"You will have to forgive me when I cannot fathom how actively meddling with a complex system, which requires a substantial investment by our species in terms of scientists, research departments, universities, government offices - is going to result in a tightly controlled, well predicted result."

Any model of atmospheric carbon dioxide which is sufficiently accurate for generating public policy should suffice in predicting the results. After all, the model itself should not care what simulated means are being employed in increasing or reducing the amount of said compound, only its' effect at each concentration level.