An interesting idea
Here's an idea I like - some European automakers are suggesting an emissions credit system for automakers. So a high emitter, say Ferrari, would have to buy credits from a low emitter, say Honda, to pay for the higher emissions of its cars. This would make higher emitting cars more expensive, and, what they didn't mention in the IHT article I heard about it in, would slightly subsidize more practical transportation. I like the idea - seems good, though the fact that emissions credits for nations didn't seem like such a good idea.