Addiction of paleoclimate reconstructions to particular proxies has been a longstanding concern at Climate Audit.

One of the battleground issues has been the addiction to Briffa’s Yamal tree ring series, while the nearby update of Polar Urals (with a pronounced MWP) was disappeared. (See CA category.)

Just before Climategate, we raised questions about the Yamal reconstruction – noticing first that, contrary to prior belief, it was not “highly replicated”, having far fewer modern trees than is standard for an RCS reconstruction, and that the reconstruction was highly sensitive to inclusion of a nearby Schweingruber site (Khadyta River, Yamal). Briffa did not deny the validity of this criticism, instead attempting to salvage the reconstruction by adding in cores from some nearby sites (but notably not Polar Urals.)

The elephant in the room remained the disposition of the Polar Urals site. A 1995 Briffa reconstruction from this site purported to show that 1032 was the “coldest” year in the millennium. Updated data had shown elevated ring widths in the MWP. However, Briffa hadn’t reported this. (Schweingruber had archived the updated measurement data at the ITRDB, but no journal article had reported the results.

The Climategate Letters have a teaser here. On April 28, 2006 (almost exactly the same date as I was being stonewalled about Yamal, Taymir and Tornetrask measurement data), Osborn emailed Philip Brohan of the UK Met Office:

To: philip.brohan@xxxxxxxxx.xxx

From: Tim Osborn

Subject: Re: Standardisation uncertainty for tree-ring series

Cc: Keith Briffa ,simon.tett@xxxxxxxxx.xxx Hi Philip,

we have three “groups” of trees:

“SCAND” (which includes the Tornetrask and Finland multi-millennial chronologies, but also some shorter chronologies from the same region). … “URALS” (which includes the Yamal and Polar Urals long chronologies, plus other shorter ones). These fall mainly within these 3 boxes:

52.5E, 67.5N

62.5E, 62.5N (note this is the only one not at 67.5N)

67.5E, 67.5N “TAIMYR” (which includes the Taimyr long chronology, plus other shorter ones). These fall mainly within these 4 boxes:

87.5E, 67.5N

102.5E, 67.5N

112.5E, 67.5N

122.5E, 67.5N We do some analysis at the group scale, and for this we take the JJA temperatures from each box and average to the group scale to obtain a single series from each of SCAND,

URALS and TAIMY. We do some analysis at the overall scale, and for this we take these three group temperature series and average them to get an overall NW Eurasia temperature for boxes

with tree chronologies in them…

So on this occasion, the long Polar Urals chronology, together with other “shorter” chronologies (presumably the Schweingruber chronologies that Gavin Schmidt condemned) were included in a larger regional RCS reconstruction – something that Rob Wilson would have been interested in seeing.

But the subsequent Briffa et al (2008 Phil Trans B) only includes the very small Yamal data – without the long Polar Urals chronology or the shorter chronologies. Wonder why?



