Natural forces have much more of an influence on earth's climate than any amount of CO2 or other 'greenhouse gas' we might put into the atmosphere.
Don't forget time-scale. Some of those extreme changes happened over thousands of years. (They look quick when the plot is millions of years long.)
I'm not even convinced we have the ability to make even small changes in the overall climate.
Do you think stratospheric ozone depletion is natural? Ozone depletion is about 50% of the reason that the stratosphere is cooling; the other 50% is caused by reduction of radiative warming due to increased tropospheric GHGs.