This Thursday past I listened to a talk by Professor Georgiy Stenchikov. Stenchikov works with the Intergovernmental Panel on Climate Change (IPCC) crew that won the Nobel recently. On Thursday he spoke of the effects that aerosols (fine particles) have in the upper atmosphere. Apparently higher concentrations of aerosols in the stratosphere reflect incoming solar radiation and reduce global temperature. Their effect can be observed when a massive volcanic eruption drops global temperature by a small amount. Stenchikov and his collaborators have created global climate models capable of reproducing this volcanic effect.
Stenchikov's talk focused on artificially increasing the aerosol content of the upper atmosphere to combat CO2-related global warming trends. Apparently it's an idea from the late 70's. Stenchikov quite literally ran 40 year simulations where humans sprayed megatons of aerosols into the stratosphere to see if we could reduce the temperature. The verdict? It works, but if we ever stop the process, global warming comes back with a vengeance.
That's some scary shit. By "that" I mean nearly every implication of living in a day when such a plan is a genuine topic of interest.