Fresh off their legislative victory against the Keystone XL pipeline, Democratic senators are pushing a bill that would tax carbon dioxide emissions from fossil fuels that would rise every year. Democrats argue it would raise $2 trillion, which could be used for things like paying down the national debt or funding green energy production. The tax would be levied on fossil fuels produced domestically or imported in the U.S. and cover large emitting facilities, possibly power plants or refineries. “Right now we are subsidizing big polluters to the tune of hundreds of billions of dollars annually by allowing them to...