1. Dear Rod,
      Thank you for pointing out Andrews’ comment on Hardy and Salby (2021). Therefore, here is my review of Andrews’ comment:

      Andrews begins with his sweeping incorrect generalization,

      “Unsurprisingly, they all subsequently reached a common erroneous conclusion that carbon is removed from the atmosphere on a time scale of years to a couple of decades.”

      Duh? Where does Andrews show the removal time (that I call e-time to be more precise) is greater than 20 years?
      He offers no such evidence, and he ignores evidence that shows the 14CO2 e-time is 10 years.

      Andrews continues,

      “The model of Harde and Salby explicitly assumes that the processes involved in removing CO2 from the atmosphere operate in parallel and depend only on the atmospheric carbon concentration. And depend only on the atmospheric carbon concentration.”

      Again, Andrews is about as precise as astrology, but he seems to claim the carbon flows from the atmosphere to land and oceans do not operate in parallel. Where is his evidence? He does not even attempt to defend his statement.

      Andrews is not arguing against Harde and Salby. Andrews is arguing against the IPCC. The IPCC itself assumes these processes operate in parallel and that outflow is proportional to the level of CO2 in the atmosphere. (See Berry, 2021, for exact references.)

      Andrews continues,

      “The true evolution of carbon 14 concentration is nothing like a single exponential decay.”

      But Harde and Salby as well as Berry (2021) show carbon-14 flows from the atmosphere with an e-time of 10.0 years. Nowhere does Andrews show that he understands this and nowhere does he attempt to show it is wrong.

      Andrews continues,

      “In summary, the assumptions of their model are shaky at best, and the validation fails.”

      Yet, Andrews makes no scientific argument to back up his claim. Nowhere does Andrews show Harde and Salby’s assumptions contradict data.

      Andrews continues,

      “I presume this choice [to begin their plot in 1959] was made in an attempt to de-emphasize the approximately 30% increase in atmospheric carbon 14 now, compared to before the testing.”

      Obviously, Harde and Salby chose the years for their plot to best present their argument. Andrews, unscientifically, “presumes” Harde and Salby are trying hide something.

      However, Andrews misses the whole scientific point when he thinks the increase in carbon-14 contradicts Harde and Salby. Andrews does not follow the evidence that shows the source of the increase in carbon-14.
      Andrews concludes,

      “We are now sixty years removed from the nuclear testing, and much of the carbon 14 produced then is still with us. We can conclude that much of the CO2 emissions from a gas guzzling ’59 Chevy are still with us too, and that our current emissions will outlive our grandchildren.

      “The human contribution to atmospheric carbon increases is incontrovertible. We should be analyzing the consequences of that increase rather than debating its reality.”

      Andrews quit his job as a physics professor at the University of Montana to go into politics. That is exactly what Andrews is doing here.

      His closing statement merely shouts his unscientific opinion that human carbon stays in the atmosphere for hundreds of years, the human contribution “is incontrovertible,” and that we should focus on the consequences of his imagination.

      Nowhere does Andrews present a rational argument to support his emotional diatribe. His argument is really with himself, because he does not understand what Harde and Salby (and Berry) have written.

  1. “These results negate claims that the CO2 increase since 1750 has been dominated by human CO2 emissions.”
    I don’t see how this can be if industrial CO2 accounts for 11.6% of total atmospheric CO2 at 48 ppm. The increase in total CO2 since 1850 has only been about (415 – 280 = 135ppm). A 48ppm increase means that industrial emissions account for 48/135 = 35.55% of the increase since 1850.

    I have serious doubts that industrial emissions represent that much of the increase, considering the enormous amounts of CO2 emitted by the oceans, 1000s of volcanoes (many undersea), hundreds of 1000s of undersea hydrothermal vents and immense amounts of decaying land plant and animal life.

    1. Dear JD,

      The confusion is in what we use for the denominator, 135 ppm or 415 ppm.

      All the percentages in the post are based on 415 ppm. It is easy to translate these to percentages of the increase or 135 ppm.

  2. The idea that human induced ‘land use change’ provides ‘additional’ CO2 is false. Any CO2 emissions caused by ‘land use change’ would have occurred anyway as vegetation in the carbon cycle decomposed or was burned naturally. The only additions to the carbon cycle caused by humans are from oxidizing carbon that’s been stored for millions of years such as fossil fuels or limestone.
    They are off by an order of magnitude, if we do the math.
    The 36 gigatons of CO2 that human activities emit per year burning fossil fuels, industrial processes and product use (combustion, flaring, cement, iron and steel, chemicals and urea) calculates to 4.6ppm of the atmosphere’s 400ppm.
    One way of approaching an estimate of our CO2 contribution to the earth’s increased greening is to calculate the atmospheric ppm from the 36 gigatons we emit per year. According to Conversion Tables taken from the Glossary: Carbon Dioxide and Climate, 1990. ORNL/CDIAC-39, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, the mass of the atmosphere is 5.137 × 10^18 kg, and the mass of CO2 in the atmosphere is:
    M x f x (44/28.9), where M is the total atmospheric mass, 5.137 x 10^18 kg, f is the molar or volume CO2 fraction, 0.0004, and 44/28.9 adjusts for the molecular weight of CO2 compared with average of other air molecules.
    5.137 x 10^18 x 0.0004 x 44 / 28.9 = 3.128 x 10^15 kg
    The annual human caused emissions are 3.6 x 10^13 kg
    Thus the current annual human contribution is 400 x 3.6 x 10^13 / 3.128 x 10^15 = 4.6ppm or about 1%. Even more insignificant than what most believe.

    1. Dear Gus,
      Your argument is not bad but it is more complicated than my paper. My Introduction says,

      “The level or concentration of atmospheric CO2 is in units of ppmv (parts per million by volume in dry air). However, it is customary to omit the “v” and write ppm. To convert CO2 in ppmv into the mass of carbon in PgC (petagrams), multiply the ppmv by 2.12. GtC (Gigatons of carbon) is numerically equivalent to PgC.”

      You can use that 2.12 to simplify and correct your argument.

      Also, it is easier and more meaningful to argue in percentages. For example, IPCC’s data say the CO2 inflow from human emissions is about 5% of the inflow from natural emissions.

      Therefore, to the first approximation, the equilibrium percentage of human CO2 in the atmosphere is about 5% or about 20 ppm. To this, we must add the effect of the new carbon that human emissions add to the carbon cycle.

      That is what my calculations do using IPCC’s data. The result from this calculation is that human emissions, as of 2020, have added about 33 ppm to the atmosphere. This means nature has added about 100 ppm.

      Also, my paper calculates the effect of land use change and finds it has no effect on the level of CO2 in the atmosphere because its small inflows are quickly moved to the deep ocean.

  3. I am a retired engineer and just a plain old country boy, but I certainly know that all life on earth depends on O2 and O2 must come from CO2. I think all of the scientific calculations are interesting, but people understand the O2 CO2 connection, and no one thought to go there. In addition, I had training in health physics at Oak Ridge Associated University.

    1. The o2 in co2 came from the atmosphere, all the plants do is undo the chemistry of the ozone layer where the vast majority of ithe o2 is formed.

  4. The biggest elephant in the room is the fact that natural processes have removed 94% of atmospheric CO2 during the past 540 million years. The present -more than welcome rise- is a delayed reaction to the medieval warm period known as the 800-year lag. The ice-core of the Dome-C location in the Vostok part of Antarctica shows just that.
    There is no warming since 1998 and there is hardly any warming possible with more CO2 due to the saturation effect (Prof. William van Wijngaarden and Prof. William Happer). Anti-CO2 policy does not work as shown by the Mauna Loa measurements and is foolish to begin with unless you want a dead planet.

  5. The problem with this theory is that we have robust measurements which disprove it. They show, unequivocally, that (since 1958, through 2021):

    1. Mankind added about 1440 Gt (180 ppmv) of CO2 to the atmosphere. We know that, because we know, quite closely, how much coal, oil & natural gas has been burned, and how much concrete has been manufactured, and how much CO2 those processes produce. Here are sources for that data:
    https://ourworldindata.org/co2-emissions (search the downloaded data file for “world”)

    2. Since 1958, we also have good measurement data showing the atmospheric CO2 concentration each year, and hence we know the year-to-year changes in concentration. (Before 1958 we have less precise measurement data, from air samples trapped in ice cores.) Here’s the annualized CO2 trend:
    https://sealevel.info/co2.html (hover your mouse over the graph for precise figures)

    3. We also know the mass of the Earth’s atmosphere, and the relative densities of CO2 and air, from which we can trivially calculate that 1 ppmv of CO2 masses 8.0 Gt.

    What those data show is that, from 1958 to 2021

    ● mankind added about 180 ppmv of CO2 (1440 Gt) to the atmosphere,
    ● the amount of CO2 in the atmosphere increased by only about 101 ppmv (808 Gt).
    ● thus other things (which we call “nature”) removed a net sum of 180-101 = 79 ppmv of CO2 (632 Gt) from the atmosphere.

    Thus all (actually, more than all!) of the increase in atmospheric CO2 concentration (since 1958, at least) is due to anthropogenic emissions. Nature is removing, rather than adding, CO2 from the atmosphere.

    Of course, “nature” consists of many processes, some of which add CO2, and some of which remove it. But the sum of all those processes is a net removal of about 632 Gt of CO2 (79 ppmv) from the atmosphere from 1858 to 2021.

    Skrable, Chabot & French (2022) is a mess. But how can you know that if you can’t read it? The publisher apparently has a policy of providing free access to articles and papers for eight weeks, but then paywalling them (except that often the first page of the article is still available online). So the paper is now paywalled.

    It took a bit of work to find a preprint of the paper, but I managed it. I also found all five of the “comments on” the paper which the journal has published. For the latter I contacted the authors of several of those responses, directly, and asked them to send me preprints.

    I put all of them (paper & responses) in a folder on my website, here:


    If I missed anything of consequence, please let me know.

    Understandably, the published responses to this regrettable paper are all critical of it. If anyone is inclined to take the paper seriously, I encourage you to read “both sides” before settling on your conclusions.

    In fact, that’s a good policy, in general, for any controversial topic: listen to both sides, before settling on conclusions. To that end I have a collection of climate-related resources, here:


    It has:
    ● accurate introductory climatology information
    ● in-depth science from BOTH skeptics & alarmists
    ● links to balanced debates between experts on BOTH sides
    ● information about climate impacts
    ● links to the best blogs on BOTH sides

  6. Dear Dave,
    As I replied to your similar comment on WUWT, your conclusion:

    “Thus all (actually, more than all!) of the increase in atmospheric CO2 concentration (since 1958, at least) is due to anthropogenic emissions. Nature is removing, rather than adding, CO2 from the atmosphere.”

    … does not logically follow from your preceding data. Your conclusion is constrained by your incorrect assumption that human CO2 has caused all the CO2 increase. There should be no such constraint.

    Therefore, your critique of Skrable et al is invalid.

    Please read Berry (2021) and comment on it if you wish. It describes the proper way to calculate the true impact of human CO2 on atmospheric CO2.

    Perhaps the most fundamental point in Berry (2021) is that it best to consider natural flows and human flows independently, which you have not done. The human carbon cycle is independent of the natural carbon cycle, so nature is not removing human carbon. Rather, human carbon flows through its carbon cycle using the same physics as natural carbon uses in its carbon cycle.

    Berry (2021) uses IPCC’s data for its natural carbon cycle, meaning e-times, to calculate the true effect of human CO2. It finds the level of human CO2 does not exceed 33 ppm as of 2020.

  7. I found Dr. Berry’s paper difficult to follow. I found the paper by Dr. Skrable et al to be tedious but understandable. Skrable et al made some assumptions about atmospheric 14C that may bear further scrutiny, but I found the paper to be persuasive and it clearly supports Berry’s conclusions derived by a different method.

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