Oceans are really big and dense heat transports. Mean depth 3682 metres.

More Ocean Heat Transport polewards is likely one +ve climate system feedbacks. With alligators and vege, in the tropics around PEM, simulations suggest more heat coming from the tropics ... The warmer climates of

the Mesozoic and Tertiary may have seen estimated global OHT

increases of 15–70% according to palaeoclimate model simula-

tions with modern day CO 2 values ...

OHT itself appears to contribute system effects adding a further few degrees of mean global temperature.

https://www.tandfonline.com/doi/abs/10.3402/tellusa.v57i4.14708