An excellent question - since that is exactly what we are doing right now by messing with the CO2 cycle. By no one's authority. That is why we are starting to crack down on the people who think they can play God and pollute the environment as much as they want, without caring about the consequences to hundreds of millions of human beings. Hmm. Our attempts at reducing particulate pollution, SOx pollution, ozone damaging chemicals and HC pollution have worked quite well. (If you had been to LA in the 1970's you would see the difference.) I see no reason we cannot do the same with CO2.