Antarctica Gets Cold Enough To Freeze CO2

Last year, Antarctica reached -135ºF, which is 27ºF below the freezing point of CO2 at atmospheric pressure. This is cold enough to freeze CO2 right out of the air.

There has been some long standing confusion about this because we do not find dry ice in Antarctica, except in their ice-cream machine.

There are different concepts which people confuse related to the partial pressure of a gas. Consider water vapor. Temperatures can drop below freezing, without frost accumulating on your windshield. This is because the number of molecules sublimating is equal to the number of molecules freezing. Until the temperature drops below the dew point or frost point, ice will not accumulate. The dew point/frost point is a function of the partial pressure of water, which is also a function of the humidity.  The humidity has almost no effect on the freezing point.

Put in simple terms, ice does not accumulate at temperatures above its dew/frost point, because it is evaporating just as fast as it is freezing. When the temperature drops below the dew/frost point, more molecules are freezing than are sublimating.

The same thing is true with CO2. At 0.0004 mole fraction of the atmosphere, CO2 has a very low partial pressure, so it won’t accumulate at -135ºF. That doesn’t mean that CO2 molecules aren’t freezing – it simply means that they are sublimating at the same rate as they are freezing, so there is no net buildup.

Partial pressure is a statistical measure which has no meaning to the behavior of any individual molecule. It does affect the numbers of molecules which are freezing. It doesn’t affect the freezing point.


About stevengoddard

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18 Responses to Antarctica Gets Cold Enough To Freeze CO2

  1. GW says:

    I thought Antarctica could only get that cold during the Southern winter, i.e. June-September. Or is this higher in the atmosphere and not at the surface ?

  2. squid2112 says:

    At 14-15 micron wavelength, that at which CO2 supposedly “back radiates” and re-heats the Earth, the temperature is -80C. So, if so-called “back radiation” from CO2 could do any possible heating, it would be only in Antarctica at locations where the surface temperature was below -80C.

    • Morgan says:

      We have been through this 100 times. All matter above absolute zero radiates. A colder object doesn’t warm a warm object, but it slows the loss of heat from it, compared to an absolute zero object. Your blanket is 70 degrees. You are 98.6 degrees. How can a 70 degree object possibly heat a 98.6 degree object?

      A colder object (the sky) doesn’t warm a warm object (earth), but it slows the loss of heat from it, compared to an absolute zero object (space).

      I’m sure you still don’t get it.

  3. Scott says:

    I didn’t know that the coldest spots on earth get below the freezing point of CO2. I guess CO2 forms the ice caps on Mars since its atmosphere is 95% CO2… a higher partial pressure.

    • The density of CO2 in Mars atmosphere is about 14X higher than on earth, so yes you are correct.

    • Morgan says:

      The temperature at the poles on Mars is so low that there is very little sublimation in the winter, but there is in the summer. Mars’ axis tips like earth’s, so when the north pole tips towards the sun, all the CO2 sublimates and moves to the south pole, where it snows CO2. The partial pressure is the same all around Mars, and both poles are below the freezing point, but one pole is colder and too cold to sublimate as fast as it freezes.

  4. R2Dtoo says:

    ?? Could this explain the low CO2 coming out of the last ice ages??

    • Gail Combs says:

      The low CO2 coming out of RECENT ice core testing is an artifact of the test method, the CO2’s diffusion through ice and politics.

      Of special interest: “…before 1985, the ice cores were showing values much higher than the current atmospheric concentrations (Jaworowski et al. 1992b).”

      The ice core data from the Taylor Dome, Antarctica, which are used to reconstruct the IPCC’s official historical record, feature an almost completely flat time trend and range, 260 to 264 ppmv (Indermuhle et al. 1999). On the other hand, fossil leaf stomata indices2 show CO2 concentrations ranging widely by more than 50 ppmv, between 270 and 326 ppmv ( Wagner et al. 2002). This difference strongly suggests that ice cores are not a proper matrix for reconstruction of the chemical composition of the ancient atmosphere.

      The CO2 ice core data are artifacts caused by processes in the ice sheets and in the ice cores, and have concentration values about 30 to 50% lower than in the original atmosphere. Ice is an improper matrix for such chemical studies, and even the most excellent analytical methods cannot be of help when the matrix and samples are wrong.

      Before basic research on gas differentiation was even started, a plethora of glacier studies on temporal trends of greenhouse gases had been published during past decades, aiming to demonstrate that: 1) these gases are responsible for climatic changes, and 2) that their level in the atmosphere was increased by human activity. These studies are beset with a unilateral interpretation and manipulation of data, and with an arbitrary rejection of both the high greenhouse gas readings from the pre-industrial ice, and the low readings from the contemporary samples (Jaworowski 1994a, Jaworowski et al. 1992b).

      Were the CO2 ice core data and their interpretation correct, then they should be treated as evidence that during the past 650,000 years, CO2 had no discernible effect on the global temperature.….

      Click to access zjmar07.pdf

      For the nitty gritty on whys and wherefores of the testing procedures read page 4 The Truth About Ice Cores

      • Gail Combs says:

        I should note “gas differentiation” is well known to chemists. It is the basis for gas chromatography. A similar method of separation of mixtures is called liquid chromatography so none of this was unknown territory. Both methods were being taught in University in the late 1960s

      • Dmh says:

        I believe the truth about CO2 levels and sea level rise will be the last to be revealed after the great AGW scam finally ends.
        The present data seems completely corrupted and meaningless in both cases.

  5. tom0mason says:

    Thank-you Steven.
    Science that can not explain itself, within the parameters of the known universe, is not science.

    • tom0mason says:

      Of course the ‘known universe’ falls within what Richard Feynman speculated on what it is to ‘know’.

      “We cannot define anything precisely.
      If we attempt to, we get into that paralysis of thought that comes to philosophers, who sit opposite each other, one saying to the other,
      “You don’t know what you are talking about!”.
      The second one says,
      “What do you mean by know?
      What do you mean by talking?
      What do you mean by you?””

  6. geran says:

    Thanks for the very good review of “partial pressure”.

    (Old chemistry humor: “If you’re not part of the solution, you’re part of the precipitate.”)

  7. Truthseeker says:

    Gee Steve, when you actually decide to more than a few words together in the one post, you can be remarkably coherent …

    Even I understood this one.

  8. Andy says:

    So you admit you were wrong in the below?

    I still think your use of the words ” freeze right out of the air” is misleading though, it gives the impression of CO2 snow which rapidly sublimates. In fact you do not get any snow at all, never mind an accumalation.


  9. Ric Werme says:

    When I go out to my car on a cold January morning with the temperature well below freezing and find that there is no frost on my car’s windshield, I never think to myself that “Wow, water is freezing right out of the air,” I think to myself, “Yep, we didn’t get down to the dew point last night.”

    What’s the minimum number of molecules needed to call something a solid? Or a crystal? For water, six might be a good number. I suspect on those dry mornings, I don’t get clusters of six water molecules.

    If you want to say we do, go right ahead, but please make it clear not many people are on that bandwagon.

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