12,000 years ago giant sheets of ice covered large parts of North America and Europe. You could walk from Siberia to Alaska. Then the Ice Age came to an end and sea level rose 120 meters.
During the Middle Age Warming period it was a degree or more warmer than it is now.
Given that climate has had such major changes before the first lump of coal was burned, how can we be sure how much current changes are driven by anthropogenic CO2 release.