I think we need to do this until we develop large scale underground CO₂ sequestration.

Unfortunately even if/when we completely stop producing CO₂, it takes at least several centuries until levels go fully back down to natural levels by themselves.

Pumping SO₂ into the stratosphere should be able to regulate global temperatures to reasonable levels while we develop effective CO₂ sequestration.

Unfortunately SO₂ injection is incredibly controversial, as it triggers the "don't mess with nature" taboo, especially among people who have seen Jurassic Park, and affects the whole planet, including those who don't want it.

We do actually know that SO₂ breaks down in the stratosphere in 1-2 years, because we've studied when volcanoes injects it. It also doesn't cause acid rain because it's above the rain cycle.

But these facts are very hard to get across to people.