A lot of the CO2 emission control schemes being considered are lame.
The key to reducing CO2 is to commit to a policy that will affect the energy market in a gradual, predictable way: A slow phase in of a carbon tax. Raise the carbon tax the equivalent of $0.25/gallon every year, forever. No increase in the year the tax passes.
That means no economic effect this year. No change at all -- except that everyone now expects gas to be $5/gallon in four years, so if you're buying a car now you better get something with an electric motor on it. If you're investing in energy you better invest in renewables rather than petroleum. And then by the time the gas tax is $1 higher than it is now, the installed base of cars has been replaced with higher efficiency ones, so the burden of the tax is already mitigated because a) you're now buying less gas, and b) so is everyone else, so demand goes down, so the pre-tax price of gas goes down and cancels out a significant portion of the tax.
Meanwhile the government collects a large pile of cash (largely at the expense of oil company profits -- what a shame) that can be used to subsidize the installation of renewable energy generating capacity, which creates jobs etc. etc.