The DailyMail explains why the Climategate scandal is real, and why nobody should trust adjusted data from the world’s leading climate research centers after this.

The claim was both simple and terrifying: that temperatures on planet Earth are now ‘likely the highest in at least the past 1,300 years’.

As its authors from the United Nations Intergovernmental Panel on Climate Change (IPCC) must have expected, it made headlines around the world.

Yet some of the scientists who helped to draft it, The Mail on Sunday can reveal, harboured uncomfortable doubts.

In the words of one, David Rind from the US space agency Nasa, it ‘looks like there were years around 1000AD that could have been just as warm’.

Keith Briffa from the University of East Anglia’s Climatic Research Unit (CRU), which plays a key role in forming IPCC assessments, urged caution, warning that when it came to historical climate records, there was no new data, only the ‘same old evidence’ that had been around for years.

‘Let us not try to over-egg the pudding,’ he wrote in an email to an IPCC colleague in September 2006.

‘True, there have been many different techniques used to aggregate and scale data – but the efficacy of these is still far from established.’

But when the ‘warmest for 1,300 years’ claim was published in 2007 in the IPCC’s fourth report, the doubters kept silent. …

some suggest that the ‘medieval warm period’, the 350-year era that started around 1000, when red wine grapes flourished in southern England and the Vikings tilled now-frozen farms in Greenland, was considerably warmer than even 1998.

Of course, this is inconvenient to climate change believers because there were no cars or factories pumping out greenhouse gases in 1000AD – yet the Earth still warmed.

Some tree-ring data eliminates the medieval warmth altogether, while others reflect it. In September 1999, Jones’s IPCC colleague Michael Mann of Penn State University in America – who is now also the subject of an official investigation –was working with Jones on the hockey stick. As they debated which data to use, they discussed a long tree-ring analysis carried out by Keith Briffa.

Briffa knew exactly why they wanted it, writing in an email on September 22: ‘I know there is pressure to present a nice tidy story as regards “apparent unprecedented warming in a thousand years or more”.’ But his conscience was troubled. ‘In reality the situation is not quite so simple – I believe that the recent warmth was probably matched about 1,000 years ago.’

Another British scientist – Chris Folland of the Met Office’s Hadley Centre – wrote the same day that using Briffa’s data might be awkward, because it suggested the past was too warm. This, he lamented, ‘dilutes the message rather significantly’.

Over the next few days, Briffa, Jones, Folland and Mann emailed each other furiously. Mann was fearful that if Briffa’s trees made the IPCC diagram, ‘the sceptics [would] have a field day casting doubt on our ability to understand the factors that influence these estimates and, thus, can undermine faith [in them] – I don’t think that doubt is scientifically justified, and I’d hate to be the one to have to give it fodder!’

Finally, Briffa changed the way he computed his data and submitted a revised version. This brought his work into line for earlier centuries, and ‘cooled’ them significantly. But alas, it created another, potentially even more serious, problem.

According to his tree rings, the period since 1960 had not seen a steep rise in temperature, as actual temperature readings showed – but a large and steady decline, so calling into question the accuracy of the earlier data derived from tree rings.

This is the context in which, seven

weeks later, Jones presented his ‘trick’ – as simple as it was deceptive.

All he had to do was cut off Briffa’s inconvenient data at the point where the decline started, in 1961, and replace it with actual temperature readings, which showed an increase.

On the hockey stick graph, his line is abruptly terminated – but the end of the line is obscured by the other lines.

‘Any scientist ought to know that you just can’t mix and match proxy and actual data,’ said Philip Stott, emeritus professor of biogeography at London’s School of Oriental and African Studies.

‘They’re apples and oranges. Yet that’s exactly what he did.’

Read the whole thing, which includes accounts of climate change activists successfully strongarming the press into altering news reports and which reports that the Russian State Security Service (FSB) has denied responsibility for the leaked emails.