Despite High Levels Of CO2, Mars Is Cold

Mars has a mean surface pressure of 600 pascals, compared with Earth’s 100,000 pascals. In other words, the atmospheric pressure on Earth is about 150 times higher than Mars.

Mars has 0.95 mole fraction CO2, compared to 0.0004 on earth. The concentration of CO2 in Mars atmosphere is more than 2,000 times higher than Earth.

So lets do the math for Mars and Earth.

Mars : 600 pascals * 0.95 = 575 pascals (partial pressure of CO2)

Earth : 100,000 pascals * 0.0004 = 40 pascals (partial pressure of CO2)

The partial pressure of CO2 on Mars is 14X larger than earth, yet Earth is much warmer. Now use your brain and figure out the connotations.

Hint : It is the pressure, not the CO2 (stupid)


About stevengoddard

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65 Responses to Despite High Levels Of CO2, Mars Is Cold

  1. Latitude says:

    I hate pop tests……………………………….

  2. Paul H says:

    Can we have a multiple choice option?

  3. bubbagyro says:

    Nicely done.
    PV=nRT does not seem to influence the true believers among the warm-earthers very much, though. CO2 has a magical, “hidden” attribute, much like the heat stored in the 0°C sub-oceans.

    Perhaps, since it hangs around for 20,000 years, this ancient CO2 has a mentoring influence,—sort of like the effect Al Gore has on geniuses like Margaret Chu—far beyond their young CO2 sycophant molecules? If we all understand these ancient principles, perhaps we can understand the surprising millions of degrees that exists under the earth’s crust?

    We can only hope that true enlightenment eventually comes to the great unwashed…

  4. suyts says:

    Altitude Pressure Temp Density
    sea level 29.92 9.0 100
    2,000 27.82 51.9 94.3
    4,000 25.84 44.7 88.8
    6,000 23.98 37.6 83.6
    8,000 22.22 30.5 78.6
    10,000 20.57 23.3 73.8
    12,000 19.02 16.2 69.3
    14,000 17.57 9.1 65.0
    16,000 16.21 1.9 60.9

    If the formatting holds, this may be helpful to the conversation.

  5. mkelly says:

    STP is standard temperature and pressure. It means that at 1 atm the temperature is 0 C.

    • bubbagyro says:

      National Institute of Standards’ STP is 20°C and 14.7 psi. This standard is more relevant to every day usage in laboratories (It is difficult to weigh every day materials, for example, at 0°C. The IUPAC standard of 0°C and 100 KPa which works better for molecular movement and extreme conditions, like in outer space.

      From Wiki:
      many technical publications (books, journals, advertisements for equipment and machinery) simply state “standard conditions” without specifying them, often leading to confusion and errors. Good practice is to incorporate the reference conditions wherever ambiguity is possible i.e. V(273.15K, 101.325kPa)m3

      • mkelly says:

        What you say is true and there is another called “standard conditions” used in aviation where 59 F and 1 atm (14.7 in)

  6. Hal says:

    Reports like this shouldn’t happen. The lunatic Leftist Media on Mars is failing to do its job.

  7. Phil. says:

    The partial pressure of CO2 on Mars is 14X larger than earth, yet Earth is much warmer. Now use your brain and figure out the connotations.

    Hint : It is the pressure, not the CO2 (stupid)

    You forgot to mention the distance from the sun! Mars is ~2x as far away as Earth so Mars receives 1/4 of the insolation.

    Hint it’s the sunlight, not the pressure (stupid)

    • Oh my Phil, so its the sun, not the CO2 which controls the climate.

    • mkelly says:

      Phil we were not talking about the distance from the Sun, but now that you brought it up you are correct the Sun is what controls the temperature here on Earth, Venus, and Mars. Thanks for the reminder.

    • suyts says:

      uhmm, well, yes and no. Sure the total energy received is less, but, given the properties of CO2, we’d assume Mars would retain significantly more. But here are the more precise numbers.

      Earth 0.9833 – 1.017 1,413 – 1,321
      Mars 1.382 – 1.666 715 – 492

      Distance is in AUs(the distance between earth and the sun.) and energy values are in w/m2 for the isolation.

  8. Andy Weiss says:

    What would Mars’ temperature be if it had the same atmosphere as Venus? Being that much further from the sun, it should be at least somewhat cooler. Would it be warmer than Earth?

    • mkelly says:

      Andy the point was that Venus and Mars both have the same relative per cent of CO2 in there atmosphere. So if CO2 is driving Venus’ atmosphere temperature up than we should see the same thing happen on Mars given its per cent. But we don’t. CO2 does not change its physical capabilities with what planet it is on. So the explanation is the variance in pressure of the atmospheres does explain the difference. Hope that helps.

    • bubbagyro says:

      ppm IS concentration. Let me help you with the words. You mean to say that it is the molar concentration that is important, that is the number of molecules in a given volume of space.

      This is a true point, notwithstanding the fact that the warm-earthers talk in terms of volume % all the time. Overhearing their conversations must be like listening to the caterpillar in Through the Looking Glass. Of course, it is mostly computer code, and little physics.

      However, CO2 saturates at very low molar concentration. This means that its capture efficiency is asymptotic. It has a threshold effect beyond which no more is captured.

      Also, in our atmosphere there is more quenching. Since CO2 is a trace gas, then it competes with many other quenching molecules that “steal” the energy from an excited CO2 molecule so it does not reradiate. On Mars and Venus there is little competition (quenching), since the atmosphere is essentially ALL CO2.

      This is a simplistic analogy that may help or confuse.

  9. bubbagyro says:

    Assuming that the only variable to consider is the insolation, assuming the planets are the same size, then the temperature on Mars should be ¼ Venus’s 1000 °K (ca. 250°K). Many spots on the equator would be a quite cozy at 300°K (although very poisonous).

  10. Andy Weiss says:

    What is 250K or 300K on the F scale?

  11. Chris Colose says:

    The discussion about the % of CO2 in the atmosphere of Mars is pointless, because it is so far in the optically thin limit, as the gaseous denisity is very low. To take an extreme example, imagine a planet with just 1,000,000 molecules of CO2 floating around. This is clearly airless, yet you could still say it is “100% CO2” and be right….yet it would obviously generate no greenhouse effect because the probability of a photon encountering a CO2 molecule would be virtually zero. The other important point is pressure broadening, which makes CO2 a far more important greenhouse gas (so the pressure does matter! Just not because a high pressure must mean a high temperature by the ideal gas law)

    • The density of CO2 on Mars is 14X higher than earth. A photon is much more likely to strike a CO2 molecule on Mars than it is on Earth. Your argument is ridiculous.

      • Phil. says:

        What counts is the chance of being absorbed and its lower on Mars.

        You should learn something about broadening.

        • That is because Earth has water vapor which absorbs almost all of the LW radiation. The chance of a LW photon being absorbed by CO2 on Mars is much larger than Earth, because there is more CO2 on Mars and much less H2O

      • chriscolose says:

        Phil is correct…even if you have more CO2 in a square meter of air on Mars, you need to include the temperature and pressure weighted equivalent paths to make sense of the radiative transfer. Unfortunately, not everything in atmpspheric physics is so easily reducible to a high school equation.

        • The absence of H2O on Mars and the higher abundance of CO2 makes it vastly more likely that a LW photon will be absorbed by a CO2 molecule than on Earth.

          I’ve run all these scenarios through RRTM (the radiative transfer model used by NCAR.)

  12. Luke of the D says:

    I don’t really want to get into this argument, for it is really quite a silly one… do people really think that Venus is hot because of carbon dioxide? I’m no chemist or physicist, but I do remember the formula, PV=nRT… assuming you change the pressure, temperature (or mass “n”) has to go up. But it also works the other way around, increase temperature will increase pressure… logical. But for anyone to think that increasing carbon dioxide will significantly increase temperature is absurd. Venus hot because of pressure (logic, yes Mr. Goddard) and Mars is cold because of lack of pressure (logic again)… forget the carbon dioxide you carbon-worshipers you…

    • UzUrBrain says:

      Doesn’t the fact that Venus is 1/3 the distance closer to the Sun count for anything????? Don’t you get warmer when you stand closer to the campfire??? Isn’t it warmer 6 feet away from the campfire than at 9 feet away from the fire? If you can’t answer these correctly quite arguing about AGW.

      • NThe albedo of Venus is much higher than Earth so the amount of SW radiation below the clouds is similar to Earth.

      • UzUrBrain says:

        And the volcanos on Venus have no effect?
        And the massive fission reactor in the core on Venus has no effect?
        And the much higher core temperature on Venus has no effect? (assuming no massive reactor)
        And the lower magnetic field on Venus has no effect?
        And etc., etc.

  13. Phil. says:

    stevengoddard says:
    April 19, 2011 at 2:16 am
    That is because Earth has water vapor which absorbs almost all of the LW radiation. The chance of a LW photon being absorbed by CO2 on Mars is much larger than Earth, because there is more CO2 on Mars and much less H2O

    No, it has nothing to do with H2O, admit it you really have no idea about the subject.
    The near surface atmosphere on Mars is equivalent to the stratosphere on earth.

    • Phil, you have no idea what you are talking about. There are broad areas of overlap in the spectral bands of H2O and CO2. When all H2O is removed from the atmosphere, the absorption of CO2 goes way up.

    • suyts says:

      Phil, not to pick on you specifically, but to anyone in general……….

      I’m tired of this circular conversation. It embarrasses the U.S. educational system. And I don’t believe it is in the best interest of our people to carry it any more. We’re not going forward in the conversation. So, in the interest in expediency, I’ll offer a challenge.

      As I understand the issue, Steve states that temperatures have a direct relationship with pressure, regardless of the conditions. As I also understand, you and several other learned people contend this is not true.

      This is where learning and understanding take place. The resolution to the question is simple. Show me and anyone else where temperature isn’t related to pressure.

      All other things being equal, other than pressure, where temps are the same, in any condition or any terrestrial body.

      If you cannot, then stfu, you don’t know wtf you’re talking about and Steve is as correct as you are. If you can, then, stfu and just spit it out and we can all move on. Disgust is a word that comes to mind. It turns out I paid for part of your education and you can’t even refute this posit that you’re so adamantly opposed towards? Simpletons.

      • suyts says:

        I worded that improperly.

        When I said, “If you cannot, then stfu, you don’t know wtf you’re talking about and Steve is as correct as you are.”

        It should read, “If you cannot, then stfu, you don’t know wtf you’re talking about and Steve is as more correct than you are.

      • Squidly says:

        well said … I am getting dizzy from all of this. Spin, spin, spin. I am no mathematician, nor am I very good at climate horoscopes, but I easily understood ALL of Steve’s post and it makes perfect sense to me. I personally don’t find this concept so damn difficult to understand, and I am in perfect agreement with what Steve has posted here. He is 100% correct! … this is the sort of thing I have been trying to get at on other posts but get my head beaten in by a bunch of BS spinning from wannabe academic alarmist sh!t heads (aka Chris, et al .. (btw, I am remember many of your other posts on other blogs. I may be getting old and a little slow, but I usually catch on eventually Chris)).

      • suyts says:

        Thanks squidly, but I’m not much. I’m just a guy that sees, just as much as you see. It is our eloquence that fails. The ideal gas law is simple and should be easy to refute. It is the simplicity which is easy to refute, this makes our simple laws, our foundation.

        If a concept runs contrary to our simple laws, then, the burden of proof is upon the people that wish to overturn our simple laws. (This should not be confused with “simpletons”.)

  14. In truth, what should happen is for the “consensus” people to up the ante, and explain exactly how, due to GHGs, the troposphere of Venus and its adiabatic lapse rate are so high as to cause the surface to be as hot as it is.

    Just like Einstein’s theories don’t invalidate Newton’s, just expand to a more general case.

  15. chriscolose says:


    Water vapor has a strong influence on the lapse rate through condensation and the release of latent heat, and the weaker lapse rate explains why the tropopause is higher in the tropics than at the poles. CO2 doesn’t condense on Earth (even if Goddard tells you otherwise, but it does condense on Mars, near the poles so this term becomes very important).

    The only thing Goddard showed in his last post is that if you assume only adiabatic processes to be relevant, then voila, he comes up with an adiabatic lapse rate!– not very impressive. He did this when he set dQ=0. Did anyone else go through his derivation? Of course, radiation is not an adiabatic process, so he assumed that there’s no radiation even before he even began his argument, and then voila, his conclusion is that it’s independent of GHG’s! Miracles do occur. The stratosphere is a good example of what happens when you have a strong solar absorber for instance….you can’t explain the stratospheric inversion through g/cp. Other greenhouse gases have their own profiles of IR heating and cooling, and understanding this structure is of vital importance when doing remote sensing. There’s other influences on the lapse rate for example in the mid-latitudes, where baroclinic waves release significant amounts of energy. Temperature inversions, a key component of severe weather events, are often radiative occurrences. I understand the attractiveness of simplicity, but really guys, all of planetary climate is not reducible to a couple high school algebra equations. There’s a great deal of irony in people who complain about the most sophisticated models in the world run on super-computers but then think pV=nRT explains global energy balance and temperature, and that the whole thermal structure of the atmosphere can be deduced by nothing but a simple equation on a blog.

    If people took my advice and picked up a textbook, there’s several that explain the importance of radiation on the tropopause height, but it’s also the topic of several papers (e.g., Held, 1982; Thuburn and Craig, 1996). It can be rather straight forward to work out that the tropopause height depends on optical thickness, particularly in the Venusian limit. If you guys don’t want to learn this stuff then stop saying it’s wrong. Goddard might be spoon-feeding here but it’s not very good food.

    • thanks Chris. It took a while but we’re finally onto something. So the GH effect plays no role in the troposphere, but determines where the tropopause is and hence has an effect on the surface temperature.

    • Please …. stop …. obfuscating. The amount of water vapor makes little difference until it reaches saturation, and even then the effect isn’t huge.

      Your discussion here is very enlightening. You come across as someone desperately trying to hide the forest behind the trees.

    • suyts says:

      Nice Chris, more baseless assumptions and sweeping generalizations. I wasn’t sure earlier, but it seems clear now, you are indeed, a climatologist.

      You’ve brought nothing to the conversation except insults. Here’s some irony for you….. I didn’t have an opinion on Steve’s and Maurizio’s assertions regarding pressure. It isn’t part of my focus. But given yours and others abject failure in refuting the assertion, but using vehement rhetoric, I see no reason for the dismissal of the claim. (She doth protest too much.)

      All you have to do is show an instance where temps operate independently of pressure. If you can’t, then your objections are noted and filed in the appropriate bin.

      I can’t speak for others here, but the sheepskin on my wall says I have picked up textbooks and do understand complex thoughts. Whereas yours probably says you know how to parrot convention.

      BTW, you’re field is using super computers because your field’s arrogance. Write code in a language current machines were built to understand. When using real data (I know, it is a rare occurrence) put the data in a proper database. You’d be surprised at the increased performance of the machines. If you ladies would hire some real programmers, DBAs and other tech type people, you could probably do your computing on a few workstations.

  16. Phil. says:

    stevengoddard says:
    April 19, 2011 at 6:20 am
    I’ve run the RRTM models for all these cases. In the absence of H2O, CO2 absorption goes way up.

    Your link didn’t show that, and that has no bearing on the fact that the low resolution cartoon you showed is useless for determining overlap.

  17. Phil. says:

    stevengoddard says:
    April 19, 2011 at 12:13 pm
    Yes, compared to Sagan’s claimed 1000%, 50% is not huge. And the point is completely irrelevant because saturated air is obviously not going to happen at high temperatures.

    What high temperatures, we’re talking about Mars and Earth? In any case saturation could occur up to the critical temperature of water (647 K). WTF does Sagan have to do with anything?

    • The reason we are having this discussion is because Sagan claimed hot temperatures on Venus were due to the amount of CO2. Mars has an order of magnitude more CO2 than Earth.

  18. yoki says:

    if you were on earth and 1/8th inch tall what % air pressure would you encounter?

  19. Aagcobb says:

    Water vapor is a greenhouse gas as well, and there is virtually none in the Martian atmosphere.

  20. David H. says:

    So, can this entire article and comment section be summed up like this:

    C02 needs pressure to be highly effective? Because that would be sort of like saying a car needs gas to function effectively – that statement would not negate the utility of gas or a car, it simply shows they are dependent on each other to be effective.

    If this is the summary, then what about earths higher pressure atmosphere? Again, the article and comments would seem to support the idea that C02 could warm earth due to its high pressure atmosphere as is happening in a supercharged fashion on Saturn…

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