"Although climate scientists keep telling that defects in their “hockey stick” proxy reconstructions don’t matter –
that it doesn’t matter whether they use data upside down,
that it doesn’t matter if they cherry pick individual series depending on whether they go up in the 20th century,
that it doesn’t matter if they discard series that don’t go the “right” way (“hide the decline”),
that it doesn’t matter if they used contaminated data or stripbark bristlecones,
that such errors don’t matter because the hockey stick itself doesn’t matter
– the IPCC remains addicted to hockey sticks:
lo and behold, Figure 1a of its newly minted Summary for Policy-makers contains what else – a hockey stick diagram.
If you thought Michael Mann’s hockey stick was bad, imagine a woke hockey stick by woke climate scientists.
As the climate scientists say, it’s even worse that we thought.
Curiously, this leading diagram of the Summary of Policy-Makers does not appear in the Report itself.
(At least, I was unable to locate it in Chapter 2.)
However, it is clearly the progeny of PAGES2K Consortium (Nature 2019) and Kaufman et al (2020), both of which I commented on briefly on Twitter (see here).
... The idea/definition of a temperature “proxy” is that it has some sort of linear or near-linear relationship to temperature with errors being white noise or low-order red noise.
In other words, if you look at a panel of actual temperature “proxies”, you would expect to see series that look pretty similar and consistent.
But that’s not what you see with the data used by the IPCC.
You’d never know this from the IPCC report or even from the cited articles, since authors of these one- and two-millennium temperature reconstructions scrupulously avoid plotting any of the underlying data.
It’s hard for readers unfamiliar with the topic to fully appreciate the extreme inconsistency of underlying “proxy” data, given the faux precision of the IPCC diagram.
Many of the series discussed in this post, including nearly all of any HS-shaped series, have been previously discussed in Climate Audit blog posts ...
The PAGES2019 is not a “random” selection of proxies, but winnowed through ex post criteria.
As Rosanne d’Arrigo explained to the NAS panel many years ago: if you want to make cherry pie, you first have to pick cherries.
The PAGES2019 dataset consists of 257 proxies,
selected from the prior PAGES2017 dataset consisting of 692 proxies,
which had previously been selected from thousands of proxy series accumulated by many authors over the years.
... a random sample of 11 PAGES2017 series.
... most of the series are non-descript and short.
Only one series in this sample (Cape Ghir temperature alkenones) has a hockey stick shape, but it goes down.
... And this is not a case where the raw proxy measurement has an inverse relationship to temperature (e.g. coral Sr or coral d18O), but a case where the temperature estimate from the proxy goes down.
Alkenones are a very unique proxy because there are widely accepted formulas for converting alkenone measurements directly to deg C.
Alkenones are widely used to estimate ocean temperature in deep time, yielding consistent estimates for millions of years.
This is totally different than tree ring measurements, where ring widths have first to be adjusted for age and location, prior to trying to develop an ad hoc local formula to estimate local temperature from a sort of average of ring widths.
Precisely why local Cape Ghir (offshore Morocco) temperatures were going down is somewhat of a quandary.
Rather than figuring out this quandary, Neukom and the woke just turn the series upside down, following the example of Upside Down Mann
by orienting the series according to its correlation with target instrumental temperature, even in their “CPS” reconstruction –
a technique that is normally resistant to opportunistic flipping of proxies to enhance HS-ness of a final reconstruction.
... (to my knowledge) in all prior reconstructions by non-woke authors is an average of scaled data that has been oriented ex ante by known properties of the proxy.
I.e. it won’t flip over an alkenone temperature estimate simply because it goes the wrong way.
But this salutary property is not maintained in Neukom’s bastardized implementation of CPS – a bastardization that ought to have been resisted by reviewers somewhere along the line.
PAGES2K produced temperature reconstructions by seven different methods, all of which yielded somewhat similar results to CPS – strongly suggesting that these other methods also flip series like Cape Ghir.
A Second Batch: PAGES2019 Proxies
Here’s a second random sample of proxies, this time all from the additionally screened PAGES2019 subset. ...
Four of the series in the sample are very short – three of them are actually shorter than the instrumental record.
These are all coral Sr or coral d18O series, which make up 25% of the PAGES2019 data set.
The extremely short records ... are typical, indeed almost universal, in this class of proxy.
They do have a pronounced trend in the instrumental period.
This contrasts with the lack of trend that one sees in the two long proxies ... a tree ring series from Mt Read, Tasmania (also used in MBH98) and a 1983 ice core series by Fisher from Devon Ice Cap on Baffin Island (also available to 1990s vintage multi-proxy studies).
The short coral series do not contribute information to the medieval and earlier periods which one is trying to compare to the modern period.
So what is their function?
Do they contribute anything? ...
The tree ring series in this sample are rather short; the screening procedures have somewhat concentrated series with slight upticks.
(The stripbark bristlecone chronologies that were so prominent in the Mann et al Hockey Stick continue to be used in PAGES2019 – as discussed below.)
... No chronology from original authors is archived at NOAA: so how did PAGES2K manage to get such a hockey stick?
I have no idea.
The most “interesting” series in this sample batch is the borehole temperature reconstruction that has such an uncanny resemblance to the eventual IPCC reconstruction.
... I’ve written multiple posts on the mathematics of borehole inversion calculations, which purport to estimate temperatures for thousands of years into the past from modern day temperatures measured downhole.
... As far as I’m concerned, nearly all the details that specialists pontificate about are a sort of Chladni pattern artifact.
... Here the problem was much stranger.
A few years earlier, I had (circuitously) managed to obtain a copy of the code used to calculate this borehole inversion (which is not archived anywhere.)
The code showed that they had deleted the top 15 meters of the core from their calculation.
I’ve had a LOT of trouble getting the underlying borehole temperatures for some famous series.
(The 2006 NAS panel cited one such result, but the original author (a US government employee) refused to make the data available, and, to my knowledge, it remains unavailable.)
However, in this case, the underlying downhole temperatures had been archived, including the values had been deleted.
Needless to say, they went down.
An inversion using all the data would not have resulted in the impressive Hockey Stick in the PAGES2019 dataset, but a substantial recent decline.
Prima facie, another example of “hide the decline”.
To be fair, as I observed in the earlier post, there is a dramatic seasonal fluctuation in temperatures in the top portion of the Antarctic ice sheet,
which makes the already formidable (and probably impossible) inversion problem even more intractable.
In my Feb 2019 post, I showed a diagram from van Ommen et al (1999) which showed the dramatic changes in downhole temperature as the seasons changed: a sort of damped sinusoidal pattern can be discerned.
In the top 15 meters of the core, seasonal changes dominate.
Note that the blade on the hockey stick in this IPCC series is entirely dependent on the choice of 15 meters as a cutoff point for the borehole inversion.
A choice of 20 meters would have probably eliminated the blade altogether.
The fact that the top portion of the core has to be excluded because of seasonal effects also creates a strange irony:
the layers at 15 meters at WAIS date back to the 1960s.
So IPCC has ended up relying on a series that purports to reconstruct temperature up to 2007, but without using any of the ice core dating from ~1965 to 2007.
The calculation is entirely done from ice core layers dated prior to the 1960s.
Does this seem reliable to any of you?
Doesn’t to me.
Furthermore, the WAIS Divide borehole temperature reconstruction yields a totally different result than the widely replicated and well understood d18O isotope series.
Given the questions and defects surrounding the WAIS borehole inversion series, it is absurd that this series (a singleton, to boot) should be used in a policy-relevant document.
That the final IPCC diagram is so similar to this garbage series also makes one wonder about what is happening under the hood of the multivariate calculations.
... They took “hide the decline” to extremes that had never been contemplated by prior practitioners of this dark art.
Rather than hiding the decline in the final product, they did so for individual trees: ... they excluded the “divergent portions” of individual trees that had temerity to have decreasing growth in recent years.
... sharp-eyed readers may recall the identifier nv512.
It is one of the classic Graybill stripbark bristlecone chronologies (Pearl Peak), which we had observed to dominate both the MBH98 PC1 and the final MBH98 reconstruction.
It (and other key stripbark sites) was listed in McIntyre and McKitrick (2005 GRL) Table 1:
Readers will also recall that the 2006 NAS Panel recommended that “stripbark” chronologies be “avoided” in temperature reconstructions.
Although the climate community has professed to implement the recommendations of the NAS Panel, they are addicted to stripbark chronologies, the properties of which are well known.
Five different PAGES2019 series
use stripbark bristlecones ...
nv512 (Pearl Peak);
nv513 (Mount Washington);
ca529 (Timber Gap Upper);
SFP (an update of San Francisco Peaks, incorporating az510) and
GB (a composite of Pearl Peak, Mount Washington and Sheep Mountain, using both Graybill and updated information). ... "