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:
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.
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.