Tag Archives: Temperature record of the past 1000 years

A concise summary of climate change – science and politics

Here’s a relatively short (26 min) video of a lecture by Michael Mann. I think it gives a very concise and accurate picture of the current science of climate change and the political attacks on climate scientists (Mann calls this the scientization of politics).

via The Hockey Stick and the Climate Wars – Michael Mann Speaks at SOS 2012 on Vimeo.

From the video description:

Michael E. Mann- Director of the Earth System Science Center gives a very eye-opening presentation at the 2012 Sustainable Operations Summit. Mann’s presentation highlighted themes from his most recent book: The Hockey Stick and the Climate Wars: Dispatches from the Front Lines. In his talk, Mann discussed the “Hockey Stick,” a graph he created with his colleagues to depict changes in Earth’s temperature dating back to 1000 AD. The graph was featured in the Summary for Policy Makers portion of the 2001 report of the Intergovernmental Panel on Climate Change (IPCC) and became an icon in the debate over human-caused climate change. Mann told the story behind the Hockey Stick, using it as a vehicle for exploring broader issues regarding the role of skepticism in science and the relationship between science and politics.

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Another anti-science attack on Mann fails – but the lies continue

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


“Good faith” science – and its enemies

Book review: The Hockey Stick and the Climate Wars: Dispatches from the Front Lines by Michael E. Mann

Price: US$18.22; Kindle US$9.99; NZ$33.34
Hardcover: 384 pages
Publisher: Columbia University Press (March 6, 2012)
Language: English
ISBN-10: 023115254X
ISBN-13: 978-0231152549

Most readers have watched nature programmes hosted by David Attenborough. So you are familiar with scenes where predators will work together to target a single animal in a herd. If they can isolate it they will usually make a kill. If not they will go hungry.

You have seen it with Arctic wolves attacking oxen and African lions attacking zebras. Over recent years we have also seen it with politicians attacking climate scientists.

Michael Mann calls this the “Serengeti strategy:”

It “is a tried-and-true tactic of the climate change denial campaign. The climate change deniers isolate individual scientists just as predators on the Serengeti Plain of Africa hunt their prey: picking off vulnerable individuals from the rest of the herd.”

Mann is an authority on this phenomena – he has seen it from the inside, as a victim, for over a decade. Now he has written up his experiences, and the lessons drawn from them, in this new book appropriately called “The Hockey Stick and the Climate Wars.”

The “Hockey Stick”

In a sense Mann was a inadvertent victim of the climate denier campaign. His work had more to do with natural climate variation than human caused effects. As he puts it: “I felt that natural climate variability might be more important than some scientists thought. Indeed, it was that very assumption that motivated my Ph.D. research topic.” But in the process of researching the history of past climate changes, earth’s paleoclimate, he produced an “icon” of the climate change wars – the “Hockey Stick.” This research was included in the 2001 IPCC Report – and the “Hockey Stick” image, a record of the global and hemispheric temperature record over the last  600 years (in its original form), made it into the Summary for policy makers.

The personalisation of attacks on Mann over the “Hockey Stick” was also misplaced because he was not making any claim about human causes of global warming:

” I was always very careful not to claim that our work could firmly establish a human role in the warming. To draw such a conclusion based on our work alone would necessarily buy into the classic logical fallacy of “correlation without causation.” We had established correlation—the anomalous warming that we documented coincided with the human-caused ramp-up in greenhouse gas concentrations—but we hadn’t established causality.”

Mann’s record was based on proxy measurements (estimations of temperature from tree rings, ice cores, etc.), as well as, for more recent times, instrumental measurements. It did show changes attributable to natural events – which you would think would make the deniers happy. But it also showed very graphically, the global warming that has occurred over the last half century. This appeared to be quite anomalous over the last 1000 years. In fact, it was most likely to be greater than that which had occurred during the so-called “Medieval Warm Period.” The deniers could not forgive Mann for that finding – they had worked hard to convey the impression that global temperatures were actually higher then than they are today. (To some extent deniers have relied on regional temperature estimates – Mann’s estimate are for hemispherical and global temperatures). The iconic “Hockey Stick” threatened the climate denier’s icon – The Medieval Warm Period!

The McKittrick/McIntyre attack

The book describes controversy around The Hockey Stick – some of it based on genuine science, some derived from contrarian and denier attacks often financed by the fossil fuel industry.

One attack, much quoted by climate change deniers and contrarians, is that of  right-wing economist Ross McKittrick and Stephen McIntyre (a self described “semi-retired minerals consultant” with close ties to the energy industry). Published in a then controversial journal Energy and Environment it claimed Mann  had made fundamental mistakes in his statistical procedures. Their own analysis could not reproduce the “blade” of the hockey stick – that is no recent warming could be found in the data.

As Mann explained, this was a result of their own faulty analysis and their mistake was pointed out in subsequent published and refereed replies. Inevitably Mann’s description of the statistical analysis is technical and may be beyond some readers. But he has worked hard to make his description understandable and it is worth persisting because so much undeserved credit has been placed on McKintrick and MacIntyre’s paper. The scientific rejection of their work has of course not stopped the deniers who till this day claim that the M&M paper had discredited The Hockey Stick.

This work was used to denounce Mann’s work in the US House of Representatives. Republic Joe Barton, then head of the House Energy and Commerce Committee, launched a specific investigation of Mann’s work. (Joe Barton became well known five years later for his infamous apology to British petroleum over the fact that the Obama administration was holding it accountable for the oils spill the the Gulf of Mexico).

 Mann describes the political manoeuvring that went on around this House investigation. Particularly useful is his description of the Wegman report, set up by Barton to vindicate the work of McKintrick and McIntyre. It is constantly quoted by climate change contrarians – despite the fact that this report, and other work by Wegman and his students, has been criticised for plagiarism.

However Barton got a lot of political flack for his anti-science manoeuvring and Sherwood Boehlert, Republican chair of the Science Committee, commissioned the US National Academy of science to review the science behind the Hockey Stick. Their authoritative report Surface Temperature Reconstructions for the Last 2,000 Years largely vindicated Mann. Of course, have a read of climate denial books like Ian Wishart’s Air Con and you will find no mention of National Academy Report – only the Wegman’s report is used to perpetuate the lie that Man’s work was found  faulty (see my review of Wishart’s book – Alarmist con).

And, as Mann points out his work has been validated by over a dozen other independent reconstructions of the paleoclimate temperature record.

I have previously discussed the way climate change deniers have lied about the Hockey Stick in Climate change deniers’ tawdry manipulation of “hockey sticks”.

“Climategate” emails

Several times in this book Mann outlines the scientific approach to understanding reality. He uses the term “good faith science” – I think it is rather descriptive in this situation. Scientists welcome good faith criticism – doubt and scepticism are central to the scientific process. But the “scepticism” and attacks on climate science by vested interests and contrarians is quite different. It is not a “good faith” criticism. It is motivated, distorted, cherry picked and very often dishonest criticism. The so-called “climategate scandal” typifies this approach. Stolen emails between climate scientists were cherry picked  in an attempt to discredit the science.

The climate denier frenzy, and the investigations which cleared the scientists involved of any wrong-doing are now history. But scientists in general were rather taken aback by all this. They started to pay attention to these and other anti-science campaigns and debated the need to be proactive in communicating their science and combating the distortions and attacks.

Cuccinelli witchhunt

I think the recent legal attempts by Virginia Attorney General, Kenneth Cuccinelli, to get correspondence and emails relating to Mann and his research are one of the worst acts of the climate denial movement. Because it smacks of McCarthyism. Cuccinelli was on a “fishing trip” – which required him to assert that Mann was guilty of fraud – without any evidence.  Like the McCarthy persecution this sort of mud sticks and its aim was obviously to intimidate scientists.

After a prolonged legal battle the Virginia Supreme Court has now ruled that Mann’s documents cannot be subpoenaed by Cuccinelli (see The chickens are hatching). But his attempted precipitated action from scientific bodies in  defence of Mann and other scientists victimised by such persecution.

A positive conclusion

This book concentrates on Mann’s story. His research and the resulting attacks and persecution by the climate change denial political machine. It has valuable information debunking the denier mythology created around the “Hockey Stick.” There are also interesting background details clarify things like the strange position taken by the Institute of Physics at the UK parliamentary investigation of the climategate email issue (see Institute of Physics in hot seat).

But don’t expect new information on the funding of the climate denial network and links with the fossil fuel industry and politicians. Mann relies on the excellent  research of others here – and references the books Doubt is Their Product by David Michaels and Merchants of Doubt, by Oreskes and Conway.

Apart from the valuable background history the book provides I think its main value is the positive spin it provides, particularly in the final chapters. These discuss the reaction of climate scientists, and scientists in general, to the attacks on the science and the profession. The final straw appears to have come with the McCarthyist political attacks on Mann and other climate scientists. As Mann describes it – the bear has awoken. Scientists are finally recognising they cannot continue to ignore these attacks,. They are starting to fight back.

“The attacks against climate scientists by politicians like Senator James Inhofe and Virginia Attorney General Ken Cuccinelli were now being identified by prominent media outlets for the witch hunts they were. . . . I believe that the climategate attacks represented a turning point for my fellow climate scientist colleagues and how they viewed their role in the public debate. These latest attacks will fade from memory, and new ones will undoubtedly be launched to take their place. But I suspect that the change in heart among climate scientists regarding their role in the debate will be enduring.”

The book is also a good read. For anyone interested in the subject, with a bit of background knowledge, Mann’s reiteration of the public events, together with his knowledge of what was going on behind the scenes, makes the book a real page turner.

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In the front lines of the “climate wars”

Here’s another book to look out for – The Hockey Stick and the Climate Wars: Dispatches from the Front Lines. It will be published at the beginning of March .

The author, Michael Mann,  has been a central figure in the “climate wars.” His research into paleoclimate has been a particular target for climate sceptics/contrarians/deniers. And despite their claims that his work was discredited it has in fact been supported and replicated by other climate scientists. It also received endorsement from the The National Research Council of the US National Academies. (See and download Surface Temperature Reconstructions for the Last 2,000 Years (2006) )

Publisher’s description of book

This is how the publisher describes the book:

“In its 2001 report on global climate, the Intergovernmental Panel on Climate Change of the United Nations prominently featured the “Hockey Stick,” a chart showing global temperature data over the past one thousand years. The Hockey Stick demonstrated that temperature had risen with the increase in industrialization and use of fossil fuels. The inescapable conclusion was that worldwide human activity since the industrial age had raised CO2 levels, trapping greenhouse gases in the atmosphere and warming the planet.

“The Hockey Stick became a central icon in the “climate wars,” and well-funded science deniers immediately attacked the chart and the scientists responsible for it. Yet the controversy has had little to do with the depicted temperature rise and much more with the perceived threat the graph posed to those who oppose governmental regulation and other restraints to protect our environment and planet. Michael E. Mann, lead author of the original paper in which the Hockey Stick first appeared, shares the real story of the science and politics behind this controversy. He introduces key figures in the oil and energy industries, and the media front groups who do their bidding in sometimes slick, bare-knuckled ways to cast doubt on the science. Mann concludes with an account of the “Climategate” scandal, the 2009 hacking of climate scientists’ emails. Throughout, Mann reveals the role of science deniers, abetted by an uninformed media, in once again diverting attention away from one of the central scientific and policy issues of our time.”

McCarthyist attacks on science

Henry Waxman, Democratic member of the U.S. House of Representatives, former chairman of the House Energy and Commerce Committee said this of Michael Mann:

“As one of the nation’s leading climate researchers, no one has felt the brunt of the attacks from politicians and the fossil fuel industry more than Michael Mann. This is his personal account from the center of the maelstrom, documenting the lies and distortions about his work and his heroic efforts to stand up for scientific truth.”

Mann has certainly been one of the most high profile victim of the current McCarthyist attacks on climate science and scientists. This still continues. But he is not the only target. This has become such a problem that A Legal Defense Fund for Climate Scientists has been set up. You can find out more about the fund at its new web site and its recent press release –  Climate Science Legal Defense Fund Gets New Backing. As the press release says:

“The fund is designed to help scientists like Professor Michael Mann cope with the legal fees that stack up in fighting attempts by climate-skeptic groups to gain access to private emails and other correspondence through lawsuits and Freedom of Information Act requests at their public universities.”

The fund will also:

“Educate researchers about their legal rights and responsibilities on issues surrounding their work;

Serve as a clearinghouse for information related to legal actions taken against scientists; and

Recruit and assist lawyers representing these scientists.”

Another important  book to look forward to.