Just thinking out loud that we can't be too far from industrial strength pollution reversal machines. Build twenty or thirty of these in a large city and watch them churn out clean air from carbon dioxide. Industrial strength photosynthesis, with machines. Would avoid the need for terraforming other worlds, too. So, how far from this technology do you think we are?
Carbon dioxide isn't pollution, really. But if you think it is, you'd have to come up with a way to generate terawatts of energy for your anti-pollution machine without creating any more CO2.
My Great Grandfather, formerly of Army Intelligence, was convinced the Soviet Union had a machine capable of manipulating weather.
If you tie together millions of six-pack holders together you can sweep the ocean clean and make a pretty darn good slurry, too.