HARRISBURG, Pa. - The centerpiece of Gov. Tom Wolf's plan to fight climate change took another step Tuesday toward the final regulatory threshold to impose a price on carbon dioxide emissions from fossil fuel-fired power plants in Pennsylvania.The Environmental Quality Board, composed primarily of Wolf appointees, approved the plan 15-4 to send it on to the Independent Regulatory Review Commission, which could take it up this fall.Wolf, a Democrat, wants to the plan to take effect next year as part of a multi-state consortium, the Regional Greenhouse Gas Initiative, which sets a price and declining limits on carbon dioxide emissions from power plants.If Wolf is successful, Pennsylvania would become the first major fossil fuel state to adopt.