I used to talk with a family friend who often sent me links to Nobel Prize winners, claiming that climate change is a myth.

Last week, we had a disagreement over a link referencing a Nobel Prize recipient (I believe it was Dr. John Clauser). This link displayed a graph of CO2 levels spanning the past 140 million years, indicating a linear decreasing trend. The article posited that we are depleting our CO2 reserves, a vital gas for plants and, by extension, the biosphere.

I responded by saying:

"Jorge, that graph is misleading. CO2 levels during the Phanerozoic era are influenced by the Wilson Cycle, and they correlate with the formation and fragmentation of Pangaea. We are not depleting CO2 as the subduction process is initiating in the Atlantic. In the forthcoming million years, CO2 stored by organisms will be released."

enter image description here

Source: Wikimedia Commons.

I heard this argument at the University of Zaragoza. However, I am uncertain if both my teacher and I have a comprehensive understanding of this matter. One of my concerns is that CO2 dissolves below the Calcite Compensation Depth. I'm unsure if all sediments dissolve or just the top layers. This uncertainty leaves me pondering whether my argument could be refuted on this basis. I couldn't find any clarifications on Science Direct either.

Could someone elucidate this matter for both my friend (who will read this) and me?

Are the Phanerozoic CO2 levels indeed linked with the Wilson Cycle? If so, why?

Bonus Question:

If humans wouldn't exist, would we run out of CO2? (To me, this seems like an absurd query, especially in the context of that Nobel Prize article, because we'll likely gain control over Earth's geochemistry and climate long before then.) To rephrase: if we exclude human influence, would shell organisms eventually consume all the CO2 by the end of the Phanerozoic era, leading to a mass extinction and the emergence of a distinct form of life? Would this scenario transpire in this cycle or the next?

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    $\begingroup$ This is a complex topic, poorly constrained, with a lot of uncertainties... Here is a recent paper about it: doi.org/10.3389/feart.2019.00263 It contains estimates of CO2 fluxes during the past 200 millions years (so not all Phanerozoic). They estimate that the deep carbon cycle is not at equilibrium, with more carbon coming out of the mantle (through volcanic activity) than carbon going back to the mantle (through subduction). $\endgroup$ Commented Sep 7, 2023 at 7:51
  • $\begingroup$ @Jean-Marie Prival My perception is foraminifera were consuming C and the nobel somehow was rigth, but maybe it is not a very popular idea. I have seen them in the field, rocks are plentifull of that shells, that sometimes finish in continental crust too. $\endgroup$
    – user29526
    Commented Sep 7, 2023 at 11:01
  • $\begingroup$ Other mass extinctions were water compared with what those terrible unicells were planing for Earth is were I am after some reflexion. $\endgroup$
    – user29526
    Commented Sep 7, 2023 at 11:23
  • $\begingroup$ worth noting this can only be a red herring, changing to those historic highs as fast as we are, would be just as destructive to humans civilization. Climate change is not a change on the scale of millions of years but a drastic change in a very short amount of time. Its like arguing getting hit by a car can't hurt you because humans can reach mach speeds in a plane. its not the magnitude of change it is the timeframe of change. their argument is irrelevant. $\endgroup$
    – John
    Commented Oct 7, 2023 at 14:15

1 Answer 1


On geological timescales, yes, the Wilson cycle (opening and closing of ocean basins) is bound to have an effect on atmospheric CO2 levels, if only because it will affect rainfall patterns, which in turn will affect chemical weathering of rocks, which is one of the things that removes CO2 from the air on very long timescales.

This obviously doesn't explain the post-industrial rise in atmospheric CO2 though, which has occurred on the scale of a century or so, rather than tens to hundreds of millions of years. So it seems like a grain of truth, but the argument is a non-sequitur.

"In the forthcoming million years, CO2 stored by organisms will be released."

Citation required.

As well as weathering (which is regarded as a thermostat that has been regulating planetary temperatures - see "The Global Carbon Cycle" by David Archer, Princeton University Press), they have also failed to mention that the sun's brightness has decreased (as it is a main sequence star) by about 6% over that timescale. CO2 and temperature are part of a feedback loop, so the gradual dimming of the sun may be expected to reduce the amount of CO2 in the atmosphere, all things being otherwise equal. It also ignores the evolution of land plants, and refinement of their photosynthetic machinery.

So while it is reasonable to expect some linkage with the Wilson cycle, the claim seems to be highlighting only a cyclic component while ignoring other factors, without giving evidence of their relative importance.

"if we exclude human influence, would shell organisms eventually consume all the CO2 by the end of the Phanerozoic era"

I very much doubt it, for a start CO2 is constantly being cycled from the sea floor via subduction and released by volcanos on the crust above. This is an ongoing process.

Would this scenario transpire in this cycle or the next?

It hasn't been established that there IS a cycle, rather than the combination of the effects of multiple factors affecting CO2 levels on geological timescales. It is very easy to look at a graph and see something that looks like a cycle, what you need to demonstrate it is not spurious is some physics that explains not only the cycle but the magnitude of the effect.

  • $\begingroup$ Are you sure "CO2 is constantly being cycled from the sea floor via subduction"? CO2 disolves below the Calcite Compensation Depth is my wonder, but I don't know if all sediments stack or some shells reach subduction as you say. $\endgroup$
    – user29526
    Commented Sep 5, 2023 at 6:12
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    $\begingroup$ There is an excellent book on CO2 in seawater which I vaguely recall has the information you want, but it was a very long time ago that I read it books.google.co.uk/books/about/… $\endgroup$ Commented Sep 5, 2023 at 8:22

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