The Case for Blaming Humans for Global Warming

Principia Scientific | Oct. 18, 2019 Written by Roger W. Cohen, PhD If 20th century warming was indeed exceptional, then previous warming episodes and all natural variations must have been smaller. Interestingly, in the first IPCC report of 1990, we saw this graphic (above) of global temperature since about the year 1000. There is a strong Medieval Warming Period, a deep Little Ice Age, and a sporadic warming trend since around 1700. But when we get to the 2001 Report, we are presented with the Hockey Stick. It was based on various proxy “thermometers” such as tree rings. It seems …