The featured image is by Josh, used with permission.

There are 20 clearly false statements and three additional problematic statements in Tinus Pulles’ “Climate Denialism.” Most of them stem from disagreements on how to interpret existing data. However, some are due to his lack of understanding of what we wrote or, intentional distortion of what we wrote. What is puzzling is I was asked to peer review this paper months ago and I sent in the review in October. Nearly all the errors you will see in the list below were pointed out then, yet they remain in the paper. To nearly everyone familiar with climate science literature and our paper, these errors are obvious. I find it more than a bit alarming that even the grammatical errors I pointed out in the paper last October are still in it. Why such a flawed paper was published is a mystery. Peer review is not working as intended.

Pulles appears to believe that dangerous human-caused climate change is an undisputed fact. He also repeatedly conflates “climate change” with “dangerous man-made climate change.” Human-caused global climate change has never been observed, either directly or statistically, only modeled. The paper is critical of our paper from earlier in the year (May & Crok, 2024), but that paper makes it clear that human-caused climate change is not an existential threat and the incidence and magnitude of recent extreme weather events have not exceeded expected natural variability as shown in the recent IPCC AR6 WGI report on page 1856 and elsewhere.

Two citations in Pulles, (Hoofnagle & Hoofnagle, 2007) and (Diethelm & McKee, 2009), are editorials and not academic articles. Further both are slanderous attacks on climate skeptics and compare them directly to people who deny the Holocaust occurred and other similarly abhorrent groups. In fact, Hoofnagle mentions the World War II Holocaust five times. The Holocaust is a historical fact, I have visited Auschwitz/Birkenau personally and know its horrors, I defy anyone to take a tour of Auschwitz/Birkenau and leave without tears in their eyes, I don’t think it is possible. On the other hand, the hypothesis that climate change is mostly man-made and potentially dangerous is based entirely on theoretical considerations and model projections, these are research topics that Hoofnagle and Hoofnagle admit they do not “understand … worth a damn.” It is disingenuous in the extreme to conflate denying the Holocaust to climate skeptics who are simply challenging a popular scientific hypothesis in a time-honored traditional way.

I normally have no problem with the phrase “climate denier,” if it is clearly defined as one who is skeptical of the idea of dangerous man-made climate change but citing editorials that directly compare May & Crok to denying the Holocaust is beyond the pale of normal civil discourse and has no place in a respectable academic journal.

If alternative views on climate change are simply dismissed thoughtlessly as “denialism,” then normal scientific discourse is no longer possible. May & Crok make a good case that climate change is not a grave threat for mankind. It would have been more interesting if Pulles had made a similar argument for the opposite viewpoint. Readers of both could then make up their own minds. Instead, Pulles only attacks May & Crok with vacuous ad hominem arguments and says little of substance.

Climate skeptics acknowledge that dangerous human-caused climate change is possible but see no observational or statistical evidence supporting such an assertion. The currently available evidence tends to dispute the idea as explained in May & Crok. To skeptics, or “deniers,” if you prefer, the idea is clearly open to scientific debate.

The authors claim our article belittles scientific evidence by saying “AR6 claims,” “they believe,” or that “we need evidence.” These phrases are hardly belittling and fairly normal and respectful language when challenging a new scientific idea. In a debate one must establish that they understand the opposing view and restate it in a clear way. They claim May & Crok ignore thousands of pages of evidence. That many pages wouldn’t be needed if real evidence of dangerous man-made climate change existed.

It seems to me the author bears the burden of proof and has not delivered. His clearly false statements do not help his case.

This is just a quick summary of the most egregious problems in “Climate Denialism.” The detailed description and documentation of each error and problem, plus a bibliography is in a separate document. I peer reviewed “Climate Denialism” and wrote a detailed critique of the paper very similar to this one. The errors I point out below were nearly all in my October 2024 review. After the paper was published, I downloaded the final version and updated my review document to match the published version, very few changes to the October original were needed.

Key problems in “Climate Denialism.”

  1. Climate change “deniers” are directly compared to deniers of the Holocaust and other abhorrent groups in the two main sources used in the paper to define “Climate Denialism.” The Holocaust is a historical fact and dangerous man-made climate change is a hypothesis, they are not comparable.
  2. Pulles claims “deniers,” and May & Crok, specifically, deny science or climate science. I know of no man-made climate skeptics who deny science and certainly May & Crok do not deny science or climate science. Pulles conflates “science” and “climate science” with a popular climate change hypothesis that he never really defines. This confirms my opinion that the “consensus on climate change” means whatever it is needed to mean at the time.
  3. Pulles claims that denialists try to disprove “a scientific consensus.” Science is the methodology civilization invented to challenge a consensus opinion, quite the opposite of the author’s meaning. What is the purpose of science, other than as a methodology for challenging a consensus opinion?
  4. Pulles claims “denialism” is a “weapon of war against climate policies.” Scientific debate is not a war or a weapon. Scientific debate is a healthy thing.
  5. Pulles claims the peer review of May & Crok was weak, but all proper procedures were followed and the paper passed peer review three votes to one.
  6. Pulles erroneously claims denialists perform no work in the field of climate science. Judy Curry, Dick Lindzen, Willie Soon, Ole Humlum, and many others would be very surprised to hear this. This is an egregious error and insulting to the hundreds, perhaps thousands of climate skeptic peer-reviewed papers.
  7. Pulles erroneously claims the imbalance of net radiation at the top of the atmosphere (TOA) is known to be 0.7 W/m2. He further claims that the global average imbalance does not change. That is the “distributional effects [changes in Earth’s surface due to weather] will not disturb the global averages” due to the law of conservation of energy. This unsupported assertion has several problems, first the satellite data shows an imbalance of 4.3 W/m2, which is clearly impossible. The various TOA imbalances in the literature (0.6, 0.7, 0.9, etc.) are all assumed because the data are not accurate enough to determine a value, although since the world is warming, recent values (since 1980) are likely positive. Second since Earth’s surface has considerable heat storage capacity, just changing the energy residence time in the climate system a small amount can have a huge impact (see here and here for more details). In reality the energy imbalance must change continuously, how much is anyone’s guess. The ocean oscillations, like the PDO, the AMO, El Niño, and La Niña (ENSO), testify to this constantly changing quantity of stored energy. The “global averages” are indeed affected by changing heat storage, look at 1945 to 1976 in figure 1 of May & Crok for an example and compare to figure 2 of May & Crok (download the complete final submitted version here). While the incoming solar radiation has varied very little recently, the outgoing longwave radiation from Earth’s surface varies with temperature refuting Pulles’ assertion about an unchanging imbalance.
  8. Pulles erroneously claims that current warming is clearly due to anthropogenic GHG (greenhouse gas) emissions, but this has not been established except in climate models. The basis for the statement is a correlation between CO2 and warming (his figure 3), yet earlier Pulles admits that correlation is not causation.
  9. Pulles claims that a disputed paper, Chen, et al., shows that McKitrick’s criticisms of the atmospheric fingerprint are incorrect. In fact, Chen, et al. mostly confirm McKitrick’s conclusions, but try and say they don’t matter and can be assumed away. For Ross McKitrick’s detailed criticisms of Chen, et al. see here.
  10. Pulles claims that if McKitrick is correct, it does not disprove that human activity is the main cause of global climate change. There is nothing to disprove, no one has proven that humans are the main cause of climate change. The human impact on climate has not even been detected.
  11. Pulles admits that climate models are inaccurate, relative to observations, in the tropical middle troposphere (see here) but erroneously claims that the “extra” heat must be somewhere else. Why? There may be no extra heat, the radiation imbalance at the top of the atmosphere is clearly unknown and constantly changing, we don’t even know if it is positive or negative. Further, as noted above, outgoing longwave radiation is increasing in a manner consistent with warming, and there is little change in incoming solar radiation, there is no “extra” heat that we can detect.
  12. Pulles erroneously claims that May & Crok state that the AMO is purely due to natural causes. In fact, we say that human-caused warming from 1976 to the present day might have been boosted by a natural AMO cycle. If true, this invalidates the IPCC idea that humans have caused all the warming since 1976.
  13. Pulles erroneously claims that Mann (2020 & 2021) provide evidence that the AMO is not a natural phenomenon. Mann conducted a climate model study that showed the AMO might be a result of volcanic activity and anthropogenic emissions, but he provides no evidence other than model runs. Mann et al., 2020 admits that internal variability contributes to the AMO.
  14. Pulles erroneously claims that the residuals after detrending the AMO and HadCRUT4 have no structure and may be due to random noise. Both sets of residuals not only show structure in figure 2 of May & Crok, the residual structures match each other. This statement is clearly false.
  15. Pulles writes “they conclude that the “detrended” data show no trends.” This is false, there is no such conclusion or statement in May & Crok.
  16. Pulles erroneously claims that ocean oscillations go up and down and can never contribute to warming trends. That depends entirely on the period of the oscillation and the beginning and ending dates chosen. This is false.
  17. Pulles erroneously claims that Pielke Jr. and Lomborg have been debunked but provide no evidence. I do not know of any articles written by them that have been debunked, they both receive a lot of criticism because they are skeptical of the dangers of man-made climate change, but they’ve not been debunked.
  18. Pulles erroneously claims that modern warming is unusual in Earth’s history. There are many examples of much more rapid and severe warming in the past, especially the very well documented rapid warming ~11,700 years ago.
  19. Pulles claims that the Little Ice Age was regional, as if that means it doesn’t matter. All climate changes are regional, including the current “global” warming. The Little Ice Age caused glaciers to advance nearly everywhere in the world except in Antarctica, but the advances were not synchronous. While this claim is true in the strictest case, it does not matter in the intended way.
  20. Pulles erroneously claims that plants evolved in an environment of around 250 PPM CO2. Modern vascular plants evolved during the Devonian Period, ~400 million years ago when CO2 was 1,000 to ~4,000 PPM, many times higher than today. It appears this error stems from a misunderstanding of his primary source Ort, 2015.
  21. Pulles erroneously claims that more CO2 will not result in improvements in plant growth, numerous controlled experiments have shown this is false. Especially C3 plants, such as rice, soybeans, wheat, most trees, and grasses, thrive in more CO2 than we have today.
  22. Pulles erroneously claims that May & Crok were “given permission” to publish their article in AJES, but in fact, they were invited to write a paper explaining the scientific basis for denialism.
  23. Pulles erroneously claims that the peer reviewers of May & Crok were “clearly not familiar with the existing science.” This is not true and not documented in the paper.
  24. Finally, this assertion, “The many flaws and misrepresentations in the paper should have resulted in rejection” has no foundation. No flaws or misrepresentations in May & Crok are identified in “Climate Denialism.”

It is a shame that the institution of peer-review has been corrupted to the extent that papers filled with obvious falsehoods can pass simply because of ideological bias. I was a peer reviewer for this paper and pointed out all the above problems to the editor in October, but the paper was published anyway, with the falsehoods left in. My full review of the paper, slightly updated, can be downloaded here.

It is amazing that papers like this get published (see other examples here and here) when all-to-often serious and carefully researched papers are rejected. Pulles and May & Crok interpret the same facts differently in many cases, but in many of the points listed above, Pulles is clearly in error. It is shocking that these obvious errors were pointed out in detail months ago, but the editors of AJES still published the paper as is.

Hoofnagle and Hoofnagle, who admit they do not understand climate models “worth a damn,” write “Global Warming denialists like Richard Lindzen [try] and explain why mainstream scientists won’t publish their BS.” Science is clearly taking a backseat to bias and misinformation. This is to the detriment of scientists everywhere.

These problems with Climate Denialism are discussed in more detail, along with additional problems not listed here, in a downloadable detailed critique here that contains a full bibliography. The detailed critique is extremely similar to what I sent in to the editors of AJES in October. For a list of other critiques of May & Crok and our responses, see here.