There's a good chance that the sudden bump in sea surface temperature is a consequence of us cleaning up marine diesel. Which is at least interesting, because it suggests we were doing geoengineering without even knowing it.
(Random thought: what's the sulphur content of automotive diesel? I know it's cleaner, but there are so many more cars than boats. Could we see another sea surface temperature bump as we phase out diesel cars?)
All these are temporary masking conditions. They also add to feedback effects, for increased warming. So could be partly accellerating heating as well.
I think some researchers are seeing accelleration in the overall trend. You can eyeball this with a ruler as well. Even though it might be too early to tell, it's hard to find any negative feedback loops to counter all these positive ones.
For cars, I think we'd probably see increase in surface temperature on land. People might care a bit more then. It could be removed from both gas and diesel. That would bring pollution down, but also remove aerosols currently masking effects from GHG.
UPDATE: As noted in another comment here. Car fuel is quite a bit different category than bunker fuel (heavy fuel oil). We might still observe "unmasking"-impacts if implemented generally though. We'd notice it more too, as the impact would be right where we use our cars.
No useful comment, except to say I thought that was a great response. Thoughtful and detailed despite being an extended "it's complicated". My ignorance feels much better informed ;)
(Random thought: what's the sulphur content of automotive diesel? I know it's cleaner, but there are so many more cars than boats. Could we see another sea surface temperature bump as we phase out diesel cars?)