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Monday, June 12, 2023

Is there enough fossil carbon in the atmosphere to create global warming? Lessons from mistakes, misinterpretations, and propaganda


The great holobiont called the "biosphere" continuously exchanges carbon with other parts of the Earth system: the hydrosphere and the geosphere. It is a fascinating section of the science of the atmosphere that, just like all other sections, is subjected to misinterpretations, mistakes, and sheer propaganda,   

Earth's climate is one of the most fascinating fields of study nowadays and if you are interest you can learn something new every time you stumble into a new report. Even the so called "debate," biased as it is, may be useful to learn something not just about climate science, but about human psychology as well. Let see an example starting from a comment that recently appeared on twitter,

"Goggle Bob" defines himself as "Engineer that likes technical financial charting (energy, precious metals, commodities, cryptos); as well, a student of the fiat money system.

First lesson learned: people will think that something they don't understand is "very good science" if it agrees with their personal biases. 

Now, let's go to the paper by Skrable et al that Google Bob cites. It is not an easy paper to digest, but it is an attempt to quantify the fraction of atmospheric CO2 that's the result of the burning of fossil fuels. It is all wrong, as we'll see in a moment, but it is a good occasion to learn something about atmospheric physics and hydrocarbon dating.

It is all about the "Suess Curve;" proposed by Hans Suess in 1967. The curve is about the fraction of the 14C isotope contained in the atmosphere as a function of time. 14C is an unstable isotope, but it is continuously created in the atmosphere by a reaction of carbon nuclei with cosmic rays, and its concentration can be taken as approximately constant, apart from human perturbations. One of these perturbations is the burning of fossil fuels. Since 14C gradually decays with time, those carbon materials which are not continuously exchanged with the atmosphere tend to lose it. So, fossil hydrocarbons contain essentially zero 14C, and burning them is expected to reduce the fraction of 14C. 

Quantifying this amount is not easy, but the final result is that fossil fuels generated about 75% of the extra 145 ppm (from ca. 280 to 425 ppm) of CO2 relative to pre-industrial times. The rest was generated mainly from deforestation and cement production. Another conclusion is that just about 45% of the carbon generated by fossil fuels remains in the atmosphere right now; the rest is stored somewhere in various reservoirs in the ocean and in the biosphere. This is a story I already knew in its main lines, but the discussion about the paper by Skrable et al. led me to go deeper into the matter. 

Second lesson learned: bad science can lead you to learn some good science. 

Now, let's go into the details. At a first read, the paper by Skrable et al. looks legitimate. For someone like me, not an expert in atmospheric radiochemistry, the way the paper is written seems to make sense: there are estimates, equations, and conclusions, all written in the standard jargon of scientific papers. But the  problem, a big one, is their statements that "the quantity of anthropogenic fossil CO2 in the atmosphere in 2018 represents about 23%  of the total amount of anthropogenic fossil-derived CO2 that had been released to the atmosphere since 1750." They also say that ""the atmospheric concentration, <CF(t)>, of anthropogenic fossil derived CO2 in 2018 is 46.84 ppm." And that "the percentage of the total CO2 due to the use of fossil fuels from 1750 to 2018 increased from 0% in 1750 to 12% in 2018, much too low to be the cause of global warming."  (boldface mine)

You only need to know the basic elements of climate science to understand that the final statement is a flag for something badly wrong. Today, we have about 425 ppm of CO2 in the atmosphere, which is about 145 ppm more than the pre-industrial concentration of 280 ppm. Let's assume that the authors are right in their estimate (47 ppm of CO2 resulting from fossil fuels). It means that there are about 100 ppm of extra CO2 in the atmosphere that are NOT the result of fossil fuel burning. And where does this huge amount of carbon come from? 

You would have to think that the total ca. 300 ppm of CO2 emitted by the burning of fossil fuels was almost wholly absorbed by the reservoirs. And not only that: this CO2 must have triggered a huge release of carbon that had been stored in some surface reservoirs for a short time. Otherwise, it would be depleted in 14C and indistinguishable from fossil carbon. Difficult to believe, but even if it were true, the current CO2 excess would still be an indirect result of hydrocarbon burning. No matter how you see it, the statement that "the total CO2 due to the use of fossil fuels ... is much too low to be the cause of global warming." simply makes no sense. It is not a specific isotope of carbon that generates warming; it is the total amount. 

From this, the authors do much worse when they state that "unsupported conclusions of the dominance of the anthropogenic fossil component of CO2 and concerns of its effect on climate change and global warming have severe potential societal implications that press the need for very costly remedial actions that may be misdirected, presently unnecessary, and ineffective in curbing global warming." In Italy we have a way of defining this kind of statements as "peeing outside the pot," and I think you understand what it means. 

Third lesson learned: bad scientific papers can often be identified by their politically-oriented statements.

So, what was actually wrong with Skrab's paper? Examining in detail a scientific paper dense with equations, numbers, and tables is a lot of work (and, in Italian, we have a principle describing how unrewarding it is, but I won't report it here because it uses scatologic terms). In this case, though, there is a crystal clear explanation provided by Andrews and Tans that highlights the trivial mistakes that Skrab et al. made. 

Without going into the details, the main mistake in Skrab's paper was to neglect the effect of nuclear explosions in creating an extra amount 14C, thus giving the impression that the fraction of fossil carbon in the atmosphere is lower than what it actually is. It is more complicated than that, but it is enough to pinpoint the most glaring mistake in the story. 

Fourth lesson learned: a good rebuttal to a bad paper can teach you a lot!

Now, how can it be that a group of scientists with a good reputation in their field choose to deal with a subject they are not familiar with and end up making fools of themselves? It may happen that a scientific revolution comes from newcomers in the field; for instance, when Galileo showed that planets couldn't possibly move because they were pushed by angels, he made a fundamental contribution to a field that wasn't his; theology. But that's rare. Making a fool of oneself is much more common. It could be easily avoided with a minimum of humility: before publishing your paper, why don't you submit it first to the experts in the field? That doesn't mean that the experts are always right, but they can point at the mistakes that you may well make if you are an amateur. Nevertheless, it happens all the time.

Fifth lesson learned: scientists can be blinded by their preconceived ideas just like everyone else. 

To conclude, as you may have imagined, the statement that "the total CO2 due to the use of fossil fuels ... is much too low to be the cause of global warming." is making the rounds on Social Media, being reported by people who made no effort to understand why it was uttered, nor why it is wrong. And so it goes

Sixth (and final) lesson learned: Politics always trumps science in the debate.  


  1. Dear Ugo,

    I am not a scientist but I have read this a while back and it still bothers me...

    What is the theoretical potential of solar energy?
    Sunlight has by far the highest theoretical potential of the earth’s renewable energy sources. The solar constant (the solar flux intercepted by the earth) is 1.37 kW/m2 . The cross-sectional area of the earth intercepting this flux at any instant is πr 2 (where r = 6,378 km is the earth’s radius), but the surface area of the earth over which this flux is averaged over time is 4πr 2 . Hence, the time-and-space-averaged solar flux striking the outer atmosphere of the earth is (1.37 kW/m2 ) / 4 = 342.5 W/m2 . In addition, enroute to the earth’s surface, about 30% of this flux is scattered, and about 19% is absorbed, by the atmosphere and clouds (Wallace 1977, pp. 320-321). Hence, the average flux striking the earth’s surface is 342.5 W/m2 · (1-0.49) = 174.7 W/m2 .

    The theoretical potential of solar power is the integral of this average flux over the earth’s surface area (4πr 2 ):
    P = (174.7 W/m2 ) · (4πr 2 )
    = (174.7 W/m2 ) · 4π · (6,378 km) 2 · (106 m2 /km2 ) · (10-12 TW/W) = 89,300 TW.

    This theoretical potential represents more energy striking the earth’s surface in one and a half hours (480 EJ) than worldwide energy consumption in the year 2001 from all sources combined (430 EJ)

    In other words, 480 /1.5 * 24 / 430 = 14.88

    24 hours of sunlight roughly equals to 15 years of energy consumption by men…

    Which also means that: that single day in 2001, the sun sent the same amount of energy that we humans used since then…

    Since january first 2001, 365 * 15 = 5475 days have passed.
    ONE of those days’ energy was used by men, the rest was just used to heat the earth...

    That was written many years ago so the correct number could be TWO days now.
    But it still is not a significant number that any sane person can take into account...

    "Global warming" and "men" cannot be used in the same sentence obscure science or not.
    To me it does make as much sense as a men thinking he's a woman and can get pregnant.

    Sorry to respectfully disagree with you...

    1. Sorry, Sysati, but I don't see your point. Your numbers look right, but what is the problem?

  2. What I am trying to say is that to me, men on earth isn't any different that an ant on an elephant's skin. A lot of people benefit from that "global warming" crap but that's just what it is a great big bowl of crap...

    If the energy used by mankind in a whole year is equivalent to a couple of hours of sunshine then maybe it is a little presumptuous of us the think that the global warming thing is caused by man and even more presumptuous to think that we can do anything to change that ?

    This whole thing has nothing to do with good or bad science, it is pure politics :(

    To quote someone I like very much (and disagree even more :)
    "scientists can be blinded by their preconceived ideas just like everyone else"

    1. Come on, SysATI, you should know better than this. It is not humans who warm Earth; it is the sun! Humans only give the sun a little leverage, but it is enough to cause it to create a lot of damage.

  3. I don't know how long I'll be here but I'm pretty sure that the Global Warming won't affect me even remotely. I said the exact same thing about the COVID hoax a few years ago, never got vaccinated and I'm still alive. Too much of the current world we are living in is linked to various interest groups and none of them have any idea of what "honor" or 'truth" means anymore :(

    Which leaves me no choice but to believe only what I see with my own eyes (like Francesco d'Assisi) and understand with my own brain. And anthropogenic global warming is not one of them by a very long shot... But I'm not a scientist and don't need funding so nobody cares what I think... and vice versa ;)

    Guess I'm just another hopeless conspiracy terrorist ;)

    But I still like reading you :))))))))))))

    1. Glad to hear that you are so sure. But you seem to me also a little confused. I suggest that you study more the matter, and don't forget that our brain can trick us badly!

    2. BTW, I don't think Francesco of Assisi ever said that. That sentence comes from St. Thomas. Or maybe he did, but in any case it is easy for our brain to remember the wrong things.

    3. I did study it a few years ago and all I remember is that, when I was a kid, everyone was certain then that the next ice age was right around the corner. Then things have turned upside down and now we will all burn in hell (or drown depending how close we are to the sea). I wasn't convinced then and I'm not convinced now :(

      Men think way too highly of themselves. "God created us to his image" and now we have to try to "save the planet"... Sure... with a few thousands of years of history on two legs we were able to destroy... and soon will save the planet. C'on the planet was here billions of years before us and will still be here long after we're gone :(

      Sorry if I hurt your feelings and your beliefs, but we are not even a microbe on the butt of the ant on the elephant...

      ooops.... You're totally right it was St Thomas...
      But religion was never my thing either sorry :(

    4. But what does "SysATI" mean? Just for curiosity....

    5. ha ha ha....
      It is a very old acronym for Sysop (system operator) Attila (my name).
      My friends used to call me like that when I was running a BBS (Bulletin Board System) in Paris in prehistoric times. Back then, there was no internet and we used a network called FidoNet to communicate. You could talk to people on the other side of the earth just like today but the delays were just a little longer. To get the answer to a message you posted on the board from your correspondent in the US or Japan would take about.... a week :))))

      Memories memories.....
      My "IP" address of the time was 2:320/7
      Continent 2 : Europe
      City 320 : Paris
      Node Nb : 7

  4. Hello, Ugo,
    could you help me to understand it? You said that they made bad science because they missed the effect of nuclear energy, among other things. But there's still another effect I'm not sure it is accounted for. Carbon from fossil fuels contains zero 14C, but carbon from deforestation should be similar than atmospheric carbon, shouldn't it? Then, they affirm that since carbon released from fossil fuels is so low (wrong affirmation), climate change is not so anthropogenic. But deforestation *is* anthropogenic, and they weren't mesuring it. And acid rain also releases CO2 to the atmosphere, and it's an anthopogenic effect too, in a sense.
    So, if they wanted to dismiss anthropogenic carbon, they should have measured other carbon release sources, not just fossil fuels.
    Or is it so obvious that it doesn't require measuring? Is the effect of burning fossil fuels so large that other carbon sources can be so easily dismissed?

  5. I am not an expert in these matters, but I think I understand the main lines of the story. It is true that the carbon emitted by deforestation has the same 14/12 carbon ratio as that of the natural composition of the atmosphere. But the fraction of carbon coming from plants in the atmosphere can be measured from the 12C/13C ratio -- it is slightly different from that of fossil fuels for arcane reasons related to "isotopic fractionation" The IPCC says deforestation contributes for about 10% of the total human emission. Skrabl et al. explicitly say in one of their comments to the rebuttals that they didn't examine this subject.

    1. Thank you. That would be 10% of GHE, not accounting for the loss of forests temperature regulation. (I admit it is smaller than I thought).
      Anyway, anthropogenic or not, it doesn't look like we will be able to address the causes and we are left to deal with the consequences.

  6. Another source of CO2 isvolcanic. I presume that it would lack C14.
    I haveseen this same paper interpreted by people with expertise in this field (which I lack) aspointing to extensive CO2 release from Atlantic Trench volcanoes, which seems to be at least somewhat supported in this analysis: https://theethicalskeptic.com/2020/02/16/the-climate-change-alternative-we-ignore-to-our-peril/

  7. It is not the main subject of the article, but I must thank you for a doubt I've been having for years. When dating using the 14C, what's the physical phenomena that puts the clock to 0? Never I've found someone who could answer, and here it is, as simple as that. I guess I never asked to the right people, or taped the correct key words. I used to speculate that it was something related with photosynthesis selecting one specific proportion of 14C, quite strange an argument, I admit. Thanks. Although now I wonder, how much this "more or less constant" affects the accuracy of 14C dating? Does this 14C concentration in the atmosphere changes with solar radiation intensity?
    Well, we unfold one doubt to find a few more.

    1. I am not sure I understand "put the clock to 0." What do you mean, exactly?

    2. Sorry, the comment was poorly written. I was feeling sleepy. It's about a doubt I've always had, now solved by your post. When one hears about 14C dating it uses to be in history, anthropology and fields like this. The person explaining has an idea about decay and explains it. But for it to be useful there needs to be an initial 14C share that is more or less constant at some point (the clock to 0), and from there we measure time, given a known decay rate. This is where things got fuzzy to me as no one ever told me when exactly this 14C constant concentration occurs and why. I mean, at school or in the rare occasions where I thought about it. Visiting a museum, for instance.
      I'm actually a physicist and I've worked as an engineer for some 10 years in an astrophysics/planetology labs, so I certainly had people around me who knew, but the question never raised at the right moment.
      No big deal. Thank you.

    3. Wow, if you are an astrophysicist, I think you know much more than me on this matter. However, if it may help, I can tell you what I understood of this story. And the basic elements are rather simple. Cosmic rays create 14C out of normal N2. This 14C decays back exponentially to 14N, but slowly enough that it has the time to be incorporated into the living matter of the biosphere (half life of less than 6000 years). If the cosmic ray flux were constant, you would have an equilibrium concentration in the atmosphere (and also the biosphere) when the decaying 14C equals the new 14C, implying that the decay flow is proportional to the size of the 14C stock. That's, I think the "zero" you are mentioning: a certain constant value of 14C in the atmosphere. Then, of course, the flow of cosmic rays is only approximately constant. Dating with 14C is calibrated using measurements mainly on tree rings. All that, of course, before humans started tampering with the atmosphere in various ways.

    4. Ui, again I see I was not quite clear. I'm actually not an astrophysicist. Just a regular physicist, recycled as an engineered. Enough to understand, from your post, the dynamics of the 14C concentration in the atmosphere without further clarifying. That is, the "zero" I was looking for is the equilibrium between the cosmic rays "making" 14C and the 14C decay destroying it, as you say. It was clear enough from the beginning. My initial comment was just to thank you for a piece of knowledge I feel I should have but I didn't. Now it's fine.
      The calibration using tree rings is something I didn't know neither, I guess it answers my doubts about the inaccuracy due to the cosmic rays not being constant, at least for as old as we can find trees. I guess there are other methods for older stuff. It's ok, I'm happy enough with this level of detail. I don't need more.
      Unluckily, the people who wrote the article you commented didn't have one of those redundant measurements to cross-check the validity of their stuff. And arguably, they might have been happy to ignore it in case they had. :)

    5. Marti, I fear that's one of the "so widely known thing that doesn't need to be said", that happens to be not so widely known outside the circle of specialists. After that, the specialists throw a bunch of statements and you have but to trust them, because you no longer can follow their reasoning.