I first found out about this book by reading Matt Ridley's Angus Miller Lecture (1), which has to be the best concise description of climate skeptics out there. In it, he recommends this book, saying that the hockey stick has been "utterly debunked by the work of Steve McIntyre and Ross McKitrick". I thought "utterly debunked" sounded a bit strong, considering how vigorously its proponents defend it. I understood the "hidden decline" or divergence problem, but I never got a handle on the validity of the long straight handle. So I read this book and some of the reviews of it for comparison. I even rechecked Michael Mann's book out of the library. I've concluded that Mann's hockey stick is indeed debunked and that, while I don't like to sound like a conspiracy theorist, the paleoclimate community, the science journals and the National Academy of Science are all complicit in covering for this bad science.
Now I want to make it clear what I mean by "debunked". It does not mean that the hockey stick's long straight handle of flat temperatures without a Medieval Warm Period is not true. It means that the flawed science in Mann's papers does not show it to be true. This point is important, because Mann's defenders often use a diversionary argument that other papers get the same result or that his critics haven't presented a different result. If Mann had chosen his proxies by flipping a coin, it would still be bad science regardless of the results.
The book provides a good narrative of Steve McIntyre's quest to understand and replicate the hockey stick and does a good job of explaining arcane statistical concepts. I have found three main arguments against the hockey stick, but there are plenty of other minor issues such as data series being extended, truncated or having gaps filled in. McIntyre is constantly thwarted in his requests for data and not just by Mann, but by the journals themselves.
The first main issue is the over-reliance on Bristlecone pines. The NAS Panel, which Mann praises as exonerating him, concludes that Bristlecones should not be used in paleoclimate reconstructions. The NAS Panel was also critical about the second main issue. This is the nonstandard method of centering series in Principle Component Analysis by only using the mean value for the twentieth century. This is dubbed "short centering" (Mann calls it "modern centering"). When fed random "red noise", it almost always produces hockey sticks! When a Mann defender who calls himself Tamino defended this by invoking an expert named Ian Jolliffe, he was rebuffed and was asked for an apology. How does the NAS Panel exonerate Mann and yet find these flaws? The panel's head, Gerald North, says they "just winged it".
The third issue is the failure of the hockey stick to pass a verification test involving a well known computed value called R2 and Mann's refusal to disclose it. IMO this is the most serious issue where one might reasonably accuse him of fraud. Mann is suing Marc Steyn of National Review Online for calling his hockey stick "fraudulent"(2). His paper says R2 was determined and his Fortran code had commands for computing it. He told journalist Marcel Crok that the hockey stick had passed it, but when John Christy of the NAS Panel asked if he computed it, Mann says "We didn't calculate it. That would be silly and incorrect reasoning." The two statisticians on the panel did not pursue it. I'll have to admit that I didn't grok all of the details on a first reading but fortunately, the author has a post(3) on his blog that concisely summarizes it in infuriating detail.
Interested readers might want to check out the aforementioned Tamino's review(4) on Real Climate. Don't miss Judith Curry's comments #74, #107, #168, #185, #290, #380, and more plus the mayhem that ensues. Steve McIntyre also has a YouTube presentation(5)(6)(7) that summarizes some of the material.
Numbered notes refer to non-Amazon links listed in the first comment.
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