The Yang Chinese composite, after the Mann PC1 and Yamal, had the third-largest hockey stick shape of the proxies illustrated in the IPCC AR4 spaghetti graph. I’d commented on this series on several occasions – see www.climateaudit.org/tag/yang. The new emails show that Bradley thought that this series was, to use the technical term preferred by climate scientists, “crap” and should not be used in multiproxy studies – an issue raised by Bradley in connection with Mann et al (EOS 2003) – their attack on Soon and Baliunas 2003.
Needless to say, Bradley did not publish a comment criticizing the use of this series. It has subsequently been used over and over again in IPCC multiproxy studies, commencing with Mann and Jones 2003. In my post a few years ago, I observed that it was, in fact, “the most heavily-weighted contributor to Mann and Jones  … The Yang composite and the North American PC1 (bristlecones) dominate the Mann and Jones  reconstruction, making other series essentially irrelevant.”
It was then used in Moberg et al . In my earlier post, I observed that “its contribution to Moberg is less marked, but it is one of only 3-4 series that provide a strong 20th century” (the other series include upside-down Bulloides.) Since then, it has been used in Osborn and Briffa 2006, the IPCC AR4 spaghetti graph (Box 6.4 Figure 1), Hegerl et al 2007, Juckes et al 2007, Ljungqvist 2010 and even Loehle and McCulloch 2010.
Here’s what Bradley and the Team said about the validity of this series behind closed doors. The exchange also has an interesting vignette on the speed of peer review when the Team is involved.
On June 3, 2003, Mann began drafting the counterattack on Soon and Baliunas for EOS, assisted by Jones, Osborn and Rutherford. Authors who commented at least once were Bradley, Briffa, Crowley, Oppenheimer, Trenberth and Wigley. Ammann and Hughes appear to have been listed as coauthors only as a courtesy, rather than because of actual input.
There are emails through June 13 discussing the drafting of the EOS article. The version as submitted to EOS for peer review did not include the Yang composite. It had the same number of series but used the Briffa 2000 composite instead.
In email 2530 on June 17 at 10:53 GMT, Jones tells Mann that EOS editor Moseley-Thompson has the article for review:
I’ve not heard any more about the EOS piece but Ellen has got it – I got an email from her to Judy….
They had just received notice of acceptance of Mann and Jones 2003 (the article that Bradley later disliked so much). Jones suggested to Mann that they replace the long Briffa series with Yang’s more hockey-stick shaped series (which they had used in Mann and Jones 2003):
I would suggest with EOS we add this series into Fig 1, back to AD200, possibly by replacing the long Briffa series.
In the rest of email 2530, Mann and Jones separately instructed Rutherford to switch the series in EOS Figure 1, with Jones saying that he would check with Moseley-Thompson to see if possible. (None of the other authors appear to have been consulted thus far.)
I’m off home now. Do you want to see if you can switch the two series around as Mike suggested. Replace the long Briffa one with the appended and alter caption accordingly. I’ll email Ellen and Judy to see if possible.
The next morning, (email 2-3637), Jones reported to the Team that the article was with AGU and should go soon to Ellen Moseley-Thompson for reviewing (Moseley-Thompson having participated in the earlier email chain discussing what to do about Soon and Baliunas.) He reported the acceptance of Mann and Jones 2003 and outlined the plan discussed the previous day with Mann to substitute the more hockey-stick shaped Yang series for the long Briffa series:
Here’s a brief update on the EOS article. It is currently with AGU and should go soon to Ellen Mosley-Thompson for assessment/reviewing. Mike and I are trying to co-ordinate its hopeful publication with the attached. This is the GRL paper that Mike has mentioned. Copy is for your info, so don’t pass around. Both reviews were positive and the attached is the resubmitted version. If co-ordination isn’t possible we will still replace the long Briffa et al series (going back over the 2 millennia) in Figure 1 with the blue line from Figure 2a in the GRL article. Text will alter, but only to refer to the new curve.
Jones explained that the substitution “should increase the impact”:
I’m in discussion with AGU and Ellen about co-ordination as this should increase the impact of both pieces. Mike or I will let you know when we hear more.
Later that day (JUne 18 – email 2530), Rutherford reported the completion of the substituted figure, which Jones distributed to Briffa and Osborn.
In the early EDT afternoon (email 2670) of the same day, EOS accepted the article, with a number of minor text changes suggested.
On June 22, four days later, (email 4207), Bradley complained to the team about the Yang composite that Mann and Jones had unilaterally substituted.
You commented that the Chinese series of Yang et al (GRL 2002) looked weird. Well, that’s because it’s crap–no further comment on what stuff gets into GRL!
You appear to have used their so-called “complete” China record. You really should consider what went into this –2 ice core delta 18O records of dubious relationship to temperature (one is cited as correlating with NW China temperatures at r=0.2-0.4), 3 tree ring series, one of which is a delta C-13 record of questionable climatic significance (to be generous). The other series include two records from a Taiwan lake–a carbon/nitrogen isotope and a total organic carbon series (interpreted as high=”warm, wet”) and an oxygen isotope series from cellulose in peat!!! (& don’t ask about the C-14 based chronology, interpolated to decadal averages!)
I loved this sentence:
“Although a quantitative relationship between the proxy records of the Jinchuan peat, the Japan tree-ring series and the Taiwanese sediment records with modern climate data are not given in the original works, the qualitative connectivity with temperature as the dominant controlling factor has undoubtedly been verified”
Oh, undoubtedly!! And these are 4 of the 9 series going into the “complete China” record..
Finally, they use another record based on “phenology” and (somehow) this provides a winter temperature series….
You just shouldn’t grab anything that’s in print and just use it ‘cos it’s there—that just perpetuates rubbish. This series needs to be removed from Figure 2 in the EOS forum piece–and if you included it in your GRL paper, I suggest that you reconsider it.
Bradley’s complaint about the loose treatment of warm and wet in Yang had particular resonance because that was the criticism that the Team was levelling against Soon and Baliunas. Mann replied immediately assuring Bradley and the inside Team that the Yang composite got “moderately low” weight in Mann and Jones 2003 (note- I don’t think that this is true. My notes indicate that it received more weight than any series other than the Mann PC1.) Mann tried to fob off further discussion until he met with Jones in Sapporo (by which time the article would have appeared)….