Climate deniers’ assault on the science of global warming is roundly dispatched and shown for the corporate, ideological fraud that it is, by the climate scientist Michael Mann, finds Elaine Graham-Leigh

Michael E Mann, The Hockey Stick and the Climate Wars. Dispatches from the Front Lines, (Columbia University Press 2012), xvi, 395pp.

In November 2009, thousands of emails between climate scientists were hacked from the servers of the Climate Research Unit (CRU) at the University of East Anglia (UEA) and the choicest released onto the internet. They seemed to show the scientists falsifying their findings, hiding data which suggested that global warming might be a natural rather than an anthropogenic phenomenon, conspiring to keep sceptical scientific papers out of respected journals because it challenged their ideas, and doing their best to prevent concerned, independent researchers from checking their conclusions, even to the extent of denying legally-binding Freedom of Information requests. Following on from ‘Climategate’, as it was called in the media, came ‘Glaciergate’; the discovery that the recent Intergovernmental Panel on Climate Change (IPCC) report had made a mistake when it claimed that the Himalayan glaciers would have disappeared by 2035; it should have been 2350.

The timing of the hack was clearly not coincidental, coming as it did on the eve of the International Climate Summit in Copenhagen, a time when media attention to climate change, and campaigns for action on climate change, were at their peak. The effect was to pull climate change denial (either that it was happening at all, or that it was caused by human activity) back from the lunatic fringe and present it again as a serious challenge to which climate campaigners had to pay attention. Coupled with the failure of the Copenhagen summit to reach an agreement on a post-Kyoto treaty on emissions, Climategate added to an atmosphere of demoralisation in the movement.

The media coverage of Climategate

The response of the mainstream media, including outlets like the Guardian which had been generally responsible on climate change issues, to the hacked emails was disappointing but perhaps unsurprising. As David Adam, the Guardian’s environment editor, explained to a meeting on the resurgence of climate change denial organised by the Campaign against Climate Change in April 2010,[i] the media had had years of the story on climate change being its reality and the seriousness of the threat. If they now embraced the idea that it was all a scientific con, this was simply because the new story is always more newsworthy than the old.

To be fair, the Guardian did not quite go as far as to argue that human activity was not causing climate change. Nevertheless, the reporting of the Climategate crisis, in particular the major pieces by Fred Pearce, was unsympathetic to the scientists under attack, seeming to conclude that the scientists had misused data, suppressed contrary arguments and conspired to deny FOI requests. George Monbiot, for his part, concluded in his Guardian columns that Phil Jones, the head of the CRU at UEA, should resign, and that some of the data referred to in the emails should be re-examined.[ii] He apologised for this in 2010, when Jones was cleared of misconduct by the Russell Inquiry into the affair, but even then commented that by reacting so defensively, the scientists at the unit kept this fake scandal alive.[iii] The overriding impression from reading the Guardian’s coverage was that, while anthropogenic global warming was in no way destroyed as a theory, some conclusions had been overstated and some climate scientists had been shown to be, if not quite the villains climate change deniers claimed they were, nonetheless pretty flawed.

Much of this was disputed by the climate scientists involved,[iv] and Fred Pearce’s book on Climategate, The Climate Files. The Battle for the Truth about Global Warming (Guardian books 2010), seems to have taken some of these corrections on board. However, the impression that the scientists were the authors of many of their own troubles remains, as does the notion that some of those challenging the climate scientists (in particular Stephen McIntyre, a researcher, blogger and filer of FOI requests) could be seen as fighters to liberate data from the cosy, elitist club in which the climate scientists existed. Pearce concludes that ‘open science’, in which anyone could participate, as opposed to the closed, traditional science conducted through peer-reviewed papers in scientific journals, is now a reality. The take-away from Pearce’s work on Climategate is that the model of climate science which the scientists believed they were defending is irretrievably discredited, and that it is the scientists’ own faults.

Enter Michael Mann

This is where Michael Mann comes in. Mann was one of the scientists in the centre of the Climategate storm. He was not at the CRU, but as a climate researcher since the 1990s he was a participant in many of the hacked email exchanges. As one of the authors of the famous ‘hockey stick’ graph of global temperatures since 1400, showing a straight ‘handle’ until the rapid rise (the ‘blade’) in the twentieth century, he was no stranger to attacks from climate change deniers. This book sets out how he has been facing them for most of his career.

In Pearce’s account, Mann appears as a controversial figure, getting into arguments with other scientists about different versions of the hockey stick graph,[v] and being at best ‘honest if hotheaded’ in dealing with attacks from deniers.[vi] Pearce described Mann as ‘a young man in a hurry [in c.2000], a fiery character who made enemies and could sometimes intimidate his friends. He hasn’t changed a lot. His ability to dominate a swathe of scientific debate almost by the force of his personality is troubling. He has sometimes lacked friends or colleagues able to rein in either his impetuosity or his temper.’[vii] While Pearce does defend the validity of the hockey stick graph, his work nevertheless gives the impression that it was flawed research.[viii] This is more stringent personal and professional criticism than is levelled at the other scientists, arguably even including Phil Jones, the head of the CRU, so Mann’s response to the Climategate controversy was always going to be interesting.

Given Mann’s reputation, The Hockey Stick and the Climate Wars should have been an intemperate tirade, but in fact it is remarkably calm and measured. It is also a fascinating discussion of the development of the science of climate change, and of why Mann feels that defending that science in the face of deliberate attacks from climate change deniers is so important.

Siberian trees and Greenland farms

Along the way, Mann provides succinct defences of the science in a number of denial cause célèbres, such as the Yamal tree ring controversy, which was going on in late 2009 when the Climategate emails appeared. The point at issue was a temperature reconstruction from the tree rings of the Yamal region in Siberia. In 2009, Stephen McIntyre accused Keith Briffa, one of the scientists behind the reconstruction, of cherry-picking the trees used, in order to show that modern warming is without precedent in the last millennium. The accusations were picked up by other climate change deniers, with some claiming that it called global warming into serious question.

Mann points out that McIntyre had reached this conclusion by cherry-picking himself, by ‘deleting tree ring records of Briffa’s he didn’t seem to like, and replacing them with other tree ring data he had found on the Internet, which were inappropriate for use in a long-term temperature reconstruction’ (p.198). In any case, even if McIntyre was right about this reconstruction, it hardly demolished all climate science in the way that climate change deniers claimed. Temperature reconstructions are unanimous in concluding that modern temperatures are higher than at any point in the last millennium or two, whether or not they include data from these tree rings. That the claims about the importance of the tree ring data are far-fetched is shown by the fact that some deniers even claim that the tree rings undermine another famous graph, used in Al Gore’s film An Inconvenient Truth, which actually shows increases in atmospheric CO2, not temperatures.

Mann, as you might expect, presents a robust defence of the hockey stick, showing how accusations that he had selected data deliberately to achieve the hockey stick shape, are based on a misunderstanding of the factor analysis techniques involved in using temperature reconstructions. He also explains why the graph is quite so controversial to climate change deniers. The rise in temperatures in the twentieth century is undeniable, recorded as it is by temperature monitoring stations around the world. The nearest the deniers can get to impugn this data is by the argument that the stations are affected by urbanisation, so that they are recording the effects of urban heat islands rather than a general warming in temperature. While this could be true for some stations – and Phil Jones was attacked in Climategate over the location of some stations whose records he used for a paper written in the 1990s – it clearly cannot be true for all of them. It would be difficult even for climate change deniers to argue credibly that there is no warming recorded. The focus therefore has been on showing that while warming is occurring, it is natural and not caused by human activity, mostly by demonstrating the existence of a recent precedent.

This, to deniers, is the Medieval Warm Period, a period of higher temperatures from around 1100-1400, which enabled English wine, farming in Greenland and so on. The deniers were therefore critical of the original hockey stick graph because it went back only to 1400, in their view to avoid the medieval high temperatures, and subsequent graphs which have used proxy temperature reconstructions to go further back have been condemned as manipulating data to retain the hockey stick shape. Mann, who began his career researching natural climate variation, points out that while temperatures in northern Europe in the central Middle Ages may have been equivalent to temperatures around 1950, temperatures by the end of the twentieth century were higher. The Medieval Warm Period also now appears to have been a more complex phenomenon than simply three centuries of warmth, with some areas, including the Mediterranean and parts of the USA, showing no increased temperatures at all.

Some of the arguments from climate change deniers about the medieval climate anomaly are astonishingly ill-informed. One sceptic claimed, for example, to be able to show that modern temperatures have not risen above medieval temperatures, but it turned out that they were only looking at modern temperatures up to 1950. They had not realised that by convention the ‘present’ in the common dating formulation ‘X years Before Present’ is always 1950. Mann’s account makes clear that while the Medieval Warm Period may not be completely understood, it does not offer any comfort that current warming is just part of natural climate variation.

Mann presents an effective defence of his science and is convincing on questions over the hockey stick, for example over the use of twentieth-century as opposed to the long-term average temperature as the baseline, which he agrees with hindsight might not have been the best choice, but would not have affected the shape of the graph. The most serious questions raised by Climategate were however not about the content of the climate science but about the way it was conducted; not so much about the science, but the scientists.

Open science?

To commentators like Pearce and Monbiot, the emails discussing how scientists could exert pressure on and sometimes boycott journals which had published deniers’ articles seemed to demonstrate how the climate scientists were operating as a privileged, unaccountable clique. In Mann’s account, these become more understandable, such as the resignations from the journal Climate Research after it published a paper which attempted to construct a medieval warm period equivalent to modern warming with ‘significant methodological flaws’ (p.120). For Mann, it is proper for climate scientists to defend the standards of climate science journals, particularly when the fact of publication in these journals gives denier articles a spurious air of scientific authority.

Mann’s account of the pressure he has been put under throughout his career from climate change deniers, including in 2005 a demand from the Republican chair of the subcommittee on House of Representatives investigations for extensive material about his entire scientific career, also casts Phil Jones and others’ exasperation with Freedom of Information requests in a sympathetic light. In demanding to see large amounts of correspondence, data and calculations, the deniers putting the requests might argue that they were simply trying to check the scientists’ conclusions, but they were certainly demanding a large amount of scientists’ time to assemble all of this material. As Mann makes clear, much of the raw data from which the scientists were constructing their proxy temperature reconstructions is publicly available, or collected by separate bodies like the Met Office. What the FOI requests were after were the scientists’ workings, in the hope of finding, or being able to allege that they had found mistakes.

By the end of Mann’s account, it’s difficult not to applaud scientist Ben Santer’s response to Steven McIntyre’s request for his data: ‘I gather your intent is to ‘audit’ the findings of our recently-published paper in the International Journal of Climateology. You are of course free to do so … In summary, you have access to all the raw information that you require in order to determine whether the conclusions reached in our IJoC paper are sound or unsound. I see no reason why I should do your work for you, and provide you with derived quantities … which you can easily compute yourself.’ [ix] The danger of diversion by climate change deniers from real work into endless debates about non-existent problems with climate science is clearly real, for climate scientists and for campaigners on climate change.

For Fred Pearce, Santer’s release of his calculations was a ‘victory for openness’, a sign of how Climategate was democratising scientific practice.[x] It is clear however that Santer was acting more to protect himself from bullying from climate change deniers than because he had been converted to the value of open science: ‘I wanted to continue with my scientific research. I did not want to spend all of my available time and energy responding to harassment incited by Mr. McIntyre’s blog.’ [xi] What this highlights is that ‘open science’ sounds like an unarguable good, but it depends on what it means in practice. Mann’s account of Climategate suggests that a situation in which the conclusions of anyone with a blog were held to be of equal weight as those of experienced climate scientists would not be good either for public debate about climate change or for our understanding of how the climate works.

To conclude that the result of Climategate would or should be more openness is to argue that the barriers to wide general practice of climate science are the gate-keeping practices of climate scientists: hogging raw data, denying access to peer-reviewed journals and all the rest of it. What Mann reveals, with as much clarity as possible, is that this is not what prevents mass participation. Much of the raw data from which climate scientists work is generally available, or could be obtained by genuine researchers, and the hacked emails did not reveal any instances of submissions to journals being censored on the basis of who wrote them, and their lack of a position at an academic institution. The real barrier to climate science for everyone is that this stuff is just hard. Reconstructing a set of proxy data for climatic conditions for a thousand years ago, for example, is difficult, technical work which requires training and experience to get right. It’s not something that anyone can knock up with an afternoon on the iPad. If we are concerned that climate science is an elitist clique, (a concern not really borne out by Mann’s account) then the solution is to fight against student tuition fees and other barriers to wide participation in the training which makes the practice of climate science possible. The answer is not to insist that the professional expertise which climate scientists have achieved is unnecessary.

Michael Mann is sceptical that the bloggers of climate change denial are representative of a real popular distrust of climate science, suggesting that many may turn out to be ‘astroturf’ campaigners, funded by businesses whose bottom lines would be threatened by moves to reduce carbon emissions. If he is correct, this would be the real undemocratic practice in the climate science arena: not the disinclination of climate scientists to waste their time on climate change deniers, but the cynical attempts of big business to subvert the science to protect their profits.






[v] Fred Pearce, The Climate Files. The Battle for the Truth about Global Warming, (Guardian Books 2010), p.49.

[vi] ibid., p.100.

[vii] ibid., p.101.

[viii] ibid., p.102.

[ix] Santer’s email is published on McIntyre’s Climate Audit blog.



Elaine Graham-Leigh

Elaine has been an environmental campaigner for more than a decade. She speaks and writes widely on issues of climate change and social justice, and is a member of Counterfire. She is the author of A Diet of Austerity: Class, Food and Climate Change and Marx and the Climate CrisisHer sci-fi novel, The Caduca, is out now from The Conrad Press.