It depends on how badly we may miscalculate the aerosol deterioration rate. If we inject a bit too much and it stubbornly stays airborne, that would be a hard geoengineering problem to tackle!

I'd say that things are not bad enough for anyone with the means to take the risk. When the things get bad enough for the Overton window to admit geoengineering, it may be too late for simple and affordable solutions, as usual.

We have some experimental data on this, though, since jetliners and volcanoes both inject sulfur into the stratosphere. The global air traffic halt of 2001 and the aftereffects of eruptions have been heavily studied.

(It would be ironic if the world's response to fossil CO2 emission is to mandate extra high sulfur jet fuel, but nothing would surprise me)