Pubpeer Comment on our recent paper by the anonymous “Phoma destructiva” – Watts Up With That?

By Andy May & Marcel Crok

An anonymous reviewer has written a critique of our recent paper “Carbon Dioxide and a Warming Climate are not problems,” published online May 29, 2024, in The American Journal of Economics and Sociology.

In the introduction to his critique, Phoma destructiva writes: “the authors and their cited sources likely underestimated anthropogenic global warming.” We provide no estimate of the anthropogenic component of global warming. All we do is point out that if some of the observed warming is natural, the IPCC AR6 estimate of anthropogenic global warming will be too high. This is trivially true.

The first part of the main critique, is actually a lengthy critique of Javier Vinós’ book Climate of Past, Present and Future, that has nothing to do with our paper. His critique compares Vinós’ projections into the future to those made by the IPCC, our paper makes no projections. We simply discuss the climate of today and the recent past (back to 1750), so this section of the critique is irrelevant to our paper and should be directed to Dr. Vinós.

While we cite some published projections in our conclusions, we deliberately avoided making any projections ourselves, our paper only considers past and present observations. The critique disputes Vinós’ predictions of the future by claiming that the IPCC predictions, based on the impact of CO₂ emissions, are more accurate. We currently have no idea whether Vinós’ or the IPCC predictions are correct or not, as the time period discussed is not over yet. Our paper discusses the state of the climate today and in the past, predictions of the future are not observations and should not be confused with them.

The next section attempts to dispute the existence of all multidecadal ocean oscillations based on two papers by Michael Mann and co-authors, Mann, et al. (2020) and Mann et al. (2021). Mann’s 2020 paper attempts to show that the most cited ocean climate oscillations, the AMO and the PDO, are not statistically significant because their signal is not sufficiently above red noise. However, he acknowledges that the historical observations of the AMO are statistically significant, and it is only climate model results that are not statistically significant. Since all models are wrong (Box, 1976), this argument is quite weak.

The PDO is usually interpreted as a long-term variation in the La Niña/El Niño ratio, and (Mann, Steinman, & Miller, 2020) do acknowledge that the ratio varies in a statistically significant fashion on a 40–50-year timescale. He just disputes the predictability of the traditional PDO.

We acknowledge that the longer-term ocean oscillations are poorly understood and poorly described. However, Mann et al. (2020) provides no valid evidence that they do not exist or that they have no natural component. In fact, he admits:

“Based on the available observational and modelling evidence, the most plausible explanation for the multidecadal peak seen in modern climate observations is that it reflects the response to a combination of natural and anthropogenic forcing during the historical era.” (Mann, Steinman, & Miller, 2020)

We agree with this sentence, and it is consistent with our paper.

Mann, et al. (2021) attempts to explain multidecadal ocean oscillations (specifically the AMO and the PDO) as an artefact of volcanic activity and anthropogenic greenhouse gases and aerosols. Again, as also noted in Mann (2020), Mann (2021) notes the absence of a multidecadal signal in climate model simulations but acknowledge that the signal can be seen in observations (Mann M. , Steinman, Brouillette, & Miller, 2021). We would argue that if the signal is seen in observations and in paleoclimate proxy data, but not in climate models, that is a reason not to trust the climate models, not a reason to reject the proposed natural oscillation.

We do believe that anthropogenic greenhouse gases and aerosols, and volcanic activity have some influence on climate, but we believe that current warming has been “juiced” by natural ocean oscillations. These oscillations are observed in nature and have been traced back as far as 1567AD, well before anthropogenic greenhouse gases and aerosols could have been a factor in climate change (Gray, Graumlich, Betancourt, & Pederson, 2004).

The evidence presented by Mann (2021) that volcanic activity has caused the “apparent” ocean oscillations is model based, and not based on observations. This is problematic for many reasons, not the least of which is that the IPCC AR6 models cannot reproduce the critical tropical sea surface temperatures (SSTs) very well, even though sea surface temperatures are a key component of most of the ocean oscillations. From AR6:

“We assess with medium confidence that CMIP5 and CMIP6 models continue to overestimate observed warming in the upper tropical troposphere over the 1979–2014 period by at least 0.1°C per decade, in part because of an overestimate of the tropical SST trend pattern over this period.” AR6, p 444

“… despite decades of model development, increases in model resolution, and advances in parametrization schemes, there has been no systematic convergence in model estimates of ECS. In fact, the overall inter-model spread in ECS for CMIP6 is larger than for CMIP5; …”AR6, WGI, page 1008.

In other words, both the AR5 and AR6 climate models overestimate sea surface temperatures in the tropics, which is nearly half of the planet’s surface. In addition, the model estimates of ECS (Equilibrium Climate Sensitivity to a doubling of CO₂) are worse in AR6 than in AR5, suggesting that the models are getting worse with time, not better, relative to observations (also see here). Other studies have also shown that the climate models are invalidated when compared to observations (McKitrick & Christy, 2020) and (McKitrick & Christy, 2018). Model evidence cannot be used to show observational evidence is incorrect.

Then the anonymous critique of our paper again resorts to comparing predictions by Vinós, (Wyatt & Curry, 2014), and others to the IPCC predictions. We made no predictions, we only cited observations. The end of the time period for the various predictions they criticize has not been reached, thus which, if any, of the predictions turn out to be correct is unknown and will not be known for decades to come. Arguing which prediction is correct at this point is a fruitless exercise. Predictions are a critical part of science, but one should wait until the prediction period is over before criticizing them.

Discussion

This critique is a poster child for all that is wrong with modern climate science. Phoma destructiva sets up obvious strawmen from articles we cite, that are unrelated to our argument that observations show no dangers or net harm from climate change today, and then attacks his own strawmen, rather than our paper. This sort of irrelevant strawman fallacy is unfortunately very common in climate science and is never credible.

Far too often even trained climate scientists mix climate model results with observations as if they were of equal importance or significance, they are not. Statements like the following from Mann et al., 2021 are clearly incorrect:

“Our analysis reveals a robust multidecadal, narrowband (50- to 70-year) oscillatory “AMO-like” signal in simulations of the past millennium; the oscillation is driven by episodes of high amplitude explosive volcanism that happen, in past centuries, to display a multidecadal pacing. We find no evidence for an internally generated 50- to 70-year multidecadal oscillatory signal despite continued claims that proxy data reveal such a signal.” (Mann M. , Steinman, Brouillette, & Miller, 2021)

Translation, our simulations show that volcanism caused the oscillation and proxy evidence that the oscillation is natural is wrong, because our models say so. This is clearly flawed logic; however we do agree that the current ocean oscillations probably have both forced (CO₂ and volcanism) and unforced (natural) components. But as stated in Mann (2020), objectively separating these two components is problematic.

Climate models, like all models, are always wrong (Box, 1976). Properly done, observations are always right, within measurement accuracy. Ocean oscillations, such as the AMO, PDO, and many others, are observed climate features, they are real, and cannot be disproven with climate model results.

Note: Neither Marcel nor Andy have a PhD, thus Phoma destructiva used the title “Dr.” incorrectly.

Box, G. E. (1976). Science and Statistics. Journal of the American Statistical Association, 71(356), 791-799. Retrieved from http://www-sop.inria.fr/members/Ian.Jermyn/philosophy/writings/Boxonmaths.pdf

Gray, S. T., Graumlich, L. J., Betancourt, J. L., & Pederson, G. T. (2004). A tree-ring based reconstruction of the Atlantic Multidecadal Oscillation since 1567 A.D. Geophys. Res. Lett., 31. doi:10.1029/2004GL019932

IPCC. (2021). Climate Change 2021: The Physical Science Basis. In V. Masson-Delmotte, P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, . . . B. Zhou (Ed.)., WG1. Retrieved from https://www.ipcc.ch/report/ar6/wg1/

Mann, M., Steinman, B., & Miller, S. (2020). Absence of internal multidecadal and interdecadal oscillations in climate model simulations. Nature Communications, 11. doi:10.1038/s41467-019-13823-w

Mann, M., Steinman, B., Brouillette, D., & Miller, S. (2021). Multidecadal climate oscillations during the past millennium driven by volcanic forcing. Science, 317, 1014-1019. doi:10.1126/science.abc5810

McKitrick, R., & Christy, J. (2018, July 6). A Test of the Tropical 200- to 300-hPa Warming Rate in Climate Models, Earth and Space Science. Earth and Space Science, 5(9), 529-536. doi:10.1029/2018EA000401

McKitrick, R., & Christy, J. (2020). Pervasive Warming Bias in CMIP6 Tropospheric Layers. Earth and Space Science, 7. doi:10.1029/2020EA001281

Wyatt, M., & Curry, J. (2014, May). Role for Eurasian Arctic shelf sea ice in a secularly varying hemispheric climate signal during the 20th century. Climate Dynamics, 42(9-10), 2763-2782. Retrieved from https://link.springer.com/article/10.1007/s00382-013-1950-2#page-1