Despite Obama’s comments, the White House is so far refusing to endorse the nation’s first-ever bill to limit emissions of greenhouse gases. As lawmakers opened hearings on Wednesday, top Obama environment officials said they are still studying the measure and have yet to make a decision. Energy industry lobbyists are vocally opposing the bill. It calls for reducing emissions to 20 percent below 2005 levels by 2020 and reducing them by 83 percent by 2050. On Wednesday, House Speaker Nancy Pelosi set a new timeline for passing legislation, saying it would take more than a year. Her comments came one day after vowing to pass legislation this year.