I've seen some divergent figures, but as far as I can tell, cars emissions are 20-30% of total US carbon emissions. The only way to reduce driving significantl

I've seen some divergent figures, but as far as I can tell, cars emissions are 20-30% of total US carbon emissions. The only way to reduce driving significantly is to create useful public transit, so any carbon tax scheme that does not increase funding for public transit is just going to take money from peoples' pockets without giving them a realistic way to avoid it -- and as other posters have noted, it will disproportionately harm the poor. This could make carbon taxes so politically unpopular that they will be repealed, and new ones will not be created. That could be pretty bad for the environment.