But temperature and CO2 went up an down in the ice ages?

How often do we hear that? Or similar statements such as;

In the ice ages, the concentration of CO₂ in the atmosphere increased after increases in temperature, so CO₂ can't be causing warming.

My short answer would be to say

Hey, how many coal-fired thermal power stations were running in the ice ages? Yeah, thats right, None!

But there is a Climate Crock of the week Youtube video explaining that the initial trigger (or forcing) for the ice age cycles has been the Earth's axis and that CO₂ can be both a forcing and a feedback amplifying the impacts of the tilt and spin changes. And, as ever, James Hansen's work plays a key role.