Not to my knowledge, which is why I used the word "suspected" since I think this falls on the "makes intuitive sense, but would not surprise me in the least if

Not to my knowledge, which is why I used the word "suspected" since I think this falls on the "makes intuitive sense, but would not surprise me in the least if it turned out to be completely incorrect" category of hypotheses. I consider "suspected" to be the least level of evidence while still taking something into consideration as a potential cause. A suspected murderer might not even have been arrested, let alone convicted. We do know that sulphur emissions have a global cooling effect, and we do know that sulphur emissions recently were reduced, so it's a reasonable hypothesis from first principles.