Oceans at warmest recorded temperatures for fifth consecutive year, page-47

Temperature of the surface of the ocean varies a lot over even short distances.

Fishing boats have thermometers to display water temperature
as fish are often concentrated in/warm cool boundaries.

The East Australian current conveys warm water from Queensland to the east coast of Tasmania.

Good luck measuring 'ocean temperature'.

Also suspect is CO2 concentration.
Planet earth is a closed system.
Almost nothing gets off the planet,
some dust and gas is attracted by gravity.

The CO2 just had to be here the whole time.