Oxygen – provider of life.

Why does the air contain oxygen and where did it all originally come from? A new book ‘OXYGEN’ by Donald Canfield helps explain. No animal life from insects to fish to humans could  have evolved or survive before oxygen first appeared in the atmosphere or dissolved in the oceans. Oxygen also protects animal life from damaging UV radiation from the sun by forming ozone in the stratosphere. The build up of oxygen in the atmosphere eventually resulted in the cambrian explosion of plant and animal life. This remarkable breakthrough was preceded by the evolution of cyanobacteria which finally cracked photosynthesis – the complex process powered by solar photons using H2O and CO2 to produce carbon compounds for cells while expelling O2 as a by product.  The carbon fixation enzyme Rubisco is responsible for all  food and fossil fuels on earth and the evolution of all multi-cellular organisms.

The complex biochemical process behind photosynthesis  was evolved  by cyanbacteria from two previous “anoxygenic” processes in iron or sulfur environments. The cyanbacteria revolution  was important because now the only environment needed was water, air and sunlight so they rapidly spread all  around the world, and especially across all the oceans. Suddenly oxygen was being generated by photosynthesis whose imprint is clearly seen in the geological record beginning with the Great Oxidation about 2.3 billion years ago. However the long term build up of oxygen in the atmosphere is a very subtle effect, that is still not fully understood. Essentially 99.5% of emitted oxygen is consequently reabsorbed, but its relationship to CO2 levels is particularly interesting. Some interesting facts about photosynthesis that need to be explained are the following.

  1. Current levels of photosynthesis on earth would deplete all CO2 in the atmosphere in just 9 years.
  2. Photosynthesis in the Oceans depletes all available phosphorous needed by aquatic plants and algae in just 86 years.

Most of the CO2 absorbed by plants is soon liberated to the atmosphere when they die or are eaten by animals, while only a tiny amount of carbon is buried in sediments. Even by including this recycling effect we still find  CO2 depletion of the atmosphere takes a mere 13,000 years while phosphorous depletion takes only 29,000 years. So what are we doing wrong?

The incredible story is that these trapped sediments are not lost from the environment for ever because plate tectonics recycles material over very long timescales today. Subduction, mountain building and sea level change continuously re-exposes the raw materials for life through weathering. Plate tectonics is essential to re-cycle the raw materials for life on earth !

CO2 re-enters the atmosphere from the mantle through out-gassing of Volcanoes and also through deep ocean vents near mid ocean ridges.  CO2 is  removed from the atmosphere by weathering due to the abundance of water on the earth. Such weathering does not happen for example on Venus. The ‘natural’ carbon cycle essentially controls the temperature on earth because weathering by liquid water is a temperature dependent phenomenon.

The total content of Oxygen in the atmosphere is equal to the total buried carbon in the sediments. This results in the current 21% oxygen content. The total CO2 content in the atmosphere is instead fine tuned to the temperature of the earth. This is roughly how it seems to work.

Diagram of carbon balance of CO2 in atmosphere and plate tectonics on earth

Diagram of carbon balance of CO2 in atmosphere and plate tectonics on earth

CO2 enters the atmosphere from volcanoes and under-sea vents driven by plate tectonics, the result of convection from the hot interior energy of the earth. CO2 exits the atmosphere through weathering of rocks driven by the  climate of the earth and the oceans. If the atmospheric temperature gets too hot so the rate of weathering increases and CO2 is removed from the atmosphere. If temperatures get too cold weathering slows down causing  a build up of CO2 in the atmosphere. This eventually increases temperatures to their optimum level which coincides with liquid oceans.  CO2 acts as a negative feedback to keep the climate stable and the oceans cool and liquid. This may be the primary explanation for the faint sun paradox, although the water cycle of evaporation and cloud formation must also play a stabilizing role.

Once photosynthesis and multi-cellular life evolved, so this balance of CO2 levels must have shifted coincident with the rise in O2. Firstly  it now became possible  to bury underground large quantities of biotic carbon including fossil fuels. Secondly there was an enhanced formation of sedimentary rocks caused by the compression of dead  sea creatures. Thirdly the large amount of oxygen in the atmosphere now led to the formation of ozone in the upper atmosphere which  is also a strong greenhouse gas. The explosion in plant and animal life coincident with a huge rise in oxygen content occurred during  the Cambrian period about 540 million years ago. Since then the optimum temperature climate control for  CO2  has shifted because the carbon cycle now includes life.

Current interglacial climate conditions on Earth all have an  average  surface temperatures of ~288K with a stable CO2 concentration of around 300 ppm which is nearly 1000 times less that the oxygen content of the atmosphere.  Can we understand how these very low value of CO2 could arise from natural-bio temperature control ?

About a year ago I wrote a simple model of  radiative transfer  from the surface to space covering the dominant CO2 15 micron band. I found  that for a surface temperature of 288K the maximum radiative loss of heat in the atmosphere occurs at exactly 300ppm.  I cannot believe this can be a coincidence. CO2 levels are fine tuned such that the atmosphere cools at its maximum rate in accordance with the second law of thermodynamics.

Fig3: Change in atmospheric OLR with CO2 concentration for fixed surface temperaure 288K.

Fig3: Change in atmospheric OLR with CO2 concentration for fixed surface temperaure 288K.

What is this result really saying ? The thermostat that controls the temperature of the earth is a mix of geochemistry and life. The earth lies within the habitable zone of our sun and  has maintained liquid oceans for 4.5 billion years while the sun brightened. Initially the natural carbon balance between the weathering sinks due to both water and CO2 was perfectly balanced with volcanic emissions from the earth’s crust to maintain the oceans. This was thanks to the internal energy. The evolution  of photosynthesis caused an explosion in life across the surface of the earth releasing huge amounts of free oxygen and sucking out CO2 as bio-carbon was drawn out of the atmosphere and buried in the ground. Life today needs carbon, water, oxygen and some essential minerals like phosphorous.  If we assume a constant rate of CO2 venting from volcanoes and under-sea vents that we can deduce the following. Too little CO2 in the atmosphere and cooler temperatures lead to both photosynthesis and the weathering of rocks to slow down thereby causing CO2 levels to increase and the climate to warm. Too much CO2 and consequent higher temperatures lead  to a reduction in  the long term weathering of rocks with  a consequent fall in CO2 levels causing the planet to cool. Underpinning everything is plate tectonics because carbon and the raw materials for life must eventually be recycled to maintain the balance. Such  balance will continue to stabilize the climate  so long as the earth’s internal energy continues to drives plate tectonics. Life is therefore probably safe for another billion years.

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10 Responses to Oxygen – provider of life.

  1. DrO says:

    Dear Mr Best:

    Plate tectonics, along with other very important forces, is routinely ignored by climate fanatics, the IPCC, et al. It is good to see some effort to account for at least a little of that. However, it would be very much more helpful to include a little more about tectonics and spectral issues in your considerations. Two of immediate interest are:

    1) The net (heat) imbalance effects due to tectonics.

    2) The (continued) omission of water vapour from the energy balance, especially as omitted from spectral analyses.

    1) Tectonic and heat imbalance: A net heat/energy imbalance for the planet is a necessary, but not sufficient, condition for the Green-House (GH) effect to be possible. That is, the amount of energy reaching the planet must be different compared to the amount of energy leaving the planet. Just like with your bank account

    in – out +sinks/sources = accumulation

    One of the “sources” of energy arriving at the planet’s surface is actually from “within” as heat travels from the millions of tons of molten rock and iron in the core of the planet (somewhere near 7,000 degree temperature).

    The climate fanatics seem to soil their trousers over as little as 2 W/m^2 “forcing” (i.e. imbalance). That is a “tiny” number in relation to massive “in” and massive “out”. Notably, by their reckoning, it requires only a small imbalance to cause the “upheaval” insisted on by the IPCC et al.

    With plate tectonics and geo-tectonic forces comes the possibility of non-stationarity in the rate at which the core’s heat reaches the surface. For example, the plates are not uniform thickness and their thickness, etc etc, can change with time. This would then lead to “small” changes in the rate at which the core of the planet is warming the surface of the planet. Thus the “source” term in the energy balance changes with time.

    Nobody knows, or can know, the values involved in the heat flux due to tectonics (since instrumentation for such things is not technically possible, and even it if were, it would be too expensive for most tax systems). However, given the estimates involved, it is trivially simple to show that it could certainly lead to a net planetary imbalance of 2 W/m^2.

    As such, for all we (humans) know, much if not most of such effects can be the result of tectonic cycles/effects.

    It is CRUCIAL to keep emphasising that CO2 is ONLY CORRELATED with temperature, but CAUSALITY is a very different matter, and as yet NOT proven.

    Put differently, CO2 could well be “caused” by other forces, rather than it being the cause of anything. Indeed, all the long dated CO2/Temp reconstructions show CO2 “lags” temperature.

    I am all for insisting on more efforts to include the many omitted huge forces currently ignored by the IPCC et al in the science and modelling of the planet’s climate.

    2) Water Vapour and the “Planet’s Spectra”: Although in principle I am completely in agreement on the need for spectral analysis in connection with GH considerations, your continued discussions of the spectral analysis focusing purely on CO2 are in serious difficulty.

    By far, and everyone agrees on this (even the IPCC), the most powerful GHG is water vapour. It has about 15 times the infra-red cross-section of CO2, and there is typically 5 – 10 times as much water vapour (WV) in the atmosphere compared to CO2.

    What is particularly important is that WV’s absorption spectra is not only very much wider (e.g. in terms of wave length), but also OVERLAPS with that of the few very narrow absorption bands that CO2 exhibits. For example, CO2’s 14 – 16 um absorption band (what I think you call the 15 um band), virtually completely overlaps with a part of the WV absorption band(s).

    I provide a “pedestrian” discussion of satellite based spectral data on pages 33 – 48 of my “Note 3: Climate Science: Bank Accounts, Telephone Polls, and Coffee” found here (http://www.thebajors.com/climategames.htm). That is REAL data, not some theory or model.

    The data clearly shows the CO2 14 – 16 um band not only overlaps with WV band, but also that WV appears to be doing much, if not most, of the absorbing in that region. As such, what we CANNOT ignore is the spectral forcing due to the WV. Put differently, any discussion of spectra based energy imbalances stated purely in terms of CO2 are, I am sorry to say, in rather grave difficulty.

    Finally, and perhaps even more important, the satellite data shows that frequencies at which GHG’s are supposed to play a role in climate change are all very nearly saturated. That is, there is virtually NO energy leaving the planet at the wavelengths absorbed by CO2 and WV. So that there is near “saturation” of the absorption spectra.

    Thus, even if CO2 were the only GHG (and clearly it is only a “secondary” GHG compared to WV, etc), it is already absorbing almost as much energy as it is capable of absorbing. THEREFORE, even if CO2 were the only GHG, increasing CO2 in the atmosphere is NOT expected to have much impact on the energy imbalance. Thermodynamics proves that all that would happen at saturation (i.e. just about now or a little higher) is that the same finite amount of spectral energy would be absorbed, but spread out over a larger number of molecules … since temperature is the “average speed of molecules”, GHG effects cease once saturation is reached.

    To add insult to injury (to the IPCC et al position), since CO2 is not the only GHG, saturation (for example at 14 – 16 um) can be reached by increasing the amount of other GHG’s, like WV. That is, even if CO2 was far below its saturation concentration, the increase in WV alone could cause the saturation of the 14 – 16 um band, etc etc.

    It is an “inconvenient truth” that WV measurements, and most especially long dated WV histories, are very difficult to obtain. Moreover, it suites the IPCC et al’s “ideological agenda” to omit WV from the story (or in some cases pretend that somehow CO2 “causes” WV). What little data there is (and which only covers the last few decades) clearly shows that WV has been steadily increasing. Thus, it is possible to consider that something like a 2 W/m^2 forcing is due to changes in WV.

    … in any case, pure theoretical utopian models of CO2 radiative effects (especially which ignore saturation, etc) are, well, meaningless in the context of climate science and climate modelling.

    In any case, volcanoes alone completely destroy any possibility of climate modelling. It is a trivially simple exercise to prove this for yourself. Just see the 4-page Note 1: The (Necessary) Impossibility of Climate Policy, the Lie of (IPCC) Climate Models, and Kneading Dough, found here (http://www.thebajors.com/climategames.htm) ).

    Notice, if climate predictions are impossible, the climate policy is also impossible.

    • Clive Best says:

      I agree that plate tectonics releases enormous amounts of energy. For example the energy released by the 2011 Japanese earthquake was 2*10^17 joules. This is not an insignificant amount of heat. I think estimates of total geothermal heating is probably underestimated and must vary in a periodic fashion. I agree that the heating effect of the surface from the earth’s core is very uncertain and likely under-estimated.

      The earth’s greenhouse effect depends on the full spectrum and not just the CO2 component – completely agree. Water vapour also has a continuum emission component which is poorly understood. If H2O were to vary naturally then it indeed would drive climate. So if for example volcanoes emitted large amounts of H2O then this would increase the greenhouse effect perhaps leading to more evaporation etc. However, the IPCC assumes that water vapor is only a feedback to surface temperature. The Claudius-Claperion equation is used to show that only through higher temperatures cam more evaporation occur leading to more greenhouse effect. If this is wrong then the whole proposal that increasing CO2 emissions is the initiator of surface warming could fall apart. However I think it physics says it must be right at least to the first order.

      The real uncertainty of H2O for me is the effect it has on the lapse rate and on clouds. The moist lapse rate reduces the greenhouse effect. This is a negative feedback. The more evaporation must mean more low clouds. More clouds increases the earth albedo and this is a very strong negative feedback.

      Inconveniently for the IPCC the two direct satellite measurements of water vapour (NVAP-m) and clouds (ISCCP) both show trends which could partly explain the small increase in temperatures since 1970. However both results have been extensively ‘rubbished’ for instrumental errors.

      My position is that all things being equal a doubling of CO2 over a 200 year period should lead to 1C rise in surface temperatures. This is the result of several different radiative transfer calculations including H2O. Short term H2O feedbacks could possibly be positive so that temperatures rise to about 2C. Longer term feedbacks are definitely negative and the climate will always stabilize to condition suitable to life. Humans have been on the planet for a blink of an eye and industrial development is just a pico-second.

      • DrO says:

        Dear Mr Best:

        I think your comments are worthy, though as is so often the case there are crucial points that are either ignored or “forgotten”. A few of the obvious ones are:

        1) The IPCC et al models ALL ignore geo-tectonic effects. The only place where anything resembling even volcanoes seems to appear is during their “fudged/sneaky verification” back-testing of data, where they pretend that somehow their models track the planet’s temperature history “reliably”. See for example Fig 8.1 in the AR4 or Fig 9.4 in the AR5. That is complete and utter rubbish, their models are completely and utterly incapable of predicting anything in relation to volcanoes etc etc, and that is necessarily so. I provide a pedestrian discussion of this FATAL flaw in the IPCC models/prediction in the 4-page Note 1: “The (Necessary) Impossibility of Climate Policy, the Lie of (IPCC) Climate Models, and Kneading Dough” (http://www.thebajors.com/climategames.htm)). This alone completely and utterly DOOMs any climate model of the sort required for the problem at hand.

        The point being, it makes no difference what CO2, H2O etc assumptions are/are not included, just the “volcano problem” on its own is more than sufficient to CRUSH any climate model.

        Notice: It makes no difference how many math geeks or supercomputers you throw at the problem, the fundamental nature of the space-time continuum ensures that fundamentally unstable phenomenon (such as the climate, volcanoes, financial markets, etc.) defy predictability as a kind of raison d’eter.

        … without predictability, there can be NO (sensible) policy … and that’s that.

        2) I think lapse rate issues are something of a red-herring. Atmospheric dynamics are much too complex to be able precipitate-out or isolate lapse rate issues. For example, how do you factor in the jet-stream etc.

        However, a more serious problem seems to be the way many latch on to pure idealised in isolation lapse rate issues, since those are amenable to pure isolated thermo-dynamical considerations. Theorists like this, since it is a place (i.e. pure idealised) where they have some understanding.

        Unfortunately, even in isolation, even pure idealised thermo-dynamical considerations are very often massively miss-represented. This seems to occur with some frequency when some attempt to explain lapse rate in terms of “adiabatic cooling” or similar terms. In many cases, they are flatly wrong.

        However, if the planet is warming, then that must mean, tautologically, that the average speed of molecular has increased. Unfortunately, how do you separate out increases in convection at different scales due just GH warming? Not an easy task, perhaps intractable.

        3) Water vapour content has much deeper considerations also. The evaporation of water from, say, the ocean consumes latent heat, so the planet could be in a state of net heat increase, without there being much change in temperature (i.e. part of “sinks/sources” term when using a balance like “in – out + sinks/sources = d/dt contents”). Now, at this point someone will insist that the evaporated water is part of the hydrological cycle, and so that latent heat is returned when , say, it rains). ALAS, that misses crucial factors. For example, if the evaporated water rains on top of a mountain, then the latent heat of condensation cannot be the same as that of evaporation, since you have “moved” water from sea level, to some high altitude. That is, you have done (thermo-dynamical) work to get it there. Yes, some of that water may eventually flow back into the ocean, but not all. For example, some of that water will be used to create life, etc etc.

        As such, the heat balance of the planet has many very complex/subtle but large forces “buried” in the “sink/source” term, and which for the most is completely omitted from the models.

        4) I LOVE the IPCC’s consistent policy on real data. They always find ways to poke holes in data that contradicts their theories. Whether or not you have misgivings about satellite data, surely it is the height of scientific BLASPHEME, to trash the instrumentation, BUT THEN INSIST that your completely unsupported theories/models must be correct.

        In proper science: if you don’t have the data (or can’t stand the data), get out of the science.

        5) Finally, I would guess that CO2 doubling, or for that matter WV doubling, would not have much effect on the climate (in the current context). The satellite spectra show the absorption bands of all the major GHG’s to be nearly, or completely saturated. That implies that the GHG’s are already absorbing just about as much heat as they can absorb. As stated earlier, the planet radiates a finite amount of energy. Once the absorption spectra’ are saturated, then you CANNOT capture any more heat, since you are already capturing the maximum of the finite amount available.

        All that would happen with a doubling of CO2 (or whatever, past saturation) is that the same finite amount of energy is then distributed over a larger number of molecules. So the net effect on temperature is trivial.

        If this was not so, you could cheat thermodynamics and create a perpetual motion machine by continuing to add GHG molecules to the atmosphere and capturing an increasing amount of energy, for ever. I think at some point the “2nd Law SWAT Team” would step in and put an end to it.

        BTW, another crucial point that is often ignored is that radiative heat loss is proportional to Temp^3 (grey-body) or Temp^4 (black-body), etc. Thus, even a small increase in the planet’s temp, say from 288k -> 300K, would result in much much much larger outbound heat flux (e.g. in relation to “AGW forcing”). That much increased “out” would soon easily provide the balance in the “in -out = d/dt content”, bringing d/dt content to zero, or ??? … ie. no more GHG effect.

  2. bob Peckham says:

    In the penultimate sentence shouldn’t “reduces” be “increases” ?

  3. Greg Goodman says:

    “CO2 exits the atmosphere through weathering of rocks ”

    Don’t follow this bit. The CO2 in HCO3 was already in the rock wasn’t it?

    Perhaps you could write the reaction equation explicitly.

    • clivebest says:

      CO2 dissolves in surface waters to form carbonic acid ions. This reacts with calcium in rocks to form CaCO3.

      Carbonate Rocks

      1. Carbon dioxide is removed from the atmosphere by dissolving in water and forming carbonic acid

      CO2 + H2O -> H2CO3 (carbonic acid)

      2. Carbonic acid is used to weather rocks, yielding bicarbonate ions, other ions, and clays

      H2CO3 + H2O + silicate minerals -> HCO3- + cations (Ca++, Fe++, Na+, etc.) + clays

      3. Calcium carbonate is precipitated from calcium and bicarbonate ions in seawater by marine organisms like coral

      Ca++ + 2HCO3- -> CaCO3 + CO2 + H2O
      the carbon is now stored on the seafloor in layers of limestone

  4. omanuel says:

    Mr. Best,

    Comments, corrections or criticisms would be appreciated on this paper under review:

    https://dl.dropboxusercontent.com/u/10640850/Preprint_Solar_Energy.pdf

    • Clive Best says:

      This is a radical theory ! If the core of the sun contains the neutron star core of a previous generation supernova, then I would have thought that the mass of the sun would so large it could not be explained otherwise. There is clearly short distance repulsion between nucleons. The strong nuclear force is really due to exchange of gluons between quarks. The net effect inside the nucleus is a result of quark confinement and is very complicated.

      Can it be true that physics got nuclear reactions in the sun wrong ? It is supposed to be a rare nuclear fusion process involving 4 protons through the weak interaction.

      • omanuel says:

        “Can it be true that physics got nuclear reactions in the sun wrong ?”

        See pages 153-154 of Fred Hoyle’s autobiography:
        _ a.) The interior of the Sun was mostly iron (Fe) in 1945
        _ b.) The interior of the Sun became mostly hydrogen (H) in 1946,

        and the change was made without discussion or debate.

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