Hoping to avert a partisan meltdown, Senate Environment and Public Works Chairwoman Barbara Boxer (D-Calif.) yesterday offered an olive branch to Republicans who are planning to boycott today's markup of a sweeping global warming bill. Boxer still plans to begin the markup at 9 a.m. with opening statements. But she agreed to suspend the markup at 2:30 p.m. for an open-door meeting with U.S. EPA officials to answer committee members' questions about the economic modeling of the legislation, she noted in a letter late yesterday.