To recap: the image shown was being shamelessly abused by the septics as purported proof that the MWP was much warmer than today and this vital evidence was being suppressed by the IPCC using black helicopters and the usual kind of stuff. I thought that the major point is that the HPS ’97 graph (the one here) just isn’t used anymore by anyone and wondered why not (not even H, P or S used it).
The reconstruction of climate over the past one to two millennia has not been free of contention… one of our publications… HPS97… was occasionally offered as evidence that the MWP was in fact warmer than late 20th century [e.g., Deming, 2004]. Yet in our later publications on climate reconstruction… HPS00… there are no references to the results of HPS97. The initial purpose of the present paper is to clarify and resolve this apparent change of perspective in our work between HPS97 and HPS00. Although science certainly allows for abandoning earlier results in favor of later results, in our case there is a different explanation. The fundamental difference between HPS97 and HPS00 is that they do not analyze the same data. Below we describe their respective datasets, and show why the results of HPS97 cannot be used for comparing MWP warmth to the 20th century.
Aha! This is just what I want (the explanation of the mystery, I mean. The side-swipes at the septics are a bonus).
So then they explain what anyone who read their paper with care could have discovered for themselves (not McI, obviously):
One very important aspect of data selection relevant to the debate about whether the MWP was warmer than 20th century temperatures, is mentioned explicitly in HPS97
in the section on Data:”We excluded data with representative depths less than 100 m . . . [because] . . .the uppermost 100 meters is the depth range most susceptible to non-climatic perturbations. . .; moreover, subsurface temperature measurements in this range yield information principally about the most recent century”. The consequence of excluding the upper 100 meters is that the 20,000 year reconstructions in HPS97 contain virtually no information about the 20th century. As the authors of HPS97 we can be criticized for not stating
explicitly in the abstract and figure caption that the ‘present’ (the zero on the time axis) really represents something like the end of the 19th century, rather than the end of the 20th century. At the time we published that paper our focus was on trying to extract a broad-brush representation of Late Quaternary surface temperature variability that might be overprinted on the ensemble of world-wide continental heat flux measurements. We did not anticipate that a comparison of late 20th century and Medieval Warm Period temperatures would later become a contentious issue.
Translation: f*ck off you septic b*st*rds and stop quoting our paper for your wacko ends.
But here is there new version. “Now” is now a lot warmer than their best-guess MWP; and warmer even than their warmest possible. Fair enough.
But the mystery of HPS97 persists. They do hint that the heat flow database is probably poor quality, as I speculated: The entries in this T-z database meet several quality
control criteria not imposed on entries to the earlier heat flow database. and HPS97 is a broad-brush look at the entire Late Quaternary (exclusive of the 20th century as noted above), using a large but noisy, low temporal resolution dataset.
There is also a mystery of reconciling the current results with those of HPS97. A brief skim of the current paper says its a meld of the HPS97 and HPS00 datasets. HPS00 is only the last 500 years, so why is the current version so different from HPS97 prior to 2000y ago? HPS97 had a range of 2.5 oC for their mid-range estimate of the difference between LGM (last glacial maximum) and HCO (holocene climate optimum). HPS08 has a difference of 5.5 oC. Thats a big change, which they don’t notice, as far as I can tell. Hopefully someone competent in these things will read the paper in detail and explain.