(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?)
https://www.theguardian.com/environment/2020/jan/01/shipping...
It could be the underwater Tonga volcano erruption, which put alot of water into the atmosphere. Water is also a GHG.
https://www.nasa.gov/centers-and-facilities/goddard/tonga-er...
It could be El Nino part of the ENSO-cycle in addition.
https://www.npr.org/2023/06/08/1181086972/el-nino-has-offici...
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.
https://www.futurity.org/potassium-fuel-sulfur-1369772-2/
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.