The idea that CO2 is a "polutant" is silly. It is an INTEGRAL part of all life on earth, and likely elsewhere too (if any). In addition, there is no direct evidence that the annual average increase in atmospheric CO2 (TWO parts per million on 380 ppm) and life survived nicely 65million plus years ago and more, with 4,000 ppm CO2 atmosphereic content.
As the Gorean superstition loses credibility, demand for credits falls . Better the nations holding credits build their own "infrastructure" using the credits than selling them off for one shot cash in the hip pocket. Eventually, carbon credits will be worth zero, and the selling nations will be left holding a pig in a poke.