At the forefront of those who found suspicious the graphs based on tree rings from the Yamal peninsula in Siberia was McIntyre himself, not least because for years the CRU refused to disclose the data used to construct them. This breached a basic rule of scientific procedure. But last summer the Royal Society insisted on the rule being obeyed, and two months ago Briffa accordingly published on his website some of the data McIntyre had been after.
This was startling enough, as McIntyre demonstrated in an explosive series of posts on his Climate Audit blog, because it showed that the CRU studies were based on cherry-picking hundreds of Siberian samples only to leave those that showed the picture that was wanted. Other studies based on similar data had clearly shown the Medieval Warm Period as hotter than today. Indeed only the evidence from one tree, YADO61, seemed to show a "hockey stick" pattern, and it was this, in light of the extraordinary reverence given to the CRU's studies, which led McIntyre to dub it "the most influential tree in the world".
But more dramatic still has been the new evidence from the CRU's leaked documents, showing just how the evidence was finally rigged. The most quoted remark in those emails has been one from Prof Jones in 1999, reporting that he had used "Mike [Mann]'s Nature trick of adding in the real temps" to "Keith's" graph, in order to "hide the decline". Invariably this has been quoted out of context. Its true significance, we can now see, is that what they intended to hide was the awkward fact that, apart from that one tree, the Yamal data showed temperatures not having risen in the late 20th century but declining. What Jones suggested, emulating Mann's procedure for the "hockey stick" (originally published in Nature), was that tree-ring data after 1960 should be eliminated, and substituted – without explanation – with a line based on the quite different data of measured global temperatures, to convey that temperatures after 1960 had shot up.
A further devastating blow has now been dealt to the CRU graphs by an expert contributor to McIntyre's Climate Audit, known only as "Lucy Skywalker". She has cross-checked with the actual temperature records for that part of Siberia, showing that in the past 50 years temperatures have not risen at all. (For further details see the science blog Watts Up With That.)
In other words, what has become arguably the most influential set of evidence used to support the case that the world faces unprecedented global warming, developed, copied and promoted hundreds of times, has now been as definitively kicked into touch as was Mann's "hockey stick" before it. Yet it is on a blind acceptance of this kind of evidence that 16,500 politicians, officials, scientists and environmental activists will be gathering in Copenhagen to discuss measures which, if adopted, would require us all in the West to cut back on our carbon dioxide emissions by anything up to 80 per cent, utterly transforming the world economy.