Flawed climate science paper “exposed potential weaknesses” in the peer review process

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How did a deeply flawed paper, which contradicts mainstream science on climate change, pass peer review?

That is what three editorial board members tried to figure out after the journal, Global and Planetary Change, faced heavy criticism for publishing the controversial paper last year. The board members published their findings earlier this month in a commentary.

Martin Grosjean, the corresponding author on the editorial, told Retraction Watch that the editors and publisher, Elsevier, share the same interest:

… keeping the good reputation of the journal and let[ting] the community know with full transparency what has happened.

Despite calls to retract the paper, the journal has chosen not to, as “no unethical action has been found in its publication,” according to the board members’ editorial.

In the 2017 paper, which proposed an alternative model for understanding why atmospheric carbon dioxide has risen so substantially over the past 60 years, author Hermann Harde concluded that experts have grossly overestimated the extent to which humans are responsible for this change.

According to Grosjean, shortly after the paper appeared online, researchersincluding members of the journal’s own editorial boardexpressed concern about how such a flawed analysis was accepted for publication. Last September, the journal published a comment by a group of climate experts critical of the 2017 paper. The critics, led by Peter Köhler, based at the Alfred Wegener Institut in Bremerhaven, Germany, explained that Harde’s analysis was based on invalid assumptions and led to flawed results; they asked the paper be withdrawn.

Harde told us he stands by his analysis and has posted a response to the situation on his blog.

Earlier this month, three of the journal’s editorial board members—Grosjean, Joel Guiot, and Zicheng Yu—published a commentary, acknowledging that “the implementation of the peer review of this paper had failed” in this instance. The editorial authors wrote:

The acceptance of this paper has exposed potential weaknesses in the implementation of the peer review system, and quality control mechanisms have failed in this particular case…

According to the commentary, the editorial board members investigated the matter. The investigation revealed that Harde, a professor of experimental physics at Helmut Schmidt University in Hamburg, had suggested five potential reviewers when he submitted the paper, “Scrutinizing the Carbon Cycle and CO2 Residence Time in the Atmosphere.” The editor in charge had invited all five to review; the two who accepted raised no concerns about the paper’s scientific content and the editor accepted the paper.

But, during its investigation, the journal found that none of the reviewers Harde suggested could “be considered an expert or authority” on the research or related fields.

According to the editorial, the journal asked three additional experts to review Köhler’s critical commentary; all three “supported the fundamental concerns raised,” noting that the 2017 paper “contains many mistakes, misconceptions and omissions and ignores a vast body of scholarly literature on the subject.” The experts also recommended the paper be withdrawn.

Ultimately, the journal decided not to retract the paper, and instead:

… let it remain to stimulate further discussion about such a highly charged and contentious topic. 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.

Transparency efforts

The editorial explains that the journal has taken “proactive steps to ensure a more robust approach to peer review in the future,” which includes no longer allowing authors to suggest peer reviewers and providing the name of the editor responsible for accepting a paper to help “increase a sense of accountability.”

The publisher told us that the editor who handled this paper is “no longer associated with the journal,” but declined to elaborate further.

When we asked Köhler if he agreed with the journal’s decision not to retract, he said it is somewhat “disappointing how little we achieved by our comment.”

Grosjean said he hopes that the editorial will encourage more transparency in these matters:

it is now clear and open to the public why the peer-review process has failed in this case.

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30 thoughts on “Flawed climate science paper “exposed potential weaknesses” in the peer review process”

  1. As a fellow journalist, I’m a huge fan of RetractionWatch.com but this post exposes one of your blind spots. Historically, much ‘mainstream science’ has later turned out to be wrong.

    Debate is central to science. If we ignore alternative perspectives, if we shut down debate by deliberately banning these perspectives from peer-reviewed journals, science ceases to function properly. It becomes just another vehicle for promulgating fashionable ideas.

    I happen to have published a blog post this morning demonstrating this exact point with respect to the UN’s Intergovernmental Panel on Climate Change:


    A few years ago, the editor of The Lancet declared that much of published science, perhaps half, was wrong. There’s no reason to believe this doesn’t apply equally to climate science. But heavens, let’s not have any debate about such matters in the scientific literature!

    1. Donna,

      Great points.

      Retraction Watch seems to assign “Climate Science” a special protected status.

      All the corrupt and corrupting elements in science and academia that result in the numerous reports of fraud, cheating, faking and worse are present in “Climate Science.”

      Fake “peer review,” fake data, political pressure to only consider acceptable results, and much, much worse appear in Climate Science.

      The whistleblower exposure of emails among and between journalists, researchers, recipients of government grants, lab officers, and others involved in Climate Science revealed for the world to see. What we saw was exactly what Retraction Watch gleefully reports every day–at least in non-Climate areas of research.

      But Retraction Watch, in lock-step tandem with the Politically Correct, CO2-is-killing-the-world journalist/academia/government behemoth, pretends that “Climate Science” is special. They continue to protect the “Green Blob” from the scrutiny that is directed at other, non-PC issues.

      Keep up the good work.


      1. Fake “peer review,” fake data, political pressure to only consider acceptable results, and much, much worse appear in Climate Science.

        Complains the person who is okay with fake peer review by the buddies of the author of this flawed paper as long as the results are politically correct.

        Do you really want to make the case that the people who were picked by the author were the objective good reviewers while the independent reviewers picked by the journal (and the authors of the comment) all had it wrong?

        Even you do not believe that. If you want people to treat your political movement seriously make worthwhile claims.

    2. Debate is important in science, however the purpose of peer-review should be to weed out those “alternative perspectives” that are obviously incorrect, and sadly Prof. Harde’s paper falls into that category. The problem here was one of “pal-review”, the editor did not select a reviewer outside those suggested by the author and did not check whether the nominated reviewers were qualified. If the editor had selected an expert on the carbon cycle, the paper would never have been published in the first place, and the debate would have been better for it as we would not have wasted time responding to it.

      The problem is demonstrated by Prof. Harde’s (and Prof. Salby’s) continued failure to distinguish between residence time (the average time a molecule of CO2 remains in the atmosphere before being taken up by another reservoir) and the adjustment time (the timescale on which the atmosphere responds to changes in the sources and sinks). The former is about 4 years, and depends on the rate at which CO2 is removed from the atmosphere, the adjustment time is about 50-200 years and depends on the DIFFERENCE between uptake of CO2 from the atmopshere and the emission of CO2 into it. These are not the same thing. This is explained by the model in my paper explaining how we know the rise in atmospheric CO2 is not a natural phenomenon, a pre-print is available here:


      In Harde’s response to the comment paper, he says of the model in my paper:

      “These claims are contradicted by the conservation law (1) governing atmospheric CO2. Because CO2 is conserved in the atmosphere, it can change only through an imbalance of the surface fluxes eT and a.”

      However, my model is derived from exactly that conservation law (first equation on page 16, symbols are different, but that is the same conservation law).

      Harde/Salby’s later comment shows they haven’t read the paper very carefully:

      “The treatment of absorption (10) is specious. Notice: Absorption of CO2 is nonzero even if CO2 concentration vanishes. CO2 is therefore removed from the atmosphere even if there is no CO2 in the atmosphere. What world such treatment describes is unclear. What is clear is that it is not the physical world.”

      On the bottom of page 16 of my paper:

      “Neither of these assumptions are satisfactory, however with a slight extension they can be used as the basis of a simple first order local linear approximation, for the period covered by the Mauna Loa record. Instead of assuming simple proportionality, the return flux is approximated by a linear function of atmospheric CO2”

      So “What world such treatment describes is unclear” is the Earth from 1959 to the present day. Of course the model would be no longer valid if atmospheric CO2 concentration “vanishes”, but that is a very extreme situation. The sort of linear approximation I used in the paper is completely standard in physics, and was used to get a simple model that would at least give a reasonable qualitative understanding of the difference between adjustment time and residence time.

      So neither of their criticisms of my paper are valid, and the response ignores the many lines of reasoning that show that the rise is anthropogenic. The simplest being that if both mankind and nature were net sources of CO2 into the atmosphere, then atmospheric CO2 (due to the conservation laws) would be rising faster than anthropogenic emissions, but it isn’t, it is rising at about half that rate. This shows the natural carbon cycle is a net carbon sink, and so is actively OPPOSING the rise, not causing it!

      I can’t remember how many times I have had to explain/argue that very fact, far too many, which shows that the contribution to the debate of this paper is simply to waste time debunking arguments that have already been debunked.

      1. I had a look at your paper, and compared your eq. (1) to Prof. Harde’s. A very basic difference concerns your assumption about Fe, the environmental uptake. In Harde’s paper, your Fe is simply proportional to the instantaneous concentration of CO2. In your paper, it is much more complicated. As a physicist, I saw no reason why Harde’s expression is wrong while yours is correct. Harde’s expression is nothing but the mass action law, which is well known in chemical physics, while yours appears to be hand waving in an ad hoc manner. I find especially convincing Fig. 1 in Prof. Harde’s comment. As far as physics is concerned, I stand with Prof. Harde.

        You said it is wasting time to debunk arguments that have been debunked. The problem is, are you sure your debunking is not dubious itself ? Why don’t you have a closer look at the argument put forth in Harde’s comment from Eq. (1) to Eq. (13)? How would you respond to them? You can fool yourself and many others, but not Mother Nature.

        1. When the amount of CO2 in the atmosphere increases because of fossil fuel emissions, within a few multiples of the residence time the amount in the the surface ocean and biosphere will proportionally increase as some is adsorbed.

          What Essenhigh, Harde and you miss is that this increases the amount of CO2 emissions into the atmosphere FROM the surface ocean and biosphere since there is more there.

          Harde and Essenhigh treat the natural emissions as constant across time (see pp above eq (12) in Harde). It is not constant but increases with the increasing amount of carbon in the surface ocean and the biosphere.

          This leads to a new equilibrium with the amount of CO2 in the three upper reservoirs, each of them higher, until some of the CO2 moves from the surface ocean down past the thermocline into the lower ocean. The time that that takes is the adjustment time (roughly) although there are other processes going on so one cannot use a single characteristic time.

        2. You think a linear relationship is “much more complicated” than a proportional relationship? All I have done is add a constant, and if you don’t include the offset, the model can’t explain the observational data shown in Fig. 6 of my paper, which is why the constant was added. The actual relationship between CO2 levels and the flux is non-linear, so all I have done is use a Taylor series approximation, I’m surprised that as a physicist you didn’t spot that, as that sort of linearisation is commonly used in physics.

          “You can fool yourself and many others, but not Mother Nature.” indeed, you only need to plot the output of Harde’s model to see that they don’t agree with the observations (which perhaps explains why Prof. Harde didn’t plot them in the paper). Here is a plot of the model against the actual Vostok data


          Note that the Vostok data includes interglacials where local temperatures were warmer, and yet the CO2 concentration is much lower and follows the linear relationship in the Vostok data. His model for the post-industrial era doesn’t perform much better either


          unlike the model from my paper, which gives a much better reconstruction.

          1. Oh, sorry, you were asking about equation 1! Equation 1 says that the rate of increase in atmospheric CO2 is equal to the difference between the rate of uptake of CO2 from the atmosphere by the natural carbon cycle and the sum of natural emissions and anthropogenic emissions. That is hardly rocket science! That is the minimal equation you need to differentiate between residence time (which depends on the uptake rate) and adjustment time (which depends on the difference between total uptake and total emissions), and you need to include anthropogenic emissions if you want to determine whether the rise is natural or anthropogenic. No simpler equation gives even a qualitative representation of the carbon cycle.

            Ironically, Harde’s main error is a failure to understand the distinction between residence time and adjustment time (a failure he continues to make), and that is exactly what is wrong with his model. As Einstein is reputed to have said, “everything should be made as simple as possible, but no simpler!”.

    3. While some “mainstream science” has turned out to be wrong, historically a huge majority of the claims that mainstream science is wrong, especially that motivated by politics, beliefs or the desire to sell books has turned out to be laughable. Ask any physics department to take a look at their slush pile of notebook scribble proving whatever.

      While those pushing the thread that “mainstream science” is wrong always point to a misreading of Popper’s falsifiability criterion they omit Kuhn’s conceptualization of normal science and the road to it. Historically once a firm consensus is reached (see IPCC reports) the paradigm is stable, changes occur around the edges, but not the central core.

      Indeed, because a consensus requires consistency and consilience covering a huge range of observations and experiments and often fields, it is just about impossible to contradict. The Earth IS round and the IPCC consensus firm, although you can read different on blogs and Twitter.

      1. …The Earth IS round and the IPCC consensus firm…

        …and the Tropospheric Hot-Spot is definitely there – no matter how often it has been measured not to be…

  2. Reviewers suggested by the authors can help increasing the pool of reviewers, but are best not used or only partially after really close scrutiny. That the editor invited them all is a big error and I am happy this editor now works on other tasks.

    While most scientists will list serious scientists because they do not want to have a flawed publication on their record, a authors-suggesting-reviewers system invites to be abused.

    This case also reveals that one-shot peer review has its limits. It made sense in the times that papers were printed on dead tress, but we can do better now.

    I propose a system where editors continually review scientific papers (not just at the beginning). In such a system this flawed paper could simply have been reevaluated as a standard procedure and the reader would have been warned of the flaws. This should be done for all papers, not just for flawed ones like on PubPeer and then provides a great way to access the scientific literature.

    A first implementation of this idea for my field of study can be found here: https://homogenisation.wordpress.com/

  3. IMHO journals should not ask authors for suggested reviewers as it is a recipe for low-quality “pal-review”. The action editors should be sufficiently aware of the field to select suitable reviewers for themselves, or pass it on to another action editor with more experience in that field. If that can’t be done, then it is likely that the paper is outside the scope of the journal and should go elsewhere.

    If one good thing has come of this mess, it is that the journal will no longer ask the author to suggest reviewers. That is progress.

  4. BTW it is interesting to compare the versions of Figure 3 is Prof. Harde’s original paper and the version in his response to Köhler et al. (Fig. 6). The error bars in the original clearly are not a good representation of the spread of the ice core data shown in the version in the response. The relationship between temperature and CO2 looks approximately linear in those ice core data, and clearly do not resemble Prof. Harde’s exponential model. Note also that there are two ice core data points with similar (local) temperatures to the present, but much lower CO2 levels, but following the linear trend.

  5. I have been am associate editor for a Elsevier journal for quite some years, and I never picked all my rewievers from the suggested list. It is unusual, and naive, in my view.

    And hey, if a paper rising unusual arguments on a hotly debated topic gets two “minor” from two suggested referees, you must ask yourself some questions…

  6. Donna Laframboise,
    although much mainstream science has turned out to be wrong, this is no argument for the article in question being of any quality. If you think it has scientific qualities then you explain why. It is not a scientific quality per se to disagree with people you also disagree with.

  7. …How did a deeply flawed paper…

    Can someone tell me what the ‘Deep Flaws’ are?

    As far as I can see the paper is controversial only because it points out flaws in the current Climate hypothesis – which we already know is ‘deeply flawed’ in that none of its predictions have come to pass.

    The complaints seem to be long on smears, and assertions that the reviewers are not the ‘right sort of person’ – but very short on what I would consider to be fundamental flaws. One might almost think that the paper was correct, and that this was deeply embarrassing to the climate establishment. Which makes me wonder whose side Retraction Watch is on….

    1. See my comments above. That the rise in atmospheric CO2 is anthropogenic in origin (rather than being a natural phenomenon) is well established by multiple lines of evidence (for a nice summary, see https://skepticalscience.com/anthrocarbon-brief.html). Prof. Harde fails to appreciate the difference between residence time and adjustment time, and hence the fundamental flaws are in his work, not that of mainstream science.

      1. Of course, you could also read the paper by Köhler et al., the purpose of which was to explain the ‘Deep Flaws’ in Prof. Harde’s paper.

  8. I need some help from those who so strongly support professor Harde’s paper. Help to reconcile a wealth of observations with the conclusions drawn by Harde.

    You see, I cannot find either a credible source or sink when I assume only 15% of the increase in atmospheric CO2 is due to anthropogenic emissions. I *can* do so, however, if I assume essentially all of the rise is anthropogenic.

    But maybe those staunch defenders can point out the flaws in my reasoning below.

    First, and to the best of my knowledge uncontested by Harde, human emissions of CO2 over the last few centuries, since about 1850, have amounted to more than 500 Gt C equivalent (note: carbon, not CO2, and it is likely more). If that amount is only responsible for 15% of the observed increase, there would have to be a source that has had a net emission of over 3500 Gt C in the last 170 years or so. That is, it has lost over 3500 Gt C.

    Second, atmospheric concentrations of CO2 have risen by roughly 250 Gt C equivalent since 1850. This means that there would have to be a sink, different from the source mentioned above, that has taken up more than 3750 Gt C.

    What credible source(s) and sink(s) would exist that fit with other observations? I posit there are none.

    The oceans cannot be the source for two reasons:
    a) measurements show an increase in dissolved inorganic carbon, not a decrease as would be expected if the oceans were a source. Note that the increase is too small for it to be the sink either
    b) measurements show a drop in oxygen concentrations in the atmosphere, and unless someone knows of a magical mechanism that results in massive outgassing of CO2 (amounting to over 5% of the total carbon estimated to be in the ocean) but not of oxygen, this does not fit the oceans as a source either

    Vegetation and soil are unlikely to be the source either, since there simply isn’t enough carbon in there to explain the huge net loss of C without us noticing an enormous decrease in vegetation and soil. This has not been observed. Moreover, it would have to be through a nonaerobic process, or otherwise oxygen levels in the atmosphere would have had to drop much faster than they have.
    Vegetation and soil as the sink are only slightly less non-credible, because we’d have noticed an enormous increase of carbon content in those reservoirs, too, and we haven’t. Yes, there has been some apparent greening, but we would need a doubling of both vegetation and soil.

    None of these problems exist when anthropogenic emissions are the prime cause of CO2 increase in the atmosphere. It explains the trend of oxygen in the atmosphere – even the slope. It explains the limited increase in DIC in the oceans. It explains some possible increase in vegetation. All comparatively small numbers consistent with about 50% of human emissions being taken up by the biosphere and oceans, and the rest contributing 100% to the observed increase in atmospheric CO2.

    Without a credible carbon accounting, papers such as those by Harde et al are simple non-credible.

  9. Blogs like this one are searching for sensations. Sometimes it is not so important to present objective and independent inquests but to write a good story. I don’t say this is the case for this story, but it doesn’t sound very impartial, when I read as the first sentence after the appeal for donations:

    “How did a deeply flawed paper, which contradicts mainstream science on climate change, pass peer review?”

    Is this blogger team so qualified in climate sciences to judge about a paper, which indeed contradicts mainstream science? Or is it more politics and climate religion, which never have been reliable guideposts for serious science?

    I presented an alternative concept for the carbon cycle, which different to the IPCC mainstream also includes time and temperature dependent variations in the natural emission-absorption cycle of CO2. We have many indications that the various mechanisms, along with their dependence on temperature and other environmental properties have not remained constant during the pre-industrial era. This inconsistency invalidates the fundamental assumption, that natural emission and absorption during the pre-industrial period did remain constant. Even less this is valid over the industrial era, a period which is characterized by the IPCC as the fastest rise in temperature over the Holocene or even the last interglacial. Science always has to question if the assumptions on which a theory is based, are reliable, and this cannot be decided by voting or by religion, only by facts and arguments which are in agreement with all physical laws.

    Before this blog was published I was contacted by Victoria Stern from Retraction Watch, but I had no knowledge about the actual commentary of Global and Planetary Change (GPC) and therefore could not respond on the editor board’s commentary. At that time I sent her all necessary information about the publication process of the paper, in particular my correspondence with the editor and publisher of GPC concerning the Comment/Reply process (see Modis Operandi: https://hhgpc0.wixsite.com/climate-unscience). This Comment/Reply process was and is the real controversy with the journal, but this is not found on this blog, instead it is a one-to-one copy of the editor board’s commentary. And it is also very unilaterally described in this commentary.

    It sounds noble that GPC installed a committee consisting of three board members to find out what went wrong in this publication process and to suggest some modifications in the reviewer process. These editorial members announced but didn’t really let the community know with full transparency what has happened, particularly not what happened with a Reply to a Comment on my paper. Therefore, I have to assist them a bit.

    The reader of this blog could learn that an author of GPC can suggest reviewers, which makes it easier for an editor to contact potential reviewers for a specific subject. The editor must not but can consult one or two of these reviewers. In my case I suggested 5 reviewers and apparently one or two of them accepted the invitation of the editor to review my manuscript. After some minor revision concerning the style and clarity the manuscript was accepted. Non of the reviewers or the editor raised any concern about the scientific content.

    After the publication, however, the editor was apparently indoctrinated by a Comment on my paper (Köhler et al., 2018) and also by some of his editorial board members, all reciting the standard claims of the climate establishment, which sound:

    (1) Before 1750 the natural carbon cycle was in equilibrium and it also didn’t change over the last 270 years. Therefore, this cycle need not be considered in a balance of the in- and out-fluxes into or out of the atmosphere.
    This blog is not the right forum for a longer scientific discussion, the journal with Comment and Reply would have been the right place. Nevertheless, here only a few remarks: When natural flux changes in forehand are excluded and only anthropogenic emissions are considered in a fitting procedure, any agreement with observations can only be traced back to human activities. This is a classical circular reasoning.
    In addition, sole consideration of anthropogenic fluxes is identical with the introduction of a new time scale for the uptake of man-made emissions. Since these emissions and also their changes are more than one order of magnitude too small to explain directly the observed concentration changes over recent years, carbon-cycle models need an additional buffer factor, the ‘adjustment’ time, which ensures a sufficiently long cumulation time of the molecules in the atmosphere and thus, a concentration level, which is in agreement with observations.
    It is against all physical principles that almost 100 ppm/yr of natural emissions are exchanged with extraneous reservoirs within 3-4 yr, and for about 2% of additional human emissions an accumulation over thousands of years in the atmosphere is assumed. The reservoirs don’t show noticeable saturation in the uptake with increasing CO2 levels but their emissions and also the uptake are changing with temperature. And in agreement with the equivalence principle and conservation law is the contribution of anthropogenic emissions in the atmosphere only determined by the man-made emission rate (actually 4.3%) to the total emission rate.

    (2) The natural environment has acted as a net carbon sink throughout the Industrial Era, taking in significantly more carbon than it has emitted. Therefore, the observed rise in atmospheric CO2 cannot be a natural phenomenon (quote of a GPC editor).
    These experts forget that the environment is always a net sink, as long as any anthropogenic emissions are present and at the same time native emissions are assumed to be the same since 270 years. Nature always tries to adjust to a new equilibrium after some perturbation, this with an absorption rate, which in first order responds proportional to the actual concentration in the atmosphere. It can easily be shown through well-established physical principles that, if human emission were removed, natural emission and absorption, through their temperature dependence, could change to nullify the deficit, achieving the same increase of CO2. Otherwise nature could never compensate for seasonal variations, volcanic eruptions or El Niño events, which are of the same order of magnitude or larger than the human contributions. It would be a serious violation of the equivalence principle, when all native emissions can be compensated within a few years but 45% of all anthropogenic emissions are cumulating in the atmosphere over thousands of years.

    In their actual commentary about this publication the editorial board writes that during its investigation the journal found that “the acceptance of this paper has exposed potential weaknesses in the implementation of the peer review system, and quality control mechanisms have failed in this particular case. They list as the main reason for the failure that non of the five reviewers I proposed, can “be considered as an expert or authority in carbon cycle, carbon or climate sensitivity or similar fields of research.” Such statement can only be understood as disparagement of the editor handling my paper or as proclamation of presumptuous editorial board members, who discredit all scientists not conform with the official IPCC party line. Four of the suggested reviewers are internationally renowned professors of climate science or meteorology working in this field for more than 40 years, the fifth is a distinguished physics professor, who is more than 10 years involved in studies of the greenhouse gases and their influence on the environment. It is also an impertinence to insinuate the two reviewers who recommended publication of the manuscript “that this may have been because the reviewers lacked the impartiality and scientific expertise to provide an adequate science-based review.” Obviously only these board members with their selective interpretation of the carbon cycle (see above) possess the unrestrained impartiality and scientific expertise to decide about the quality of these reviewers.

    1. “When natural flux changes in forehand are excluded and only anthropogenic emissions are considered in a fitting procedure, any agreement with observations can only be traced back to human activities. This is a classical circular reasoning.”

      This is a straw-man; nobody is assuming that natural fluxes have remained constant. Indeed we know from the mass balance analysis that the pre-industrial carbon cycle was approximately in balance in the pre-industrial era, but is now a net carbon sink, taking more CO2 out of the atmosphere that it puts in. Nature is actively opposing the rise.

      Let Ea(n) represent annual carbon emissions from anthropogenic sources in year n (fossil fuel use and land use change), En(n) represent the carbon emissions from all natural sources in that year (the oceans, soil respiration, volcanos etc.) and Un(n) represent the uptake of carbon by all natural carbon sinks (oceans, photosynthesis, etc.), Ua(n) would be the uptake of carbon due to anthropogenic activities, but this is essentially zero, so we can safely exclude it from the analysis. Then assuming that the carbon cycle obeys the principle of conservation of mass (any carbon emitted into the atmosphere that is not taken up by natural sinks remains in the atmosphere), the annual change in atmospheric CO2 in year n is given by:

      C'(n) = Ea(n) + En(n) – Un(n)

      This can be rearranged to give an estimate of the difference between annual emissions from all natural sources and annual natural uptake by all natural sinks.

      En(n) – Un(n) = C'(n) – Ea(n)

      We have accurate, reliable data for the growth of atmospheric CO2 and for anthropogenic emissions (for details, see Cawley, 2011). Both of these are displayed below, along with an estimate of the net natural carbon flux En(n) – Un(n). The fact that the net natural flux is negative clearly shows that natural uptake has exceeded natural emissions every year for the last fifty years at least (see diagram below), and hence has been opposing, rather than causing the observed rise in atmospheric CO2.


      So we know with high certainty that the natural carbon cycle is a net carbon sink. So we are then left with the problem of explaining how the natural carbon cycle can be causing atmospheric CO2 to rise whilst taking more CO2 out of it each year than it puts in.

      I would go through and deal with all of Prof. Harde’s arguments, but until he can show this mass balance analysis is incorrect, his theory is falsified by the observations.

      1. Note in the above analysis, natural emissions and natural uptake are not assumed to be constant, and indeed if you look at the outcome of the mass balance analysis shown in the figure, you can see that not only is there a good deal of year-to-year variability, but also the net sink is growing in magnitude. Obviously that couldn’t happen if the natural fluxes were constant. As it happens, both natural emissions and natural uptake are thought to have grown over the industrial era, but with uptake growing faster. See the IPCC carbon cycle figure mentioned in my paper.

  10. As already mentioned in the preceding comments, the real controversy with GPC emerged from excluding my Reply to a Comment of Köhler et al. To make the journal’s philosophy transparent for the community, I try to briefly list the main facts (in more detail this can be found under Modis Operandi):

    – When GPC received the Comment, about one month later not the editor but the publisher of GPC informed me about this Comment. In his email he asked, if I would like to respond with a Reply to the Comment.

    – He also explained that they were already starting the review process for the Comment, and due to their framework the reviewers would be the same for the Comment and Reply.

    – The authors of the Comment proposed 7 reviewers, all known as representatives of the IPCC industry, and the review process already started with two or three of them, before I could submit my Reply and suggest own reviewers.

    – Therefore, before submitting the Reply, I contacted the publisher, how under these circumstances a neutral review process can be ascertained.

    – His answer: “The intention of the Comment/Reply exchange is to further develop the arguments supporting the previous paper, and also to respond to critical points of the authors of the Comment. Even when the reviewers disagree with the content of the Reply, they would be aware of this aspect, and their comments should be considered as suggestions to strengthen the Reply or to add clarity. A Reply would normally only be rejected, if it fails to add significantly to the scientific debate and/or becomes a personal attack on the authors of the Comment.”

    – On 2 October, 2017, the editor informed me that reviewers had advised against publishing the Reply and therefore he must reject it. Attached were two, not three reviewer reports.

    – Already two days prior the Comment had been published by GPC in electronic form.

    – I neither failed to add significantly to the scientific debate (see Reply under Modis Operandi) nor made any personal attacks against the authors of the Comment.

    – I never had a chance to respond on any claims or wrong interpretations of the reviewers.

    – Since I had serious concerns about the treatment of the review process and particularly concerns over due process, I sent the editor a letter with a copy to the publisher explaining in detail my reservations (see Modis Operandi).

    – I never received a reply to this letter.

    – Although with the rejection of the Reply to the Comment the review process was terminated, a sent the editor and publisher a longer clarification concerning the review reports, which were full of misinterpretations, unacceptable claims and imputations.

    – I never got an answer.

    Therefore, in December I informed several institutions and colleagues about this review process and the censorship of GPC with a link to Modis Operandi. Apparently only this link provoked GPC to publish the commentary of the editor board with its selective perception.

    It sounds more than preposterous when these board members write: The Reply by Harde to the Comment by Köhler et al. (2018) was rejected because it did not add any significant information to the argument put forward in the original paper. In reviewing the Reply, the reviewers felt that Harde’s argument is “…too simplistic, based on invalid assumptions, ignores a whole body of observational evidence, and cites selectively literature that has long-time been disproved”.

    It is the easiest way to insult a publication ex post and to suppress any further discussion in a highly polarized debate between two scientific positions, in which the pre-selected reviewers exclusively
    advocate the fundamentally restricted view of the IPCC’s interpretation of the carbon cycle. The reader may convince himself/herself, if the Reply to Köhler et al’s Comment wouldn’t contain any significant information.

    By the way, it is already a well documented procedure to defame authors and publications that contradict the IPCC’s claims. In the “Climategate” release of emails the reader can find a discussion which specifically outlines the tactics (including names of editors and journals that would be amenable to it) to write a Comment on an unpleasant article, in which the results of the paper are impeached. This mostly happens without any serious refutations, only the standard claims of the IPCC have to be echoed. The author/s of the Comment propose their own reviewers, as done in this case, the rest is disposed by the editorial process of the journal as described before. So, any serious disputation of the paper’s content can be suppressed, and in the future it is simply argued that with the published Comment it has been shown that the paper is erroneous, is in conflict with observations or violates physical laws.

    This is our so highly recognized and independent science and publication process, which indeed urgently needs reformation. It stays for itself, when the editors and publisher of GPC allege in the addendum of their commentary that my article attracted considerable attention due to its flawed content, a defaming assertion without any evidence. The arbiter of this highly polarized subject cannot be prejudiced editors. Nor shall it be individual reviewers – certainly not reviewers who have been discriminated to one side of this polarized debate. The arbiter must be the scientific community – inclusive of both sides of the debate. As a scientific publisher, Elsevier’s responsibility should have been to provide the scientific community with both opposing positions, to enable the community to judge for itself.

    So, future and hopefully more rationally thinking generations have to find out, if all is wrong which contradicts the mainstream in climate science.

  11. While I appreciate the further explanations by professor Harde on some procedural aspects, I would prefer he’d answer my question to identify source(s) and sink(s) for the proposed >3500 Gt C excess emissions (for the source(s)) and >3500 Gt C excess uptake (for the sink(s)). As I noted, without those, the conclusions drawn in your paper are simply not credible and suggest a major error somewhere.

    This question is very pertinent to professor Harde’s comments here:
    “Nature always tries to adjust to a new equilibrium after some perturbation, this with an absorption rate, which in first order responds proportional to the actual concentration in the atmosphere.”
    So, what is that perturbation if not the extra CO2 entering our atmosphere through human activity?

    And please also note that in terms of the law of mass action (as referenced by an earlier commenter), Nature would then react to this increase in absorption rate by also increasing the emission rate, until both are again equal (but different from, as in higher than, the original rates).

    1. Reply to Marco

      First let’s make clear the order of magnitude of human emissions, although this is not the right forum to discuss this here:

      If you are integrating all anthropogenic emissions since 1750, giving 660 PgC (fossil fuel emissions and land use change together, CDIAC and CICERO-data), then you have also to sum up the natural emissions of 200 PgC/yr (see AR5-Chapt.6-Fig.6.1) over 267 yr which gives 53,400 PgC.
      From this humans have contributed 660/(53,400+660)*100 = 1.2%. Actually is the anthropogenic emission rate 4.3% (average over last 10 yr) of the total emission rate.
      Of course, all these emissions do not cumulate in the atmosphere but under steady state conditions the same amount is again absorbed by extraneous reservoirs.

      The fraction of man-made to native CO2 in the atmosphere is the same as the respective emission rates. This is a consequence of the fact that all emitted CO2 to the atmosphere – human or native – is absorbed with the same probability (equivalence principle). Therefore, 4.3% from 393 ppm (again average last 10 yr) gives 16.9 ppm, and from an increase over the industrial era of 113 ppm the 16.9 ppm are 15%.

      So, 85% or 96 ppm of this increase apparently must have natural origin. Generally is the total increase a combination of the time dependent anthropogenic emissions, the time dependent and thus temperature dependent native emissions and a reduced uptake by the extraneous reservoirs due to the increasing temperature (a limiting uptake due to saturation effects of the reservoirs is not observed). The time and temperature dependent in- and out-fluxes determine the balance equation, the conservation law of mass. Due to fundamental physical and chemical relations and due to an observed exponential decay of carbon-14 in the atmosphere the uptake of CO2 in this balance is considered to be proportional to the instantaneous concentration. With the CDIAC-data for anthropogenic emissions and the temperature evolution (e.g., GISS-data) this equation is integrated numerically over time (see: my paper and Reply under Modis Operandi).

      This, of course, is in strong contradiction to the simplified interpretation that from the 660 PgC about 45% (297 PgC) would accumulate in the atmosphere and the rest is absorbed. This airborne fraction (AF) of 45%, as found in AR5, would be equivalent to 139 ppm increase since 1750, explaining an even larger incline than observed. However, an approach, where the absorption is assumed to be proportional to the emissions (55%) – not proportional to the concentration -, suffers from the fact that with any additional emissions above those from 1750 the CO2 concentration further rises and never comes to equilibrium, independent if these are natural or anthropogenic emissions. In this way mother Earth could never compensate for seasonal variations, volcanic activities or El Niños; all contributions are summed up ad infinitum. When you trust such model, you can do, I have strongest concerns.

      Sources of CO2, or better a changing natural influx can have different origin. So, the CO2 partial pressure in sea water changes exponentially with temperature (Takahashi et al., 2009), and 1 °C increase already contributes to an atmospheric concentration incline comparable or larger than all actual human activities. Also new estimates of dark respiration suggest that under global warming conditions whole-plant respiration could be around 30% higher than existing estimates (Huntingford et al., 2017). Further contributions may result from defrosting permafrost and volcanic or tectonic activities (up to now they cannot be quantified very accurately).

      But with increasing water temperature not only outgassing of CO2 rises, at the same time the uptake decreases, and also the vegetation is affected, when with reduced precipitation a reduced plant-growth is observed.

      Altogether this means: when over the last 270 years the native emission rate has changed by 10-15% and the residence time increased from 3.5 to 4 years, the missing 85% of the increase since 1750 can well be explained.

      Nobody must be afraid that 660 PgC of anthropogenic emissions over the industrial era would already surpass the storage capacity of the oceans and continents, it is less than 1% of the estimated capacity.

  12. Reply to Gavin Cawley

    This will be my last post on this blog, which is not the place to exchange scientific arguments, particularly not a blog which starts with an opening statement, how a “deeply flawed paper” could pass peer review. I would have preferred an exchange with Comment and Reply without censorship, but after my experience and the commentary of the editorial board members of GPC, this journal is surely also not the right address for such an exchange.

    Only in short :
    I don’t know what Dr. Cawley understands as a straw-man in this context, I can only refer to AR5, Chapter 6, where negligible atmospheric concentration changes before 1750 are reported, the natural fluxes over the industrial era are considered to be the same as 1750, and any concentration changes in the atmosphere or reservoirs are almost exclusively traced back to anthropogenic emissions (see, e.g., AR5-Chapt.6-Fig.6.1). Even in coupled climate-carbon cycle models the input comes only in the form of anthropogenic CO2 emissions, which can increase the CO2 and as response to this the natural carbon cycle exchanges CO2 between the atmosphere and land and ocean components.

    I agree with Dr. Cawley 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.

    The uptake gets even maximum, when C’ = 0. However, steady state can only be achieved with a balance equation, where the absorption rate is proportional to the concentration C, as in my case, never with an absorption scaling with the anthropogenic emission rate as assumed in a model with constant airborne fraction (AF) or also with a time-varying AF as in the Bern-Model.
    The equilibrium level C_eq is determined by the total influx (sum of anthropogenic and natural emissions) times the residence time (my paper, eq.(14)), and of course, can and will this level increase when native emissions are increasing, e.g., due to temperature effects or volcanic activities. Solution of the conservation law with a time-dependent increasing native flux is plotted under Modis Operandi (Reply, Fig.3) and shows full agreement with the Mauna Loa observations.

  13. Prof. Harde says “the natural fluxes over the industrial era are considered to be the same as 1750”

    This simply is not true, Prof. Harde cites AR5-Chapt.6-Fig.6.1, but in that diagram the black arrows represent the pre-industrial fluxes between reservoirs in the carbon cycle. The red arrows show the changes in those fluxes over the industrial era, showing that the natural fluxes have changed. The reason they have changed is *in response* to the increase in atmospheric CO2 away from its equilibrium due to anthropogenic emissions.

    “Even in coupled climate-carbon cycle models the input comes only in the form of anthropogenic CO2 emissions, which can increase the CO2 and as response to this the natural carbon cycle exchanges CO2 between the atmosphere and land and ocean components.”

    Well where else can inputs of fresh carbon enter the carbon cycle? The natural carbon cycle exchanges CO2 all the time, not just in response to anthropogenic emissions.

    “I agree with Dr. Cawley 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.”

    This is the key point, if the natural carbon cycle is a net carbon sink, it is taking more CO2 out of the atmosphere than it puts in, so it seems hard to argue that this activity is causing atmospheric CO2 to rise! It is a bit like saying that I am causing my bank balance to rise by withdrawing more than I put in.

    “However, steady state can only be achieved with a balance equation, where the absorption rate is proportional to the concentration C, as in my case, never with an absorption scaling with the anthropogenic emission rate as assumed in a model with constant airborne fraction (AF) or also with a time-varying AF as in the Bern-Model.”

    An approximately constant airborne fraction is the result of driving an approximately first-order dynamical system with an approximately exponential signal (anthropogenic emissions). First order dynamical systems can reach equilibrium without that ssumption being made, as demonstrated in my paper (where the relationship is linear, rather than proportional – a simple proportional model doesn’t fit the observations, as demonstrated in my paper).

    “The equilibrium level C_eq is determined by the total influx (sum of anthropogenic and natural emissions) times the residence time (my paper, eq.(14)),”

    No, again Prof. Harde is failing to make the distinction between adjustment time and residence time. It could be that he is right and the world’s carbon cycle researchers for the last 50 years have completely misunderstood the basic operation of the carbon cycle, but I doubt it.

    “Solution of the conservation law with a time-dependent increasing native flux is plotted under Modis Operandi (Reply, Fig.3) and shows full agreement with the Mauna Loa observations.”

    and completely fails to explain the changes in atmospheric CO2 on the ice-core record, unlike e.g. the Bern model. Prof. Harde fails to mention that “The temperature anomaly ∆T(t) is prescribed from the GISS record of global temperature (GISS, 2017), following a 5 yr moving average.”, if the carbon cycle actually did respond on the timescale of the residence time (i.e. about 4 years) then the predicted CO2 levels would rise and fall in step with decadal changes in temperature, but the observations don’t do that, so Prof. Harde introduces this five year smoothing of temperature to doubly damp down these variations. The need for this step shows the model is flawed. The model in my paper, however, needs no such “adjustments” to the data.

  14. I am a physicist but not a climate physicist. In general, either of these 2 POV may be correct; but I don’t think either makes the case for it adequately (but I think Cawley is closer to making a case and to finding the truth). In general rates of emission and absorption can be limited by supply or by concentration (including size of emitter/absorber). So each rate (in and out) will be a constant term plus a proportional term. The fact that the yearly CO2 Mauna Kea results almost balance (to within ~10%) says that the constant emission term is about 10 times greater than the proportional term. So in general, IMO the amount of CO2 added by man is about 1/10th the amount burned. (10% is not to be taken as scientific–just a back of the envelope from eyeballing.)

    1. I don’t quite follow how you reach your conclusion that “the amount of CO2 added by man is about 1/10th the amount burned”. Maybe because “The fact that the yearly CO2 Mauna Kea [sic] results almost balance (to within ~10%)” makes no sense to me either.

      Can you please clarify what you mean?

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