It's hard to say for sure. Assuming it works (which seems likely given past volcano eruptions), it could reduce planetary temperatures by up to a couple of degr

It's hard to say for sure. Assuming it works (which seems likely given past volcano eruptions), it could reduce planetary temperatures by up to a couple of degrees, giving us a few extra decades to get emissions down to zero. Downsides are it does nothing to address ocean acidification, once we start we really can't stop ever, it'll kill N thousand people yearly from pollution/ozone depletion, potential for increased drought in some regions and political issues (eg it greatly benefits China but India suffers devastating droughts as a result).