...Ice Ages and Thaws took place within the CO2 atmospheric concentrations of 180 - 300 ppm...within the last ~150 yrs we're now over 425 ppm...and rising rapidly...plus, it takes generations for the CO2 to come out of the atmosphere acidifying oceans...etc, etc.
Link: https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide