As an externality, the price of emitting 1kg of carbon should be a little greater than the cost of capturing and storing 1kg of carbon. That's too expensive a

As an externality, the price of emitting 1kg of carbon should be a little greater than the cost of capturing and storing 1kg of carbon. That's too expensive a target to be realistic right now, so the real question is what's a level of taxation that won't cause social unrest, but that will change behaviour?