Wednesday, September 30, 2009 ... Deutsch/Español/Related posts from blogosphere

Beaten with hockey sticks: Yamal tree fraud by Briffa et al.

I will open a discussion thread about this development, too. Steve McIntyre has broken another hockey stick:

Yamal: a divergence problem (click)
... a copy at Climate Audit (click)
Because Climate Audit is overloaded, here's the Google cache.

The finding is very easy to describe. Briffa et al. (Science, published September 2009, see also Briffa et al., Philosophical Transactions 2008) offered another version of a "hockey stick graph", a would-be reconstruction of the temperatures in the last 2000 years that claimed to show a "sudden" warming in the later part of the 20th century, much like the discredited paper by Michael Mann et al.

Papers by Mann, Bradley, and Hughes in 1998 and 1999, included as a symbol of global warming into the previous IPCC report in 2001, indicated constant temperatures before 1900 and a dramatic warming afterwards. However, the papers have been proven wrong.

If you haven't heard about the lethal bug of the Mann methodology yet, the problem of the MBH98, MBH99 papers was that the algorithm preferred proxies - or trees (or their equivalents) - that showed a warming trend in the 20th century, assuming that this condition guaranteed that the trees were sensitive to temperature.

But even if such a 20th century trend occurred by chance for a certain tree (and a fraction of the trees inevitably satisfies this condition), the corresponding tree would influence Mann's final graphs a lot. Effectively, the algorithm picked a lot of trees that didn't show any correlation with the temperature but they were rather composed out of random data - red noise - before 1900, and an increasing trend in 1900-2000.

You can't be surprised that the average of such trees looked like a hockey stick even if the temperature didn't. The noise before 1900 averages to a constant temperature or something close to it while the 20th century warming survives. See
PDF preview, Mathematica notebook
demonstrating this mechanism. But let us return to 2009 and the new paper by Briffa et al. In this case, the problem is less mathematically sophisticated so please don't stop reading.

The new authors used trees from the Yamal Peninsula, Northern Siberia, so their hockey stick was supposed to be an "Arctic hockey stick". Yamal means the "end of the world" in the local native language of the "Nenets" tribes (see the picture above) - which you may interpret in various ways. ;-)

However, as Steve found out, if they had used the full canonical and well-known ensemble of the proxies for the region - the so-called Fritz Schweingruber collection of trees (34 of them fit squarely into the area) - they would have obtained the white curve that shows no warming in the 20th century (in fact, there's a slight cooling before 2000, and even in the combined set, which is depicted in green, there's no 20th century warming):

However, Briffa et al. cherry-picked the trees, eliminated the Schweingruber set, and obtained the alarming, red "hockey stick" graph, instead. You may want to see a detailed graph of the last 150 years where the two curves dramatically deviate from one another:

The white lower curve should have been obtained. By playing with the data, to put it euphemistically, Briffa et al. obtained the upper curve instead. See a National Post comparison of the three charts.

Some environmentalist journalists and bloggers, including Alexander Ač, were promoting the new Arctic hockey stick. They still apparently believe that the hockey stick is alive and well (see the picture on the left). The situation has changed and there are growing calls to eliminate the researchers who have abandoned their scientific integrity from the scientific process, see e.g. Jennifer Marohasy.
See also Ross McKitrick in National Post, Chris Horner in Planet Gore, Joanne Nova, The Yamal implosion, a Telegraph blog, The Register,, Jeff Id, Small Dead Animals, Tamino's detailed debunking of McIntyre's work (Tamino is Grant Foster), Real Climate humor website, Blog Search, and Google News.
Why I am not surprised

Well, it's been quite some time since we learned that the variations of the global mean temperature during the last 1000 or 2000 years don't reveal any "manifestly unprecedented" (warming) patterns in the 20th century. The Mann hockey stick was based on well-known methodological errors. If there were any "global warming" signal, it was clearly small enough to be hidden in the noise.

Reconstructions by Moberg et al. 2005 (up) and Loehle 2007 (down). Both of them are newer and more viable than Mann's reconstructions. Moberg is considered a "believer" while Loehle is a "skeptic". But you can see that aside from the "teenage contest" whether our current era is strictly warmer than the Middle Ages, the difference between the two reconstructions is pretty small. None of them resembles a hockey stick.

If we reconstruct the temperatures from the trees, it is guaranteed that the signal-to-noise ratio will be even smaller - more noise - because the trees are affected by many more factors. Moreover, the noise increases even more if we look at a regional climate which is affected by much more "local weather", too.

Moreover, it's been known from very many studies that the temperatures reconstructed from the trees don't show any substantial warming signal since the 1950s that one would expect from the thermometer readings and from a hypothetical growth-temperature relationship. This discrepancy is known as the divergence problem. This fact makes it obvious that any reconstruction based on trees that shows such an intense warming is guaranteed to be wrong, whether the "wrongness" is a result of mistakes or fabrication of the data.

For general problems of the tree reconstructions, see a paper by Craig Loehle. He argues that the temperature-tree_width relationship is nonlinear in the realistic regime and even the sign of the relationship is likely to flip at realistic temperatures which means that the map is not one-to-one and any reconstruction is tough.
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In the case of... I erased this paragraph because I was asked to do so by Steve McIntyre, not because I see a fair reason behind it.

But I think it is pretty obvious that pretty much all the relevant authors of the article must know that without any fabrication of the data, they don't get any hockey stick from the trees. It means that it can't be an innocent mistake and all of them, and not just Keith Briffa, are fraudsters who know very well what they're doing and why they're doing it. The next question is whether the society knows what it should be doing with such people.

More seriously, you may ask why the champions of the fight against climate change keep on publishing papers with similar flawed arguments, despite the existence of a community of "auditors" that has become really powerful in the last 5 years or so and that is able to catch certain problems rather efficiently. Isn't it because they have no valid arguments?

And this question is the memo.

P.S.: Consider buying the NIPCC report (880 pages).

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