Climate Audit

Four Twelve (Alaska) was one of the 11 Jacoby and D’Arrigo series used in MBH98. In our original 2003 article, we observed that the MBH98 version of this chronology differed substantially from the chronology officially archived at NOAA, and, in our sensitivity study, used the archived version (after using the MBH version for benchmarking.)  Among other things, Mann objected vehemently to the very idea of the sensitivity analysis that we had carried out:

An audit involves a careful examination, using the same data and following the exact procedures used in the report or study being audited.  McIntyre and McKitrick (“MM03”) have done no such thing, having used neither the data nor the procedures of MBH98. Their effort has no bearing on the validity of the conclusions reported in MBH98, and is no way a “correction” of that study as they claim. On the contrary, their analysis seriously misrepresents MBH98. 

However, the different Jacoby versions were a secondary issue in the contemporary debate and the inconsistency between MBH98 and Jacoby versions wasn’t pursued further at the time.  

Analysis was further frustrated by peculiar inconsistencies in the Jacoby archive itself.  For Four Twelve (and several other sites), the archived chronology ended in 1990, whereas archived measurement data ended in 1977.  The period of the archived measurement data was consistent with the period of the MBH98 version of Four Twelve (treeline1.dat), but there was no measurement archive corresponding to the archived chronology.  It was the sort of dog’s breakfast that was all too typical.  Jacoby’s death-bed archive once again provides an answer (as discussed below).

First, here is a comparison of the MBH98 chronology (treeline1.dat) versus the chronology calculated from the ak031.rwl measurement data (covering exactly the same period) using Bunn’s ModNegExp option (which corresponds to contemporary Jacoby methodology).  The two chronologies are highly correlated and cover the same period, but the elevated mid-20th century values of the MBH98 version were not replicated.   I presume that the MBH98 version came from Jacoby and/or D’Arrigo and that this version was used in Jacoby and D’Arrigo 1989 as well.  Mann’s composite of Jacoby and D’Arrigo treeline series was also used for the MBH99 bodge of the North American PC1 (to shave down the blade to “get” a passing RE – as Jean S showed long ago).

One of the “new” measurement datasets in Jacoby’s death-bed 2014 archive was ak109.rwl, described as a Four Twelve Update. It covered exactly the same period as the ancient ak031.crn chronology (1524-1990). Application of ModNegExp chronology algorithm yielded an almost exact replication of the archived chronology, as shown below.  This confirms that (1) that the ak031.crn chronology was derived from ak109.rwl measurement data – an inconsistency unique to the Jacoby treeline data; (2) the ModNegExp algorithm is a reliable equivalent to the methodology used by Jacoby for the chronologies archived in the early 1990s.

Inconsistent Information on Updates

In the early 1990s, Jacoby updated multiple sites in the northern treeline network published in 1989.  In this article, I’ve commented on the Four Twelve Update in 1990, for which the chronology was archived in the early 1990s, but the measurement data not until 2014, more than 20 years later and more than 30 years since the original collection.

A much more troubling example (cited in early Climate Audit articles) was the corresponding update for the Gaspe, also carried out in the early 1990s, where the measurement data yielded a totally result than the big bladed hockey stick used in MBH98, but was withheld by Jacoby et al for a further 20+ years until a few months before Jacoby’s death.   

D’Arrigo et al 2006 NWNA Composite

Four Twelve (Alaska) is one of four sites that contribute to the D’Arrigo et al 2006 Northwest Alaska (NWNA) Composite, illustrated below. However, the NWNA Composite goes up in its closing period, as opposed to the closing decline of both Four Twelve versions.  Curiously, the NWNA Composite only uses the second (1990) tranche of Four Twelve measurement data, excluding the original (1970s) tranche, whereas for nearby Arrigetch, it incorporated both tranches. 

An odd inconsistency. I’ll look at the D’Arrigo NWNA Composite in due course.