The problem is that ground-level SOX gives you acid rain, and washes out too fast to be useful for GCC mitigation. Increasing volcanism would arguably be even iffier than nuclear sulfur blimps.

Good point about the acid rain, the washout. I wonder if there's some way to dope solid rocket booster fuel to produce SOX at higher altitudes? As we launch more and more, maybe we could harness that to ease the burden on something like your blimp idea... thus avoiding the need to nuke the planet.

I was just riffing on the nuclear winter thing. But actually, blimps would be unworkable, because we would need to inject millions of tons of SOX per year into the stratosphere. And energy requirements are mostly for lifting, not dispersion.

Perhaps nuclear devices could be designed to produce upward-directed jets.

I wonder if a slower, but maybe safer alternative is just to increase the burning of SOX producing fuels. If we could scrub the carbon, we'd have a net-cooling effect.

That or we have to seriously consider induced volcanism.