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Maybe Michael Mann is seeing the writing on the wall because it looks as if he is taking a giant step backwards away from his invention, the climate change hockey stick. The Penn State professor now says his  hockey stick should not have become ‘climate change icon’ and it was ‘somewhat misplaced’ to make his work an ‘icon of the climate change debate’.

The climate change hockey stick is a graph created a little over decade ago that was supposed to show global temperatures for the last 1,000 years. The graph plots out  a sharp rise in temperature over the last 100 years as man made carbon emissions increased, creating the shape of a hockey stick. The problem is that Mann’s data has been proven bogus many time over.

speaking to the BBC recently, Prof Mann, a climatologist at Pennsylvania State University, said he had always made clear there were “uncertainties” in his work.

“I always thought it was somewhat misplaced to make it a central icon of the climate change debate,” he said.

Mann’s claim that he never wanted his hockey stick belies the truth.  At the time the graph was developed, there were actually two graphs being developed. Scientists didn’t want to use the Mann version because they weren’t sure about his numbers.  Mann insisted that his version was the one that should be used because it looked more dramatic.

According to uncovered documents, Mann and his team wanted to present a simple story for policy makers, Others wanted scrupulous honesty about uncertainties contained in Mann’s chart.The IPCC’s core job is to present a “consensus” on the science, but in this critical case there was no easy consensus.

The tensions were summed up in an email sent on 22 September 1999 by Met Office scientist Chris Folland, in which he alerted key researchers that a diagram of temperature change over the past thousand years “is a clear favourite for the policy makers’ summary

But there were two competing graphs – Mann’s hockey stick and another, by Jones, Briffa and others. Mann’s graph was clearly the more compelling image of man-made climate change. The other “dilutes the message rather significantly,” said Folland. “We want the truth. Mike [Mann] thinks it lies nearer his result.” Folland noted that “this is probably the most important issue to resolve in chapter 2 at present.”

The evidence shows that while people were suspicious of Michael Mann’s research, Mann wanted his graph used because it more compelling. His “walking back” from the graph has more to do with the fact that it has been proven bogus, than any previous desire that it “not become an icon.”

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