But who killed the Medieval Warm Period?
Before we begin the investigation into the usual suspects, some background for people who those who don’t follow climate science closely, which certainly includes most of the disinformers and apparently at least two statisticians.
- There is a high probability that the recent warming is unprecedented for 1000 years and probably much longer (see “Sorry disinformers, hockey stick gets longer, stronger: Earth hotter now than in past 2,000 years” and here and here).
- This conclusion is based on an analysis of multiple proxies for temperature, which individually engender much uncertainty and collectively still engender a fair amount. It is a canard of Curry-esque proportions to assert that scientists have not clearly explained the nature and extent of these uncertainties. They have bent over backwards to do so.
- The temperature trend in the past millennium prior to about 1850 is well explained in the scientific literature as primarily due to changes in the solar forcing along with the effect of volcanoes, whereas the recent rise in temperature has been driven primarily — if not almost entirely — by human activity (see Scientist: “Our conclusions were misinterpreted” by Inhofe, CO2 — but not the sun — “is significantly correlated” with temperature since 1850 and Part 3 [to come]).
- Absent human emissions, we’d probably be in a slow long-term cooling trend due primarily by changes in the Earth’s orbit — see Human-caused Arctic warming overtakes 2,000 years of natural cooling, “seminal” study finds.
- Thus, the rate of human-driven warming in the last century has exceeded the rate of the underlying natural trend by more than a factor of 10, possibly much more. And warming this century on our current path of unrestricted greenhouse gas emissions is projected to cause a rate of warming that is another factor of 5 or more greater than that of the last century. We are punching the climate beast — and she ain’t happy about it!
Back to the investigation of attempted murder — and the ‘innocent victim’ who may have been killed in the attempt. The folks who don’t follow climate science closely have been trumpeting a new paper “A Statistical Analysis of Multiple Temperature Proxies: Are Reconstructions of Surface Temperatures Over the Last 1000 Years Reliable?” by McShane and Wyner about to be published in Annals of Applied Statistics. Supposedly it is fatal to the Hockey Stick.
Here is the police lineup. Take a look at three independent reconstructions of the past one to two millennia and the new one by the statisticians — and see if you can pick out which one allegedly killed the others (with apologies to Deltoid):