For 250 years starting around the year 900AD, the Anasazi had the dominant culture in what is now the southwest US. Their structures at Chaco Canyon were the largest buildings in North America until the 19th century.
They were driven out of Chaco Canyon by 175 years of nearly continuous drought between 1125 and 1300. Was this drought caused by CO2? Probably not.
We are fortunate that we live in a period of time when the climate is so mild. What is unfortunate is the return to ignorance and superstition.