A cunning bid to shore up the ruins of the IPCC

Since then several inquiries, including three into the leaked "Climategate" emails, have tried to hold the official line, all following a consistent pattern. Each has made a few peripheral criticisms, for plausibility, while deliberately avoiding the main issue. Each has then gone on to put over the required message: that the science of global warming remains unchallenged.

At first sight, last week's Inter-Academy report on the "processes and procedures of the IPCC" seems to have played it more cleverly. It criticises the IPCC's abuse of its own procedures in very trenchant terms, and suggests some radical reforms to them. Passages on "conflict of interest", and a recommendation that top officials should serve only one term, seem to hint that Dr Pachauri, reappointed to serve until 2014 after presiding over the IPCC's last controversial report, should step down. But, as with the reports that preceded it, this one also tiptoes round a mighty elephant in the room, in order to put over the familiar message: the IPCC has generally "served society well", the science remains unchallenged. It is as one might expect of a report produced on behalf of bodies such as Britain's Royal Society and the US National Academy of Sciences, which have long been leading advocates for the belief in global waming.

When, some years ago, I began the research for my book The Real Global Warming Disaster, nothing surprised me more than discovering how widely the nature of the IPCC is misunderstood. It is invariably portrayed as a body representing the top scientists in the world, objectively weighing the complex forces that shape Earth's climate. In reality, it's nothing of the kind.

The men who set up the panel – led by its first chairman Bert Bolin, a Swedish meteorologist, and John Houghton, then head of the UK Met Office and first chairman of the IPCC's scientific working group – were already believers in what they called "human-induced climate change". The IPCC was, from the start, essentially a political pressure group, producing evidence to support the view that global warming was the most serious crisis facing the planet. This guided the selection of all the key scientists chosen to compile the IPCC's findings (such as those involved in the Climategate affair). And this explains all the searching questions that have built up around its hugely influential reports ever since.

The first major row over the IPCC came when it was revealed that the most widely publicised and alarmist claim in its second report, in 1995, was inserted after the text had been signed off by the other scientists involved – while 15 passages which countered alarm over climate change had been excised. This famously provoked Professor Fred Seitz, former president of the US National Academy of Sciences, to say that in 60 years as a scientist he had never seen a "more disturbing corruption" of scientific procedure.

Perhaps the most telling controversy arose over the notorious "hockey stick" graph, the centrepiece of the IPCC's third report in 2001. It rewrote climate history to show a world that was now dramatically hotter than it had been for at least 1,000 years. Promoted by Houghton and others as the ultimate emblem of the cause, it was eventually shown to have been no more than the result of trickery with a computer programme. But even after it been exposed, the IPCC establishment made the most tortuous efforts to defend it for their fourth report in 2007.

This became the most comprehensively discredited IPCC report of all. It was the first produced under the chairmanship of Dr Pachauri, who was appointed in 2002. One after another, its scariest and most widely publicised predictions – such as that Himalayan glaciers would largely have vanished by 2035, that climate change would kill off 40 per cent of the Amazon rainforest, that African crop-yields would be halved by 2050 – were found to have been based not on science at all, but on the reckless claims of environmental activists.

Not the least indictment of the IPCC's 2007 report was the revelation that, in clear breach of its own rules, more than 5,000 of its supposedly scientific claims were not peer-reviewed but came from advocacy groups, press releases, newspaper articles, even student theses. Yet Dr Pachauri himself has repeatedly insisted that everything in his report was based on "peer-reviewed" science.

Again and again the 2007 report has been found to be in flagrant breach of the IPCC's own rules. For instance, it cited no fewer than 16 articles from a single issue of one climate journal – which had been published after the IPCC's official cut-off date and should therefore have been disallowed. In each of the thousands of instances where the IPCC broke its rules, the claims it made were all in one direction: to hype up alarm over the extent and effects of climate change beyond anything science could justify. The most shameless instance was the claim about Himalayan glaciers, which two of the IPCC's own expert reviewers had pointed out was ridiculous even before it was published. Dr Pachauri dismissed this criticism as "voodoo science" (having employed the author of the claim at his own Delhi research institute).

Through all this the IPCC has been exposed for what it truly is: not a proper scientific body but an advocacy group, ready to stop at nothing in hijacking the prestige of science for its cause. But little of this might be guessed from the Inter-Academy report (jointly commissioned by Dr Pachauri himself and Ban Ki-Moon, the UN's Secretary General). Even if Dr Pachauri is forced to resign at a UN meeting in Korea next month, as seems possible, he will merely have been thrown off the sledge so that the all-important cause can survive.

Yet the IPCC is the body on whose authority our Parliament voted for the Climate Change Act, passed all but unanimously two years ago. This will land us, on the Government's own figures, with by far the biggest bill we have ever faced: up to £18 billion every year for the next 40 years – £734 billion in all – in order to cut our CO2 emissions by 80 per cent, something impossible to achieve except by closing down virtually all our industrial economy.

On the same authority, the rest of the world is being told that it must take similar steps, to avert a catastrophe dreamed up and promoted by no one more than those joint winners of the 2007 Nobel Peace Prize, Al Gore and the IPCC. Does this not all add up to the most bizarre and outrageous scandal in the history of the world?