Life on Earth: Principal control knob governing Earth’s temperature

April 17th, 2014 by Roy W. Spencer, Ph. D.

tropical-rainforestThe title of this post is a purposeful play on the title of a 2010 paper by Lacis, Schmidt, Rind, and Ruedy, entitled Atmospheric CO2: Principal control knob governing Earth’s temperature.

In that paper, the authors claimed that the existence of CO2 is what provides enough warming to keep the Earth from becoming an ice planet. They also claim that, because CO2 is “non-condensing” (whereas water vapor, Earth’s most abundant greenhouse gas, does condense) this gives it special status as some sort of primary control knob governing Earth temperatures.

That latter argument has never quite convinced me of anything…both CO2 and water vapor have various sources and sinks, and just because water vapor goes through a phase change and CO2 doesn’t is, in my mind, irrelevant. Yes, the CO2 source/sink processes act more slowly than the water vapor ones (evaporation and precipitation) do, but on the long time scales of Earth’s history, who cares?

But the main point of the current post is to stimulate some thought regarding another possibility regarding how we view carbon dioxide: rather than the existence of CO2 being the primary warming mechanism of climate, maybe it is the existence of life on Earth which provides the primary cooling mechanism.

Think about this: What is the natural state of of the planets closest to Earth? Both Mars and Venus have atmospheres which are nearly 100% carbon dioxide. Presumably, without life on Earth, we too would have a planet with nearly 100% CO2.

So doesn’t it make more sense to use THAT as a starting point for discussion, rather than a hypothetical Earth with NO carbon dioxide?

The small amount of CO2 in Earth’s atmosphere (about 4 parts per 10,000) is presumably due to biological processes “sucking on” that “food” source as hard as possible (further evidenced by the fact that our production of CO2 through fossil fuel burning is 50% consumed by natural processes).

So, maybe it is life on Earth that should be viewed as the primary CO2 cooling mechanism for the Earth’s climate system, by reducing atmospheric CO2 concentrations from nearly 10,000 parts per 10,000, to only 4 parts per 10,000.

Just thinking out loud…

85 Responses to “Life on Earth: Principal control knob governing Earth’s temperature”

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  1. Lewis Guignard says:

    Along that line an interesting piece of math would be to estimate/guess how much CO2 would be in the atmosphere without the effects of plant life. This would include decaying matter, live plants, cellulose in landfills, wood in houses, animal and plants in the ocean and on land etc. Toward that end, I believe a pound of cellulose equates to about 2 lbs of CO2.

    Then there is all the hydrocarbons tied up underneath the surface which, it would seem, at one time must have been atmospheric CO2.

    Interesting thought.

  2. Ample physical evidence shows that carbon dioxide (CO2) is the single most important climate-relevant greenhouse gas in Earth’s atmosphere. This is because CO2, like ozone, N2O, CH4, and chlorofluorocarbons, does not condense and precipitate from the atmosphere at current climate temperatures, whereas water vapor can and does. Noncondensing greenhouse gases, which account for 25% of the total terrestrial greenhouse effect, thus serve to provide the stable temperature structure that sustains the current levels of atmospheric water vapor and clouds via feedback processes that account for the remaining 75% of the greenhouse effect. Without the radiative forcing supplied by CO2 and the other noncondensing greenhouse gases, the terrestrial greenhouse would collapse, plunging the global climate into an icebound Earth state.

    Which I agree with but what really controls how effective the greenhouse gas effect is? Why does CO2 follow the temperature trends?

    I keep thinking if less energy comes into the climate system via the sun, that the greenhouse gas effect would become less. Cooling oceans playing a big part in all of this. Does this make sense?

    • Why does CO2 follow the temperature trends? You can go to a site with the Vostok ice core data and see a close correlation between CO2 and temperature. The assumption has been that varying levels of CO2 produce varying levels of temperature. The comparison of CO2 and temp is difficult to do by looking at the graphs that are typically presented, which are separate plots. However a search of the internet also turns up the original numeric Vostok data, and by scaling this data so both CO2 and temp vary between 0 and 1, the curves can be plotted on the same graph….this shows that temp precedes changes in CO2 by about 12,000 years, especially when the temp drops rapidly, during the transition to an ice age. This could represent the thawing of plant material in permafrost, or similar effects, during a transition from ice age to warm period, with the CO2 being released as rapidly as the temp rises, but when the temp goes from a warm period to cold ice age, the previously released CO2 doesn’t have a good way to be reabsorbed, so it just stays in the atmosphere for thousands of years.

    • Robert JM says:

      The concept of CO2 being essential for keeping water vapour from freezing out of the atmosphere is an absurd notion when you consider a peak solar heating of 1300w/m2 at the top of that atmosphere at midday.

  3. Gary says:

    Biologists and ecologists are well-aware of how the biota modifies local environments. So what’s taking physicists so long to realize these mechanisms scale up to the whole climate? (Hint: they start with spherical organisms.)

    Seriously, biological activity is immensely diverse at multiple scales which semi-independently co-evolve with habitats to produce relatively stable conditions at a balanced optima for all components. It’s a system that obeys the principles of Constructal Theory (

    As for CO2 or H2O being the control knob, it seems obvious that the molecule that can undergo phase changes in a narrow temperature range provides more opportunity for regulatory feedbacks. And feedbacks are what provide fine-tuning. CO2 is more akin to the ON/OFF switch and H2O to the volume control.

  4. MarkB says:

    My, admittedly limited, understanding of mainstream geology theory is that there is strong evidence for a very high level of atmospheric CO2 which has been almost entirely sequestered in carbonate rocks and hydrocarbon deposits.

    Respectfully, isn’t the line of reasoning in this post problematic for a young earth creationist?

    • Bil Danielson says:

      Troublemaker.. ;>

    • It is not at all “problematic” for an “Old Earth Creationist”, such as Dr. Hugh Ross, PhD (Astronomy) and the Author of such books as “Creation and Time” and “The Creator and the Cosmos”.
      Dr. Ross is also a Christian Minister.

      Dr. Ross’ Jewish counterpart is another Old Earth Creationist, Dr. Gerard Schroeder, PhD (Nuclear Physics), who is also a Jewish Talmudic Scholar and who has studied the Book of Genesis in the original Hebrew.

      Dr Ross has written such books as : “The Science of God” and “Genesis and the Big Bang”

      You may want to check them out.

  5. An observation, at the end of the JURASIC PERIOD when animal life and plant life(biological processes) flourished and were much more prevalent then today CO2 concentrations were some 2000 ppm much greater then today.

    This tends to show life versus CO2 concentrations is not the only item that effects the amounts of CO2 concentrations in our atmosphere.

    I think it is oceanic water temperature, limestone, and volcanic activity, all which I put ahead of life.

    • Salvatore:
      I am not a Scientist, but I think at the end of the Jurassic Period, there were NO Humans, so the CO2 could be 2,000 PPM or 20,000 PPM and it would not be relevant to us in the 21st Century.

      However, have you ever wondered why Venus is about 8% HOTTER than Mercury, even though Mercury is closer to the Sun? Mercury’s orbit takes it to within 20 million miles of old Sol, while Venus’s more circular orbit means it is 66 to 67 million miles away from our Star. Venus is about 864 Degrees Fahrenheit and Mercury is 800 Degrees F.

      Could it be that the above is due to Venus’ atmosphere being much thicker than Mercury’s and the Venusian atmosphere is 95% CO2?

  6. Then again without life there would be nothing to consume Co2. I see that point of this article.

  7. Arfur Bryant says:

    [“Noncondensing greenhouse gases, which account for 25% of the total terrestrial greenhouse effect, thus serve to provide the stable temperature structure …”]

    This is bonkers. There is no substance (or evidence other than models) to this statement. If Lacis et al think CO2 and the other nghgs account for 25%, then maybe they should consider this:

    The GHE is, according to the IPCC, 33 deg C.
    25% of 33 is 8.25 deg C
    In 1850 (IPCC data start date) the GHE would have been 33-0.8 (enhanced GHE) = 32.2 deg C
    25% of 32.2 is 8.05 deg C

    So… a massive 40% increase in this major contributor (nghg) since 1850 has, according to them, caused a barely significant 0.2 deg C rise in temperature and that is only true if they assume that ALL the warming since 1850 is due to nghgs!

    It is beyond stupid. To invoke either assumed feedbacks or assumed thermal inertia lag is their next line of argument and both lines fail the logic or data test.

    There is absolutely NO evidence to suggest CO2 has any discernible effect on global temperature. Why keep pretending it does without any adherence to the scientific method?

    I suggest that WATER, not life on Earth, is a better candidate for a control knob.

    Actually, come to think of it, Pachauri is probably a good candidate for a control knob…

    • Aaron S says:

      So if water caused the recent century of warming, what drove it up, and what caused it to pause?

      • Lewis says:

        I suggest that water is more a moderator of climate differential from equator to poles. It absorbs huge amounts of energy then moves with the winds poleward, distributing that energy to other parts of the globe. Without the heat absorbtion ability, the winds could become pretty interesting in moving the heat. Of course, without water, we wouldn’t be having this discussion.

        CO2 and other GHGs have some effect on heating and cooling, but don’t do much more or less than nitrogen and oxygen on moderation of differentials.

      • Arfur Bryant says:

        I didn’t say water caused the recent warming; I said it was a good candidate for a control knob. It is the only element that exists naturally in all three forms and what Lewis says below is a fair call. It is capable of distributing energy around the globe – what better control knob?

        • Aaron S says:

          But what drives the water cycle- I understand that this is a chicken and egg sort of argument, and I agree atmopheric water is dominantly what creates our planet’s climate. However, water responds to other parameters- like the orbital forcing from Precession, Obliquity, and Eccentricity. I also think the sun’s activity (eg, irradiance, magnetics, and CME) plays a underestimated role in controling atmospheric water. As you state water can exist in many forms- some warm the system (high clouds, vapor as a GHG), some cool (low clouds via albedo) and because the sun’s input (irradiance) changes the primary heat into the system and it also appears the sun partially controls the state of water (cosmic rays via magnetics affect cloud cover)- The sun is my prefered candidate for a bigger piece of the control knob for climate sensitivity. Also, CO2 is a non-compressible gas, which means it is capapble of continuous warming via green house- so I think it does play a role as a feedback (naturally it increases as oceans warm). However, if I did a mixing model for the sun or CO2 as the stronger knob- I’d go with the sun’s activity as significantly stronger at forcing the water system. Unfortunately, you can not tax the sun to subsidize the alternative lifestyle some politicians and their consituents desire, thus the politicians and media prefer to emphasize CO2 and it gains favor in public opinion. It is scary that somehow the public opinion has somehow influenced science, but it obviously has…. in many issues.

          • Arfur Bryant says:

            Aaron S,

            I’m sorry I missed this reply. I do not have time to address all your many good points now but I will do later. I wasn’t ignoring you! 🙂


          • Arfur Bryant says:

            Aaron S,

            I really don’t disagree with anything you say, especially your last two sentences (which are bang on). I agree the Sun is the power source (albeit not always consistent), I just would have thought H2O was a better candidate for a control knob (and certainly when compared with CO2) which has the ability to minimise (but not always negate) the impact of the inconsistent power source. It’s semantics really but, as I say, I am coming from the same place as you in the debate!



    • m says:

      Greenhouse gases radiate heat in all directions, including back down to earth.

      There is evidence, empirical evidence, that CO2 causes warming. You can measure the radiance of gases using FTIR spectroscopy.

      Energy trapped in our atmosphere corresponds exactly to the wavelengths of energy captured by CO2.

      • Arfur Bryant says:


        Just repeating the IPCC dogma doesn’t make it the truth.

        The fact that CO2 can radiate is not in question. The point is what happens to that radiation?

        Go on, then, provide one single piece of empirical evidence that shows that the radiation emitted by CO2 molecules actually ADDS to the thermal energy of the planet.

        • m says:

          Firstly, can you explain how radiation from CO2 in the atmosphere wouldn’t add to the thermal energy? Because that would be a violation of the laws of nature.

          Again, empirical evidence that it actually is:

          Here it is again in case you missed it for the second time:

          • Aaron S says:

            M are you aware that the .04% of CO2 in our atmosphere is a very minor GHG to the total system and the reason it is considered significant is because it has been coupled with water vapor, which is the dominant GHG and mostly overlaps the absorption band of CO2. I love the passion, and willingness to contribute, but you have lots to learn- and the learning from this page is to express alternative explanations and theorys- some are crazy, some are probably partially correct. The issue for me isn’t if CO2 is a GHG, but if it is the knob that drives the entire earth’s climate system. This is called climate sensitivity and the issue is that the earth’s temp is not as sensitive to CO2 as considered by the IPCC and mainstream science that is part of a group. THere are other opinions out there and abundant literature supporting some of them. My favorite is that the SUN is the dominant driver of climate.

    • Arfur:
      As Andrew Lacis, et al, say in their above NASA Paper, the Historical Annual Rate of CO2 increase was 0.005 PPM per year, in the 11,000 years since the end of the last Ice Age.

      I am in the process of drafting an Email to Dr. Lacis, to obtain the Source for the 0.005 PPM number. (Not to satisfy ME, but Dr. Lacis’ critics.) However, for argument’s sake, let us assume that Dr. Lacis and his 4 Co-Authors were correct with the 0.005 PPM number.

      Today, on, the CO2 PPM number for Sep 10, 2023 was unavailable for some reason.

      But we DO have it for June 2023 = 423.68 PPM
      and June 2022 = 420.99 PPM
      so it increased by 2.69 PPM in one year

      If my Calculator is correct, then 2.69 PPM is 538 (five-hundred-thirty-eight) times the Historical Annual Rate of 0.005 PPM in the NASA Paper. I am not a Scientist, but 538 times anything would seem to be a bit “high”.

      CO2 PPM is not the only Rate that shows a great increase, when placed in Historical Perspective.

      Most articles on Climate Change and its subset, Global Warming, will say in the 20th Century, the Earth’s Average Global Temp (AGT) increased by 0.6 Degrees Celsius (“C”) or 1.08 Degrees Fahrenheit (“F”). And the Author goes no further down the “Historical Perspective” route.

      However, although 1.08 Degrees F seems pretty tiny, it is over 23 times the Average Warming Per Century of 1/22nd of a Degree F (Decimal 0.04545 Degrees F), in the 110 Centuries since the end of the last Ice Age.

      As for the 21st Century, 23 times the Historical Rate will seem “small”, if the AGT increases as many believe it will in this Century.

  8. Arfur Bryant says:

    Sorry, erratum,

    The fourth paragraph above should read:

    “So… a massive 40% increase in this major contributor (nghg) since 1850 has, according to them, caused a barely significant 2.5% rise in GHE…


  9. Noblesse Oblige says:

    The idea splashed some time ago as James Lovelock’s Gaia Hypothesis. In full regalia, it says that the earth’s biosphere operates as a unitary system with feedbacks arranged so as to maintain the conditions for its own health and welfare. Lovelock later backed away from it, as I recall. He also later backed away from global warming alarmism Gaia may have suffered from a certain lack of rigor, but it is a very interesting concept.

  10. Geoff wood says:

    Without an atmosphere, the Earth’s effective black body temperature is 269K. It’s grey body temperature without an atmosphere is 279K for an emissivity of 0.96, both taken from lunar data. Some 9K below surface temperatures we are accustomed to on average. So the total ‘atmospheric effect’ is 9K.

    All matter forced to interact radiates. Gravity provides the containment, the initial heating through collapse of celestial bodies and the subsequent cooling mechanism in gases and liquids (I’ve included liquids because without gases the liquids become gases). The isothermal condition of ‘free expansion’ maintains kinetic distribution through lack of interaction. Imperfections in the not quite totally elastic interactions produces thermal radiation. If anyone believes otherwise then they are suggesting that monatomic or many diatomic gases cannot, even at several hundred Kelvin lose energy to space without ‘special’ triatomics. Nitrogen, for instance absorbs, according to spectral analysis between 3.9 and 4.3um directly from the solar flux, but according to climatology this energy thermalised to 288K or less produces no radiation, because 10e+18kg of nitrogen in a purely nitrogen atmosphere, at a mean of around 255K would not radiate anything!

    In reality, a purely nitrogen atmosphere only has to radiate a tiny amount to both raise the effective radiative height above the solid surface by 900m, and reduce the system emissivity from 0.96 to 0.93 to give the same surface temperature of 288K.

    There is no 33K enhancement.

    Just thinking out loud.

  11. Christopher Game says:

    Dr Spencer makes an important point. He questions which variable should be given precedence in the climate discussion.

    I would like to go a little into the distinction between the amplifier designers’ analysis preferred by the IPCC and the general dynamical systems analysis that I think is perhaps safer.

    The two analyses have different logical structures.

    The amplifier designers’ analysis pre-supposes a purpose for the analysis. It does so by fixing on a special branch in the circuit diagram, the link that contains the active power-adding element, that draws added power from an arbitrarily accessible source. That is what makes for an amplifier. Further special-purpose choices are of the signal source and of the load variables. A special node is chosen in the circuit. That node brings together just three special branches: a branch that carries a signal from the source, a branch that carries a feedback signal from the load, and a branch that carries a signal to the active power-adding element. The presence of this special node dictates that there is necessarily a loop in the circuit. That present is a special feature also. Amplifier designers have a special purpose in mind.

    This is quite different from the general dynamical system theorists’s approach. They do not pre-suppose a special purpose. Their analysis is not distinguished by a necessary loop. Their analysis is more like thinking of a star than of a loop. The star is a metaphor for the system as a whole. All variables are treated on an equal footing. All of them are listed as ‘outputs’ and all of them are listed as ‘inputs’. They all relate to the centre of the star, the system as a whole.

    Dr Spencer’s post is about the choice of temperature as the distinguished load variable, and about the question of the choice of the controlling variable. The controlling variable is more or less the source variable of the amplifier designers.

    This may suggest that the amplifier designers’ approach is suitable. But the fact that there is radical questioning about which variables to choose suggests that it may be safer to use the general dynamical systems theorists’ approach, which does not pre-judge which variables are the variables of interest; it tends to leave it to the system to tell us that.

    • Geoff wood says:

      Christopher , would you hazard a guess at the Earth’s surface temperature with a pure diatomic atmosphere?

  12. David L. Hagen says:

    Interesting thought.
    Exploring further, does GEOLOGIC CHEMISTRY control CO2 by precipitating limestone?

    Three quarters of the earth’s surface is covered with various types of sedimentary rock. Of these, about 20 to 25 percent are carbonate rocks.

    Earth Science: Carbonate Rocks
    i.e. 15% to 19% of earth’s surface is carbonate rocks. Most CO2 is stored in carbonate rock.

  13. Bill Norton says:

    Dr. Spenser’s point about life on earth being an important regulating force is well taken. Oxygen comprises 20.95% of the atmosphere, far more than CO2. Consider this statement from the Wikipedia section on atmospheric oxygen.

    “Oxygen is an important part of the atmosphere, and is necessary to sustain most terrestrial life as it is used in respiration. However, it is too chemically reactive to remain a free element in Earth’s atmosphere without being continuously replenished by the photosynthetic action of living organisms, which use the energy of sunlight to produce elemental oxygen from water.”

    If that statement is true, doesn’t it support the concept that life is a major force regulating the composition of gasses in the atmosphere and thus the “Green House” effect?

    • Geoff wood says:

      Bill, what is the total atmospheric effect upon the Earth’s surface temperature? Is it 9K or 33K?

      • Bill Norton says:

        I have no idea. I have yet to see a full explanation that answers that question for me.

      • Robert JM says:

        Black body equations do not apply to earth due to energy storage.
        Energy storage (springs) reduce energy losses raising the effective temp.
        Temp is also not directly related to area energy input, instead it is a function of energy per molecule and is more akin to voltage.

      • coturnix says:

        I think it is more like 13С

      • coturnix says:

        …and only around 8C at equator. If heat transport away from equator is taken into account, who knows if there even is any kind of ghe on earth: hydrosphere almost completely compensates for co2 where there is the most wv in air.

  14. While reading Dr Spencer’s comments, I became mindful of a concept that has been lingering around in my mind for some time. The idea comes from the likes of Malthus and the nature of populations more than it comes from atmospheric physics.

    I understand that one of the concepts involved with Malthus and the theory of how populations work – populations of anything, wild animals, fish, birds etc – is that an animal will continuously eat its food source to its complete exhaustion. When the food source is finally depleted, the population of the animal eating it will also collapses. This is the normal course of events unless there is some intervening mechanism to prevent the animal eating all it wants. The role of predation in nature is one such mechanism. Other mechanisms include change of seasons, migration of the food source to some other place and droughts.

    But the underlying concept is that an animal – or other life form – will eat its food source to its extinction. In this case ‘extinction’ means both the extinction of the food source as well as the animal.

    The vague thought that has been floating around in my mind for years now is the idea that this concept should apply to plant life in the same way as we have previously applied it to animal life. It would seem therefore that, when the CO2 content of the atmosphere was extremely high, plants started eating it as an abundant source of food and this process has continued ever since. Part of the carbon sucked down by this process becomes sequestered in soil (and other deposits such as coal) and this means that the atmospheric carbon is never quite balanced. It (the carbon in the atmosphere) is continually being eaten by a life form (plants) and it will continue to be eaten and stored in a very slow process until it reaches a stage where plant growth becomes marginal. As I understand it, around 200ppm is that threshold.

    I am not a scientist or a mathematician so I’m not quite sure where this concept leads to – whether it is useful or not. I think it may provide a different way of looking at things. I suppose I am paralleling, in some ways, what Dr Spenser has just said but I am doing it from a slightly different angle – a Malthusian angle.

    Does anyone think there is any value at looking at the relationship of plant biology and atmospheric CO2 in this way?

    • Robert JM says:

      Populations will generally only expand till they reach the limit of their food supply.
      The bust only comes because the food supply is variable (usually due to climate)
      This allows the population to exceed the average available food supply limitation in the good years resulting in overpopulation and collapse in the bad years.

      The populations that eat themselves to death do sometimes occur when a fast breeding predator is introduced to a food source with a slow growth rate.

    • Ron C. says:

      Bob Carter said that the biosphere collapses at 150 ppm CO2, and that the planet came close to that twice in geologic history.

      It follows that we are doing a good thing to release sequestered CO2 faster than nature would do it on her own.

    • Aaron S says:

      I have extensive experience with plants and CO2 through time. First Malthusian population modeling included multiple scenarios (eg. shapes of curves through time). One was a collapse, two was stability at a sustainable level, and three was an ongoing rise and fall through time. Plants have responded to CO2 through time in different- there are multiple metabolic pathways (C3, C4, and Cam) and there was a big shift at about 5 million years ago from nearly exclusively C3 plants to abundant C4 plants at mid latitudes in response to CO2 decreasing. (THere are several Cerling papers from the 90’s and 2000’s on this… including Science and Nature versions). Then in this very cold geologic time with decreased CO2 the plants have fluctuated greatly with the expansion of glaciers during cold, low-CO2 phases and warm interglacials. (Paul and Hazel Delcourt did some key work on this subject using pollen records in the USA). Point is CO2 is dynamic and flora have responded through time…. so it is more like a dynamic equilibrium model. By the way if you ever ask yourself where did I come from and why am I here- thank the tanking of atm CO2 which created the open C4 grasslands that our ancestors exploited leading to our evolution. I do love the creative synthesise of the different feilds. Google (Shunk Gray Fossil Site- if you want to read some of my personal (not that important) work in the field).

      • Aaron S says:

        I do love your creative synthesis… sorry that wasn’t clear.

        • Thanks for your comments Aaron. After writing my initial comment, and reflecting on the comment from Ron C above, I was rather thinking that the ‘dynamic equilibrium’ idea you refer to, above, would likely be the case. (That is, if I’ve got the concept of dynamic equilibrium right.)

          Under the line of thought I was taking, plants would continue to ‘eat’ CO2 until its availability got down to the low level at which it would become a marginal or extremely scarce ‘food’ source. Then the plants would go into some sort of decline and stop thriving or die. With the plants dying – or just failing to thrive – there would then be a wholesale process of oxidation of the carbo hydrate chains in the plants and this would result in a huge release of CO2 to the atmosphere. This would set off a new round of plant growth (ie, plants thriving) and so the growth ‘dynamic’ part of the dynamic equilibrium would have a period of ascendency. Then the whole thing would repeat over and over again on a vast time scale.

          Of course, this process of dynamic equilibrium could be interfered with, or interrupted, by new sources of CO2 to the atmosphere such as large scale volcanic activity.

          • Aaron S says:

            Yes volcanism, but also just temperature change. For example, when eccentricity warms the planet the oceans release more CO2. THink of two cans of Coke, one in a fridge the other in a car on a warm summer day. If you open them at the same time- the warm one will likely explode, whereas the cool one just fizzes a little. Warmer fluids can not hold as much gas. Even the IPCC agrees with this. They then suggest that the CO2 drives a feedback that greatly amplifies the warming. Orbital forcing on the earth’s climate is a very, very powerful force and it works like a clock… in that it is highly periodic. So CO2 fluctuates regularly with this cycle- this is based on >400k yr of ice core data.


  15. Adam Gallon says:

    Without life, we would have an atmosphere without appreciable amounts of Oxygen.
    Where we also differ is the Nitrogen content. Venus with a mere 3.5% compared to our 78%. Venus has 70ppm of Argon vs our 0.9% too.
    Where’s the Martian & Venusian Nitrogen gone too?
    One big difference, is we have plate techtonics to remove the carbonates produced by lifeforms, from the ecosphere.

  16. Aaron S says:

    The C cycle is a critical part of the Earth, and Biology is a large component of it. The CO2 humans produce is a by product of exploitation of energy derived from hydrocarbons that are from organic matter. Coal was originally a swamp forest (not created in situ…LOL), whereas oil was usually derived from an algae-rich mudrock, and both were created during thermal cooking by burial within the earth. In both cases the organic material is converted to a high energy hydrocarbon, Methane is from the extreme high temperature cooking of either a coal or an alge source rock, wheras oil is cooked off at lower temperatures from algae (Have more fatty cellular structures than cellulose). I do wonder: Does the endothermic reaction photosynthesis remove enough energy (heat) from the Earth’s system to affect the global temperture? In other words is the rate of production of a coal swamp (Or high organic content marine mudrock) cooling the earth directly and therefore a direct negative feedback to increasing CO2 (which increases plant and algae growth rates)?

  17. pochas says:

    I think life certainly has a major effect on CO2 levels. The following graphic by Scotese can no longer be found on their site, so I don’t know whether they have deprecated it. But looking at the graphic one might say that when CO2 declines below ~ 500 ppm temperatures drop below 22C as at present and during the Carboniferous. But by the graphic 22 C (72 F) is a cap; temperatures can never go higher. If your theory is correct and the graphic is correct it will take a catastrophe such as the Permian extinction or the K-T extinction to get us back to 22 C.

  18. Paul says:

    An important detail:

    There are many comments above about plants “eating” CO2 as food. CO2 does not fit well under the category of what we ordinarily call food as it provides no available chemical energy content. Rather, plants use it as a substrate to “eat” solar energy, which they store in other carbon compounds and use for growth.

  19. Arfur Bryant says:

    What everyone seems to dance around is the basic assumption of the Lacis paper that CO2 is a significant contributor to the ‘GHE’. The paper assumes this and provides no empirical evidence to support the assumption.

    From the paper:

    [“Besides direct solar heating of the ground, there is also indirect longwave (LW) warming arising from the thermal radiation that is emitted by the ground, then absorbed locally within the atmosphere, from which it is re-emitted in both upward and downward directions, further heating the ground and maintaining the temperature gradient in the atmosphere.”] My bold.

    Just how does this work? How does the radiation from the (almost exclusively) cooler atmospheric GHG molecules warm the surface? Heat cannot flow from cool to hot. Radiation from a cooler source cannot add ‘heat’ to a warmer surface. Solar radiation – short wavelength/higher frequency – can add thermal energy to the surface. Radiation from a cooler source – longer wavelength.lower frequency – cannot. The only molecules that can be warmed by radiation from CO2 and other nghgs are those which are ‘cooler’ than the source. As there is so little nghg concentration in the atmosphere, the amount of warming of the cooler molecules is extremely limited and, more importantly, is demonstrably so by the observable lack of correlation between nghg concentration and global temperature.

    The Lacis paper is a bunch of assumptions speciously endorsed by model ‘experiment’. It is, in my opinion, anathema to science.

    I thought the Gaia hypothesis was, in its basic form, quite reasonable. Lovelock may be turning against ‘CO2 = catastrophic global warming’ but this does not necessarily invalidate the Gaia hypothesis.

    • BBould says:

      I’m not able to do this myself but, shouldn’t we be able to measure how much heat/energy a co2 molecule would need to emit to warm the 10000 other molecules surrounding it?

      It seems to me this may be important?

      • Arfur Bryant says:


        Not sure where you’re getting 10000 from – I make it appx 2500 ‘other’ molecules for each CO2 molecule. But your point is well made. People seem to forget the ‘trace’ nature of all the nghgs.

        I do not think you can attribute a temperature to one single molecule – it is a measure of the average kinetic energy of a material composed of a number of molecules/atoms.

        But, yes, a single CO2 molecule can absorb energy of a suitable wavelength and, in so absorbing, raise its energy level (electron orbit) to a higher level. It will then emit this higher level radiation (different wavelength). This new radiation will only be absorbed by a surface, object or molecule which is ‘cooler’ than the emitter.

        I can’t answer your question either, even if you specified by how much the other molecules would have to be ‘warmed’.

        • BBould says:

          Thanks, bad math on my part forgot 400ppm.

          It doesn’t seem feasible to me, that 1 molecule could effectively heat 2500 other molecules sufficiently enough to increase warming or even measure.

          Surely somebody would know?

        • Arfur Bryant says:


          First, knowing the truth and making that truth available comes away down the list of priorities for those who want Joe Public to be worried about CO2! 🙂

          Second, it is probably not the case that CO2 could ever make all those 2500 molecules ‘warmer’.
          The only molecules which could absorb the radiation emitted by the CO2 molecule are other so-called ghgs. Of these, only water vapour exists in quantities approaching the CO2 concentration (and water vapour is not well-mixed throughout the atmosphere like CO2, so that absorption is not uniform across the atmosphere). The other nghgs (eg methane) are far less abundant, so the chance of absorbing the CO2 emitted radiation is small. The only other way a CO2 molecule could transfer (thermal) energy to a non-ghg (N2 or O2 or Argon) is by conduction (or low energy collision). As it exists in 1 to 2500 of these ‘inert’ molecules, it is unlikely to ‘spread the love’ that efficiently, in my opinion. Of course, it has to be remembered that the atmosphere is a very fluid situation and the molecules are in constant motion, making the estimate difficult.

          I’m sure somebody does know the mathematical answer; unfortunately I don’t.


  20. Thomas says:

    You might also say that water is the principal control knob governing Earth’s temperature. Even without life rain causes erosion, and erosion of silicate rocks consumes CO2. Higher temperatures gives a stronger hydrological cycle, more erosion and a decrease in CO2 which cools the climate. If the climate gets too cool, on the other hand, emission of new CO2 from volcanoes gets the upper hand and the CO2 concentration rises. This mechanism provides a negative feedback that can keep the climate steady *as long as you have liquid water*.

    Venus probably lost too much hydrogen to space, and without water there was no way to get rid of all the CO2 that accumulated into the atmosphere causing a runaway greenhouse effect.

  21. Thanks, Dr. Spencer. An interesting article.
    “maybe it is life on Earth that should be viewed as the primary CO2 cooling mechanism for the Earth’s climate system, by reducing atmospheric CO2 concentrations from nearly 10,000 parts per 10,000, to only 4 parts per 10,000.”
    I see the green Earth as a temporary triumph of life over entropy. Thanks to the biosphere and the oceans we have a nice atmosphere to breathe and fly, and food everywhere else.

  22. Ossqss says:

    I would recognize cyanobacteria as a control know for life in general on this planet.

  23. Ossqss says:

    That would be knob not know! Darn autocorrect :-}

  24. Nabil Swedan says:

    Carbon dioxide content in the atmosphere is not the climate temperature knob, its change with time is what controls the temperature. The change, of course, is caused by life as Dr. spencer suggests.

    If the change in the concentration of carbon dioxide is zero, surface temperature remains steady regardless of the content of carbon dioxide. This is what the geological record and Antarctic ice core data show, math is in agreement.

  25. Norman says:

    Will there be an actual albedo satellite launched some day? One that maeasures actual albedo of Earth in real time. Maybe one of the geosynchronos orbits at 23,000 miles.

    I pulled up an albedo calculator.

    The initial value for global albedo they use is 0.31.
    This gives a global temp of 288.18K
    Just changing the albedo from 0.31 to 0.3 raises the temp to
    289.22K. Over a full degree C.

    I am thinking albedo may be a much bigger control knob on global temperatures. Without actual measurements to see how it might change, assuming it is always 0.31 is a stretch.

  26. Norman that is great. It shows as you pointed out how important albedo is.

    • Norman says:

      Salvatore Del Prete,

      I have read many of your posts. Isn’t your claim that solar cycles are the major cause of global temperature variations? I think you are of the camp that states that solar intensity determines the amount of low clouds which in turn warm or cool the climate depending upon which way it goes.

      If you have two variables that both can effect an outcome (global temperature) it would be wise to really get some solid data on the other one. We have many monitoring stations for Carbon Dioxide in the atmposphere. We should also devote some effort to collect albedo data. We know that global warming is not following Carbon Dioxide very well. What if it did closely follow global albedo? It might be nice to know rather than continue massive investment in highly sporatic wind energy.

      • Arfur Bryant says:

        norman and Salvatore,

        I agree albedo is an important measurement in the debate but, basically, the largest contributor to albedo – globally – is H2O in its various forms, is it not? Land management changes are probably a much smaller factor.

        • Norman says:

          Afrur Bryant,

          Yes the oceans would be the largest contributor to albedo. My point is we should have some actual measurements of Earth’s albedo to determine its effect on global temperatures. Since CO2 and albedo are assumed to have about the same influence on global temperatures we should not ignore the effects of albedo.

          Also, land does still make up 30% of the Earth’s surface and you would only have to alter the land albedo 3% to get an total change of albedo of 1% which is enough to change global temperatures by over 1 C.

          Here is a graph of albedo ranges. If you look at crops you can see the type of crops has an albedo range of 10%. Since crops do cover a large amount of surface, they could have a large effect on global temperatures, or cutting down forrest areas and converting to crop land.

          I am reading that ocean choppiness has an impact on albedo. So higher ocean winds may increase the albedo and cause cooling. Too big a factor to ignore!

          • Arfur Bryant says:


            Yep, agree with all of that.

            Obviously not a scary enough problem for the CO2 hype-ers to tackle! How do you tax albedo? 🙂

  27. Jody says:

    They’re making a new video on climate change on show time. The first episode is the second video on the page. They have NASA scientists claiming man made global warming is real:

    Would love some info on what you think of the data they presented.

    • Darren says:

      As I recall Dr Spencer is not in the “Man-made global warming is not real” camp. I’m not either. I believe that point is conceded by most — but certainly not all who post here.

      The question that is very much under scrutiny is whether man’s CO2 emissions and any resulting global warming are significant.

      That all comes down to the sensitivity of the climate to changes in atmospheric CO2.

      So far the data supports the contention that climate is NOT as sensitive to CO2 as the Alarmists claim — and therefore spending billions of dollars to change our energy model is a waste of money and effort (at least as far as global warming is concerned).

      I clicked on the link and found several statements and insinuations that are NOT supported by any science anywhere — they are the sole province of hyperventilating (thereby creating more CO2) activists.

      This is an activist piece, not a science piece.

      The globe has been warming since the end of the last little ice age (1850). Between ice ages, glaciers melt, polar caps recede, etc. etc. etc. All that would be happening if man were still living in grass huts without having discovered fire at all. That won’t stop RYOT from trying to blame modern society for this perfectly natural cycle.

      The only question is how much faster are all those natural changes happening because we drive cars and have electricity powered by fossil fuels.

      The data seems to say: not much faster.

      I support efforts to move energy generation to renewable sources and increase efficiency of fossil fuel consumption for a number of reasons but global warming gloom and doom is not one of them.

    • Arfur Bryant says:

      I completely agree with Darren.

      That link was pure, unadulterated warmist hyperbole, using carefully selected parts of the whole to give an impression that the whole is different to that which it is.

      But, if Harrison Ford says its true… lol.

      ‘Climate sensitivity’ is a purely theoretical construct. All the predictions of climate sensitivity so far are made from models and assumption. There is absolutely no observed evidence of CS unless you make assumptions.

    • Gordon Robertson says:

      @Jody “They have NASA scientists claiming man made global warming is real…”

      It was the scientists from NASA GISS who started the alarm. None of them are bona fide climate scientists.

      James Hansen, who began his scientific career in astronomy came to NASA GISS as a climate modeler. He was convinced that the atmosphere of Venus was caused by a runaway greenhouse effect, which is being seriously questioned today since the surface temperature is far too hot to have been caused by greenhouse warming. Nevertheless, Hansen set out to prove that planet Earth is heading in the same direction due to anthropogenic emissions.

      In a TV presentation in the summer of 1988, backed by Al Gore, and with the air conditioning turned off to emphasize the heat, Hansen announced warming of 1C every 20 years. He was not even close.

      His assistant, Gavin Schmidt, who is likely one of the NASA scientist you mention, is not even a scientist. He has a degree in mathematics as do most of the alarmist NASA scientist. They are all climate modelers. All of the people mentioned by Roy above are mathematicians.

      It has been suggested that climate modelling is more a social science than physics.

      Here’s something recent on the IPCC, AR5, and models from Climate Etc on Judith Curry’s site:

      Schmidt became embroiled in a debate a few years ago with engineer Jeffrey Glassman, who literally tore his understanding of physics apart. Glassman zeroed in on statements Schmidt had made about CO2 solubility and positive feedback, proving that Schmidt had no idea about the latter. Yet, Schmidt has been programming his false understanding of PF into climate models.

      Schmidt runs the uber-alarmist site realclimate with his buddy from Climategate fame, Michael Mann. Mann is a geologist. So, we know one front line alarmist site is run by a mathematician and a geologist. Another alarmist site, desmogblog, is run by James Hoggan, a public relations expert who sits on the board of the David Suzuki Foundation, another uber-alarmist site run by a geneticist.

      Another alarmist site is run by a musician and another by a chemist, trained as a physicist, who goes under the nym Eli Rabbett. Another uber-site, skepticalscience, is run by a retired solar physicist who seem to hate everything skeptical, when it is skeptical of climate science.

      Is there a pattern here between NASA GISS and strange science?

  28. Gordon Robertson says:

    Lacis, Schmidt, Rind, and Ruedy….mathematicians and climate modelers.

    Say no more.



    One solar climate mechanism/connection theory which has much merit in my opinion, is as follows:

    A BRIEF OVERVIEW. At times of low solar irradiance the amounts of sea ice in the Nordic Sea increase, this ice is then driven south due to the atmospheric circulation (also due to weak solar conditions) creating a more northerly air flow in this area.(-NAO) This sea ice then melts in the Sub Polar Atlantic, releasing fresh water into the sub- polar Atlantic waters, which in turn impedes the formation of NADW, which slows down the thermohaline circulation causing warm air not to be brought up from the lower latitudes as far north as previous while in lessening amounts.

    This perhaps can be one of the contributing solar/climate connection factors which brought about previous abrupt N.H. cool downs during the past.

    This makes much sense to me.


    To elaborate on the above, when the sun enters a prolonged solar minimum condition an overall reduction takes place in solar spectral irradiance, namely in UV light (wavelengths less then 400 nm). The shorter the wavelength, the MUCH greater the reduction.

    UV light reduction likely will cause ocean heat content and ocean surface temperatures to drop, due to the fact that UV light in the range of 280 nm-400nm penetrates the ocean surface to depths of 50-100 meters. A reduction in UV (ultra violet) light then should have a profound effect on the amount of energy entering the ocean surface waters from the sun extending down to 50-100 meters in depth, resulting in cooler ocean temperatures.

    This ties into what was said in the above in that if ocean waters in high latitudes such as the Nordic Sea, were to be subject to cooling the result would be much more sea ice which could impede the strength of the thermohaline circulation promoting substantial N.H. cooling.

    Adding to this theory is fairly strong evidence that a decrease in UV light will result in a more meridional atmospheric circulation (which should cause more clouds, precipitation and snow cover for the N.H.0), due to changes in ozone distribution in a vertical/horizontal sense which would cause the temperature contrast between the polar areas of the stratosphere and lower latitude areas of the stratosphere to lesson, during prolonged solar minimum periods. Ultra Violet light being likely the most significant solar factor affecting ozone concentrations ,although not the only solar factor.

    This could then set up a more -NAO, (high pressure over Greenland) which would promote a more Northerly flow of air over the Nordic Sea, bringing the sea ice there further South.


    A reduction of the solar wind during a prolonged solar minimum event would cause more galactic cosmic rays to enter the earth’s atmosphere which would promote more aerosol formation thus more cloud nucleation. The result more clouds higher albedo, cooler temperatures.

    Compounding this would be a weaker geo magnetic field which would allow more galactic cosmic ray penetration into the atmosphere , while perhaps causing excursions of the geo magnetic poles to occur in that they would be in more southern latitudes concentrating incoming galactic cosmic rays in these southern latitudes where more moisture would be available for the cosmic rays to work with, making for greater efficiency in the creation of clouds.


    MILANKOVITCH CYCLES overall favor N.H. cooling and an increase in snow cover over N.H high latitudes during the N.H summers due to the fact that perihelion occurs during the N.H. winter (highly favorable for increase summer snow cover), obliquity is 23.44 degrees which is at least neutral for an increase summer N.H. snow cover, while eccentricity of the earth’s orbit is currently at 0.0167 which is still elliptical enough to favor reduced summertime solar insolation in the N.H. and thus promote more snow cover.

    In addition the present geographical arrangements of the oceans versus continents is very favorable for glaciation.


    High latitude major volcanic eruptions correlate to prolonged solar minimum periods which translates to stratospheric warming due to an increase in SO2 particles while promoting more lower troposphere cooling.

    One theory of many behind the solar/volcanic connection is that MUONS, a by product of galactic cosmic rays can affect the calderas of certain volcanoes by changing the chemical composition of the matter within the silica rich magma creating aerosols which increase pressure in the magma chamber and hence lead to an explosive eruption.

    Muon densities increase more in higher latitudes at times of weak solar magnetic activity, which is why volcanic activity in the higher latitudes will be affected more by this process.

    These four mechanisms make a strong case for a solar /climate connection in my opinion, and if the prolonged solar minimum meets the criteria I have mentioned going forward and the duration is long enough I expect global cooling to be quite substantial going forward.


    Solar Flux avg. sub 90

    Solar Wind avg. sub 350 km/sec

    AP index avg. sub 5.0

    Cosmic ray counts north of 6500 counts per minute

    Total Solar Irradiance off .015% or more

    EUV light average 0-105 nm sub 100 units (or off 100% or more) and longer UV light emissions around 300 nm off by several percent.

    IMF around 4.0 nt or lower.

    The above solar parameter averages following several years of sub solar activity in general which commenced in year 2005..

    IF , these average solar parameters are the rule going forward for the remainder of this decade expect global average temperatures to fall by -.5C, with the largest global temperature declines occurring over the high latitudes of N.H. land areas.

    The decline in temperatures should begin to take place within six months after the ending of the maximum of solar cycle 24.

    NOTE 1- What mainstream science is missing in my opinion is two fold, in that solar variability is greater than thought, and that the climate system of the earth is more sensitive to that solar variability.


    A. Ozone concentrations in the lower and middle stratosphere are in phase with the solar cycle, while in anti phase with the solar cycle in the upper stratosphere.

    B. Certain bands of UV light are more important to ozone production then others.

    C. UV light bands are in phase with the solar cycle with much more variability, in contrast to visible light and near infrared (NIR) bands which are in anti phase with the solar cycle with much LESS variability.

    Norman my latest.

    • Norman says:

      Salvatore Del Prete,

      Interesting and developed thought process. The AGW crowd is always asking for mechanisms to explain a global warming besides CO2 (thinking there aren’t any) and you have provided 4.

      The UV connection heating or cooling the deeper ocean is something that should be looked at. I found a .pdf on solar energy and UV makes up over 7% of the total solar output. At 1300 watts/meter at Earth that is 90 watts of energy in the UV range. Changes in this would have effect.

      Looks like you have been spending some time developing your ideas. Thanks for sharing.

    • Gordon Robertson says:

      @Salvatore….you should read the book by astronomer Syun Akasofu on the solar wind. He was a pioneer in the study of the same and he is adamant that the IPCC erred by failing to take into account recovery from the Little Ice Age.

      Akasofu explains that the solar wind interacts with the Earth’s magnetic field, producing thousands of volts of electrical potential. That drives electrical currents not only through the atmosphere but through the oceans and the continents.

      It’s quite possible that electrical currents circulating in the atmosphere affect clouds and produce lightning and precipitation.

  30. The chart above shows a very strong solar geomagnetic index /temperature correlation.

  31. Dr. Strangelove says:


    Plants did cool the planet. In the pre-Cambrian era, CO2 was 7,000 ppm and no polar ice. Plants reduced CO2 to 280 ppm and now the Arctic and Southern oceans are frozen and 43% of all land is covered with snow and ice on winter.

  32. coturnix says:

    I think it is more like 13С, as for according to donohoe & battisti (2011) the atmosphere contributes as much 85% of earth’s albedo, the rest 15% is sunlight reflected off the ground. If the atmosphere were instantly removed, the temperature by the most crude calculations of mine would be not 33C but around 12-13C lower than it is now. While I do not know how that atmospheric albedo partitions between the clouds and gases of the atmosphere (i only know that absorption and scattering by the gases and dust is much larger than most spectators think), but I strongly believe that the cloud-atmosphere albedo should be included into the feedback and not into forcing.

    Thus, the greenhouse effect of the atmosphere in the ‘short run’ (not taking into account ice-albedo feedback, carbonate feedback or even vegetation feedback) is around 13C.

  33. Thanks Norman.

    They all want to say the very thing that DRIVES the climate somehow does NOT change the climate. If that were not bad enough they then proceed to push CO2 a trace gas with a trace increase is going to somehow be the main driver of the climatic system of the earth. It is absurdity.

    Four main factors which trump CO2 may times over when it comes to the climate are the following:

    Beginning state of the climate

    Solar variability with associated primary and secondary effects

    Earth’s magnetic field which can compound or moderate solar activity.

    Milankovitch Cycles and where the earth is at in relation to those cycles.

    • Terry Krieg says:

      Dr Strangelove,
      Are you saying that plants were around in the pre-Cambrian? The only metazoans[ multi-celled organisms]around at that time were the ediacarans. These were a suite of organisms including worms, jellyfish and sea pens which evolved around 600 million years ago. The sea pens may have been plants but they lived on the bottom of a shallow sea. They were first discovered by the late Dr. Reg Sprigg at Ediacara in the Flinders Ranges in 1946. Before then, the only metazoans were known to be of Cambrian age and so Sprigg’s discovery put multi celled life back into the pre-Cambrian. That gave palaeontologists at the time a hell of a headache. But in recent years following acceptance by the international palaeontological community, a new period in the Relative Geological Time Scale has been named. It’s called the Ediacaran Period and named after the hills of Ediacara where Sprigg made the first discovery of them. It is the last Period of the Pre-Cambrian Era [That’s 6/7 of all geological time and includes the Archean and the Proterozoic Eras. I checked the fossils out last week in Brachina Gorge in the Flinders Ranges in South Australia. Why not pay them a visit.



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