Exactly. Tax the negative externality [1]. Let people make decisions factoring in more of the costs.

[1] http://en.wikipedia.org/wiki/Pigovian_tax

Taxing carbon emissions is a fine idea, but gasoline (and other petroleum products such as diesel) also need to pay for the costs of US mid-east policy. We've never had terrorists blow up buildings or a marine barracks because of our coal mining activity.