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Michael Mann

Once again legal action by climate change deniers/contrarian/cranks has failed. In the US attempts by the  American Tradition Institute, a climate change denial think tank, to obtain personal emails and documents from  the University of Virginia. These documents belong to well known climate scientist Michael Mann and the court action was part of a fishing expedition by climate change deniers to repeat the “climategate” scandal. To obtain emails from which cherry-picked material could be used in the ongoing campaign to discredit climate scientists. See University of Virginia prevails against climate science attack groupfor further information on this case.

But Michael Mann is certainly the scientist that the climate change deniers/contrarians/cranks love to hate. Just recently I was assured by a local climate change deniers/contrarian/crank that Michael Mann had been thoroughly discredited. That his so-called Hockey Stick image, which had appeared in the 2nd to last IPCC review (AR3) had been dropped from the most recent IPPC review (AR4). This local denier/contrarian/crank asserted, for example:

“You’re going to have to come up with someone other than Mann, to be taken seriously.”

“I don’t need to prove Mann wrong, plenty of far better people have already done that.”

“Mann has been so often deprecated he is without authority.”

“The Mann saga is over, even the IPCC has dropped Mann’s hockey stick graph.”

This attempt to discredit Mann and his work is a lie – but its not a new lie. It’s one I had dealt with almost three years ago in my post Climate change deniers’ tawdry manipulation of “hockey sticks”. I am repeating that post here, with slight amendments. Hopefully this will at least lead to some climate change sceptic who may have accepted that lie getting some of the real facts.

The “infamous, discredited” hockey stick

The charge is:

“Mann’s hockey stick has been thoroughly discredited and the IPCC has dropped it from its reports.”

But it’s simple enough to check the IPCC reports – they are on-line for all to see. If you do check you will find this figure below in the 2007 reports. The original data from Mann (MBH 1999) is included with, of course, more recent data. Here is the reference for anyone doubting my claim - Figure 6.10, page 467,  Chapter 6: Palaeoclimate,The Fourth Assessment Report (AR4), WG I The Physical Science Basis.

And far from this work being “thoroughly discredited” or abandoned, it has been expanded with more, recent, data. The graph below is from Mann’s 2008 paper (Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia).

National research Council report vindicates Mann

In this paper Mann was responding to suggestions made by the National Research Council in its report  Surface Temperature Reconstructions for the Last 2,000 Years. This thorough and rigorous investigation formed part of US House of Representatives Committee hearings on Mann’s “hockey stick” figure arising from criticisms made by climate change sceptics. It is very authoritative.

Anyone who has ever had their work reviewed knows that a reviewer worth their salt will always find your weaknesses and suggest amendments, even though they endorse your work. And climate changer deniers/contrarians/cranks have hunted out the criticisms, taken them out of context and are usually well versed in those cherry-picked quotes. They must be repeated ad nauseum in those unreliable books deniers rely on as sources. But the fact is the National Research Council report basically supported Mann’s findings:

“The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators, such as melting on ice caps and the retreat of glaciers around the world, which in many cases appear to be unprecedented during at least the last 2,000 years.”

In fact the NRC produced their own “hockey stick,” using more than just Mann’s data, in the report (see figure below):

Lord Monckton’s lies about the “hockey Stick”

These false assertions on the “hockey stick” graph are, unfortunately, very common. It’s one bit of mudslinging that has found purchase with most deniers repeating the lie. Even some sceptics believe the story.

Lord Mockton has been a prolific propagator of this lie. He even appears in the infamous “climategate” emails saying of the “hockey stick”: “the US National Academy of Sciences has described as having “a validation skill not significantly different from zero”. In plain English, this means the graph was rubbish.”

Problem is – search through the NRC report and you just won’t find those words (“a validation skill not significantly different from zero”). Nevertheless this allegation has been repeated innumerable numbers of times in conservative newspapers and websites. Some of these also claim that the IPCC had abandoned the data (see for example the policy Brief from the Commonwealth foundation – Climate & Penn State – demanding a McCarthyist-style investigation of Mann). But even Mockton acknowledges that the UN continues to use the defective graph.”

I guess it just makes a good story so these conservative sources tack it on. But  where is the integrity in that?

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See also:
Journalist thinks world climate-science publications are controlled by cabal
Analysis of stolen CRU emails by NZ blogger shows tawdry manipulation of facts – Poneke’s credibility now in tatters — Hot Topic

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