WASHINGTON -- Republicans yesterday boycotted a Senate panel considering a climate change bill.

But Sen. Barbara Boxer, the California Democrat who chairs the Senate Environmental and Public Works Committees, said yesterday she will move ahead with or without Republican lawmakers -- perhaps as soon as this morning -- and will not give in to their demands for a five-week delay for additional analysis from the Environmental Protection Agency.

Committee rules require two minority members to be present to conduct business. But the rules of the Senate allow a bill to be voted out of committee by a majority of senators -- something Ms. Boxer appears to have, since Democrats hold a 12-7 edge on the committee.

Among them is Sen. Arlen Specter, D-Pa., who denounced Republican tactics yesterday.

"We have seen a pattern of partisanship, really excessive partisanship," Mr. Specter said.

"During my tenure in the Senate, I have been a party to some very heated disagreements, but they have been disagreements on the merits, on the substance, and we have a practice in the world's greatest deliberative body: disagreeing without being disagreeable. But you can't disagree with an empty chair," he said.

Shortly thereafter, Sen. George Voinovich, R-Ohio, arrived to fill one of those chairs. But he was only there to deliver the message that Republicans would not participate in the panel's deliberations on the bill until the EPA conducts a full economic modeling of the impacts of the proposed legislation.

"The time to take a detailed look at these issues is now," Mr. Voinovich said. "These are not issues that can simply be fixed on the Senate floor."

Mr. Specter has yet to offer his full support for the legislation -- which would create a cap-and-trade market in which companies would swap pollution credits -- but in his opening statement he called it "a good start."

Mr. Specter and Sen. Bob Casey Jr., D-Pa., have been working to insert language into the bill to protect the coal industry, long a pillar of Pennsylvania's economy. This partisan impasse could affect Mr. Specter's ability to amend the bill in committee since, without any Republicans in attendance, Democrats might only be able to vote out the existing draft.

But Mr. Specter, in an interview, supported Ms. Boxer's methods, though he stopped short of accusing the Republicans of stall tactics.

"When you ask for something that's going to cost a five-week delay, it really raises the basic point as to whether it's reasonable," Mr. Specter said. He later added: "I'm not going to call any names because I still want to talk to them."

Yesterday, Ms. Boxer and her fellow Democrats gave opening statements in the morning and then delayed further consideration of the bill until after they had a chance to question EPA Associate Administrator David McIntosh later in the day.

But Republican senators continued to boycott the meeting, and none showed up to question Mr. McIntosh.

EPA Administrator Lisa Jackson had already testified last week and was subject to Republican questioning.

Mr. McIntosh said that a more in-depth analysis wouldn't differ much from the report the EPA has already prepared on the economic impact of the climate change bill pending before the committee. That bill is sponsored by Ms. Boxer and Sen. John F. Kerry, D-Mass.

Mr. McIntosh said the EPA's level of analysis was unprecedented at this point in the legislative process. Majority Leader Harry Reid, D-Nev., said yesterday he would order a full economic analysis of the legislation once it is merged with bills that may pass other committees and before he takes a final version to the Senate floor.

But that did not appease the Republicans, who spoke to reporters in the afternoon.

Mr. Voinovich asked the EPA to consider additional scenarios, and said their assumptions about technological advancements were too rosy. Both Mr. Voinovich and ranking Republican James Inhofe, R-Okla., said EPA's analysis of the House bill was insufficient, too. They accused Democrats of trying to ram through legislation too quickly.

Mr. Inhofe and Ms. Boxer also disagreed on the import of a letter they both received yesterday from the United States Chamber of Commerce expressing the organization's support for climate change legislation, but in a new direction.

The letter did not express support for the cap-and-trade system -- at the heart of both the House and Senate bills -- but did encourage Congress to pass a bill to reduce greenhouse gas emissions.

"The challenge of drafting comprehensive climate legislation is not 'whether' to do something, but 'how,'" wrote R. Bruce Josten, the chamber's chief lobbyist.

The letter pointed to an op-ed piece written by Mr. Kerry and Sen. Lindsey Graham, R-S.C., in The New York Times as the path to a possible bipartisan solution on climate change.

Ms. Boxer said the letter was "a breakthrough the likes of which we've never seen before" and evidence that businesses were coming around on climate legislation.

The chamber has actively opposed climate change legislation in the past, and several high-profile companies have left the organization to protest that opposition.

Ms. Boxer said the letter's release was a positive end to a frustrating day of Republican roadblock. She wouldn't say exactly what she will do if the Republicans do or don't show up this morning at 10, when the markup is scheduled to resume, but she made clear she will report the bill out of committee.

With Democrats almost certain to need Republican votes to pass the final bill, a procedural end-around of committee Republicans might not bode well for future debate.

"You're destroying the integrity of the committee system," Mr. Inhofe said.

"This hasn't happened before. We have committees for a reason. By setting that precedent, that could come back to haunt them. And, in fact, I'm sure it will."

Washington correspondent Daniel Malloy writes the "Pittsburgh On The Potomac" blog exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.