Response to May's "Rebuttal" of my critique of his multi-part blog on AGW

May's "rebuttal" can be found here:
https://andymaypetrophysicist.com/2024/03/13/a-rebuttal-to-a-critique-of-my-climate-model-bias-series/


My original blog post, to which it refers, can be found here:
http://planetarycfo.weebly.com/bloghome/review-of-andy-mays-multi-part-blog-on-agw-march-2024


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May pointed out, in response to my comments about lack of proper referencing, that he had included a bibliography link at the foot of each post.  The way that was done, however, was misleading.  At the foot of each part, May put:
“Download the bibliography here.”

It was reasonable to assume (without any information to the contrary) that the link provided was going to be an opportunity to download the list of (incomplete) references already provided at the foot of the text.  There was no indication that the downloadable “bibliography” would provide any more information than was set out already in the text of each blog part.
 
While May’s subsequent response to my “critique” now helps (in retrospect) to identify references he has properly provided in that downloadable bibliography, it begs a question.  Why did he include, more prominently, a list of footnotes, which omitted proper referencing, immediately below each post, rather than state something like “full referencing is included in the bibliography...”? 
The approach he has used to referencing is likely to confuse many readers and lead them to think that references are incomplete.
 
Re May’s Part 1

May then states “[Calver] launches into a long discussion of the NAO that is pointless, it was only one example of dozens of possible examples.”


If a rebuttal of what May said about NAO was going to be pointless, why did May use NAO as his only example of an ocean oscillation in his part 1 in support of his claim that this oscillation was “not incorporated into [IPCC models]” and that this somehow invalidated their results regarding either their support for AGW being a significant phenomenon or in constructing scenarios of future warming and its likely global impacts?


I note that May has not offered any counter to the following excerpts from my comments:


For [May’s] claim [about NAO] to be a successful challenge to the results from climate models regarding the impacts of human activities on long-term climate change trends, May would have to demonstrate:

1. that NAO effects are significant in terms of global climate change, and that they are not significantly affected by human drivers, and
2. that climate models were not currently including these effects accurately enough to draw valid conclusions from them, and
3. that the 30 -year base timeline in the main source would be sufficient to draw valid conclusions from, and
4. that incorporating NAO effects more accurately in climate modelling would significantly alter the conclusions drawn from them about human drivers of climate change

It should be noted that the … sources [including Eade, Scaife et al – 2022] do not specifically establish any support for any of the points 1 to 4 above.


May then sidesteps the issue by saying:
“A discussion of the various ocean oscillations is beyond this post or my series and is very well covered elsewhere. Like everything in Earth’s climate, the overall climate oscillation comprised of the individual ocean oscillations is complicated, but it is a fascinating story.”

Let’s move on, as May seems to be keen to do the same.
 
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May then introduces a new topic of discussion – “discussion on the “AMV” (AMV is what AR6 calls the AMO) in AR6 WGI page 504.”

I suggest that, rather than include that in a response, it would be better for him to include it in a revised version of his part 1, where it could be reviewed and assessed in a better context.  Otherwise, it might look like he is engaging in a gish gallop.

He summarises his response to my critique of his part 1 thus:

“Mr. Calver concludes that my part 1 was 'a cherry-picked strawman red herring, presented with very poor scholarship.' Clearly, he cherry-picked an example, turned it into a strawman to attack, attacked it badly, and completely missed the obvious link to the bibliography at the end of the post, probably because he did not read the whole thing.”

Clearly, one person’s “he cherry-picked an example” is another person’s “picked the only example that was provided as purportedly evidence supporting the core claim of part 1”.

As for “turned it into a strawman to attack, attacked it badly”, I’ll let readers decide how effective my rebuttal of the NAO example was, especially considering that the rebuttal of the NAO example has not been addressed or countered by May in his response.

 
Re May’s Part 2
 
May says:
“Mr. Calver seems to have a problem with my statement that the AR6 conclusion that CO2-caused warming feedback changes radically in the past 150 years is a very desperate reach (AR6, page 996). This is discussed thoroughly in Crok and May (2023) in Chapter 7 and the appendix to the chapter.”
 
Rather than expect readers to read an entire book, or even a chapter and appendix, it would have been more courteous of May to at least summarise the main points and pieces of evidence from those texts in his part 2.  He chose not to. 

He makes a controversial statement that “the AR6 conclusion that CO2-caused warming feedback changes radically in the past 150 years is a very desperate reach”. 

That AR6 conclusion is at the core of the IPCC AR6 WG1 conclusion that:
“It is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred.”
 
So, for May to think that it is sufficient to make his generalised rebuttal statement and then merely rely on the reader delving into an entire book chapter without further explanation is going to be seen by some as an attempt to bluster and to hope that people won’t have the inclination to invest that sort of time in some line of enquiry that might be a red herring.

May then misrepresents what I said, using a form of quote-mining in the process and creating a strawman out of it.

He says:
“[Calver] also takes issue with my statement that the proportion of warming that is due to humans is unknown, but it falls somewhere between zero and 100%. This is the conclusion of two very important peer-reviewed papers.”
 
What I actually said was:

“May then makes another unsubstantiated claim, without any evidence to support it:
‘The proportion of the warming that is due to human activities is unknown, but as we have seen in this post, it is very unlikely to be either zero or 100%, it falls in the middle somewhere, and may be small.”’
In fact, the warming from human drivers is very unlikely to be small, as shown in the ... diagram from IPCC AR6 WG1 (2021), which indicates that human drivers are highly likely to be the main driver of warming since industrialisation.  AR6 references many lines of credible evidence for this (not just climate models).”



Re May’s Part 3
 

May says:

“[Calver] goes on to say Irvine’s work should be discounted because it was not in a journal, which is not true, as the bibliography plainly states, Irvine’s initial paper was published in the peer-reviewed volume: Heat Transfer XIII: Simulation and Experiments in Heat and Mass Transfer.”

There was a misunderstanding here, and I can now see why it happened.  I was referring to Irvine’s 2023 work (whereas it is now clear that May had listed two of Irvine's works in his bibliography, which I had not accessed for my original critique, for reasons described at the top of this post). 

The relevant references in May’s bibliography are:

“Irvine, B. (2014). A comparison of the efficacy of green house gas forcing and solar forcing. In B. a. Sunden, Heat Transfer XIII: Simulation and Experiments in Heat and Mass Transfer. WIT Press. Retrieved from https://books.google.com/books?id=0ZmbBAAAQBAJ
Irvine, B. (2023, December 20). A Thought Experiment; Simplifying the Climate Riddle. Retrieved from Wattsupwiththat.com: https://wattsupwiththat.com/2023/12/20/a-thought-experimentsimplifying-the-climate-riddle/”
 

What I actually said was:

“…  the core of [May's] argument seems to be work by Irvine (2023) on warming at the surface of the oceans.  Unfortunately, Irvine’s work on this is not published in a peer-reviewed journal, so no credence can be placed on it.”


I have corrected this to the following excerpt:
 

Excerpt starts -------------
“…  the core of [May's] argument seems to be work by Irvine (2023) on warming at the surface of the oceans.  Unfortunately, Irvine’s 2023 work on this is not published in a peer-reviewed journal, so no credence can be placed on it.  However, his earlier (2014) work was published in a peer reviewed source.”

May said in his part 3:
“The difference in the surface warming effect can be a factor of three or more, Watt-per-Watt, relative to a change in greenhouse gas back-radiation. Evidence that Bob Irvine’s hypothesis is correct includes… “ 
The details of that hypothesis and discussion are beyond my level of expertise, and so I’ll make no further comment about it here, except to say I’d welcome any views from credible people with more expertise than mine.
Excerpt ends -----------------------
 

I’ve amended my original rebuttal accordingly.


May then says:
 
“[Calver] says that the IPCC reports cover solar variability, cleverly changing the time period from 1750-2019, that I referred to, to “millennial-scale.” His quote says the same as my quote and my figure 2 (AR6 p 961, figure 7.7), the IPCC ignores potential solar influences on climate from 1750 to 2019. Mr. Calver does not seem to understand what I or the IPCC wrote.”
 
This excerpt shows what I said:

Excerpt --------------------
May concludes:
“…  [that] solar variability is responsible for all or part of modern global warming… the IPCC reports and the CMIP models do not consider or investigate this possibility”
 
That is incorrect.  IPCC reports cover solar variability, citing credible sources to support it’s assessments.  For example, IPCC AR6 WG1 (2021) says:

“The AR5 … concluded that the best estimate of radiative forcing due to TSI [solar radiation] changes for the period 1750–2011 was 0.05–0.10 W m–2 (medium confidence), and that TSI very likely changed by –0.04 [–0.08 to 0.00] W m–2 between 1986 and 2008… A new reconstruction of solar irradiance extends back 9 kyr based upon updated cosmogenic isotope datasets and improved models for production and deposition of cosmogenic nuclides (Poluianov et al., 2016), and shows that solar activity during the second half of the 20th century was in the upper decile of the range. TSI features millennial-scale changes with typical magnitudes of 1.5 [1.4 to 2.1] W m–2 (C.-J. Wu et al., 2018). Although stronger variations in the deeper past cannot be ruled out completely (Egorova et al., 2018; Reinhold et al., 2019), there is no indication of such changes having happened over the last 9 kyr. ”

This evidence directly contradicts May’s claim.

Excerpt ends --------------------
 
I stand by what I said.  For May to rebut it, he would have to show:

1. That the “millennial scale” changes in solar output May mentions would significantly alter the results of the IPCC’s work, and 

2. That the IPCC ignored those effects

May has not provided evidence for either of those.
 
May then says:

"Considering most of my evidence was from AR6, [Calver] seems to be saying AR6 is not credible."
 
That is a misrepresentation of my views and comments, which is quite discourteous. 

 

Re May’s Part 4
 
May says:
“[Calver] tries to discredit Chris Scotese’s many peer-reviewed publications…”
 

No.  I simply commented on Scotese’s work of relevance to this discussion, specifically on his attempts to counter the fact that, as May himself says:
“Theodore Shepherd argues that global climate is driven by thermodynamics, and only regional climate is driven by convection and atmospheric circulation”


As I said in my critique, Scotese’s work on this has generally been rebutted.  See:
https://www.realclimate.org/index.php/archives/2014/03/can-we-make-better-graphs-of-global-temperature-history/

from which:
“Scotese is an expert in reconstructions of continental positions through time and in creating his ‘temperature reconstruction’ he is basically following an old-fashioned idea (best exemplified by Frakes et al’s 1992 textbook) that the planet has two long-term stable equilibria (‘warm’ or ‘cool’) which it has oscillated between over geologic history. This kind of heuristic reconstruction comes from the qualitative geological record which gives indications of glaciations and hothouses, but is not really adequate for quantitative reconstructions of global mean temperatures. Over the last few decades, much better geochemical proxy compilations with better dating have appeared (for instance, Royer et al (2004)) and the idea that there are only two long-term climate states has long fallen by the wayside.”
 

So, the real issue is whether theories about thermal dynamics and heat transfer around the globe (as described by May) have any impact on, or provide alternative explanations for, the well-evidenced phenomenon of AGW. 


That question is beyond my expertise, so I’ll move on from it and simply invite anyone with more expertise than mine in the climate science community to comment.
 
 
 
 
Re May’s Part 5
 
May says:
“Mr. Calver’s reading skills are extraordinarily poor.”
 
That is a personal insult, and shows that May has descended to the lower levels in the Graham’s Hierarchy of Disagreement at this point.
 
May says:
“[Calver] starts out by claiming the book that Marcel Crok and I edited… was not peer reviewed, which is nonsense, every part of the book was peer reviewed” 
 
What I actually said was:

“[May] cites a book written by himself and Marcel Crok.  That does not constitute peer-reviewed science.”

For more support for this view, see:
https://www.quora.com/Do-textbooks-count-as-peer-reviewed-sources
from which:

“Do textbooks count as peer-reviewed sources? No. Because text books are usually not peer reviewed. Even when they are, the review rules for text books as well as chapters in them are very loose. For example only one reviewer is usually asked to supply a review and that person is usually recommended by (and a close friend of) the author.  The review of text books and chapters within never results in a rejection. Only advice for changes or additions.  But unlike research papers, text books and chapters don't offer anything new. Just a compilation of previously accepted results.”

So, if May wants to use peer-reviewed sources, books will not suffice and he should refer to the underlying peer-reviewed work (eg papers), where they exist, instead, to support his claims.

May’s other comments about my critique of his part 5 are just more of the same sort of thing, so I’m not going to address it in any more detail.

He seems to have descended into making personal insults at this point rather than dealing with the substance of my critique of his part 5.
 


Re May’s Part 6

Regarding the IPCC’s conclusion that:
“It is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred.”

May claims that:
“The bottom line is that there is no evidence for this conclusion by the IPCC other than their models”
 
That is countered by, among many sources, this from the Royal Society at:
https://royalsociety.org/news-resources/projects/climate-change-evidence-causes/basics-of-climate-change/
 
“Rigorous analysis of all data and lines of evidence shows that most of the observed global warming over the past 50 years or so cannot be explained by natural causes and instead requires a significant role for the influence of human activities.
In order to discern the human influence on climate, scientists must consider many natural variations that affect temperature, precipitation, and other aspects of climate from local to global scale, on timescales from days to decades and longer. One natural variation is the El Niño Southern Oscillation (ENSO), an irregular alternation between warming and cooling (lasting about two to seven years) in the equatorial Pacific Ocean that causes significant year-to-year regional and global shifts in temperature and rainfall patterns. Volcanic eruptions also alter climate, in part increasing the amount of small (aerosol) particles in the stratosphere that reflect or absorb sunlight, leading to a short-term surface cooling lasting typically about two to three years. Over hundreds of thousands of years, slow, recurring variations in Earth’s orbit around the Sun, which alter the distribution of solar energy received by Earth, have been enough to trigger the ice age cycles of the past 800,000 years.
Fingerprinting is a powerful way of studying the causes of climate change. Different influences on climate lead to different patterns seen in climate records. This becomes obvious when scientists probe beyond changes in the average temperature of the planet and look more closely at geographical and temporal patterns of climate change. For example, an increase in the Sun’s energy output will lead to a very different pattern of temperature change (across Earth’s surface and vertically in the atmosphere) compared to that induced by an increase in CO2 concentration. Observed atmospheric temperature changes show a fingerprint much closer to that of a long-term CO2 increase than to that of a fluctuating Sun alone. Scientists routinely test whether purely natural changes in the Sun, volcanic activity, or internal climate variability could plausibly explain the patterns of change they have observed in many different aspects of the climate system. These analyses have shown that the observed climate changes of the past several decades cannot be explained just by natural factors.”
 
 
May claims:
“There is plenty of doubt about the whole AGW (Anthropogenic Global Warming) idea, AGW has never been observed or measured, only modeled. We cannot even be sure it exists at all, it is just a reasonable hypothesis that humans might have some impact on climate, nothing more.”
 
Every credible scientific institution in the world would dispute that claim from May.


 
Re May’s Part 7
 
May claims:
“Mr. Calver does trash the Nobel Prize winning economist William Nordhaus, just as AR6 does.”
 
What I actually said was:
“… the economic approach of William Nordhaus, which May relies heavily on in this part, has been counteracted by many economists (some of them even mainstream).  An example is Keen (2023) “Loading the dice against pension funds” (discussed earlier).”

I’ll leave readers to decide whether or not this constitutes “trashing … William Nordhaus”.
 
May says:
“I think William Nordhaus is one of the best economists of our day. Nordhaus is sort of a lukewarmer and thinks that climate change should be dealt with, and I don’t agree with him on that, but he is a smart guy and he did win a Nobel Prize. Show some respect.”

I maintain that I showed no disrespect for Nordhaus.  I merely pointed out that some of his relevant work has been countered by other (also respectable) economists. 

​May would be well advised to make sure he avoids falling into the trap of using "Appeal to Authority" or "Argument from Authority", as discussed here:
https://en.wikipedia.org/wiki/Argument_from_authority

from which:
"An argument from authority (argumentum ab auctoritate), also called an appeal to authority, or argumentum ad verecundiam, is a form of argument in which the opinion of an influential figure is used as evidence to support an argument.  All sources agree this is not a valid form of logical proof, that is to say, that this is a logical fallacy (also known as ad verecundiam fallacy) , and therefore, obtaining knowledge in this way is always fallible."
 

​
Summary
 
In May’s final summary on my critique of his 7 part multi-blog, he claims:
“[Calver’s] contrary claims were generally from very biased and unreliable blogs, like realclimate and desmog.”

The record will show that the majority of my rebuttals refer to credible scientific sources.  Where I’ve referenced blogs, those blogs are authored by credible climate scientists and/or make references to credible scientific works.  In contrast, I’ve noted where May has referenced wholly unreliable sources on AGW such as WattsUpWithThat, Bjorn Lomborg and so on.

My summary of May’s “rebuttal” is that it only addresses some of the matters I raise as difficulties in placing reliance on his main assertions and supposed counterevidence about AGW in general and climate modelling in particular.  And most of his counters are weak.  In addition, he has resorted to making personal insults rather than properly addressing the criticisms of his work.