Why were the CO2 levels on the atmosphere 20 times higher during the Cambrian Period than today's levels, yet global temperatures were not high? How do scientists integrate this fact on global warming models?

https://www.quora.com/Why-were-the-CO2-levels-on-the-atmosphere-20-times-higher-during-the-Cambrian-Period-than-todays-levels-yet-global-temperatures-were-not-high-How-do-scientists-integrate-this-fact-on-global-warming-models