Skeptic vs Warmist, page-13

Probably the closest I can think of would be the exit from the snowball Earth phase that terminated the Great Oxygen Catastrophe (perhaps the most fascinating epoch in the very early history of the planet, and the period when all the iron ore deposits that Australia currently mines were laid down). The oceans were covered in ice all the way to the equator, and so decoupled from atmospheric CO2. It's believed that therefore volcanic CO2 was able to accumulate unchecked in the atmosphere, eventually driving the temperature high enough to melt the ice and bring things back to a new equilibrium. A much slower process than what's going on now, of course, but a situation where CO2 did lead.