In what the Bush administration hailed as proof that voluntary environmental initiatives can work, representatives from 13 different industries gathered in the Energy Department cafeteria yesterday to pledge their commitment to reducing greenhouse gas emissions. The industries, ranging from energy companies to paper manufacturers, have agreed to commit to reductions targets to help the administration reach its goal of cutting “greenhouse gas intensity” (the ratio of emissions to economic output) 18 percent by 2012. Environmentalists scoff at that goal, saying that total emissions will still increase under the Bush plan, by as much as 19 percent. A pledge by the energy industry to reduce its emissions 3 to 5 percent over the decade — somewhat less than the 7 percent reduction it had predicted before the Bush administration unveiled its plan — only added fuel to environmentalists’ claim that the program is a charade.