Pannell Discussions

No. 163, 30 November 2009

ClimateGate part 1: Background

The recent release of thousands of hacked emails and documents from a leading climate research centre (the Climatic Research Unit (CRU) at the University of East Anglia) has been making headlines and has been a hot topic in the blogosphere. This article provides background to the controversy.

Before looking at the leaked material itself in the next PD, I think it is worthwhile going through some of the background to the story, which has its roots back in 2003.

This story is about a fairly small group of influential scientists who’ve drifted into a culture of behaviour that would be anathema to most scientists. It is not about whether or not climate change is real or serious, although it does raise doubts about the work of these particular scientists.

For readers of the Climate Audit blog, run by Canadian statistician Steve McIntyre, the revelations contained in the leaked material are not surprising. It was already apparent that there exists a small group of senior climate scientists (usually called the Hockey Team, or the Team for short, for reasons that will become obvious) who routinely behave in questionable ways to prevent outside scrutiny of their work. These scientists are mainly in the area of paleoclimatology – studies of historical climate patterns using proxy data like tree ring widths. Some of them have played leading roles in the IPCC, including as lead authors of chapters in different IPCC reports - a position that empowers them to determine which science gets into the reports.

The beginning of the story was an attempt by Steve McIntyre to replicate the famous “hockey stick” study of Michael Mann and colleagues. Mann is not at the university where the emails were hacked, but he has close connections to the CRU and is one of the most frequent senders or recipients of the leaked emails.

The original Mann et al. studies, based on statistical analysis of historical tree-ring-width data, purported to show that global average temperatures have been fairly constant for 1000 years or more, until the 20th century when they kicked up sharply, so that the graph overall has the shape of an ice-hockey stick.

The hockey-stick diagram seemed to offer dramatic evidence that mankind was affecting climate, and it was used for a while by the IPCC as its most prominent graphic.

Given its prominence, Steve McIntyre’s interest was perked. Did all the data series have hockey-stick shapes? How was the model estimated? How robust and statistically significant was it? He asked Mann for the raw data, and was actually given a data set. He found numerous problems with the data set and he found that the statistical model was not robust. Mann rejected the criticisms, saying that McIntyre wasn’t even using the right data set, implying that this was McIntyre's fault, even though it was the data provided by Mann.

The published journal articles did not provide enough details to allow McIntyre to fully replicate Mann's results (exactly which data series were used, exactly which statistical technique was used) and Mann simply refused to provide the information. But McIntyre has tremendous perseverance, and slowly over time he was able to fill many of the knowledge gaps. One key event was when he found a copy of the programming code for Mann’s statistical analysis sitting on a publicly accessible internet site. Analysing this, he found that Mann’s statistical technique was non-standard, and indeed was rather dodgy. Because of the way it worked, it selectively mined the data set for hockey-stick-shaped data series and hugely inflated the weightings they were given.

McIntyre found that the hockey stick shape of the final graph depended on a small number of series whose weightings had been inflated in this way. Most of the data series did not actually have a hockey stick shape. Notably, data representing the ring widths of bristlecone pines in one area of the US were crucial – Mann would not have got a hockey stick shaped final result without them. There were serious doubts about whether the pattern of ring widths for these particular trees reflected temperatures. The people who collected the data didn't think so. Now it’s thought that it is a result of trees having had their bark removed at some point, after which their growth was altered.

McIntyre also showed that the R2 for the hockey stick graph was zero – as a statistical model, it provided no explanation for the data whatsoever.

Mann refused to accept all these points, and persisted in claiming that his analysis was valid. Eventually there were two official public inquiries in the U.S. – one consisting of scientists and one of statisticians. The scientist one concluded that the "strip bark" bristlecone pine data should not be used, and the statistical one concluded that McIntyre’s criticisms of the statistical analysis were correct in all respects.

Mann and his colleagues ignored these findings and continued to use the same dodgy data and the same dodgy statistical technique in subsequent publications. Their influence and stature within the world of climate science seemed to be unaffected by all this. Many climate scientists seemed to assume that McIntyre must be wrong because he’s not a real climate scientist and because Mann and his collaborators are so famous. The Team set up a blog site ( which poured scorn on McIntyre and heavily censored any dissent among the blog respondents. There developed a mutual distrust and personal dislike between the two factions.

Over time, McIntrye has broadened his focus to other studies and other data, including that of the CRU (the body whose computer system was hacked). He has looked at a variety of other important statistical studies on climate, and he regularly picks up problems. Mostly he gets abused or ignored by the scientists. Occasionally the scientists do pick up his findings and adapt their analysis, but they almost never acknowledge his contribution.

The Team has continued to obstruct the attempts of McIntyre (and others) to get data and information about methods at every turn. They don’t seem to recognise that there is anything wrong with this behaviour. For example, back in 2005 Phil Jones from the CRU told Warwick Hughes (an Australian, I think) who was requesting data, “I will still not pass on the data. We have 25 or so years invested in the work. Why should I make the data available to you, when your aim is to try and find something wrong with it?” How about, because you are supposed to be a scientist? How about, because you are are publicly funded? How about, because there’s a lot riding on your results?

When Team scientists refused to meet requests to provide data, McIntyre and others resorted to making requests under Freedom of Information legislation. In the case of the CRU, this proceeded as follows.

1. Initially they refused to provide the raw data to Steve McIntyre because he "isn't an academic". Since he has published peer-reviewed articles in climate journals, they presumably mean that he isn’t employed by a university. This criterion would have disqualified Albert Einstein and Charles Darwin from being considered legitimate scientists at the times when they wrote their major works.

2. Then, when a university-employed academic requested the same data, they said that the information is already available elsewhere and that they couldn't provide it because of confidentiality agreements (not noticing the the contradiction). They said that releasing the data would have an "adverse effect on international relations", although they didn't mention that they had previously provided it to another pro-warming academic (apparently without the feared adverse effect).

3. When requested to provide the confidentiality agreements, they said: there are too many to provide; it is too much work. In response, several individuals asked for copies of confidentiality agreements that applied to specific small amounts of temperature data.

4. They responded to these requests with: we can only provide two of the many confidentiality agreements, we can't find the others and we don't know who they were with, and by the way we have just discovered that we no longer hold the original raw data.

All this to prevent an obviously skilled statistician from getting hold of data that was publicly funded, and which is being used to influence massive policy decisions.

The detailed account of another person’s attempt to use the Freedom of Information Act to get data out of the CRU is documented here. It’s fascinating to see the CRU’s ingenuity, and their brazenness. It seems that Freedom of Information officers at the University were courted and effectively enrolled by the Team.

Given this context, you can see why somebody might want to hack into Team computers. I don’t think it was a random attack.

One of the tragedies in all this is that the Team could learn from Steve McIntyre. It’s obvious that he has statistical knowledge that would be valuable to the Team, if they would take his advice constructively. Even though they consider him to be not a proper scientist, he seems to have a better grasp on some of the core principles of science. As far as I can see, he has won every single substantive battle in this ongoing war (in the sense of being correct, not in the sense of convincing his opponents), but the Team continues to claim the opposite, at least in public. What about in private? One of the leaked emails has a former Director of the CRU saying:

"I have just read the M&M [McIntyre and McKitrick] stuff critcizing MBH [Mann et al.]. A lot of it seems valid to me. At the very least MBH is a very sloppy piece of work — an opinion I have held for some time." here

McIntyre’s emphasis on due diligence, arising from his experience in the mining industry, is one of the interesting angles on the story. The scientists consider peer review to be sufficient due diligence, but it’s become plain that for analyses that affect decisions with massive financial or social implications, it is not sufficient. Someone independent should be made responsible for actually replicating the key studies.

McIntyre’s blog is frequented by people who are, in the main, in the “sceptical” camp, but interestingly McIntyre himself has repeatedly said that if he were making policy decisions, he would use the IPCC as the best available evidence. He just wants to make sure that the information is up to scratch.

Hopefully, his contributions will be appropriately recognised in paleoclimatology one day. I guess it might not happen until after the Team has retired or otherwise lost its influence.

David Pannell, The University of Western Australia,

Further reading

McKitrick, R. 2005. What is the hockey stick debate about? Paper presented to APEC Study Group, Australia, 4 April 2005,

There was a nice item about the scandal on ABC Radio National today, available here.

Pannell Discussions are brief pieces on issues and ideas in economics, science, the environment, natural resource management, politics, and agriculture.

162. CSIRO and Clive Spash  23 Nov 2009

164. ClimateGate part 2  7 Dec 2009

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