A Harde response

Earlier this year, I wrote a post about a paper by Hermann Harde that argued that most of the rise in atmospheric CO2 was natural. If you want more details of why this suggestion is nonsense, you can read my earlier post. What I was going to mention in this post is that a number of us have just published a response.

The history of this is essentially that Gavin Schmidt, as he suggested in this Realclimate post, set up an Overleaf document and contacted those who had shown interest. It was lead by Peter Köhler, and colleagues, from the Alfred-Wegener-Institut, but also included myself, Eli Rabett, and Richard Zeebe from the University of Hawaii at Manoa. Gavin Cawley also provided some very valuable comments and suggestions.

I don’t need to say too much about the details of our paper. It essentially highlights that the Harde paper confuses the residence time of an individual molecule (years) with the adjustment time for an enhancement of atmospheric CO2 (centuries). It also points out that you can’t model the evolution of atmospheric CO2 with a single equation. You need to consider at least two reservoirs (atmosphere and surface ocean) and this requires at least two equations that are solved simultaneously.

We also point out that it’s important to consider the Revelle factor, which limits how much of our emissions can be taken up by the oceans (we would expect – depending on how much we emit – that 20-30% of our emissions will remain in the atmosphere for thousands of years). Additionally, there were issues with Harde’s application of his model to paleoclimate, and there were a number of papers that he really should have cited (such as citing Essenhigh 2009 paper, while failing to cite Gavin Cawley’s response).

We end our paper by suggesting that Harde’s paper be withdrawn. I’m normally a little uncomfortable with suggesting that a paper that does not involve fraud, or plagiarism, be withdrawn. However, Harde’s paper is so obviously flawed that it is remarkable that it made it through the editorial, and review, process without being rejected. It might be better if it were withdrawn, but at least there is now a formal response that highlights the numerous issues.

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63 Responses to A Harde response

  1. Kevin ONeill says:


  2. Marco says:

    Quite a few papers have been retracted recently for making mistakes. In those cases, however, it supposedly(*) is the author that takes the initiative.

    (*) In reality, in some cases there very likely is pressure from the Editor(s) to retract.

    COPE actually states that “Journal editors should consider retracting a publication if they have clear evidence that the findings are unreliable, either as a result of misconduct (e.g. data fabrication) or honest error (e.g. miscalculation or experimental error)”

    Moreover: “Retraction should usually be reserved for publications that are so seriously flawed (for whatever reason) that their findings or conclusions should not be relied upon.”

    Harde’s paper definitely fits this category…

  3. Marco,
    Thanks, I hadn’t seen the suggestion that retraction should be considered if a paper’s findings are unreliable. It does make sense in cases where it’s obvious that the paper’s results are clearly flawed.

  4. dikranmarsupial says:

    Bravo indeed!

    I think the reason Prof. Harde’s paper made it through review can be found in the author information pack for the journal:

    Please submit, with the manuscript, the names, addresses and e-mail addresses of five potential
    referees. Note that the editor retains the sole right to decide whether or not the suggested reviewers
    are used.

    which seems to me a recipe for pal-review, I suspect I can guess some of those likely to have been on any such list. I suspect that is also how the earlier carbon cycle paper by Humlum et al. (which also was the subject of peer-reviewed comments) that was published in the same journal. IMHO journals should never do this. For any paper within the scope of the journal, there should be an action editor sufficiently familiar with the sub-field to identify suitable reviewers for themselves and if they can’t they shouldn’t handle it. However, they are only human and we all make mistakes…

    The problem with the paper is made very obvious by the fact that Prof. Harde doesn’t provide a plot of the output of his models against the observations, which is a very natural thing to do if you want to show that your model provides a good fit to the data. The closest we get in the paper is figure 3:

    I tried reproducing this myself, but plotting the actual ice core data, rather than giving error bars:

    Not so good. In particular it is clear that in the ice core data, the relationship between temperature and CO2 is linear, and the modern observations don’t fit the pattern of the ice core data (and neither does Prof. Harde’s model). It isn’t at all clear how the error bars for the observations for Harde’s figure 3 were calculated, I suspect they may be “subjective”.

    Note there are substantial problems with my diagram as well (I learned a lot from my discussions with the authors of the paper!), particularly the Vostok temperatures are regional Antarctic temperatures, rather than global temperatures. IIRC the Vostok core includes interglacial periods that were about as warm as it is now (if not warmer?), so if Prof. Harde’s model is correct, it is hard to see why CO2 concentrations were not approaching 400ppm then (I’d need to go and check the details on that, so caveat emptor).

    Anyway, it is a shame that the effort it takes to respond to ill-informed misleading papers, such as this one, is so much higher than it is apparently to produce them, but I’m glad someone took the trouble to do it in this case.

  5. dikranmarsupial says:

    Here is my attempt at implementing Prof. Harde’s model of post-industrial conditions, using an ODE solver to drive the model with observed temperatures:

    This shows why a temperature driven model for atmospheric CO2 with a short “residence” time can’t explain the observed rise in atmospheric CO2. The temperature data has lots of decadal+ scale variability, and a “residence” time of only 4 years isn’t enough to smooth it out, so it will predict that CO2 will rise with similar decadal+ scale variability. The trouble is that it doesn’t, the observed rise in atmospheric CO2 is pretty smooth, and a simple (and conventional) one-box carbon cycle model (based on the one in my paper) with an approx. 50-70 year adjustment time (don’t worry, it also has a residence time of 4-5 years ;o) does a much better job.

  6. dikranmarsupial says:

    Cheers, I’m glad there was a suitable venue to share the diagrams at last! I like your new avatar/icon BTW, if I had an avatar representing my work it would have to be an animated GIF of (apparently meaningless) numbers changing very slowly ;o)

  7. “It also points out that you can’t model the evolution of atmospheric CO2 with a single equation. “

    I can. It’s variously referred to as dispersive diffusion — a classical diffusion equation solved with a MaxEntropy distribution of diffusivity values. This maps to the heuristically determined set of factors known as the Berne formulation.

  8. Geo,
    Well, okay, but that is presumably determining net flux and your diffusion coefficient is presumably implicitly incorporating information about the two reservoirs.

  9. The numerical solution to diffusion in that geometry is a slab model, which is an infinite set of differential equations representing the flow between an infinite number of reservoirs. The analytical solution to that geometry is an erf. As an analogous application, the ocean/atmosphere interface is equivalent to the solid/vapor interface used for diffusional doping of a semiconductor. The industry has this process characterized very well and the erf works effectively.

    But with a range of diffusivities representing the different pathways to CO2 sequestration, the erf can be replaced with another formulation that takes into account the variability. So the Berne formulation is a heuristic for the description of the actual diffusional physics. They use the heuristic because that’s all they need apparently. There’s nothing wrong with it but they will never be able to approximate the diffusional fat-tail at infinite time because they are using a set of exponentials instead of an erf. The slowest exp decay is what they use for the fat tail.

  10. Everett F Sargent says:

    So, who will reply to Harde’s latest missive missile that misses massively? …
    Radiation Transfer Calculations and Assessment of Global Warming by CO2

    “Including solar and cloud effects as well as all relevant feedback processes our simulations give an equilibrium climate sensitivity of Cs = 0.7°C (temperature increase at doubled CO2) and a solar sensitivity of Ss = 0.17°C (at 0.1% increase of the total solar irradiance). Then CO2 contributes 40% and the Sun 60% to global warming over the last century.”

    Rust Never Sleeps

  11. Everett,

    So, who will reply to Harde’s latest missive missile that misses massively? …
    Radiation Transfer Calculations and Assessment of Global Warming by CO2

    I don’t know if anyone is going to bother with that one.

  12. cce says:

    Is there a link to this paper?

  13. cce,
    Good point. I managed to forget to provide a link in the post (fixed now). It’s here, in case you don’t want to read the post again 🙂

  14. angech says:


  15. KHome1990,
    Below is a figure that might help. It shows the cumulative emissions for the 4 different Representative Pathways (RCPs) and shows how the warming depends more on how much we emit, rather than on how fast. It also shows atmospheric concentrations (bubbles) and each dot on each line is a decade. The range is represented by the width band.

  16. Marco says:

    Wrong thread, ATTP!

  17. Everett F Sargent says:

    Figure 2.3 | Global mean surface temperature increase as a function of cumulative total global carbon dioxide (CO2) emissions from various lines of evidence. Multi-model results from a hierarchy of climate carbon-cycle models for each Representative Concentration Pathway (RCP) until 2100 are shown (coloured lines). Model results over the historical period (1860 to 2010) are indicated in black. The coloured plume illustrates the multi-model spread over the four RCP scenarios and fades with the decreasing number of available modelsin RCP8.5. Dots indicate decadal averages, with selected decades labelled. Ellipses show total anthropogenic warming in 2100 versus cumulative CO2 emissions from 1870 to 2100 from a simple climate model (median climate response) under the scenario categories used in WGIII. Temperature values are always given relative to the 1861–1880 period, and emissions are cumulative since 1870. Black filled ellipse shows observed emissions to 2005 and observed temperatures in the decade 2000–2009 with associated uncertainties.(WGI SPM E.8, TS TFE.8, Figure 1, TS.SM.10, 12.5.4, Figure 12.45, WGIII Table SPM.1, Table 6.3)

    (page 63)

  18. Comment on “Scrutinizing the carbon cycle and CO2 residence time in the atmosphere” by H. Harde, needed proof-reading.

  19. Pingback: 2017: A year in review | …and Then There's Physics

  20. Good news, the journal has published a commentary on the failure of the review process, see RealClimate for details. For once writing a comment paper has actually had an effect (from the journal response bit):

    In order to lessen the possibility of introducing bias into the peer review process, authors are no longer able to suggest the names of possible reviewers for their manuscript. To give more credit to the Editors for their work and increase a sense of accountability, published manuscripts will additionally provide the name of the editor who made the final decision.

    This is real progress. Journals really should never ask authors to suggest reviewers, it is a recipe for pal-review. If the editor is unable to identify suitable reviewers for themselves, then they are likely to be too inexperienced (not sufficiently aware of the broader research field, rather than their own specialism, which takes time), or the paper is outside the scope of the journal. If nothing else, an editor that wasn’t able to select reviewers ought to pass the paper on to another editor where the paper is closer to their expertise (I’m not sure that journals should allow authors to select the editor either – that also has resulted in problems in the past).

    I was rather less impressed by:

    “After much consideration by the editors at the time of publication, it was felt that the paper should not be retracted, but rather let it remain to stimulate further discussion about such a highly charged and contentious topic.”

    This is just ridiculous. The cause of the rise in atmospheric CO2 is not remotely a highly charged or contentious topic, and stimulating further debate on this issue (unless some startling new evidence comes along) is just an egregious waste of everybody’s time.


    All five suggested potential reviewers were invited by the Editor to provide formal reviews on the submitted manuscript. Two of them accepted the invitation and suggested ‘major revisions’ and ‘minor revisions’, respectively. Both reviewers asked the author for more clarity and better presentation, style and language; none of them raised any concern about the scientific content of the manuscript. We believe that this may have been because the reviewers lacked the impartiality and scientific expertise to provide an adequate science-based review.

    This implies, but doesn’t explicitly state, that the only reviewers invited to review were those suggested by the author, which is, shall we say, “sub-optimal”.


    During the initial manuscript submission, H. Harde suggested five potential reviewers. Most if not all of them are prominent individuals advocating that currently raising CO2 concentrations would be natural and not related to human influence.

    I think they have just identified the reviewers. It isn’t that easy to think of more than five scientists that would advocate rising CO2 concentrations being natural.

  21. I should add, I fully agree with

    It was also felt that although the implementation of the peer review of this paper had failed, no unethical action has been found in its publication.

    as a reason not to withdraw the paper. Much better than the reason that immediately preceded it! ;o)

  22. Pingback: An editorial response | …and Then There's Physics

  23. Story about this at RetractionWatch, which gives a link to Prof. Harde’s rejected response paper (with help from Murray Salby).

  24. Apparently there is another paper in review (?) on this topic by Ed Berry. So I suspect Harde’s paper might not be the last that time will be wasted on, by the reviewers if not the rest of the research community.

    Yet again it is a failure to understand the difference between residence time and adjustment time:

    3.3 IPCC confuses residence time

    IPCC (1990) properly concludes that the residence time of carbon dioxide molecules in the atmosphere is about 4 years. But the IPCC defines residence time incorrectly. The IPCC says residence time is “turnover time.” Here is a quote:

    The turnover time of CO2 in the atmosphere, measured as the ratio of the content to the fluxes through it, is about 4 years. This means that on average it takes only a few years before a CO2 molecule in the atmosphere is taken up by plants or dissolved in the ocean.

    This short time scale must not be confused with the time it takes for the atmospheric CO2 level to adjust to a new equilibrium if sources or sinks change.

    What IPCC calls “turnover time” is the 1/e residence time.

    IPCC defines two kinds of residence times: one residence time equals the average lifetime of molecule, and the other residence time equals the time for the “level to adjust to a new equilibrium” level.

    But both residence times are the same thing. All definitions of residence time are the same because all definitions measure residence time according to the change in the level of carbon dioxide. No one measures how long an individual carbon dioxide molecule stays in the air.

    [emphasis mine]

    The hubris of this is staggering. The IPCC carefully explain the difference between the two, but Berry insists that they must be the same thing. The highlighted bit is so obvious an error it is hard to see how even Berry has missed it. The residence time is not measured by changes in the level of carbon dioxide; if sources and sinks were constant the adjustment time would be infinite (as the carbon cycle would not adjust to an exogenous pulse of CO2 and atmospheric level would remain raised indefinitely), but there would still be a finite residence time because of the exchange flux.

  25. I had lengthy discussion with Ed Berry on this post. He’s completely unreachable with, as you say, a staggering amount of hubris.

  26. Apparently the article was submitted to an Elsevier journal, I wonder if it was “Global and Planetary Change” (as it has already published two papers on this topic). Hopefully the reviewers will spot the obvious errors (and hopefully not selected by Berry) and/or the editors will be more cautious this time.

    It is bizarre how people can refuse to accept they are wrong on this one, when the evidence is so strong (common sense ought to be sufficient to strongly doubt it being a natural phenomenon!).

  27. Marco says:

    “It is bizarre how people can refuse to accept they are wrong on this one”

    If your ideology depends on you understanding something the wrong way…

  28. True, but it would be more sensible to attack a later, weaker link in the chain, rather than whatis probably the strongest! It is quite some ideology if it means you can’t accept any part of it.

  29. Marco says:

    No need to attack those later links if you can cast doubt on an earlier one!

    Note also that some are deadly afraid that accepting A brings them one step closer to also accepting B. The infamous “slippery slope”.

  30. I glanced through Ed Berry’s text and I got the impression that he is not giving a correct description of previous scientific understanding of the carbon cycle. His three analogies at the beginning of his paper are all missing the point.

    A better analogy would be that there are two water pools, A and B, equal in size. Water is pumped from A to B through one tube. Then there is a recycling tube in which there is an equal flow of water from B to A. If undisturbed the water will circulate between the two pools and the water level will remain the same. This is a simple analogy of the undisturbed circulation of carbon dioxide between the atmosphere, corresponding to pool A, and the mixed layer of the ocean, corresponding to pool B. The water level corresponds to the carbon dioxide concentration level. The flow from B to A corresponds to the natural carbon dioxide emissions from the ocean to the atmosphere, the flow from A to B is the absorption of carbon dioxide from the atmosphere¨to the ocean.

    Now, assume that there is a drain connected to the wall of pool B in order that the water should not overflow the pool brims of the two communicating pools. If water from a hose flows into pool A the water level in the pools will increase. At first, all the water from the hose will increase the water level but then gradually the drain will begin to receive more and more water and finally, the water level will stabilize on a higher level. The flow from the hose corresponds to human carbon dioxide emissions, say 10 % of the natural emissions from the ocean to the atmosphere, and the flow through the drain corresponds to the flow of carbon dioxide from the mixed layer of the ocean to the main part of the ocean.

    Unfortunately, the carbon dioxide flow from the mixed layer to the main part of the ocean corresponds to a very narrow drain. The carbon dioxide level has to increase very much before the drain will stabilize the level at a much higher carbon dioxide concentration than we have today. We are still in the part of the process where most of the human carbon dioxide remains in the two pools and only a small fraction leaves through the drain pipe.

    I have based my analogy on the fundamental principles that were developed many years ago by Revelle and Suess (1957) and Bolin and Eriksson (1959). Those fundamental principles are a well-established and a widely accepted scientific basis for models of the carbon cycle, for example, the Bern model.

    Bolin, B., and Eriksson, E., 1959: “Changes in the carbon dioxide content of the atmosphere and sea due to fossil fuel combustion,” Rossby Memorial Volume (New York: Rockefeller Institute Press), pp. 130-142.

    Roger Revelle & Hans E. Suess (1957) Carbon Dioxide Exchange Between Atmosphere and Ocean and the Question of an Increase of Atmospheric CO2 during the Past Decades, Tellus, 9:1, 18-27, DOI: 10.3402/tellusa.v9i1.9075

  31. Marco says:

    There also is a case to be made against the increase being primarily natural because of a lack of credible sources and sinks for that increase.

    If we take, for example, Harde’s claim that only 10% of the increase is anthropogenic, this means 90% of the increase must be natural. Since the annual increase in atmospheric CO2 has been relatively constant at about half the annual anthropogenic addition, this means the natural net flux to the atmosphere must be about ten times bigger (and weirdly scaling with the anthropogenic contribution over the last few centuries, but let’s ignore that happy coincidence). This is an enormous amount of carbon. We’re talking about 80 Gt C per year at the moment, and while that gets progressively lower as we get back in time, we’d still talk about several thousand Gt C (around 3-3.5) since the industrial revolution.

    And then the accounting problems start: The net source isn’t the oceans, because we’ve measured an increase in dissolved inorganic carbon (and there is too little dissolved organic carbon in there for that to be the source). It isn’t vegetation, or there’d be no more vegetation. It isn’t soil, because there’d be no more carbon in the soil. So, where’s that source that Harde and Salby and Berry etc conclude must exist? A little bit from everything still doesn’t cut it. Volcanoes? Gee, another problem in getting that to go up to the required amount (it really is a lot of CO2 – we’re talking 10% of Deccan trap-like levels of emissions, but in a much shorter time period). And besides, what made volcanoes suddenly spew so much more CO2 in the air, and so happily in tune with anthropogenic emissions?

    If they would argue that the oceans are the source, but it’s from the deep oceans somewhere, where good DIC measurements are lacking, we still lack a credible sink. Sure, vegetation may have increased, but we’d have to talk about an increase of many factors to get to the required thousands of Gt carbon that needs to be taken up. We would have noticed that. Soil could potentially be easier to ‘sell’ as the sink, as it is more difficult to measure an increase in carbon content in the soil by about a factor 2-3 or so. That lacks a mechanism, though.

  32. Neither Hermann Harde nor Ed Berry seems to have read and understood the two seminal papers by Revelle and Suess (1957) and Bolin and Eriksson (1959). Harde has not cited any of those papers. Although Berry cites Revelle and Suess he is not aware of why this paper is so important. Perhaps someone should recommend Harde and Berry to study more climate science. A good beginning could be Spencer Weart’s“The Discovery of Global Warming”

    Spencer Weart, in that work, has written about the importance of the two papers Revelle and Suess (1957) and Bolin and Eriksson (1959) in the following essay with the title “Roger Revelle’s Discovery”:

    The introduction of this fairly detailed essay is :

    Before scientists would take greenhouse effect warming seriously, they had to get past a counter-argument of long standing. It seemed certain that the immense mass of the oceans would quickly absorb whatever excess carbon dioxide might come from human activities. Roger Revelle discovered that the peculiar chemistry of sea water prevents that from happening. His 1957 paper with Hans Suess is now widely regarded as the opening shot in the global warming debates. This essay not only describes Revelle’s discovery in detail, but serves as an extended example of how research found essential material support and intellectual stimulus in the context of the Cold War.(1)

    At the end of Weart’s text the importance of Bolin and Eriksson (1959) is described:

    Another two years passed before Bert Bolin and Erik Eriksson explained the sea water buffering mechanism in clear terms and emphasized what it meant. Unlike Revelle, they figured industrial production would indeed climb exponentially, and they calculated that atmospheric CO2 would probably rise 25% by the end of the century. Now the small community of geophysicists began to grasp that they could not rely upon the oceans to absorb all the emissions of fossil fuels.(31)

    It is rather impressing that Bolin and Eriksson in 1959 predicted that the rise of carbon dioxide content in the atmosphere could be 25 % in the year 2000 compared to 1880. Carbon dioxide had risen to 369 ppm in 2000. Assuming that it was 300 ppm in 1880 that is a 23 % rise:

  33. Marco says:

    “Perhaps someone should recommend Harde and Berry to study more climate science.”

    Yeah…people have. They just dig in more. Remember that both seem to come from a position that mainstream climate science is wrong, hence no need to understand the scientific papers by mainstream scientists.

  34. FWIW at Retraction watch, Prof Harde writes:

    I agree with Dr. Cawley [i.e. me – DM] that nature is a net sink, as long as anthropogenic activities are not zero. I had never doubts on this assertion. But I can’t follow the conclusion that in addition to human emissions increasing natural emissions cannot be the reason for an observed growing CO2 concentration.

    At least Prof. Harde agrees that the natural carbon cycle is a net carbon sink. However it seems to me to require some cognitive dissonance to accept that the natural carbon cycle takes more CO2 out of the atmosphere than it puts in, but at the same time to believe that the rise in atmospheric CO2 is a natural phenomenon.

  35. …and Then There’s Physics, you said in one of your previous comments here that:

    “I don’t know if anyone is going to bother with that one.”

    You were referring to whether anyone would bother with this trite “paper” from Harde and published in a predatory journal:
    “Radiation transfer calculations and assessment of global warming by CO2”

    Well, I think someone should write a formal comment or rebuttal to that paper, since Knutti et al. cited that “paper” in their recent review of climate sensitivity estimates:

    “Beyond equilibrium climate sensitivity”, figure 2 on page 4

  36. dikranmarsupial says:

    FWIW Murry Salby responds to Köhler here:

    Pretty much packs all of the climate skeptic carbon cycle myths into one “convenient” 90min talk. The above link is about where the stuff about Harde’s paper starts.

  37. Massimo Polo says:

    Dr Berry has come up with a refined version of his carbon cycle theory, that you can find in this preprint : https://edberry.com/blog/climate/climate-physics/human-co2-has-little-effect-on-the-carbon-cycle/
    Although I am not a scientist but just an engineer, he seems to show some very good points highlighting those that seem evident errors in the IPCC human carbon cycle. Despite some attempts made by a few physicists (including the swiss professor Aegerter) to rebut his findings, he has been able to brilliantly answer (in my view) to all of them. My view is that his arguments are looking quite more convincing than those against him (at least from what I have read so far).
    Since he looks an open minded and respectful person, I recommend that those that know these matters better than me, should challenge Dr Berry directly in his blog/website, as others have already made.

  38. Massimo,
    I have interacted with Ed Berry before and don’t have much interest in doing so again. His arguments are clearly wrong. There is no question that the rise in atmospheric CO2 is anthropogenic. The ocean PH levels are going down, which means the ocean is taking up more CO2 than its emitting. The biosphere, similarly, is taking up more than its emitting. Hence, neither the oceans nor the biosphere can be the source of the rise in atmospheric CO2. The only source for which the emissions exceed the uptake is human emissions (i.e., we emit CO2 but don’t sequester any). There is really no point in debating this with someone who doesn’t get this very basic issue.

  39. dikranmarsupial says:

    I tried to have a discussion with Berry, but he is not able to accept that his theory is contradicted by the observations. The simplest is that if the natural environment were a net source of CO2 into the atmosphere, then the rate at which atmospheric CO2 were rising would be faster than the rate of anthropogenic emissions, because both nature and mankind would be contributing to the rise. However, that is not what we observe – the average annual increase in atmospheric CO2 is only about half the rate of anthropogenic emissions (fossil fuel use and land use change emissions). That establishes that the natural environment is a net carbon sink and hence is opposing the atmospheric rise, rather than causing it. The uncertainty in the data is way to low to cast any substantive doubt on that analysis. See

    I have raised this on Berry’s blog here. Note that his response does not address in any way the criticism that I made and just tries to change the subject. When I pointed out his repeated evasion of the point I raised, he resorted to ad-hominem attacks:

    “Now that I see you are a “computer scientist” and not a physicist, I better understand your problem. You simply do not understand physics well enough to understand climate physics … but you attempt to play physics anyway. …”

    I also pointed out here how he had misrepresented my work. Again, his response did not address my criticism.

    That post did give me a laugh though, where he wrote


    Cawley [22] is a key paper for the IPCC theory. Cawley claims human CO2 caused all the increase of atmospheric CO2 above the 280 ppm in 1750. …

    Which is hilarious. My paper is of no importance whatsoever for the “IPCC theory”, it is just setting out some basic concepts that anybody working on the carbon cycle should understand and was written purely to address some misundestandings that have been promulgated by skeptics in the public debate on climate. It has precisely zero novel scientific content, and was never intended to be otherwise!

  40. dikranmarsupial says:

    Sadly this particular issue (i.e. the rise in CO2 is natural) is a strong indicator that someone is not reachable by rational scientific discussion, because the evidence that the rise is anthropogenic is conclusive (beyond reasonable doubt). Unfortunately nothing can be established beyond unreasonable doubt. I agree with climate skeptic Fred Singer, that such arguments only serve to marginalise climate skeptics from the discussion (and also wastes everybody else’s time and energy as well – but perhaps that is a feature rather than a bug ;o)

  41. Marco says:

    “The simplest is that if the natural environment were a net source of CO2 into the atmosphere, then the rate at which atmospheric CO2 were rising would be faster than the rate of anthropogenic emissions, because both nature and mankind would be contributing to the rise. ”

    …unless there suddenly, and at the same time as anthropogenic sources of CO2 became substantial, has emerged a magical sink that has started taking up *massive* amounts of CO2. I once calculated that this sink must have taken up 1500 (IIRC) gigatons of CO2 more than it emitted over the same time period, if natural sources were the predominant contributor to CO2 rise (90%-10%, I think I took as assumptions of natural vs anthropogenic).

    That would have more than halved the amount of CO2 in the upper ocean layers, if it were the upper ocean layer that was the source.

  42. dikranmarsupial says:

    “unless there suddenly, and at the same time as anthropogenic sources of CO2 became substantial, has emerged a magical sink that has started taking up *massive* amounts of CO2.”

    It is only meaningful to consider the net effect of natural sources and sinks together and the net effect of anthropogenic sources and sinks (negligible) together. If I want to know whether I am causing my bank balance to rise or fall, I need to look at the net of my deposits and withdrawals. If a magic sink appeared, that would still be the natural carbon cycle opposing the rise in atmospheric CO2.

  43. Marco says:

    I agree, Dikran, but it can be fun to ask all those who claim the oceans are the source to explain what sink must then have increased by so much, and how this fits with the measurements.

  44. dikranmarsupial says:

    Yes, they only know about *half* of Henry’s law ;o)

  45. Max Polo says:

    Thanks guys, appreciated your explanation and respectful discussion.

  46. dikranmarsupial says:

    Max, no problem. Has it changed your view of Berry’s theory? The line of evidence I suggest is more than sufficient to demonstrate that it is incorrect.

  47. dikranmarsupial says:

    I should add there are several other in my paper on the topic (which Berry references and misrepresents), you can find a free pre-print here.

    Gavin C. Cawley, On the atmospheric residence time of anthropogenically sourced carbon dioxide, Energy & Fuels, volume 25, number 11, pages 5503–5513, September 2011 (https://pubs.acs.org/doi/10.1021/ef200914u)

    Here is a very good summary.

  48. Max Polo says:

    Thanks Gavin,
    all look very interesting.
    But : reading your linked articles, and then re-reading Berry’s remarks on each single alleged “line of evidence”, I honestly find it difficult to think that Berry may have misinterpreted or circumvented anything. Rather, my impression is that he has perfectly understood where the key points (and tricks) are. My humble view is that IPCC human CO2 model is a mathematical artefact with major physics flaws. Trying to support an assumption (even one that looks sensible and reasonable) by skewing physics laws is never a good idea. But, as I said, I’m just a M.Sc. in mechanical engineering and not a climate scientist. Time will tell.

  49. David B. Benson says:

    Max Polo, I encourage you to read “Principles of Planetary Climate” by Ray Pierrehumbert.

  50. Max,
    Maybe consider this a little. There are essentially 3 reservoirs that contain CO2, the oceans, the biosphere, and the atmosphere. For a long time prior to the industrial revolution the atmospheric CO2 concentrations were roughly constant. We also know that the oceans and the biosphere emit and take up quite a lot of CO2. That the atmospheric CO2 concentrations were constant tells us that the fluxes must have been in balance. In other words, the amount of CO2 emitted into the atmosphere from the oceans matched the amount being taken up by the oceans, and the amount being emitted by the biosphere matched the amount being taken up by the biosphere.

    Now, we came alone and started to burn fossil fuels, emitting CO2 into the atmosphere. However, we’re only a source of CO2, there is no human uptake of CO2. So, when we started emitting we pushed the natural carbon cycle out of balance. No longer did all the fluxes balance, which meant that atmospheric CO2 started to rise. However, it’s actually rising slower than our emissions. So, at least some of what we’re emitting is going somewhere. It’s going into the oceans and into the biosphere. You can even see evidence for this in the form of the ocean pH levels dropping, and greening of the land biosphere.

    So, if the rise is not anthropogenic, we have a real problem. Somehow, all of what we’re emitting is being taken up by one of the natural sinks while one of these sinks has suddenly also become a source of CO2. This doesn’t really make much sense; how can a natural sink be both a sink of CO2 and a source? I actually can’t even really construct a plausible argument that would illustrate this (it really doesn’t make much sense).

    There are also plenty of other lines of evidence. Whatever is emitting the CO2 is rich in C12, but poor in C14. This tells us it’s biological, but old (fossils). There’s a corresponding decline in atmospheric oxygen, which suggests combustion, not volcanoes.

    You can read more about the various lines of evidence here.

  51. Marco says:

    Maybe I should not be doing this, but…

    “I’m just a M.Sc. in mechanical engineering…”

    Why am I not surprised?

  52. dikranmarsupial says:

    Max. If the natural environment is not a net sink, how do you (or Berry) explain the observed fact that atmospheric CO2 levels are rising more slowly than the rate of anthropogenic emissions. This is not a rhetorical question.

  53. Max Polo says:

    Dikran, I am not sure to have understood what you mean. I do not think this is what Berry is saying (however, better would be asking him – theory is not mine).
    Quoting: IPCC also claims nature has been a “net carbon sink” since 1750, so nature could not have caused the observed rise in atmospheric carbon dioxide. Of course, nature is a “net carbon sink” because nature absorbs human CO2 emissions. But absorption of human CO2 does not prevent nature from increasing its own CO2 emissions because inflow and outflow are two different processes.

  54. Max Polo says:

    Then there’s Physics : obviously the human inflow alters the nature balance. This is what also Berry finds. The problem is by what amount. The way Berry calculates such amount, doesn’t differentiate between nature and human CO2 molecules. Absorption rates are calculated in the same manner for human and natural CO2, reproducing the physical mechanism described by the Henry’s law. On the other side, the Bern model creates this “artifact formula” just for the poor human molecules, that are condemned to stick to the atmosphere forever (at least part of them). Why ? Because otherwise its initial hypothesis (= all the increase of CO2 is due to humans) would fall down. This is why I talked of skewing the laws of physics. But then, I am not an expert, and as Marco noted, I may be wrong. Rather than challenging me, you should challenge Dr Berry. This is why I posted in this forum.

  55. David B. Benson says:

    Max Berry, just ignore the confused Dr. Berry.

    Instead study whatever parts of the extensive online “The Discovery of Global Warming” by Spencer Weart capture your attention. Weart is correct, Berry is not.

  56. Max,
    I don’t actually understand what you or Berry are really claiming. The Bern model doesn’t – as far as I’m aware – have some kind of “artifact model” for just the human molecules. I don’t even know what this means. Just to clarify something, that the increase in atmospheric CO2 is entirely anthropogenic does not mean that every single molecule in that enhancement is from an anthropogenic source. The molecules that we emit cycle through the different reservoirs just like all the other CO2 molecules. What it means is that atmospheric CO2 would not be rising in the absence of our emissions.

  57. Marco says:

    Max, let’s take a few small steps at a time:
    “But absorption of human CO2 does not prevent nature from increasing its own CO2 emissions because inflow and outflow are two different processes.”

    The point Dikran makes, and Berry and many others (you included) ignore, is that natural increases in CO2 emissions MUST be compensated by natural increases in CO2 uptake, or otherwise the CO2 in the atmosphere would rise *faster* than the anthropogenic contribution, not at half the rate. It is really that simple, and I’ll illustrate that with an example that many can relate to a lot easier, as it is about money flows:
    Supposed you get a 2000 euro net salary per month. Your monthly expenses are also 2000 euro. What does your account show over a year? A flat line, no increase nor decrease. Now someone, let’s take an old friend, decides to give you 100 euro a month. What happens? Unless you increase your spending, your account will show, after a year, a surplus of 1200 euro. 100% of the extra money on your account is due to your old friend giving you money. What would happen to your account if you get a raise of 100 euro on top of your friend giving you 100 euro? Your account now increases at 2400 euro a year, 200% of the contribution of your old friend. The only way to get your account to increase by only 50% of your friend’s contribution is to increase your spending. In the case of just your friend contribution, you’d be spending 2050 euro a month, in the case of your old friend’s contribution + the salary increase, you’d need to spend 2150 euro a month. Notice how no matter what, your spending is LARGER than your salary?

  58. Marco says:

    Although ATTP already points it out, I’ll repat: the Bern model does NOT treat anthropogenic CO2 any different from any other CO2 molecule. It just takes into account that exchange rates are interrelated. Let’s take a very simplistic Gedankenexperiment: we inject a lot of CO2 into the atmosphere, giving an instantaneous doubling. This higher partial CO2 pressure means the oceans will take up a lot of that CO2. Let’s say 50% and let’s say again this is instantaneous. In the new equilibrium, the rate of ocean out = ocean in. Now say there is a slower process that removes CO2 from the surface (exchange) layer of the ocean into the deeper ocean. This means CO2 concentrations in the surface layer decrease, and thus more atmospheric CO2 is taken up (as ocean out < ocean in). But since this decreases atmospheric CO2, ocean in reduces. And so the process goes on, with constantly altering exchange rates.

    And regarding challenging Berry, Dikran already pointed out he tried to have a civilized discussion with Berry on this, but got bullied away.

  59. dikranmarsupial says:

    Max, you need to read the paper. The natural sinks don’t just take up human emissions, they take up natural emissions as well. The total uptake by natural sinks of atmospheric CO2 is greater than total emissions of CO2 not the atmosphere. We know that because the rate of atmospheric rise is less than the rate of anthropogenic emissions. Somebody with an msc in mechanical engineering should be able to understand conservation of mass.

  60. dikranmarsupial says:

    Max as others have said, the Bern model does not differentiate between anthropogenic and natural CO2. Sources and sinks may have isotopic preferences, but there is no way for nature to distinguish one sourace from another. Berry may claim that it does, but that is because of his lack of understanding of carbon cycle modelling and his resistance to correction.

    Max, do you agree that CO2 in the atmosphere obeys conservation of mass, i.e. any CO2 that is emitted into the atmosphere that isn’t taken out of the atmosphere stays in the atmosphere? Yes, or no.

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