Over at WUWT Anthony Watts has accused the UEA of being liars. If like me you went there hoping to get a quick summary and found it very difficult to understand, then hopefully this will help.
It appears this assertion from Anthony Watts comes as a result of a decision by the UK Information Commissioner that the University of East Anglia’s must release details of the sites it used to create the Yamal-Urals regional chronology. This is the reconstruction of past temperature using the size of tree rings showing the rate of growth of trees in this area.
The reason this is important is because it purports to show a period when temperatures did not change much followed by a rise as we approach the modern time. Many other people have used this regional temperature reconstruction which tends to give them all a “hockey stick” shape. For example, it underpins the infamous “hockey stick” graph of Michael Mann. Whilst Michael Mann’s infamous hockey stick graph relied on bristle cone pine trees and predated Yamel, the similar hockey stick shape of Yamal and all studies using Yamal was cited as validating the hockey stick: in other words “proving” that modern warming was unprecedented.
The nub of the story is that Steve McIntyre has taken the tree-ring records from the 17 sites released by the UEA and used these to reconstruct past temperatures (link). The following graph appears to be a comparison of the UEA reconstruction and Steve McIntyre’s:
Comparison of UEA temperature reconstruction (black) with that of Steve McIntyre(Green).
Although both the UEA and McIntryre produce similar results from 800 to 1900, there is a very stark and very difficult to explain difference after 1900.
The other important point is that there are very few trees in the Yamal area compared to the total number of trees in the region. If the UEA were being honest, we would expect them to have used all the tree cores in the area. Instead they seem to have picked a few trees cores from an area which create this rise in the 20th century. Now that Steve McIntyre knows which areas were used he is able to quantify this “cherry picking”:-
Modern core counts for the regional chronology are about 20 times higher than core counts in the reported Yamal chronology, reaching nearly 400 cores in the 1960s. In the 1980s, core counts are still around 300, as compared to 12 in the Yamal chronology.
As Steve McIntyre puts it:
The question for CRU defenders is to justify their preference of such a small core count, when they had already calculated a regional chronology with an order of magnitude more cores. Since the original criticism in September 2009, CRU has given a variety of different responses, but none, in my opinion, answer the question. Indeed, none of their responses to date have even admitted or disclosed their prior calculation of a regional chronology, let alone explain why they didn’t report it, preferring instead to attack their critics.
Addendum
After a great deal of effort, I think I understand the basis of the specific allegation. What follows is based on what I read on WUWT & Climate Audit:-
The key is a paper written by Keith Briffa of the Climatic Research Centre of the University of East Anglia (UEA) in 2008 in which he attempted to reconstruct past temperature in the Yamal & Ural regions of Russia. There were very few tree cores available in Yamal. This was a very glaring problem, one with a ready solution which was for Briffa to have used tree core samples gathered in the same area in a locality called Khadyta River by his co-worker Schweingruber.
We know Briffa was aware of Schweingruber work and would know he had tree core samples. This is because Briffa had done another reconstruction of temperature for a nearby on the Taimyr Peninsula using Schweingruber’s tree core data. We also know that the distance was not a problem because the tree cores Briffa had included for Taimyr were much further away (400km) than equivalent tree cores samples for Yamal.
Why would Briffa add Schweingruber’s data to Taimyr which already had enough tree core samples, but did not add them to Yamal where there were far too tree cores?
When Steve McIntyre looked at the reconstruction he noticed this rather peculiar selection and showed that the inclusion of Schweingruber core data from Yamal did not produce the hockey stick graph (which is used to suggest past temperatures changed little until the “unprecedented warming” of the 20th century). McIntryre began to ask the UEA to explain their strange behaviour. The affair rumbled on with various climate scientists associated with the affair criticising McIntyre. Eventual in October 2009 the UEA, changed tack and instead of ridiculing inclusion of Khadyta River, conceded that the site met their criteria. Now however, they claimed that when reconstructing the past temperature for the Yamal & Ural area they had “simply not considered” using the Khadyta River tree cores from Schweingruber.
This assertion seemed to be contradicted by a Climategate email (1146252894.txt) copied to Keith Briffa which discussed the very regional chronology combining “Yamal, Polar Urals and shorter chronologies”. This email revealed that UEA had, after all, calculated a Yamal & Urals regional chronology as early as April 2006. Steve McIntyre thought the “shorter” chronologies very likely referred to the Khadyta River tree cores. So, Steve McIntyre raised an FOI asking for details to see if this was true.
This FOI was refused by the UEA.However, the information commissioner has now ruled that the UEA should hand over the list of sites they used in 2006 when reconstructing past temperatures in the Yamal area. Now we have that list, we can see the 2006 temperature reconstruction for the Yamal-Ural area included the Khadyta River tree cores. So these samples were included in 2006 but excluded by Briffa in 2008. Later the UEA said they had “not considered” them.
How can we square this previous reconstruction in 2006 for the same area using Khadyta River tree cores, with the statement that they “did not consider” using the Khadyta River tree cores in 2008? How did they “not consider” adding data they knew was available when they did not have enough samples to be valid? It seems impossible that an intelligent person with data available who needed that data would not “consider” using it.
Therefore, based on what I have read at WUWT and Climate Audit, it would appear that someone at the UEA has lied.
On CA’s website, you asked for comments on your summary. I’m an interested observer, but no more than that. For a summary of this nature, the devil, as always, is in the details. I think the following paragraph needs clarification:
“The reason this is important is because it purports to show a period when temperatures did not change much followed by a rise as we approach the modern time. Many other people have used this regional temperature reconstruction which tends to give them all a “hockey stick” shape. For example, it underpins the infamous “hockey stick” graph of Michael Mann.”
In general, Mann’s “infamous” Hockey Stick is the one that came out of his work in 1998/99 and was incorporated as a graphic in IPCC’s TAR. Mann’s analyses, at the time, depended on using (and significantly overweighting) bristlecone pines, which are not considered good temperature proxies.
Mann has subsequently tried to justify his earlier work. These justifications have relied on, among other things, the contaminated Tiljander sediment cores – where the hockey stick shape does not emerge if that set of proxies is in not included.
Other tree-ring chronologies, which also obtain a hockey stick and are cited in support of the “correctness” of Mann’s view (even if his 98/99 papers were flawed), also rely heavily on either bristlecone pines or (material to Steve’s latest post) on Briffa’s Yamal series. As McIntrye notes:
“The Yamal chronology is relevant both because, since its introduction in 2000, it has been used in virtually all of the supposedly “independent” IPCC multiproxy studies (see an October 2009 discussion here) and because it is particularly influential in contributing an HS-shape to the studies that do not use bristlecones.”
I think it is fair to say the the Yamal series has been relied upon by the AGW industry as “independent validation” of the hockey stick obtained by Mann’s 1998/99 work, which most agree was heavily flawed, both for its principal component analysis and its dependence on bristlecone pines. Mann’s iconic and flawed hockey stick graph, which became the poster child for the IPCC’s Third Assessment Report, actually pre-dates Briffa’s Yamal work.
I’d also revise this sentence slightly: “The other important point is that there are very few trees in the Yamal area compared to the total number of trees in the region.”
Of course, what you are referring to is the number of core samples used, versus the total data available. In the 2008 Briffa paper, some new material was added for certain areas, but other material was ignored. Steve indicates that they appear to have analyzed the larger database of material in the Yamal-Urals region, but then didn’t use it, probably because it did not fit their thesis. They still have not released this regional analysis, which is the subject of another FOIA request by Steve, who has simply taken the data they did release and tried to emulate what they (likely) did. Since there is little detail on how they have performed their statistical analyses, it’s not certain whether his emulation matches theirs (a point he acknowledges).
You might see if you could get the Bishop to look at your summary: as you well know, Andrew Montford certainly has ample familiarity with the topic and an ability to summarize the difficult statistical/scientific issues into a comprehensible form without losing the nuances.
The general convention is you want n>30 especially if the population may not be normally distributed. This is why you see raised eyebrows when the GLOBAL temperature is estimated by 12 trees especially when there are up to 400 other samples available.
Thanks.
G.Combs,
My main concern was that I could see anything that said: “this graph shows my calculation versus that of the UEA”. All I wanted to know was what was the lie. Even after reading Anthony and McIntyre’s post and posting my own article saying “it appears to be this”, I’m still not 100% sure.
If I can’t understand this, the chance of any journalist going with this story is zilch … unless they are themselves highly partisan, in which case they are just preaching to the converted.
Scottish Sceptic, you need to reread the sections below “CRU Statements and Evidence” which you quote. The essence of the accusation of “lies” is not that CRU should have performed these calculations, but rather that CRU had in fact done equivalent calculations, but then lied about having done so.
The reason you’re having trouble specifically identifying “the lie”, is that if there was a lie, and just one lie, it is difficult to know which “the lie” was. You see, there have been a LOT of contradictory statements issued about Yamal from the CRU, and RealClimate have muddied the waters further by making their own other contradictory statements, even though they were not involved in the Yamal chronology.
The latest FOI response contradicts several previous statements by the CRU (and also RealClimate, but that’s a side point, as RealClimate weren’t actually involved in the Yamal construction). So, I guess that’s why Anthony feels justified in calling the CRU “liars”, i.e., at least one of their previous statements was false, and it is plausible they knew it was false.
To be honest, the Yamal controversy is shocking and definitely worth reading up on. But, I wouldn’t focus on whether the CRU are “liars” or not. The key question is whether the Yamal chronology accurately represents temperature trends of the last few millennia or not, when it suggests that recent temperatures are “unprecedented”. The answer to that question seems to be no. The implications of that become profound when you realise how widely used Yamal has been.
As Ian pointed out, Michael Mann’s infamous “MBH98/99” study didn’t use Yamal, but about half of the “spaghetti graph” studies which are frequently used as “vindication” of MBH98/99 use Yamal.
The problem is that in most of those studies, the “hockey stick” shape appears to disappear (or become considerably reduced), if the Yamal chronology is replaced with other chronologies from the same region.
This should have made any good scientist (at the very least!) wonder if Yamal’s unusual “hockey stick” shape might perhaps be non-climatic. For this reason, McIntyre has put considerable effort in trying to work out how it was constructed and what were the justifications used in its construction. Unfortunately, the CRU have been exceedingly reluctant to share that information, and so McIntyre has resorted to several years of FOI requests. So far, every time he has received a bit of information from the CRU, it makes the Yamal chronology seem even more bizarre & unrealistic, and raises more questions for McIntyre.
Bishop Hill tried to do a “layman’s introduction” to McIntyre’s audit of Yamal back in the pre-Climategate era (as in just a few weeks before Climategate!): http://bishophill.squarespace.com/blog/2009/9/29/the-yamal-implosion.html
Though, to be honest, I’m not sure it’s a simple enough introduction, and there are quite a few mistakes. He did a far better description in his “The Hockey Stick Illusion” book (have you read it?).
Does that help in any way?
Actually, re-reading Bishop Hill’s 2009 post, it is relatively accurate, though it only describes the story up to September 2009, and in my opinion, the implications that the CRU were deliberately trying to create a hockey stick are invalid. It’s possible they were, but I think it’s more likely they were expecting a hockey stick, so when they found one, they didn’t question it.
Anyway, there have been a number of relevations and insights since September 2009.
But, that post will probably give you the basic background. The current post on ClimateAudit that you’re discussing is mainly about the technicalities of how exactly Yamal was constructed. There are two main aspects:
1. What tree ring cores should be included?
Briffa used a VERY small sample of cores for the modern period, even though there are plenty of other cores in the area: http://climateaudit.org/2009/09/30/yamal-the-forest-and-the-trees/ Briffa hasn’t satisfactorily explained his selection criteria.
2. What standardisation technique should be used?
There are a number of problems in combining different tree ring cores together, e.g., the rate of tree ring growth changes as trees get older, so if you’re using the width of tree rings as a “temperature proxy”, then you would need to account for these “age effects”. Nobody has come up with a definitive way for doing that. Briffa claims that his “Regional Curve Standardization” (that’s the “RCS” McIntyre refers to) is one of the best attempts to do that. But, he has refused to provided the details of it & so McIntyre has had to instead emulate it as best he can: http://climateaudit.org/2009/09/29/verifying-my-rcs-emulation/
P.S. If you’re unfamiliar with how the cores are collected, this YouTube demonstration is helpful: http://www.youtube.com/watch?v=VWsqGoNji4o
In light of the evidence I have seen I feel that I have to inform the police of this matter.
As such further commenting is being disabled.