Climate change skeptics argue that “climate change has always existed”. That they have “done the research on the internet.” These broad statements contain a kernel of truth, but without details and scientific data to back up the claims, they are misleading.

In his book “Rise and Reign of Mammals” (p, Steve Brusate describes the Paleocene-Eocene Thermal Maximum, 56 million years ago,  when volcanic activity caused atmospheric CO2 to rise to between 650 and 3500 ppm. Average land temperature in the Arctic reached 25 degrees C. You know what the earth looked like then?