Earlier quoted context omitted.
Not sure what the "conspiracy" would be, but yeah, the sulfur reductions in ship emissions is definitely a factor. Someone needs to figure out large scale injection of SO2 to the stratosphere. Don't wait for permission, just do it!
This is literally just taken from a fiction book. It's a good book, I enjoyed it. But,it's just a story. Geo engineering should probably be done pretty carefully
But the idea itself is much older, and AFAICT very safe. The only thing missing is a practical way to get millions of tonnes of SO2 to the stratosphere aside from burning dirty oil on the ground.
These guys are supposedly working on it: https://makesunsets.com/