Sometime back, a scientist suggested that one of the most cost-effective ways to prevent global warming would be to toss a bunch of sulfur into the air. The sulfur would reflect solar rays -- and therefore heat -- back into the atmosphere. You do enough of it, and the Earth would cool.
This was tested science -- not some hypothetical thought experiment. When Mt. Pinatubo in the Phillippines erupted, the sulfur dioxide it spewed into the atmosphere cooled the Earth by 0.5 degrees Celsius with a year.
Of course, the scientists/environmentalists screamed bloody murder that anyone would even make such a suggestion. After all, practical solutions that don't entail a complete restructuring of Western civilization and the continued impoverishment of the Third World are not acceptable.
You may not have heard about it on the news, but it's happening again. A couple weeks back, the Kasatochi volcano in the Aleutian islands let loose.
You better put on a jacket.