Former Clinton adviser Jeff Schweitzer seems to think no one knew anything about climate before Michael Mann et al. came along.
Schweitzer writes in “Opinion, Fact and Hubris: Our Response to a Changing Planet” at Huffington Post:
… Skepticism about climate change comes with a particularly rich irony. Many doubters cite the earth’s past cycles of glaciation and warming to discount what we are seeing today as nothing but natural variation. How do the skeptics know of that climate history? From the very scientists whose conclusions they now doubt! As if the scientists themselves are unaware of their own conclusions about the earth’s past, or if they are aware, did not take that history into account. Doubters preferentially believe one set of facts from those scientists but dismiss other facts as liberal nonsense. Doubters can do this because they confuse opinion and fact…
Of course, if what Schweitzer said was true then skeptics would know nothing about the Medieval Optimum or the Little Ice Age since Michael Mann’s hokey stick deleted both historical temperature swings.
Below is historical climate as represented in the first IPCC report.
Below is Mann’s hokey stick as represented in the third IPCC report.