This sounds very similar to cap and trade, no? Place a cap on total emissions, and decrease that cap over time. Correspondingly, have pollution permits that are allocated according to this cap. Companies that are especially CO2 efficient can sell their extra pollution allowances. Companies that are not can purchase these pollution allowances. As the cap is set lower and lower every year, the pollution allowances become more valuable, raising the price to pollute, or emit CO2. Over time, using fossil fuels becomes more and more prohibitively expensive, until we eventually transition to a near zero carbon society.