See http://www.sff.net/people/teaston/front7.htp. The piece appeared in 1998, but it's relevant.

A little while ago there was a proposal to launch small orbiting "parasols" that would reflect solar heat and help stop global warming (http://earthobservatory.nasa.gov/Newsroom/MediaAl erts/2006/2006110323537.html). As proposed, they would be spacecraft with circuitry, but the proposal did call for electromagnetic launching (i.e., railguns). I would think you could also send reflectors without circuitry; they would be reflective chaff, and they would need more frequent replacement, but what the heck. Railguns are loads cheaper than rockets.