I found a Scientific American article that corroborates your statement about rising CO2 levels causing warming at the end of the last ice age: https://www.scientificamerican.com/article/what-thawed-the-last-ice-age/

And…no one is saying only humans can cause such increases. The point is, we are causing an increase in CO2 levels - that’s easy to agree upon right? You can measure the output of burning fuel, and the changes in atmospheric CO2. So, if you can agree on the science of CO2, what’s the cause of your skepticism?