Greenwire: A provision in the House climate bill that offers a controversial hedge against high costs for curbing carbon is a top target for lobbyists — with one pack fighting to expand it and another to strip it out. The focus is on emission offsets. Added to the bill at the behest of industry and large environmental groups, offsets let polluters avoid some fines by investing in projects that draw carbon dioxide and other greenhouse gases from the atmosphere. As the climate measure …