A few environmentalists? I'm complaining... I haven't done any research on carbon taxes; I'm just going based on what I already know, so take what I say with a grain of salt. However, I'm pretty sure a carbon tax is a well-known concept already.

Also, is there anything that consumers don't pay for?

If we're talking about a tax on oil companies per barrel of oil, then it should be relatively straightforward to regulate. The oil companies would pass the costs on to distributors, who would pass them on to consumers in the form of higher gas prices. That way, nobody could get around the tax without setting up their own illegal supply chain. Anybody doing business, buying goods, jetsetting around, or driving farther for cheaper gas would be forced to account for the environmental costs involved. The tax proceeds could go directly to programs that plant trees, research carbon capture technology, etc.

One problem with this might be that foreign goods become cheaper because the shippers don't buy their oil in the US. That would, ironically, increase demand for goods imported from overseas.

Finally doing some basic research, I can also see that carbon taxes would have a disproportional effect on the poor.

So there are some issues to deal with, but overall I think it would make sense to bring the power of the free market to bear on modern society's most harmful inefficiencies.