Go to https://www.youtube.com/watch?... and stop at time 27:12.
CARTA:The Orangutan Neandertal and Denisovan Genomes
You will see a chart that shows very periodic and sudden changes of earth CO2 content, and glacial cycles. The rapid CO2 increases at 160K years and at 400K years look faster and greater than our own era's jump. In addition, the graph makes it look like our era's CO2 jump was already overdue.
Given the controversial topic I ask that you keep comments about the graph and data, and not flame me for pointing the graph out.