While there exists no solid evidence that higher atmospheric CO2 levels cause extreme climate change, there is certainly a plethora of evidence that extreme climate change does happen during a low CO2 environment. Case in point: researchers just completed a new study, which determined that the disappearing of the ancient Harappan Civilization was due to extreme climate change - during a low CO2 environment.
"An international, interdisciplinary team of geologists, archeologists, mathematicians and geomorphologists collected samples from the area once occupied by the little-known civilization...analysis suggested that climate change that weakened monsoon rains and tamed the tributaries of the Indus River and reduced run-off from the Himalayan mountains enabled the Harappans to practice agriculture on the river banks...But when monsoon rains began to decline, the rivers and regular flooding the civilization relied on to maintain a strong agriculture dried up, and they were forced to move east toward the Ganges River basin and were no longer able to sustain large cities."
Conclusion: Extreme climate change happens. It happened in the past. It will happen in the future. Although there is more historical evidence pointing to a relationship between low CO2 and climate change, it is likely not caused by either low or high levels of atmospheric CO2. More likely, it is a result of combined natural/cosmic forces that are unaffected by human CO2 emissions and cannot be controlled by the insane politician-priestly class and their bureaucrat-scientist acolytes.