There are plenty of methods that can be used to manipulate climate in highly targeted ways, without resorting to blanket measure with few to zero methods of procedural reversal.One of the most exciting methods, that can be easily reversed if we find that it causes more harm than good, is orbital solar farming. Putting up massive solar sails in the right places will cause subtle temperature differences on the surface of the earth. The size and distance of the sails can be tailored to meet the needs of changes that you wish to effect, the avoidance of debris to minimize repairs, etc etc.The power collected can be used, first and foremost, to power ionic drives that are available today, constantly repositioning the sails using the Lorentz force to maintain geostationary orbit over the target area. NASA went live with these this April. Excess power could be used for space telescopes, transfer to other space platforms, space elevator use, etc.And if it has negative effects? It can nudge itself into an eventual collision course with the sun, getting out of any sort of effective shielding, fairly rapidly. Or it can fold itself up, or reposition in deep space, or self destruct, or whatever you want.So let's avoid massive chemical changes that are impossible to reverse, until we've tried the things we have full control over, shall we?