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The claim in an IPCC report that 40 per cent of the Amazon rainforest could disappear through global warming turned out to be unfounded
It is now six weeks since I launched an investigation, with my colleague Richard North, into the affairs of Dr Rajendra Pachauri, chairman of the UN's Intergovernmental Panel on Climate Change (IPCC), the hugely influential body which for 20 years has been the central driver of worldwide alarm about global warming. Since then the story has grown almost daily, leading to worldwide calls for Dr Pachauri's resignation. But increasingly this has also widened out to question the authority of the IPCC itself. Contrary to the tendentious claim that its reports represent a "consensus of the world's top 2,500 climate scientists" (most of its contributors are not climate experts at all), it has now emerged, for instance, that one of the more widely quoted scare stories from its 2007 report was drawn from the work of a British "green activist" who occasionally writes as a freelance for The Guardian and The Independent.

Last week I reported on "Glaciergate", the scandal which has forced the IPCC's top officials, led by Dr Pachauri, to disown a claim originating from an Indian glaciologist, Dr Syed Husnain, that the Himalayan glaciers could vanish by 2035. What has made this reckless claim in the IPCC's 2007 report even more embarrassing was the fact that Dr Husnain, as we revealed, was then employed by Dr Pachauri's own Delhi-based Energy and Resources Institute (Teri). His baseless scaremongering about the Himalayas helped to win Teri a share in two lucrative research contracts, one funded by the EU.

The source the IPCC cited as its "scientific" authority for this claim, however (as Dr North first reported on his EU Referendum blog), was a propagandist pamphlet published in 2005 by the WWF, the environmentalist pressure group, citing a magazine interview with Dr Husnain six years earlier.

Dr North next uncovered "Amazongate". The IPCC made a prominent claim in its 2007 report, again citing the WWF as its authority, that climate change could endanger "up to 40 per cent" of the Amazon rainforest - as iconic to warmists as those Himalayan glaciers and polar bears. This WWF report, it turned out, was co-authored by Andy Rowell, an anti-smoking and food safety campaigner who has worked for WWF and Greenpeace, and contributed pieces to Britain's two most committed environmentalist newspapers. Rowell and his co-author claimed their findings were based on an article in Nature. But the focus of that piece, it emerges, was not global warming at all but the effects of logging.

A Canadian analyst has identified more than 20 passages in the IPCC's report which cite similarly non-peer-reviewed WWF or Greenpeace reports as their authority, and other researchers have been uncovering a host of similarly dubious claims and attributions all through the report. These range from groundless allegations about the increased frequency of "extreme weather events" such as hurricanes, droughts and heatwaves, to a headline claim that global warming would put billions of people at the mercy of water shortages - when the study cited as its authority indicated exactly the opposite, that rising temperatures could increase the supply of water.

Little of this has come as a surprise to those who have studied the workings of the IPCC over the years. As I show in my book The Real Global Warming Disaster, there is no greater misconception about the IPCC than that it was intended to be an impartial body, weighing scientific evidence for and against global warming. It was set up in 1988 by a small group of scientists all firmly committed to the theory of "human-induced climate change", and its chief purpose ever since has been to promote that belief.

The blatant bias of each of its four reports has been pointed out by scientists - notably the rewriting of key passages in its 1995 report after the contributing scientists had approved the final text. This provoked a magisterial blast from Professor Frederick Seitz, a former president of the US National Academy of Sciences, who wrote that in all his 60 years as a scientist he had never seen "a more disturbing corruption" of the scientific process, and that if the IPCC was "incapable of following its most basic procedures", it was best it should be "abandoned".

The centrepiece of the IPCC's 2001 report was Michael Mann's notorious "hockey stick", the graph purporting to show temperatures in the late 20th century soaring at an unprecedented rate - later exposed as a statistical artefact. Another new book, The Hockey Stick Illusion by A W Montford, brilliantly tells the bizarre tale of how Mann's colleagues, calling themselves "the Hockey Team" and now at the heart of the IPCC, managed to resurrect the discredited graph for inclusion in its 2007 report. Montford's book, if inevitably technical, expertly recounts a remarkable scientific detective story. And of course, it was incriminating leaked emails between members of the Hockey Team that were at the centre of the recent "Climategate" scandal at the University of East Anglia.

Most disturbing of all are the glimpses the story gives of the inner workings of the IPCC, an institution now so discredited and scientifically corrupted that only those determined to shut their eyes could possibly defend it. This is now compounded by the recent revelations by Dr North and myself in these pages of how its chairman, Dr Pachauri, has built a worldwide network of business links which provide his Delhi institute with a sizeable income.

It is noticeable how many of those now calling for Dr Pachauri's resignation, led by Professor Andrew Weaver, a senior IPCC insider, are passionate global warming believers. Fearing that Pachauri damages their cause, they want him thrown overboard in the hope of saving the IPCC itself. But it is not just Pachauri who has been holed below the waterline. So has the entire IPCC process. And beyond that - and despite the pleading of Barack Obama, Gordon Brown and the BBC that none of this detracts from the evidence for man-made global warming - so has the warmist cause itself. Bereft of scientific or moral authority, the most expensive show the world has ever seen may soon be nearing its end.