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How Much Atmospheric CO2 is Actually 'Anthropogenic'? 'The Science' Has Some--Surprising--Answers For Us
Another instalment of the burning question as to how much of 'the climate science' is actually 'settled'
Editorial preliminary: this post is too long for email; please read it in the app or online.
A few months ago, another interesting study appeared. Entitled, ‘World Atmospheric CO2, Its 14C Specific Activity, Non-fossil Component, Anthropogenic Fossil Component, and Emissions (1750–2018)’, it was written by Kenneth Skrable, George Chabot, and Clayton French. Appearing in Health Physics 122, no. 2 (2022): p. 291-305 [DOI: 10.1097/HP.0000000000001485], here is its abstract (emphases here and in the following mine):
After 1750 and the onset of the industrial revolution, the anthropogenic fossil component and the non-fossil component in the total atmospheric CO2 concentration, C(t), began to increase. Despite the lack of knowledge of these two components, claims that all or most of the increase in C(t) since 1800 has been due to the anthropogenic fossil component have continued since they began in 1960 with ‘Keeling Curve: Increase in CO2 from burning fossil fuel’. Data and plots of annual anthropogenic fossil CO2 emissions and concentrations, C(t), published by the [US] Energy Information Administration, are expanded in this paper. Additions include annual mean values in 1750 through 2018 of the C14 specific activity, concentrations of the two components, and their changes from values in 1750. The specific activity of C14 in the atmosphere gets reduced by a dilution effect when fossil CO2, which is devoid of C14, enters the atmosphere. We have used the results of this effect to quantify the two components. All results covering the period from 1750 through 2018 are listed in a table and plotted in figures. These results negate claims that the increase in C(t) since 1800 has been dominated by the increase of the anthropogenic fossil component. We determined that in 2018, atmospheric anthropogenic fossil CO2 represented 23% of the total emissions since 1750 with the remaining 77% in the exchange reservoirs. Our results show that the percentage of the total CO2 due to the use of fossil fuels from 1750 to 2018 increased from 0% in 1750 to 12% in 2018, much too low to be the cause of global warming.
That does sound…well, interesting, to say the least, if we would like to discuss what amounts to perhaps the most important question of our age: what share of ‘climate change’ (I’m old enough to remember that it used to be called ‘global warming’) is actually man-made?
Curiously enough, while a worthwhile, if not existential question to consider, it is virtually absent from public policy debates. ‘The science is settled’, and ‘there is a 97% consensus’, are but two of the most commonly-cited, if evasive, propositions.
Sure, the IPCC typically states some form of disclaimer that since WW2 or 1950-ish, it was anthropogenic emissions that drove ‘global warming’ or ‘climate change’. Put differently, prior to the mid-20th century, CO2 and other greenhouse gas emissions that drove ‘global warming’ or ‘climate change’ would have had to be predominantly non-anthropogenic, or natural, eh?
Strange, though, that this—in my opinion crucial—distinction never really comes up in polite society. I am inclined to believe that it is, in fact, even stranger not to consider this issue as atmospheric CO2 is actually a trace gas that comes in at some .0407% of the entirety of earth’s atmosphere.
So, shall we go through the paper? I think it is actually worthwhile to do so. For readability, I have omitted the references.
At an elapsed time of t years since 1750 (the start of the industrial revolution with the onset of the use of fossil fuels in vehicles and power plants), atmospheric CO2 concentrations, C(t), increased along with increases in temperatures. Atmospheric measurements of C(t) were not available until 1958 at the Mauna Loa, HI, observatory of the National Oceanic and Atmospheric Administration (NOAA), which has provided the longest record of atmospheric measurements of the total CO2 initiated by Charles Keeling in 1958 at the Mauna Loa observatory (Keeling 1960). Based on our knowledge, the anthropogenic fossil component, CF(t), and non-fossil component, CNF(t), in C(t) have never been estimated by NOAA at its observatories or at any other observatory from atmospheric measurements of CO2. Despite the lack of knowledge of the components of C(t), claims have been made in the scientific literature that all or most of the increase in C(t) since 1800 has been due to the anthropogenic fossil component, CF(t).
The paper itself is concerned with the amount of carbon in the atmosphere, as explained by the authors:
Other atmospheric measurements of C(t) began in 2003 at the NOAA observatory in Niwot Ridge, including measurements of the three isotopes of carbon: C-12, C-13, and C-14. Carbon-14 is a radioactive isotope of carbon having a half-life of 5,730 y. Carbon-14 atoms are produced in the atmosphere by interactions of cosmic rays, and they have reached an essentially constant steady state activity, i.e., disintegration rate, in the total world environment. The age of fossil fuels is much longer than the 5,730 y half-life of the C-14 radioactive isotope; consequently, fossil fuels are devoid of the C-14 isotope. When the anthropogenic fossil component of CO2 is released to the atmosphere, the specific activity of C-14,S(t) in C(t), decreases…
Both the d13C and D14C statistics represent 1,000 times the relative deviations of their respective (C-13/C-12) and (C-14 /C-12) atom ratios from those of a 1950 standard…This magnification increases their underlying relative deviations and slopes in plots by a factor 1,000 [i.e., a linear change, it would seem, as opposed to, say, PCR cycle thresholds, which are exponential]. While such amplification techniques often are useful for displaying very small changes in quantities of interest, the interpretation of such magnified changes must be attended with some care. In the cases of concern here, the resultant steep slopes in plots likely have led persons throughout the world to conclude that the anthropogenic component has dominated the increase of CO2 and caused global warming. We believe that both statistics have been misused to validate the anthropogenic fossil component, CF(t), as the major cause of the increase of C(t).
Here we can see two premises:
the proportion (share) of non-anthropogenic CO2 emissions since ±1750 has never been studied
modelling (hypotheses) lead to uncertainty, which ‘likely have led persons…to conclude that the anthropogenic component has dominated the increase of CO2 and caused global warming’
Please keep both of them in mind.
Of Glaciers, Ice-Ages, and Solar Cycles
Fig. 1: Glacial-interglacial cycles. Solar radiation varies smoothly through time (top, orange line) with a strong cyclicity of ~23,000 years, as seen in this time series of July incoming solar radiation at 65°N (Berger and Loutre 1991). In contrast, glacial–interglacial cycles last ~100,000 years (middle, black line) and consist of stepwise cooling events followed by rapid warmings, as seen in this time series inferred from hydrogen isotopes in the Dome Fuji ice core from Antarctica (Kawamura et al. 2007). Atmospheric CO2 measured from bubbles in Dome Fuji ice (bottom, blue line) shows the same pattern as the temperature time series (Kawamura et al. 2007). Yellow columns indicate interglacial periods.
The cause of glacial-interglacial cycles in the figure is stated to be due to variations in Earth's orbit through time, which changes the amount of solar radiation received by Earth…
During the last long glacial period, the oceans absorbed a large amount of CO2 from the atmosphere. It appears in the figure that Earth is still in the Holocene interglacial period that started 11,500 y ago. Its peak temperature change over the 11,500 years, thus far in 1950, appears to be significantly less than those over the three previous interglacial periods. Its peak CO2 appears less than 300 ppm and less than the peak value in the previous interglacial period. Thus, the increase in CO2 that Earth has been experiencing since 1800 appears to have started more than 5,000 years ago.
Note here, as explained in the paper, ‘present in the figure is defined as 1950 AD, the convention used in radiocarbon dating because H-bomb testing in the 1950s distorted radiocarbon ages in many materials’.
I’ll omit the long-ish section on these distortions caused by atmospheric nuclear (mostly H-bomb) testing in the 1950s.
Note, moreover, that, if earth is (still) in an inter-glacial period, the authors’ claim about rising CO2 levels is extremely important, as it causes a lot of questions to come up as regards humanity’s contribution to the greenhouse effect in general and fossil fuel burning in particular.
I’ll also skip the equation-heavy section on ‘methods’ and ‘data input’; while the paper is, sadly, not fully OpenAccess, please drop me an email if you’d like a PDF copy.
From Data to Outcomes
NOAA has provided limited D14C data for the Niwot Ridge, CO, observatory beginning in 2004 and ending in 2012 [this is the baseline] these data have been used in this paper to calculate nine annual mean input specific activities, S(t), in Table 1. Despite the fact that the D14C program has continued, we have been unable to obtain from NOAA the data for 2013 through 2020 [I wonder why that may be…]. To make up for the limited D14C data, a process is used to estimate expected specific activities, <S(t)>, from an approximation fitting function applicable to the years 1750 through 2018. The process used to estimate the parameter values for the approximation fitting function is described as follows.
The solid trend line in Fig. 2 is obtained from the approximation fitting function estimated from 10 input-specific activities, S(t), including our chosen value, S(0), of 16.33 dpm (gC)−1 in 1750 and the 9 input S(t) values in 2004 through 2012…
Naturally, the lack of data points between 1750 and 2004 makes the exact shape of the curve uncertain in this interval. Parameter values are chosen so that the <S(t)> values yield a fit that does not deviate significantly from the points for the input S(t) values, most importantly the value of 14.87 dpm (gC)−1 for S(t) in 2004 and our chosen S(0) value of 16.33 dpm (gC)−1 in 1750. Parameter values, however, have been chosen so that the 10 points for the S(t) values and the solid line for the expected <S(t)> values in the figure provide a realistic representation of the initial small decreases and later more significant decreases in the specific activities expected after the start of the industrial revolution in 1750 and the increased burning of fossil fuels each year. The S(t) value of 14.05 dpm (gC)−1 for 2018, based on extrapolated values of D14C and d13C, is 0.09 dpm (gC)−1 more than the expected <S(t)> value of 13.96 dpm (gC)−1 in 2018.
Again, I’m skipping the equation-heavy modelling section for the sake of readability.
Table 2 (https://links.lww.com/HP/A210) contains a listing of all the same quantities as those in Table 2a. Each table contains a listing of seven annual mean CO2 quantities in 1750 through 2018. The symbol C(t) and the numbers (2) through (7) heading other columns are used as labels for the plots of all CO2 quantities in Figs. 3, 4, and 5. The plot for C(t) is labeled as such. The numbers are placed before the symbols in legends, equations, and at the end of a line for a plot in each figure. Equations listed in the figures are used to calculate the quantities listed in columns (2) through (6) of each table. It is important to recognize in the following discussion that the value for <CF(t)> is identical to its annual change, D <CF(t)> since 1750 and that the sum of D <CF(t)>, which is not specifically listed, and the annual change, DCNF(t), in the non-fossil component equals the annual change, DC(t), in the total CO2 concentration, C(t).
Results in Table 2 are plotted in the figures versus the time t since 1750, and they are discussed along with plots in Figs. 3 as follows. In 1750 (t = 0), the initial value of 276.44 ppm listed for both C(0) and CNF(0) in Table 2a has been estimated from the Table 2 values of C(t) in 1751 and in 1752 of, respectively, 276.40 ppm and 276.36 ppm [I’m personally unsure how this was done as the ‘average’ of these two values would be 276.38, but let’s set this aside]. Except for these values and the initial S(0) value of 16.33 dpm (gC)−1, the initial values of other quantities are assumed to be zero. In 1751, a value of 0.01 ppm is listed for CF(t), and slightly negative values of −0.05 ppm and of −0.04 ppm are listed respectively for DCNF(t) and DC(t) in Table 2 and Table 2a, both of which do not become positive until 1765 and thereafter. These negative values may be associated with the Little Ice Age9 when temperatures and CO2 concentrations coincidentally had their lowest values in about 1750 [one of the core criticisms of the standard explanation is that the Little Ice Age was ending as industrialisation—and thus human CO2 emissions—began, which is a bit like claiming that getting out of bed each morning causes the sun rise]. Values for the anthropogenic fossil component, <CF(t)>, in Table 2a and in plot 3 of Fig. 3 slowly increase from 0.01 ppm in 1751 to a value of 4.03 ppm in 1950…After 1950, values of <CF(t)>, DCNF(t), and DC(t) in Fig. 3 begin to increase rapidly. The increase in <CF(t)> coincides with the rapid increase after 1950 in the values of the annual emissions, DE(t), of anthropogenic fossil CO2 in Table 2 and Table 2a as well as in plot (7) in Fig. 3. Coincidentally, for the scale used on the primary vertical axis, the values for plot (3) of <CF(t)> and the plot (7) of DE(t) overlap until about 1900. The values in plot (5) of DCNF(t) and in plot (6) of DC(t) overlap each other early on, and then their plots slowly separate until 1950. After 1950, plots of both quantities increase more rapidly and their separation becomes greater each year. This separation is the value of <CF(t)>. In Table 2a in 2018, <CF(t)> is 46.84 ppm and DCNF(t) [annual changes of non-anthropogenic fossil emissions relative to 1750] is 82.12 ppm. Their sum of 128.96 ppm equals the value of DC(t).
One thing to remember here is that correlation ≠ causation, even though the rise of anthropogenic emissions is clearly visible, it is hard to determine what caused the rise in global temperatures: is the rise in CO2 levels the reason for ‘global warming’ or are the former a function of the latter that has not too much to do with whatever we humans do? (For what it’s worth, the authors consider rising temperatures to be related to the earth’s orbit around the sun.)
And this finally brings us to the second big claim the authors make: human-induced emissions couldn’t ‘cause’ global warming because of their small numbers:
Anthropogenic fossil CO2 in 2018 relative to the total of its annual emissions
The Table 2a value of the atmospheric concentration, <CF(t)>, of anthropogenic fossil derived CO2 in 2018 is 46.84 ppm. It is assumed that <CF(t)> is representative of its molar concentration throughout the entire atmosphere and that the total mass of the atmosphere is 5.148 × 1018 kg with an effective molecular weight of 28.96 g mole−1. The number of moles, NF, of anthropogenic fossil CO2 present in the atmosphere then is calculated:
Based on a molecular weight of 44.01 g mole−1 for CO, the total mass of anthropogenic fossil CO2 present in the atmosphere in 2018 is calculated as 3.664 × 1017 g. The Table 2 value of 1,589.86 billion metric tons of anthropogenic fossil-derived CO2 emitted into the atmosphere in 1751 through 2018 represents 1.590 × 1018 g. The inference is that the quantity of anthropogenic fossil CO2 in the atmosphere in 2018 represents about 23% of the total amount of anthropogenic fossil-derived CO2 that had been released to the atmosphere since 1750.
Therefore, 77% of the total anthropogenic fossil emissions of CO2 then would be present in the atmosphere’s exchange reservoirs in 2018. These results differ significantly from those reported by others: ‘Using these data, Keeling was able to compare the amount of CO2 accumulating in the atmosphere against estimates of the amount of CO2 being released by burning fossil fuels. The atmospheric fraction appeared to be approximately 55%, meaning that roughly half of all CO2 released by coal, oil, and natural gas was remaining in the atmosphere, thus causing the Keeling Curve’s annual rise’.
Remember that the ‘standard’ view holds that ‘at least’ half of all CO2 emissions since 1950 are due to human burning of fossil fuels. Keeling’s work is the root of it, and his data starts in 1957/58. Even so, what the authors of the study discussed here argue is that anthropogenic emissions pale by comparison to the ‘natural’ carbon content of the atmosphere. In other words, Skrable and colleagues are committing heresy.
From the Paper’s Conclusions
Results in this paper and citations in the scientific literature support the following 10 conclusions.
The scientific literature does not appear to provide estimates of either the annual mean values of the anthropogenic fossil component, CF(t), or of the non-fossil component, CNF(t), present in the total atmospheric CO2 concentration, C(t), nor their respective changes from values in 1750.
The annual mean values of all CO2 quantities provided in this paper automatically account for the redistribution of CO2 among its reservoirs, including all of its isotopic forms. Results depend on chosen values in 1750 of 276.44 ppm for C(0) and 16.33 dpm (gC)−1 for S(0), both of which may be somewhat overestimated as indicated in the text. Based on the simple equations used to calculate all CO2 quantities, smaller values for these chosen quantities would yield smaller values of the anthropogenic fossil component, CF(t), and larger values of the non-fossil component, CNF(t).
In 1950, the <CF(t)> [anthropogenic carbon emissions] value of 4.03 ppm in Table 2a is 1.29 % of C(t) and 11.48% of the increase, DC(t), of 35.10 ppm since 1750. After 1950, values of the two components of C(t) begin to increase rapidly, and this increase continues through 2018. This rapid increase, however, is not triggered by the greenhouse effect and global warming associated with either the 1950 value of 4.03 ppm for CF(t) or the relatively small increase in the annual change, DCNF(t), of 31.07 ppm in the non-fossil component, which is 88.5% of the DC(t) value of 35.10 ppm. This DCNF(t) value of 31.07 ppm in 1950 results from the annual redistribution of CO2 among its reservoirs, primarily a net release of CO2 from the oceans due to increases in temperatures from solar insolation in 1950 and afterwards.
In 2018, the <CF(t)> value of 46.84 ppm is 11.55% of the C(t) value of 405.40 ppm, 36.32% of the DC(t) value of 128.96 ppm, and 57.04% of the DCNF(t) value of 82.12 ppm. These results negate claims that the increase, DC(t), in C(t), since 1750 has been dominated by the increase of the anthropogenic fossil component, CF(t).
In 2018, the total content of anthropogenic fossil CO2 in the atmosphere is estimated as 3.664 × 1017 g, which is 23% of the total emissions of 1.590 × 1018 g since 1750. Thus, in 2018, 77% of the total emissions is estimated to be present in the atmosphere’s exchange reservoirs.
Claims of the dominance of the anthropogenic component, CF(t), in the increase of the CO2 concentration, C(t), first began in 1960 with: ‘Keeling Curve: Increase in CO2 from burning fossil fuel’. Despite the lack of knowledge of the two components of C(t), these claims have continued in the scientific literature…
An article on Glacial-Interglacial Cycles (NOAA) suggests that recent increases in CO2 and temperatures are due primarily to cyclic changes of solar radiation associated with Earth’s orbit about the sun. The annual change, DCNF(t), in the non-fossil component has positive increasing values in Table 2 (https://links.lww.com/HP/A210) after 1764. It will eventually become negative in the next glacial period when average temperatures decrease again as they have done over all of the previous glacial-interglacial cycles. [now that’s what I call a hypothesis that can be empirically proven over time]
The assumption that the increase in CO2 since 1800 is dominated by or equal to the increase in the anthropogenic component is not settled science. Unsupported conclusions of the dominance of the anthropogenic fossil component of CO2 and concerns of its effect on climate change and global warming have severe potential societal implications that press the need for very costly remedial actions that may be misdirected, presently unnecessary, and ineffective in curbing global warming.
A Note on The Scientific Method
It is hardly surprising that legacy media was loath to report on this paper so far, to say nothing about ‘serious’ practitioners of the field of ‘climate science™’ to weigh in on this in a public forum.
As neither of these two things has happened, we may consider a peer-reviewed piece of such heresy an interesting feature of the post-Covid practice of ‘the Science™’, which is, in general, characterised by the rapid retraction of politically incorrect findings (here’s looking at you, The Lancet, among others). I knew of the paper for some time, but I wanted to find out whether or not the above study would be retracted.
Yet, the above study by Skrable and colleagues has not been retracted, despite the ‘best’ efforts by others, as the ‘comment section’ of the journal Health Physics shows.
Upon publication in spring 2022, several ‘letters to the editor’ arrived. So far, so unsurprisingly ‘normal’ in terms of scientific activities. Please bear with me about the criticisms of Skrable et al. whose two main claims are:
the share of anthropogenic carbon emissions since 1750 has never been studied
as they’ve done so, the authors claim that anthropogenic CO2 emissions, clocking in at 23% since 1750, are too small a fraction to be the key driver of ‘climate change’ deriving from anthropogenic burning of fossil fuels.
Comment 1 by Schwartz et al. (source; emphases mine)
The paper by Skrable et al. is fundamentally flawed in at least four respects: (1) erroneous history of 14CO2 in air that is at odds with direct observations; (2) neglect of the consequences of the large input of 14CO2 into the atmosphere from nuclear weapons tests in the 1950s and 1960s; (3) failure to account for isotope exchanges between the atmosphere, ocean, and land biosphere that occur independent of net change in amount of atmospheric CO2; and (4) neglect of multiple independent lines of evidence that CO2 emitted from fossil-fuel combustion is the principal contributor to the increase of atmospheric CO2 over the industrial era. We detail these flaws here and conclude that the paper of Skrable et al. should be retracted in its entirety.
As regards (1), Schwartz et al.note that both ‘the specific activity given by Skrable et al. at the beginning of the record (1750)…is erroneously high, mainly because of their use of an outdated and erroneous value for the cosmogenic production rate of C14 in Earth’s atmosphere. The several values of specific activity given by Skrable et al. toward the end of the record (2002-12)…were obtained from contemporaneous measurements in air.’
So far, so good, yet it is also pointed out that
It is clear that the historical specific activity given by Skrable et al. is completely at odds with the measurements over virtually the entire record and thus cannot be relied upon in apportionment of the source of the increase of atmospheric CO2 over the industrial period to fossil-fuel and non-fossil-fuel sources or for any other purpose.
Note the sleight-of-hand here: Keeling and virtually everyone following his lead considered the overwhelming majority of chemical measurements of atmospheric carbon concentrations before 1957/58 irrelevant for his reconstruction of the earth’s atmospheric CO2 concentration because of the non-standardised methods employed, the heterogeneity of measuring stations, and the like.
Schwartz et al., by contrast, now state that ‘virtually the entire record’—read: canon of measurements deemed acceptable by Keeling and his followers—has dependable records, a statement that Keeling himself would probably find quite hard to support. Note, moreover, that Skrable et al.’s claim that there is no such record of measurements has not been disputed by Schwartz et al.
As regards (2), the impact of H-bomb atmospheric testing, Schwartz et al. hold is ‘the most prominent feature in the measurement record of atmospheric C14O2’. While atmospheric nuclear testing ceased almost entirely in 1964, its C14O2 signature ‘has persisted substantially to the present time’. While this has been noted by Skrable et al., Schwartz et al. note that the former are basing their information ‘on a citation to Wikipedia’ (which holds that C14 isotopes from atmospheric nuclear testing ‘would be significant only to about 2005’), the latter point to Graven et al. (2020) who modelled the persistence of just these isotopes. In other words: Schwartz et al. have been reading the footnotes and are extra-harsh in their comment:
Failure to include this residual bomb C14O2 in their apportionment of the increase of the increase of atmospheric CO2 to fossil fuel and non-fossil fuel sources completely vitiates this apportionment.
Let’s keep in mind that, as per Table 2a, the anthropogenic value of CO2 was 4.03 ppm vs. 46.84 ppm in 2018, a difference of approx. 42 ppm. In other words, the paper by Graven et al. 2020 would impact that approx. 42 ppm difference by…well, what amount exactly?
Here is the paper in question (source), which was—what a coincidence—co-authored by Keeling’s son Ralph (talk about possible conflicts of interest here). The key take-away from Graven et al. 2020 are—literally two paragraphs (as above, references omitted, emphases mine):
The Nuclear Bomb Effect for C14
In the 1950s and 1960s, nuclear weapons testing produced C14 in the atmosphere, strongly enriching C14 and counteracting the Suess Effect. This effect was termed the ‘Atom Bomb Effect’ when first reported; we refer to it as the ‘Nuclear Bomb Effect’. The process for C14 production was similar to the natural production of C14 in the atmosphere: Neutrons produced by the hydrogen bomb explosions react with atmospheric nitrogen to produce C14. Most of the nuclear explosions and C14 production took place in the Northern Hemisphere, and most tests and particularly the largest tests occurred shortly before the Partial Test Ban Treaty came into effect in 1963.
There is an ongoing production of C14 by the nuclear industry at nuclear power plants, with the C14 production varying by type of reactor. The amount of C14 produced by the nuclear industry and released to the atmosphere is only about 10% of the natural production of C14, so the effects on ΔC14O2 are much smaller than the effects from the nuclear weapons testing, which, in contrast, exceeded the rate of natural production by 2 orders of magnitude. Nuclear power plant emissions ramped up between the 1970s and 1990s as the nuclear industry expanded, but they appear to have recently started to fall.
That is all with respect to (2) by Schwartz et al.: a 10% difference of approx. 42 ppm. I’m not saying that’s nothing, but it certainly puts the harsh statement by Schwartz et al.—Skarble et al.’s alleged ‘Failure to include this residual bomb C14O2…completely vitiates this apportionment’—into much-needed perspective. Lest I forget to notice, Graven et al. speak about the need to include nuclear CO2 isotopes into ‘future’ studies, further contradicting the ‘argument’ put forth by Schwartz et al.
As regards (3), Schwartz et al. posit that Skarble et al. ‘assumes that carbon in the environment can be divided into two categories: (1) preindustrial carbon…and (2) fossil carbon’. There is another point about the exchange of carbon between the atmosphere, ocean, and land biosphere.
The flows of different carbon isotopes are not connected as assumed by Skrable et al. Each carbon atom and isotope is exchanged independently. Thus, importantly here, C14 can be exchanged between the atmosphere and ocean with no net exchange of carbon as a whole…Dilution of atmospheric CO2 by the C14-free fossil-fuel carbon is therefore not a straightforward proxy for the impact of fossil-fuel on the buildup of atmospheric CO2. Correct handling of these independent exchanges requires information on the sizes and exchange rates between different carbon reservoirs, as has been clear since the 1950s. Additionally, the isotopic ratio of preindustrial carbon is not uniform, with older reservoirs such as the carbon in the deep ocean having lower C14/C12 ratio. These differences are the basis of radiocarbon dating. These critical aspects were not considered by Skrable et al., causing their calculations to underestimate the input of fossil-fuel CO2.
Finally, as regards (4), Schwartz et al. hold that ‘the present understanding of the controls on atmospheric CO2 buildup importantly rests on many convergent strands of evidence in addition to radiocarbon’.
While these range from rates at which CO2 builds up in the atmosphere vs. CO2 release from the burning of fossil fuels,
it is clear that around 50% of the emitted carbon remains in the atmosphere, with the balance absorbed by other reservoirs, of which the oceans and the land biosphere are the most important. The ocean and land biosphere are thus together acting as a major sink not a source of CO2…This understanding of the rate at which excess carbon is being redistributed into the ocean and land is independently supported by measurements of trends in atmospheric O2 and C13/C12 ratio in addition to radiocarbon.
So, Skarble et al. apparently failed to cite a paper—Keeling and Graven 2021 (incidentally, co-authored by the same two people who also wrote the above paper about future carbon modelling whose absence has been criticised in (2). Talk about coincidenes…).
Based on these four points—at least two of which I consider problematic as to their validity as an argument—Schwartz et al. ‘conclude’ that Skarble et al. ‘should be retracted in its entirety’. Note, as an aside, that one of the people ‘hiding’ behind the moniker ‘Schwartz et al.’ is none other than Ralph F. Keeling, co-author of at least two studies that were not included in the original paper, and, at least in part based on this fact, Keeling calls for the retraction of Skarble et al. To me, this reeks of wounded ego rather than a valid scientific argument that disproves the results of Skarble et al. to such a degree that the paper should be retracted (note, by the way, that papers relating to, say, Ivermectin or HCQ, the ‘proximate origins’ of Sars-Cov-2, or vaccine injuries have been retracted on grounds of way less grounds).
There is another comment, by Stephen Musolini, written in June 2022, who also argues for the retraction of Skarble et al., albeit for a quite different reason (again, my emphases):
From the perspective of publication of the Skrable article in Health Physics, the question arises as to its suitability for this Journal. Their analysis has no connection to any concept related to radiation effects to the environment (radioecology) or health effects to people (dosimetry and risk assessment), which are in the purview of the Journal…
Notwithstanding, the authors put forth an interesting hypothesis and good faith effort to prove the hypothesis, but they did not appear to attempt a direct engagement with the primary scientific community of atmospheric scientists to whom they posed a widely divergent and controversial opinion. The draft was presented for peer review to experts in health physics but not to scientists who are expert in CO2 emissions and who study CO2 and C14 in the atmosphere. Conversely, if an atmospheric science journal editor had sent me the manuscript to referee, I would have declined without hesitation.
I’m super-glad you told us that anything as simple as earth’s atmosphere should never be studied in an inter-disciplinary way (/sarcasm). I find this extra-laughable, in particular as it’s a proud declaration of parochialism that, if anywhere, should not exist in as pluralistic a field (sic) as ‘climate science’.
Certainly, the authors believe they have arrived at a finding and conclusion that the atmospheric science mainstream does not currently embrace. Why not then publish in a disciplinary journal such as Journal of Geophysical Research or Geophysical Research Letters where precisely this type of research is published, or in a high-impact multidisciplinary journal such as Proceedings of the National Academy of Sciences or Nature?
The relationship of C14 behavior to global climate behavior has no characteristic of radiation protection. The Journal was not the correct venue for the content of the paper by Skrable et al.
Despite the venue of publication, I feel confident that the paper of Skrable et al. 2022 will receive scrutiny from the atmospheric science community.
Should we talk about wounded pride, schizophrenia, and the like in ‘climate research now’? (Still, In only reproduced that second comment as it’s…hilarious.)
The Editor Responds—in July 2023 (source)
The commentors argued that the Skrable paper is outside the scope of Health Physics. I disagree. The journal’s scope is clearly articulated in our Instructions for Authors (https://edmgr.ovid.com/hpj/accounts/ifauth.htm):
‘Health Physics, first published in 1958, provides the latest research to a wide variety of radiation safety professionals including health physicists, nuclear chemists, medical physicists, and radiation safety officers with interests in nuclear and radiation science. The Journal allows professionals in these and other disciplines in science and engineering to stay on the cutting edge of scientific and technological advances in the field of radiation safety. The Journal publishes original papers, technical notes, articles on advances in practical applications, editorials, and correspondence. Journal articles report on the latest findings in theoretical, practical, and applied disciplines of epidemiology and radiation effects, radiation biology and radiation science, radiation ecology, and related fields’ (emphasis added [by the editor]).
A bit further down, Ulsh Brant, the editor of Health Physics, deals with the allegations of misconduct in a really good way (emphases mine):
The commentors asserted that the authors should have submitted their paper to a more relevant (in their opinion) journal (e.g., Journal of Geophysical Research or Geophysical Research Letters). It is not clear to me how the commentors could know what journals the authors submitted their manuscript to prior to submitting it to Health Physics. In their response to this criticism in this issue, Skrable and his co-authors revealed that they had indeed previously submitted a similar version of this manuscript to the Journal of Geophysical Research, but that journal was unable to secure two qualified peer-reviewers. I am assuming—though the authors did not state so—that part of the difficulty in securing peer-reviewers stemmed from the interdisciplinary nature of their work, which straddles radiation and atmospheric sciences. This leads to the last criticism I will address.
The commentors stated that the peer-reviewers selected by the Journal are unqualified to review Skrable et al. (2022) due to a lack of expertise in atmospheric sciences. Again, as Health Physics employs double-blind peer-review, and the identities of reviewers are kept confidential, it is not at all clear how the commentors could have known who reviewed this paper and their qualifications to do so. Regardless, this claim is without foundation. In fact, both peer-reviewers were selected specifically for their expertise in atmospheric science/meteorology/climate science.
A Reply by Skarble et al. to Schwartz et al. Rounds off the Comment Section
I’ll include the following response by Skarble et al. to indicate how science works. Submitted in November 2022, it Skarble et al. address the four points raised by Schwartz et al. in June of that same year (emphases mine):
None of the four letters to the editor in the June 2022 issue of Health Physics include any specific criticism of the assumptions, methodologies, and simple equations that we use in our paper to estimate the anthropogenic fossil and non-fossil components present each year in the atmosphere. We have estimated from the ‘No bombs’ curve, modeled in the absence of the perturbation due to nuclear weapons testing, an approximation fitting function of annual expected specific activities. Annual mean concentrations of CO2 in our paper are used along with our revised expected specific activities to calculate values of the anthropogenic fossil and non-fossil components of CO2. These values are presented in revisions of Table 2a, Table 2, and figures in our paper. They are included here in a revised supporting document for our paper, which provides a detailed discussion of the assumptions, methodology, equations, and example calculations of the two components of CO2 in 2018. Our revised results support our original conclusions and produce an even smaller anthropogenic fraction of CO2 in the atmosphere. The file for the revised supporting document, including Table 2, is available at the link: (Supplemental Digital Content link, https://links.lww.com/HP/A230 provided by HPJ).
For the sake of complete-ness, I shall mention one more comment that arrived in March 2023, i.e., almost a year after publication. Written by David E. Andrews (U Montana), the following is held (my emphases):
Fossil fuel emissions more than account for the entire rise in atmospheric CO2, but only a small fraction of the cold carbon added to the carbon cycle since 1750 remains in the atmosphere. One could summarize: ‘What happens in the atmosphere does not stay in the atmosphere.’
Like Skrable, Chabot, and French, the author of this letter is concerned that important public policy decisions be based on sound science. The advantage of the scientific method over other approaches to obtaining knowledge is in its ability to use empirical evidence to cull innovative and creative but wrong ideas. In most instances, peer-review brings broadened viewpoints that expose weaknesses in arguments early in the communication process. Peer-review failed the authors in this case, leaving them with the unpleasant responsibility of making things right after publication. We thank them for acknowledging data errors in Skrable 1. But the conceptual errors clearly pointed out by Schwartz et al. and detailed further here remain in Skrable 2 [the corrections offered by Skrable et al.], nullifying their conclusions [this is quite interesting, as the corrections are, as pointed out above, actually re-inforcing the original conclusions]. Health Physics, along with Skrable, Chabot, and French, needs to decide whether to continue calling the issues discussed here ‘controversial’ or acknowledge that human responsibility for atmospheric CO2 rise during the Industrial Era is as settled as science gets.
I have excluded two paragraphs from Andrews’ letter: the first one is a laudatory brief of Schwartz et al.; the second relates to the corrections offered by Skrable et al., which is based on their accounting of the critique offered by Schwartz et al. This has resulted in an even lower anthropogenic ‘fossil component’ of about 20% for the period 1750-2018 (as opposed to approx. 23% in the original paper). Andrews explains ‘that a decade was about the mixing time observed with the bomb pulse’. Based on this notion of a one-time, massive injection of atmospheric nuclear testing, Andrews deduces the following (I only highlighted the ad hominem attacks that substitute for arguments):
We can then expect the magnitude of the dilution of atmospheric specific activity by cold fossil fuel carbon to be dominated by the most recent decade’s emissions. The dilution from earlier decades’ emissions has largely been erased by mixing. Therefore, an analysis that naively infers a ‘fossil component’ from the observed dilution may be expected to return a number approximating one decade’s worth of emissions, and Skrable 2 does just that. Their 321 GTon ‘fossil component’ is close to the 346 GTon’s of CO2 estimated to have been emitted between 2009 and 2018. Because of this dynamic situation, the very notion of ‘fossil’ and ‘non-fossil’ atmospheric components is not useful, accounting for the inability of the authors to find tabulations of these quantities in the peer-reviewed literature.
Two brief points here:
Ad hominem attacks are the antithesis of science. To claim that the one-time pulse resulting from atmospheric nuclear testing dissolved in a decade after testing ceased is one thing, to extrapolate—i.e., project—this backwards, is about as unscientific as it gets, mainly because Andrews puts the proverbial cart before the horse.
Note that Skrable et al. originally proposed a rapid rise in anthropogenic CO emissions since 1950, which also ‘explains’, to me at least, the ‘fossil component’ emitted between 2009-18. This has, by the way, nothing to do whatsoever with the authors’ alleged ‘inability’ to find such data in the peer-reviewed literature (which is also a weird way of Andrews proving Skrable et al. actually correct, as, if you care to remember, the latter pointed out—decried—the absence of such studies that discussed the proportion of human vs. natural carbon emission in the literature).
Just a few—this paper, as ‘controversial’ as it seems, has withstood the peer review and a bunch of post-publication attacks on its findings. Skrable et al. has not been retracted, hence it is quite clear as to why the paper was not widely reported on this or last summer.
Instead of a public debate of Skrable et al., we got this:
It is evident by now that something doesn’t add up in the field of ‘climate science’. As with ‘the vaccines’ during the declared ‘Covid pandemic’, though, we should keep in mind that sunlight is the best disinfectant, i.e., more debate, not censorship on grounds of ‘disinformation’, is the answer.