Sounds like it to me. What about the methane from those teaming herds of pre-historic bison, mammoths and other critters that man hunted to extinction. Weren't they simply rolling back greenhouse gas emissions?
These guys a grasping at straws now. They can't document their 20th century temp model so they invent a new fake model. Less than a million humans on earth 8000 years ago with very slow population growth were able to warm the global climate, but when global population started to take off big time in the early 17th century, we had two centuries of global cooling! Maybe they should model that.