I guess it depends on how it's structured. I know there are two different ways of structuring it. One is based on international energy and one is based on domestic energy. From what I've read, it appears that if you structure a carbon tax based on domestic energy, it's more effective.
There would be disadvantages, as this gentleman said, to low-income people, because consumption taxes affect them more than income taxes. There would have to be something for them so they weren't overly disadvantaged by that.
Sorry, what was the other question?