Stratospheric sulfur injection might be something we need to put off until we are firmly on the path of reducing greenhouse gas emissions and have reached a point where it would be more expensive to leave that path than to continue reducing.

That's because, if what the internet has told me is correct, sulfur injections only stay in the atmosphere for a couple of years. If we use them to mitigate warming before we've addressed greenhouse gases the injections have to be ongoing. Stop the injections and in a couple of years the warming comes back.

You really don't want a situation where you end up doing injections for a decade or two and then it stops for some reason. You then get in a couple of years a level of warming that without the injections would have happened over a decade or two. Getting that warming rapidly is probably a lot harder for people to deal with.