That is kind of the point. If the history of earth was a year human's existence would be about a second. The earth has had extreme periods of high CO2 and low CO2. Also ice ages and warming period. We have been coming out of an ice age and warming long before man started burning fossil fuels.
If we quit putting any man made CO2 into the atmosphere, ice caps are still going to melt. Biggest impact it is going to have is big cities on the coast.
And yes Hedleo we have had life ending events due to massive amounts of greenhouse gasses released in the atmosphere and none was man made. It will most likely happen again and man will be extinct.
I for one think we should be trying to do something to slow down our "footprint" just get tired of dumb asses pointing to every hurricane, drought or bug infestation as some sort of man made global warming issue. It is not.