[Reminder for locals: NCAR MESA Lab, 3PM Friday, talk by Hans von Storch and subsequent panel on hockey stick issues!!]

A while back we commented that here at Prometheus we don’t do hockey sticks. Well, now we do. What follows is an unbearably long post on issues associated with the Hockey Stick. I am sure that it will be of interest only to those with a deep interest in this issue. For others, move along, nothing to see here …

The “hockey stick” refers to a graph (see figure b here and figure 2.20 here) which shows the results of a reconstruction of global average temperature for 1,000 years. The hockey stick has been the subject of an intensifying debate that now has reach comic/tragic proportions. Last week Congressman Joe Barton (R-TX), Chair of the House Energy and Commerce Committee sent letters to three scientists who authored the hockey stick studies, as well as the head of the National Science Foundation and the head of the IPCC, asking for a range of information.

From the perspective of climate science or policy Rep. Barton’s inquiry is simply inane. There will be little insight gained on climate or how we might improve policies on climate change through his “investigation.” As Congressman Henry Waxman (D-CA) has written in response to Rep. Barton, “These letters do not appear to be a serious attempt to understand the science of global warming. Some might interpret them as a transparent effort to bully and harrass climate change experts who have reached conclusions with which you disagree…. If the Committee indeed has a genuine interest in the science of global warming, you should withdraw these letters and instead schedule a long-overdue Committee hearing on climate change.”


Of course, it is doubtful that Rep. Barton’s Committee (on Energy and Commerce, I remind you) actually has any real interest in the science of climate change, except as a tool of tactical advantage in the continuing political battle over global warming. Rep. Barton and others opposed to action on climate change will continue to gnaw at the hockey stick like a dog on a bone so long as they perceive that it confers some political benefits. The great irony here is that in many instances the supporters of the hockey stick have often been their own worst enemies and fed the flames of this debate, which now threatens the integrity of all of climate science, and to turn all of climate science into climate politics. The debate also consumes a lot of scarce attention on the climate issue – attention that would be better devoted to debates about policy options.

Can the climate science community do anything about this situation? To understand how the hockey stick issue might be de-emphasized and moved beyond requires understanding the debate and its political context.

The hockey stick is a symbol. It represents much more than the results of two studies by Mann et al.; it represents the integrity of the IPCC, claims of a human influence on climate, demands for action on climate change, and no doubt other things as well. Consider the range of emotions and issues evoked when you think of other examples of symbols that condense a great deal meaning – for example, the United States flag, a swastika, or a religious cross. Symbols serve as a sort of short cut when we try to make sense of a complicated world. The manipulation of symbols is consequently a high political art. As political scientist Murray Edelman wrote in his book The Symbolic Uses of Politics (at pp. 31-32), “It is characteristic of large numbers of people in our society that they see and think in terms of stereotypes, personalization, and oversimplifications, that they cannot recognize or tolerate ambiguous and complex situations, and that they accordingly respond to symbols that oversimplify and distort.” It is important to recognize that symbols take on meaning far beyond the “reality” referred to by the symbol. Edelman writes, “… reality can be irrelevant for persons very strongly committed to an emotionally satisfying symbol… commitment to a belief is likely to be strengthened and reaffirmed in the face of clear disproof of its validity where there is a strong prior commitment … and where there is continuing social support of the commitment by others …” This apparent disconnect helps to explain (for both sides) why the larger symbolic and political debate over the hockey stick won’t be resolved by completing claims to factual correctness made by either side.

The hockey stick became a symbol because of the IPCC. In its 2001 report of Working Group 1 the Summary for Policymakers (SPM) included only 5 graphs. The entire report has probably 100 graphs (perhaps more, I have not counted). So the IPCC was in effect saying, “We’ve looked carefully at all of the evidence of climate change and from all of those studies and reports the best example that we’d like to share with you policy makers of changes in the earth’s climate is represented with this graph.” Of course, most Prometheus readers will know that the case for a human influence on climate is well established through multiple independent lines of research. But remember, we are talking about the hockey stick as a symbol. For the uninformed outsider reading the SPM, none of this richness and context would be apparent. The IPCC offers that not only is the hockey stick the best example that it can provide of climate change, but that it has been peer-reviewed at a level more stringent than normal journal articles. Representative of such claims, the scientists at RealClimate have written, “IPCC reports undergo several additional reviews and revisions involving a large number of independent referees. Thus, the IPCC reports undergo a more stringent review process than common papers in the scientific literature.” The hockey stick is thus a powerful political symbol in the climate debate.

With the hockey stick established as a symbol it is to be expected that it attracted both support and opposition as a tactic of politics. Those advocating particular actions on climate change would, for example, prominently display the hockey stick in talks, no doubt referring to its endorsement by the IPCC. Those opposed to action on climate change (or just generally skeptical) would be drawn to the hockey stick target number one in debate over climate change. The hockey stick is debated because it is a key symbol of a an intense and meaningful political debate.

How should an outsider make sense of the hockey stick debate? The debate is technical, and includes references to all sorts of obscure statistical techniques and paleoclimate proxy methodologies, and thus may seem impenetrable. But the technical debate may be less important than the proponents on either side might claim.

The technical debate centers on the authors of the original two hockey stick studies referenced by the IPCC, Mann, Bradley and Hughes (MBH) and their primary antagonists, McIntyre and McKitrick (MM). Mann et al. often make their case at www.realclimate.org and McIntyre (and sometimes McKitrick) make their case at www.climateaudit.org.

There are several characterizations of this debate readily available in the blogosphere. One claims that MM are tools of the oil and gas industry, ready to spread misinformation and lies in order to discredit the noble truth-seeking scientists whose work is beyond reproach, all in hopes of derailing action on climate change. Another characterization holds that MM are the proverbial Davids up against the Goliaths of the IPCC and the global warming juggernaut intent on remaking the world in its environmentally-correct image.

While such stories will resonate strongly with black hat/white hat types, from where I sit the reality seems a bit more complicated. Here is how I see it — MBH conducted several studies that, by the conventional norms of the climate science community, represented excellent work and were published in leading journals in the field. But the norms of the climate science community for peer review and replication are not widely shared in other fields. So when MM were drawn to MBH (indirectly or directly by the IPCC SPM no doubt) from outside the climate science community with an eye to take a close look at the their work I’d venture that MM likely brought along with them a perspective on norms of peer review and replication quite different from MBH. This alone would be enough to generate some push back from MBH. But add the fact that McKitrick had already established himself as a collaborator with the climate skeptics, and this probably was enough to engender some serious opposition from MBH, who no doubt were used to dealing with their traditional climate skeptic opponents with loudness and bluster. MM did not go away or back down.

Now it turns out that science can be messy and scientists can be among the more disorganized people you might meet (I could show you some offices). Perhaps MBH were both unprepared to deal with an outside request to replicate the entirety of their work, and their behind-the-scenes work had enough inelegant shortcuts and ugly warts involved so as to make a full, public replication maybe uncomfortable and potentially embarrassing. To be clear — I am not suggesting anything close to scientific misconduct or fraud, but the standard messiness and disorganization associated with the scientific research in this particular community where requests for computer codes and inside info rarely are made. For example, when asked about responding to a letter such as that sent by Rep. Barton to MBH Hans von Storch’s reply exemplified such messiness when he replied, “”If I did get such a letter, I would become desperate,” he said. His colleagues often write the code for his studies, and he said, “if I asked my colleagues whether they still had the code, I’m not sure they would.”” Climate scientist James Annan makes the point more generally on his blog, “I don’t know of any scientist who could answer such questions. It’s just not the way our work is done – there is far too much pressure for rapid and new results for us to maintain full “audit trails” and answer an unlimited number of questions from any troublemaker with too much time on their hands. By the time 5 years have passed, our work is either irrelevant and forgotten, or else superceded, either because it really was wrong, or because someone else improved on it.” (See the similar comments of Kooiti Matsuda here.) Other disciplines no doubt have different norms of conduct. Undoubtedly part of the dispute between MBH and MM is about norms of scientific inquiry, something that won’t be resolved through the technical arguments.

Bottom line – It seems reasonable to think that while MBH did not engage in scientific misconduct, that a full public replication of their work may prove potentially uncomfortable or embarrassing. (Note that no matter what it is that MBH are not revealing, it could have no consequences for either the scientific consensus on human influence on climate or perspectives on recent temperature trends in historical perspective, as these issues are supported by a larger literature.) So they resisted, and have stood fast. For their part, MM did not give up. MM publish in the peer reviewed literature, giving some credence to their critique, the Wall Street Journal weighs in, a few guys at NCAR claim to vindicate MBH and now the issue has gone all the way to the U.S. House of Representatives.

In the long run I am confident that the technical dispute between MBH and MM will be resolved in the peer-reviewed literature. But so what? Already research on paleoclimate modeling and proxies by von Storch et al. and Moberg et al. has superceded the work of MBH.

Resolving the technical dispute will do little to address the larger issues of climate science policy or the symbolic and real political implications of the hockey stick debate. Let me conclude this lengthy post with some unsolicited advice for many of the parties in the science community involved in this messy and ugly debate.

1. For the IPCC. You have a real problem here. If you do anything other than staunchly defend the hockey stick, you run the risk of being perceived as taking a step back on climate science (rightly or wrongly). Given the political agenda advanced by IPCC leadership this will be perceived as damaging. But consider also that a step back can serve to increase your credibility. It was clearly a mistake to use the MBH studies in the SPM (this RealClimate post makes this point abundantly clear enough). The case for human impacts on climate is wide and deep. In the future consider some different options for the SPM such as handing off the job of the SPM to a separate group with expertise in such things, or not even doing an SPM. You have a conflict of interest problem (real or perceptual) as well, given that M of MBH was involved with reviewing his own work as an IPCC lead author. Again, this may be acceptable given the norms of the climate science community, but those are not the norms at play in the larger political world of climate science. Consider getting some good advice on institutional design and public relations. And above all, avoid the hubris that too often characterizes climate scientists in their interactions. What works in the academy often does not in the broader world.

2. For MBH. By all means stop invoking the funding and political agenda of your opponents, which you often offer with fire and vitriol. This only serves to legitimize inquiries into your own funding and political agenda. It is easy for me to say, but I recommend not complying with Rep. Barton’s request. Be respectful, but decline or bury him with paper. Let him subpoena you if he dares (and then watch him then get buried). Add no more fuel to the fire, on RealClimate, in the press, etc. Unless you really have something serious to hide, give the world access to your original computer code and whatever else MM are asking for. Whatever benefits you get from invoking the principle of the matter seem to be dwarfed by the continuing reality of having to deal with this issue. Swallow hard, cut your losses and move on.

3. For MM. Continue to publish your work in the peer reviewed literature. Steer clear of those with political designs on your work, you’ll have more standing if you focus on the substance (M has done better than M in this regard.) Work to understand the norms of the climate science community, and don’t place blame for these norms on MBH. You might have a case to make for changing these norms, but make that case in the right venue. Focus more of your attention on the IPCC and its processes rather than MBH. There are larger issues here. Think about taking on another project. I am confident that the hockey stick issue will very soon resemble a dead horse.