In chatting with someone in the oil industry, he said humanity was undergoing its largest accidental geo-engineering exercise via sulphur containing heavy oil being burnt on ships. Somewhat recently high sulphur content was banned from heavy oil and we stopped that experiment.

https://clearseas.org/en/blog/marine-fuels-what-is-heavy-fue...

We need not wonder. Nature has already given us a trial run.

All this brouhaha over unintended consequences are going to ultimately be secondary to the known and catastrophic consequences of runaway global warming.