Christian Science Monitor: People who have tried to reduce their carbon footprint can relate to the tough choices now facing Congress and the Environmental Protection Agency as they decide how to cut greenhouses gases for a whole nation. Hearings on climate-change bills open this week on Capitol Hill. And last week the EPA declared CO2 to be a health danger which, under the Clean Air Act, could require rigorous regulation of almost any source. Whether by law or regulation, will government be able to …