Audit of an Audit of an Auditor
Posted by Jeff Id on September 29, 2009
Just a short post tonight I hope. Tom P, an apparent believer in the hockey stick methods posted an entertaining reply to Steve McIntyre’s recent discoveries on Yamal. He used R code to demonstrate a flaw in SteveM’s method. His post was on WUWT, brought to my attention by Charles the moderator and is copied here where he declares victory over Steve.
Steve McIntryre’s reconstructions above are based on adding an established dataset, the Schweingruber Yamal sample instead of the “12 trees used in the CRU archive”. Steve has given no justification for removing these 12 trees. In fact they probably predate Briffa’s CRU analysis, being in the original Russian dataset established by Hantemirov and Shiyatov in 2002.
One of Steve’s major complaint about the CRU dataset was that it used few recent trees, hence the need to add the Schweingruber series. It was therefore rather strange that towards the end of the reconstruction the 12 living trees were excluded only to be replaced by 9 trees with earlier end dates.
I asked Steve what the chronology would look like if these twelve trees were merged back in, but no plot was forthcoming. So I downloaded R, his favoured statistical package, and tweaked Steve’s published code to include the twelve trees back in myself. Below is the chronology I posted on ClimateAudit a few hours ago.
The red line is the RCS chronology calculated from the CRU archive; black is the chronology calculated using the Schweingruber Yamal sample and the complete CRU archive. Both plots are smoothed with 21-year gaussian, as before. The y-axis is in dimensionless chronology units centered on 1.
It looks like the Yamal reconstruction published by Briffa is rather insensitive to the inclusion of the additional data. There is no broken hockeystick.
The !temp in Steve’s line removes 12 series of Yamal for the average while Tom’s version includes it. I’m all for inclusion of all data, but I am a firm believer that Briffa’s data is probably a cherry picked set of trees to match temp or something. Therefore by inclusioin of the sorted Briffa Yamal version, we have an automatic exclusion of data which would otherwise balance the huge trend. However, this is not the problem with Tom’s result. The problem lies in this plot, also created by TomP’s code.
Here is the zoomed in version:
Above we can see that everything in TomP’s curve after 1990 is actually 100% Briffa Yamal data.
So the question becomes – What does the series look like if the Yamal data doesn’t create the ridiculous spike at the end the curve?
I truncated the black line at 1990 below.
The black line is truncated at the end of the Schweingruber data and it looks pretty similar to the graph presented in the green line by Steve McIntyre again below.
Don’t be too hard on Tom P, he honestly did a great job and took the time to work with the R script which is more than most are willing to. Steve is a very careful worker though and it’s damn near impossible to catch him making mistakes. Trust a serious skeptic, it’s not easy to find mistakes in his work and some of us check him just as I spent over an hour checking Tom’s work. In my opinion Tom deserves congratulations for his efforts and checking, this way we all learn.
I’ve now been all the way through SteveM’s scripts from beginning to end and can’t find any problems with the script, maybe others can!