I'm mainly talking about how this will be a free rider problem. Geoengineering isn't free and has to be continually maintained. The issue is that since everyone will benefit, there isn't the incentive to contribute to the cause. Or, assuming the end goal is to eventually ween ones self off of geoengineering, free riders will have to be "strong-armed" (for lack of a better term) into going carbon zero (or carbon negative). Otherwise, once one of more parties stop the practice, we'll be right back at square one in regards to problems.