Some Japanese articles have been in the news recently. CA readers will be interested in the fact that CA was cited (thanks to a CA reader for the heads up). Here’s a graphic from their SI showing differences between Gaspé versions. As CA readers know, similar discrepancies occur for bristlecones between Ababneh and Graybill or between the Polar Urals updata and Yamal – but you can predict the version used in Team reconstructions with almost total accuracy through a very algorithm. 🙂 Anyway,- I sort of like the look of the citation in Japanese and thought I’d share it with you.
They also circle the uptick in the upside-down Tiljander series, which we discussed here, and again it looks kinda cool in Japanese.
In this context, I thought that I’d briefly review the PNAS exchange on this topic. I reported that the Mann 2008 graphic was upside down from the orientation in the original study. So that the HS goes down in the 20th century. The original authors (Tiljander et al) discounted the 20th century portion as compromised by agriculture, ditches and bridges and so the increased varve thicknesses were not considered to be evidence of global cooling.
Upside down proxies are obviously a bad thing in CPS reconstructions (one of two legs in Mann 2008); and non-climatic contamination is a bad thing for correlation based reconstructions.
We referred to this in our PNAS comment as follows:
Their non-dendro network uses some data with the axes upside down, e.g. Korttajarvi sediments, which are also compromised by agricultural impact (Tiljander, pers. comm.)
To which Mann replied:
The claim that ‘‘upside down’ data were used is bizarre. Multivariate regression methods are insensitive to the sign of predictors. Screening, when used, employed one-sided tests only when a definite sign could be a priori reasoned on physical grounds. Potential nonclimatic influences on the Tiljander and other proxies were discussed in the SI, which showed that none of our central conclusions relied on their use.
I think that even Mann sympathizers should not accept this response. The claim that “upside down” data was used may be “bizarre”, but it’s also true. You can see that the data was used upside down by comparing Mann’s own graph with the orientation of the original article, as we did last year. In the case of the Tiljander proxies, Tiljander asserted that “a definite sign could be a priori reasoned on physical grounds” – the only problem is that their sign was opposite to the one used by Mann.
Mann says that multivariate regression methods don’t care about the orientation of the proxy. But that doesn’t solve the problem for Mann as big problems remain. There are two methods – CPS and EIV. CPS methods directly care about the orientation and the upside down data are directly used in the CPS recons. In the regression methods, the data is also used upside down. The meatgrinder picks up a spurious correlation between agricultural ditches and the proxy and assigns the wrong orientation to the series in the EIV reconstruction as well. All one needs to do is follow the series through.
Mann says “potential nonclimatic influences on the Tiljander and other proxies were discussed in the SI, which showed that none of our central conclusions relied on their use”. These are not “potential” influences; they are clearly identified as actual influences by Tiljander. The SI alludes to problems, but falls well short of providing anything like a rational explanation of why this data was used given the problems. The SI also failed to disclose that the proxies were used upside down.
At this point, there are also issues of whether the SI actually shows that “none of their central conclusions” relied on their use. One of their central conclusions was that they could “get” a stick without dendro proxies – but their non-dendro recon used upside-down Tiljander. Their SI showed that they could “get” a stick without Tiljander but, as far as I can tell, the non-Tiljander comparandum used dendro series and, in particular, relied heavily on a Graybill bristlecone. It’s a large job analyzing the impact of this sort of thing. At the time, I didn’t have a working version of Mannian EIV; one of the reasons for working through Steig RegEM in such detail was to get a handle on Mannian RegEM and I may well re-visit this matter in the near future.
Their non-dendro network uses some data with the axes upside down, e.g. Korttajarvi
sediments, which are also compromised by agricultural impact (Tiljander, pers. comm.)