For the growing band of AGW “Sceptics” the following story is dynamite. And for those who do believe in Al Gore’s highly profitable myth about “Man-Made Global Warming”, it will no doubt feel as comfortable as the rectally inserted suicide bomb that put paid to an Al Qaeda operative earlier this week.

Now read on.

Those of you who saw An Inconvenient Truth may remember, if you weren’t asleep by that stage, the key scene where big green Al deploys his terrifying graph to show how totally screwed we all are by man-made global warming. This graph – known as the Hockey Stick Curve – purports to show rising global temperatures through the ages. In the part representing the late twentieth century it shoots up almost vertically. To emphasise his point that this is serious and that if we don’t act NOW we’re doomed, Al Gore – wearing a wry smile which says: “Sure folks, this is kinda funny. But don’t forget how serious it is too” – climbs on to a mini-lift in order to be able to reach the top of the chart. Cue consensual gasps from his parti pris audience.

Except that the graph – devised in 1998 by a US climatologist called Dr Michael Mann - is based on a huge lie, as Sceptics have been saying for quite some time. The first thing they noticed is that this “Hockey Stick” (based on tree ring data, one of the most accurate ways of recording how climate changes over the centuries) is that it seemed completely to omit the Medieval Warming Period.

According to Mann’s graph, the hottest period in modern history was NOT the generally balmy era between 900 and 1300 but the late 20th century. This led many sceptics, among them a Canadian mathematician named Steve McIntyre to smell a rat. He tried to replicate Mann’s tree ring work but was stymied by lack of data: ie the global community of climate-fear-promotion scientists closed ranks and refused to provide him with any information that might contradict their cause.

This is the point where British climate change scientists appear – and in a most unedifying light. As Christopher Booker has reported the Met Office, its Hadley Centre in Exeter and the Climate Research Unit (CRU) at University of East Anglia are among the primary drivers of global climate change alarmism. Their data has formed the basis for the IPCC’s “we’re all doomed” reports; their scientists – among them Professor Phil Jones and tree ring expert Professor Keith Briffa – have been doughty supporters of Mann’s Hockey Stick theory and of the computer models showing inexorably rising temperatures.

Hence their misleading predictions of that “barbecue summer” we never had. As Booker says: “Part of the reason why the Met Office has made such a mess of its forecasts for Britain is that they are based on the same models which failed to predict the declining trend in world temperatures since 2001.

When McIntyre approached the Met Office and the CRU for more information they refused, claiming implausibly that it would damage Britain’s “international relations” with all the countries that supplied it. Later they went a step further and claimed the data had been mislaid.

And there McIntyre’s efforts to uncover the mystery of the Hockey Stick might have ended, had he not had a stroke of luck, as Chris Horner explains at Planet Gore.

“Years go by. McIntyre is still stymied trying to get access to the original source data so that he can replicate the Mann 1998 conclusion. In 2008 Mann publishes another paper in bolstering his tree ring claim due to all of the controversy surrounding it. A Mann co-author and source of tree ring data (Professor Keith Briffa of the Hadley UK Climate Research Unit) used one of the tree ring data series (Yamal in Russia) in a paper published in the Philosophical Transactions of the Royal Society in 2008, which has a strict data archiving policy. Thanks to that policy, Steve McIntyre fought and won access to that data just last week.”

When finally McIntyre plotted in a much larger and more representative range of samples than used those used by Briffa – though from exactly the same area – the results he got were startlingly different.

Have a look at the graph at Climate Audit (which broke the story and has been so inundated with hits that its server was almost overwhelmed) and see for yourself.

http://www.climateaudit.org/wp-content/uploads/2009/09/rcs_chronolo...

The scary red line shooting upwards is the one Al Gore, Michael Mann, Keith Briffa and their climate-fear-promotion chums would like you to believe in. The black one, heading downwards, represents scientific reality.

We “Global Warming Deniers” are often accused of ignoring the weight of scientific opinion. Well if the “science” on which they base their theories is as shoddy as Mann’s Hockey Stick, is it any wonder we think they’re talking cobblers?

Update: Friday 2 October. Since I posted this piece Keith Briffa has vehemently denied having “cherry picked” his data, explaining rather that this was the result of his having inherited a subset of tree ring data preselected by the Russians. For the latest on this complex story, I recommend a visit to Steve McIntyre’s Climate Audit site.

http://blogs.telegraph.co.uk/news/jamesdelingpole/100011716/how-the...