Read here and here. Global warming scientists and activists constantly remind anyone who is still listening that extreme climate change is happening, even accelerating, all because of increasing human CO2 emissions. Fortunately for all of us, there is no actual empirical evidence that extreme climate change is happening other than the natural variation in climate that occurs.
As scientists have discovered and documented in peer-reviewed research, past climate change was quite extreme without any involvement from CO2. The recent research done in Siberia is a case in point. (click image to enlarge)
"...authors collected several sediment cores from the deepest area of Teletskoye Lake in the Altai Mountains of southern Siberia, for which they measured the spectra of numerous elements - including Ba, Cd, Ce, I, La, Mo, Nb, Rb, Sb, Sn, Sr, Th, U, Y, Zr - after which they report that "artificial neural networks were used for reconstruction of annual temperature and precipitation by sediment properties""...."from their plot of the pertinent data, it can be seen that the mean peak temperature of the latter part of the Medieval Warm Period was about 0.5°C higher than the mean peak temperature of the Current Warm Period, which occurred at the end of the record....During the peak warmth of the Medieval Warm Period, when there was fully 100 ppm less CO2 in the air than there is currently, it may well have been half a degree C warmer in southern Siberia than it is now."
More historical charts here. Other climate history postings here. Modern temperature charts.