Guest post by Mike Jonas
A few days ago, on Judith Curry’s excellent ClimateEtc blog, Vaughan Pratt wrote a post “Multidecadal climate to within a millikelvin” which provided the content and underlying spreadsheet calculations for a poster presentation at the AGU Fall Conference. I will refer to the work as “VPmK”.
VPmK was a stunningly unconvincing exercise in circular logic – a remarkably unscientific attempt to (presumably) provide support for the IPCC model[s] of climate – and should be retracted.
The background to VPmK was outlined as “Global warming of some kind is clearly visible in HadCRUT3  for the three decades 1970-2000. However the three decades 1910-1940 show a similar rate of global warming. This can’t all be due to CO2 “.
The aim of VPmK was to support the hypothesis that “multidecadal climate has only two significant components: the sawtooth, whatever its origins, and warming that can be accounted for 99.98% by the AHH law “,
· the sawtooth is a collection of “all the so-called multidecadal ocean oscillations into one phenomenon“, and
· AHH law [Arrhenius-Hofmann-Hansen] is the logarithmic formula for CO2 radiative forcing with an oceanic heat sink delay.
The end result of VPmK was shown in the following graph
Fig.1 – VPmK end result.
· MUL is multidecadal climate (ie, global temperature),
· SAW is the sawtooth,
· AGW is the AHH law, and
· MRES is the residue MUL-SAW-AGW.
As you can see, and as stated in VPmK’s title, the residue was just a few millikelvins over the whole of the period. The smoothness of the residue, but not its absolute value, was entirely due to three box filters being used to remove all of the “22-year and 11-year solar cycles and all faster phenomena“.
If the aim of VPmK is to provide support for the IPCC model of climate, naturally it would remove all of those things that the IPCC model cannot handle. Regardless, the astonishing level of claimed accuracy shows that the result is almost certainly worthless – it is, after all, about climate.
What VPmK does is to take AGW as a given from the IPCC model – complete with the so-called “positive feedbacks” which for the purpose of VPmK are assumed to bear a simple linear relationship to the underlying formula for CO2 itself.
VPmK then takes the difference (the “sawtooth”) between MUL and AGW, and fits four sinewaves to it (there is provision in the spreadsheet for five, but only four were needed). Thanks to the box filters, a good fit was obtained.
Given that four parameters can fit an elephant (great link!), absolutely nothing has been achieved and it would be entirely reasonable to dismiss VPmK as completely worthless at this point. But, to be fair, we’ll look at the sawtooth (“The sinewaves”, below) and see if it could have a genuine climate meaning.
Note that in VPmK there is no attempt to find a climate meaning. The sawtooth which began life as “so-called multidecadal ocean oscillations” later becomes “whatever its origins“.
The two main “sawtooth” sinewaves, SAW2 and SAW3, are:
Fig.2 – VPmK principal sawtooths.
(The y-axis is temperature). The other two sinewaves, SAW4 and SAW5 are much smaller, and just “mopping up” what divergence remains.
It is surely completely impossible to support the notion that the “multidecadal ocean oscillations” are reasonably represented to within a few millikelvins by these perfect sinewaves (even after the filtering). This is what the PDO and AMO really look like:
Fig.3 – PDO.
Fig.4 – AMO.
Both the PDO and AMO trended upwards from the 1970s until well into the 1990s. Neither sawtooth is even close. The sum of the sawtooths (SAW in Fig.1) flattens out over this period when it should mostly rise quite strongly. This shows that the sawtooths have been carefully manipulated to “reserve” the 1970-2000 temperature increase for AGW.
Fig.5 – How the sawtooth “reserved” the1980s and 90s warming for AGW.
VPmK aimed to show that “multidecadal climate has only two significant components”, AGW and something shaped like a sawtooth. But VPmK then simply assumed that AGW was a component, called the remainder the sawtooth, and had no clue as to what the sawtooth was but used some arbitrary sinewaves to represent it. VPmK then claimed to have shown that the climate was indeed made up of just these two components.
That is circular logic and appallingly unscientific. The poster presentation should be formally retracted.
[Blog commenter JCH claims that VPmK is described by AGU as “peer-reviewed”. If that is the case then retraction is important. VPmK should not be permitted to remain in any “peer-reviewed” literature.]
1. Although VPmK was of so little value, nevertheless I would like to congratulate Vaughan Pratt for having the courage to provide all of the data and all of the calculations in a way that made it relatively easy to check them. If only this approach had been taken by other climate scientists from the start, virtually all of the heated and divisive climate debate could have been avoided.
2. I first approached Judith Curry, and asked her to give my analysis of Vaughan Pratt’s (“VP”) circular logic equal prominence to the original by accepting it as a ‘guest post’. She replied that it was sufficient for me to present it as a comment.
My feeling is that posts have much greater weight than comments, and that using only a comment would effectively let VP get away with a piece of absolute rubbish. Bear in mind that VPmK has been presented at the AGU Fall Conference, so it is already way ahead in public exposure anyway.
That is why this post now appears on WUWT instead of on ClimateEtc. (I have upgraded it a bit from the version sent to Judith Curry, but the essential argument is the same). There are many commenters on ClimateEtc who have been appalled by VPmK’s obvious errors. I do not claim that my effort here is in any way better than theirs, but my feeling is that someone has to get greater visibility for the errors and request retraction, and no-one else has yet done so.