Solar activity, ‘milankovitch’ cycles have a big effect on temperatures. I’ve heard Solar scientists call out the nonsense that CO2 is driving temperatures. CO2 change is a down stream effect of temperature change as you say.
There's also some newer work on latent heat in the Earth's mantel and core. There are geophysical cycles where more mantel is melting than solidifying, which releases latent heat to the surface.
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