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The magical faraway tree: a larch in the Yamal Peninsula in Siberia, sampled by Dr Keith Briffa, has been called 'the most influential tree in the world' Photo: NATIONAL GEOGRAPHIC CREATIVE

Leaked emails from the Climatic Research Unit show how the world's weightiest climate data has been distorted.

Coming to light in recent days has been one of the most extraordinary scientific detective stories of our time, bizarrely centred on a single tree in Siberia dubbed "the most influential tree in the world". On this astonishing tale, it is no exaggeration to say, could hang in considerable part the future shape of our civilisation. Right at the heart of the sound and fury of "Climategate" – the emails leaked from the Climatic Research Unit (CRU) in East Anglia – is one story of scientific chicanery, overlooked by the media, whose implications dwarf all the rest. If all those thousands of emails and other documents were leaked by an angry whistle-blower, as now seems likely, it was this story more than any other that he or she wanted the world to see.


To appreciate its significance, as I observed last week, it is first necessary to understand that the people these incriminating documents relate to are not just any group of scientists. Professor Philip Jones of the CRU, his colleague Dr Keith Briffa, the US computer modeller Dr Michael Mann, of "hockey stick" fame, and several more make up a tightly-knit group who have been right at the centre of the last two reports of the UN's Intergovernmental Panel on Climate Change (IPCC). On their account, as we shall see at this week's Copenhagen conference, the world faces by far the largest bill proposed by any group of politicians in history, amounting to many trillions of dollars.

It is therefore vitally important that we should trust the methods by which these men have made their case. The supreme prize that they have been working for so long has been to establish that the world is warmer today than ever before in recorded history. To do this it has been necessary to eliminate a wealth of evidence that the world 1,000 years ago was, for entirely natural reasons, warmer than today (the so-called Medieval Warm Period).

The most celebrated attempt to demonstrate this was the "hockey stick" graph produced by Dr Mann in 1999, which instantly became the chief icon of the IPCC and the global warming lobby all over the world. But in 2003 a Canadian statistician, Steve McIntyre, with his colleague Professor Ross McKitrick, showed how the graph had been fabricated by a computer model that produced "hockey stick" graphs whatever random data were fed into it. A wholly unrepresentative sample of tree rings from bristlecone pines in the western USA had been made to stand as "proxies" to show that there was no Medieval Warm Period, and that late 20th-century temperatures had soared to unprecedented levels.

Although McIntyre's exposure of the "hockey stick" was upheld in 2006 by two expert panels commissioned by the US Congress, the small group of scientists at the top of the IPCC brushed this aside by pointing at a hugely influential series of graphs originating from the CRU, from Jones and Briffa. These appeared to confirm the rewriting of climate history in the "hockey stick", by using quite different tree ring data from Siberia. Briffa was put in charge of the key chapter of the IPCC's fourth report, in 2007, which dismissed all McIntyre's criticisms.

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.

Little of this extraordinary story been reported by the BBC or most of our mass-media, so possessed by groupthink that they are unable to see the mountain of evidence now staring them in the face. Not for nothing was Copenhagen the city in which Hans Andersen wrote his story about the Emperor whose people were brainwashed into believing that he was wearing a beautiful suit of clothes. But today there are a great many more than just one little boy ready to point out that this particular Emperor is wearing nothing at all.

I will only add two footnotes to this real-life new version of the old story. One is that, as we can see from the CRU's website, the largest single source of funding for all its projects has been the European Union, which at Copenhagen will be more insistent than anyone that the world should sign up to what amounts to the most costly economic suicide note in history.

The other is that the ugly, drum-like concrete building at the University of East Anglia which houses the CRU is named after its founder, the late Hubert Lamb, the doyen of historical climate experts. It was Professor Lamb whose most famous contribution to climatology was his documenting and naming of what he called the Medieval Warm Epoch, that glaring contradiction of modern global warming theory which his successors have devoted untold efforts to demolishing. If only they had looked at the evidence of those Siberian trees in the spirit of true science, they might have told us that all their efforts to show otherwise were in vain, and that their very much more distinguished predecessor was right after all.

Christopher Booker's The Real Global Warming Disaster (Continuum, £16.99) is available from Telegraph Books for
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