Carbon dioxide, a covelently bonded molecule, constitutes about .039% of the atmosphere, less than 400 ppm by volume. The entire atmosphere contains 3.16x10^15 kilograms of the stuff. So what would it take to drag it out of atmosphere and convert it, say, to reels and reels of carbon-fiber monofilament for use in construction and manufacturing? We are not all that far away from the kind of molecular manipulation needed to do this on an industrial scale, and it would reset the imbalance of anthropogenic greenhouse effect to a merked degree. Probably netter than killing all those pine trees to make cheap 2x4s out of. I dunno...