I would still be a bit reluctant to advocate climate engineering, though. The main worry, of course, is that if we choose that route, we need to commit to in the long term, like you said. Openly embracing climate engineering would probably also cause emissions to soar, as people would think that there's no need to even try to lower emissions any more. So, if for some reason the delivery of that sulfuric acid into the atmosphere or whatever was disrupted, we'd be in trouble. And do we know enough of such measures to say that there safe?. Of course, if we believe that history will end anyways within decades or centuries because of singularity, long-term effects of such measures may not matter so much.

Also, many people, whether or not they're environmentalists strictly speaking, care about keeping our ecosystems at least somewhat undisrupted, and large scale climate engineering doesn't fit too well with that view.

But I agree that we're not progressing fast enough with emissions reductions (we're not progressing with them at all, actually), so we'll probably have to resort to some kind of plan B eventually.