> In fact, I was under the opposite impression because of the benefit that sulfur enriched shipping exhaust had for our climate.

It isn't quite accurate to state that ship tracks have/had a "benefit" on our climate. Their existence creates a transient decrease in OLR and increase in albedo. If anything, they simply masked some GHG-induced warming that had a much longer half-time, and cleaning up ship emissions has "unmasked" some of that hidden warming. But, again, the warming was already committed.