full of petitions, former Vice President Al Gore and his wife, Tipper, arrive on Capitol Hill in Washington to testify on climate change. Gore's return to Congress marked the first time he had been in the Capitol since January 2001, when he was the defeated Democratic nominee still presiding over the Senate in his role as vice president.

Since the release of his film documenting the dangerous buildup of heat-trapping pollution blamed for rising temperatures, melting polar ice caps and radically changing weather patterns, Gore has become the most famous face in the battle to curb global warming.

The testy exchange came in an otherwise laudatory hearing before the Senate Environment and Public Works Committee, which Boxer leads.

During an unusual 30-minute statement before the committee, Gore called global warming “a challenge to our moral imagination” and equated the battle to solve it to defeating fascism during World War II.

He laid out a series of proposals to reverse course, starting with an immediate freeze on the levels of carbon dioxide emissions and passage of emergency legislation instituting a nationwide, if not global, market system for trading pollution credits in an effort to drive down emissions through economic incentives.

Gore said he also favors cutting income taxes and offsetting the loss to the government with new taxes on emissions.

“We ought to be increasing employment and discouraging pollution, and not the other way around,” Gore said.

Gore, who ran for president in 2000 but was narrowly edged out by President Bush in the contested Florida vote, for the most part was politely if not warmly received, even by some Republicans who are converts to the global warming battle.