Michael Mann says hockey stick should not have become 'climate change icon'

(The Telegraph)

The scientist behind the controversial 'hockey stick' graph has said it was 'somewhat misplaced' to make his work an 'icon of the climate change debate'. Professor Michael Mann plotted a graph in the late 1990s that showed global temperatures for the last 1,000 years. It showed a sharp rise in temperature over the last 100 years as man made carbon emissions also increased, creating the shape of a hockey stick. The graph was used by Al Gore in his film 'An Inconvenient Truth' and was cited by the United Nations body the Intergovernmental Panel on Climate Change (IPCC) as evidence of the link between fossil fuel use and global warming.

But the graph was questioned by sceptics who pointed out that is it impossible to know for certain the global temperature going back beyond modern times because there were no accurate readings. The issue became a central argument in the climate change debate and was dragged into the 'climategate' scandal, as the sceptics accused Prof Mann and his supporters of exaggerating the extent of global warming. However, 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.

In a BBC Panorama programme, scientists from both sides of the debate agree that global warming is happening and it is at least partly caused by mankind. But they differ on how much the recent rise in temperature has been caused by man made emissions and what will happen in the future. Professor John Christy, an atmospheric scientist from the University of Huntsville in Alabama, said just a quarter of the current warming is caused by man made emissions. He said that 10 to 30 per cent of scientists agree with him and are fairly sceptical about the extent of man made global warming.

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