Idiot. The flip from an ice age to an interglacial is a complicated process, and the primary variable and driving force is ice cover in the northern hemisphere.
Once the ice cover is reduced, the climate warms up, more CO2 comes out of the ocean, and the climate warms up some more. That's what did happen back then.
What we are doing is dumping lots of extra CO2 into the atmosphere which produces direct warming (and reduces ice cover in the northern hemisphere).
Cause and effect have been flipped.
It's no kind of argument that extra CO2 in the atmosphere now isn't causing warming now - extra CO2 produced extra warming back then too, and the mechanism is perfectly obvious.