UPDATE2: The question has been resolved, please see this new WUWT story on the issue. – Anthony
UPDATE: There is a debate raging in comments about the validity of the statement “That is four degrees below the freezing point of CO2 and would cause dry (CO2) ice to freeze directly out of the air.”
On one hand we have an argument from several commenters that says that the temperatures, pressures, and phase diagrams only apply to a pure state of CO2, such as in the manufacture of dry ice.
“Certainly, at least some of the CO2 in the atmosphere at the poles does freeze out (of the air) during the winter.”
So there appears to be a debate. If it turns out the statement is wrong, and some empirical proof can be presented, I’ll retract and/or amend the article. There appears to be a wide interest in this question, so I’m not opposed to find the true answer, even if it means the statement is entirely wrong.
Feel free to post in comments, but leave the snark and ad hom out of it. I’m more interested in settling the question.
I’ve also changed the title to be more reflective of the question before us now. – Anthony
By Steven Goddard
The south pole of Mars (seen below) similarly has an eight metre thick layer of dry (CO2) ice on top of the H2O ice.
Mars, too, appears to be enjoying more mild and balmy temperatures. In 2005 data from NASA’s Mars Global Surveyor and Odyssey missions revealed that the carbon dioxide “ice caps” near Mars’s south pole had been diminishing for three summers in a row. Habibullo Abdussamatov, head of space research at St. Petersburg’s Pulkovo Astronomical Observatory in Russia, says the Mars data is evidence that the current global warming on Earth is being caused by changes in the sun. “The long-term increase in solar irradiance is heating both Earth and Mars,” he said.
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Adam from Kansas (10:33:04) :
Is there any legitimacy in this?
…
They seem to be forecasting a heatwave …
They were produced by the Center for Ocean-Land-Atmosphere Studies (COLA). “COLA and IGES make no guarantees about and bear no responsibility or liability concerning the accuracy or timeliness of the images being published on these web pages. … These products are not a substitute for official forecasts and are not guaranteed to be complete or timely.”
The President of COLA is Jagadish Shukla, who among other things was Lead Author (2007), Intergovernmental Panel on Climate Change (IPCC). I believe he’d be predicting a heatwave if the daily high in Panama City was -10C in the middle of August.
To answer your question, I doubt they’re worth the electrons it takes to transmit and render them.
[ital]
Good luck finding it, CO2 doesn’t have a freezing point at a pressure below 5.11 atm![/ital]
Sorry, Phil, this is just bogus. You can get a gas cylinder of compressed (liquid) CO2 with a dip tube and spray the CO2 into a closed box. Some of the CO2 will vaporize, the resulting heat of vaporization draws heat out of the CO2 so some of it will freeze solid in the box. I’ve used this method to make dry ice many times. It’s not as dense or as long-lasting as commercial dry ice pellets, but it’s more economical in a small scale lab where you only need small amounts of dry ice occasionally. It may be colder than -113F, but I assure you this occurs at normal seal level atmospheric pressure.
Sorry I can’t find a link to the actual supplier of the equipment.
REPLY: That is true for pure CO2, which is what you were working with. The question revolves around CO2 in trace gas amounts in the free atmosphere – Anthony
REPLY: Maybe so, but for us that don’t deal with the subject every day, could you provide a link or citation for “CO2 doesn’t have a freezing point at a pressure below 5.11 atm”. I’ve looked for references about CO2 freezing point and pressure, and so far have found none. I’ll be away for a bit, so take your time. – Anthony
I don’t think Phil understands the phase diagram. From the Wikipedia article on dry ice,
In 1835 the French chemist Charles Thilorier published the first account of dry ice.[3][4] upon opening the lid of a large cylinder containing liquid carbon dioxide, he noted much of the carbon dioxide rapidly evaporated leaving solid dry ice in the container.
I’m prepared to believe that the behavior of trace amounts of CO2 in air is different than that of pure CO2, just as the behavior of trace amounts of water vapor in air is different than that of pure water. But Phil, even if you were 100% right your behavior is appalling, and you are not 100% right. I wonder what university you are affiliated with.
The triple point temperature of carbon dioxide is 216.55 kelvins (-56.6 C or -69.88 F). This is the lowest temperature for which a transition between the liquid and solid state is definable (freeze/melt). I.e., there is no lower temperature for a “freezing point.”
The triple point pressure is also approximately 5 atmospheres, which means that liquid/solid state transitions cannot occur below that pressure. This is why liquid carbon dioxide is always under pressure, and why it forms dry ice “snow” when allowed to expand to ambient pressure (CO2 transitions to lower pressure at same temperature; expansion process chills the CO2, but it can only deposit as solid crystals due to the “low pressure” environment).
Ref. entries in Wikipedia for “Carbon Dioxide” and “Triple Point.”
Sorry if I’ve covered ground redundantly; can’t take the time to review the entire discussion.
In my misspent youth, I was a Cryogenics Cargo Engineer on a couple of 125,000 cubic meter LNG tankers. We carried about 125,000 cubic meters of Liquefied Natural Gas cooled to minus 158-160 C. It was my job to maintain/operate the cargo handling equipment. I was on several runs back then: from Algeria to the East Coast of the United States, later between either Sumatra or Borneo to Japan.
http://en.wikipedia.org/wiki/LNG_carrier
If anyone cares, one load port is at Bontang, Borneo. It is on the east coast, eight miles north of the equator. Google Earth shows a tanker similar to the one that I was one with five spherical cargo tanks. (It is in the harbor at the end of a long pier-it “crosses the “T”.)
The tanks I am familiar with were some 33 meters in diameter and made of aluminum (aluminum doesn’t display a non-ductility transition at low temperatures as does carbon steel).
The loading/discharge piping was not insulated so the surface temperature of the lines dropped to near the temperature of the cargo during the times we were loading or discharging.
Finally to the point:
When we disconnected the pipe lines, we had to remove the ice before un-bolting the joints. At that time, the solid CO2 and mixed with the water ice would crack and pop on the deck, especially if it had been raining.
So……
Yes, I know from personal experience that CO2 will condense out of the atmosphere. I don’t know from that experience the temperature at which it first starts to condense.
Regards,
Steamboat Jack
Are my posts getting through?
Based on my mental model of what happens to gas molecules under pressure, I would think the pressure of the mixture of gases would be what applies in these phase diagrams. It’s also quite possible that it is neither partial pressure nor mixed gas pressure but something intermediate. I seem to remember a college chemistry lab that involved determining the eutectic point of a solution of waxes. This brings up the next question: is a mixture of gases a solution or just a mixture?
Richard Alley in his book “The Two Mile Time Machine” describes ice popping and snapping after deep samples are relieved of pressure on them. ( see page 49 and 50 of the preview at http://press.princeton.edu/titles/6916.html ). I always wondered if he was entirely correct about that since we’ve all heard ice cubes crack when making cocktails. I also wondered if he handled the cracking of the ice in the best possible way. It occurred to me that letting the cracking process occur could change the data being collected, and there was no mention of trying to contain, collect and analyze anything coming out.
Being a skeptic has natural advantages. All you really need to demonstrate is that the other guy is ignorant and hasn’t imagined all possibilities.
I am puzzled and entertained by people who have convinced themselves that a compound can drop below it’s freezing point and not tend to freeze. The freezing point of CO2 at 1atm is -109F.
Sublimation equilibrium between gas and solid involves complex interactions such as surface roughness, atmospheric turbulence, radiation balance, surface chemistry, other boundary layer conditions, etc. Who cares?
The point is that Antarctica is freaking cold, and that if Abdussamatov is correct, Mars’ polar ice caps should either be growing or have slowed down their wasting. Why do people get distracted so easily?
wattsupwiththat (11:29:55) :
I believe he’s wrong. I likely won’t have time tonight to find his Email address and send him my frost-on-the-windshield analogy, along with the more basic physics description in the old thread but I’ll see what I can do.
“So is the Argonne National Lab Scientist wrong?
Yes!
This is basic physical chemistry and shouldn’t be a matter for discussion.”
LMFAO!!!
Phil., bud, between an anonymous poster and an Argonne National Labs scientist, I think I’ll go with the ANL scientist.
Unless you drop you anonymity and tell us who you really are and why we should listen to you…you know, put your credentials out there for all to see…
Again, the phase diagrams are for atmospheric pressure – not for partial pressure of the compound. For example, the boiling point of water is a function of atmospheric pressure – it is not a function of humidity. Water boils at the same temperature in the desert and jungle.
My two cents:
One needs to look at physical chemistry books, specifically chapters on surface science (adsorption, BET theory, etc.). The answer lies there (I’m too lazy to find my old notes).
I would expect CO2 to sublime onto cold surfaces that are at temperatures less than -78.5 C (or whatever the sublimation temp for CO2 is at 1 atm). Eventually you will have CO2 molecules adsorbed on top of other CO2 molecules. At that point, local CO2 concentration is 100% (i.e., vapor concentration of CO2 is not relevant assuming it is not depleted).
This is basic physical chemistry and shouldn’t be a matter for discussion.
REPLY: Maybe so, but for us that don’t deal with the subject every day, could you provide a link or citation for “CO2 doesn’t have a freezing point at a pressure below 5.11 atm”. I’ve looked for references about CO2 freezing point and pressure, and so far have found none. I’ll be away for a bit, so take your time. – Anthony
It’s there on the phase diagram, liquid CO2 doesn’t exist at pressures below the triple point, which is at 5.11 atm. Since freezing is the transition between the liquid and solid state it can only occur at pressures above 5.11 atm. Below the triple point the only phase change that is possible is between solid and gas, sublimation/deposition.
http://scifun.chem.wisc.edu/chemweek/CO2/CO2_phase_diagram.gif
Note on this phase diagram that the equilibrium point on the sublimation line is about -120ºC for 0.01atm of CO2 which is about the Martian CO2 level and way above the Earth’s. The Earth’s atmospheric partial pressure of CO2 is around 0.3 torr which is off the scale of that chart but corresponds to a temperature of at least -140ºC.
You’ll find a discussion of phase diagrams at the site below where the specific issues re CO2 are given at the bottom of the page, in particular:
“The only thing special about this phase diagram is the position of the triple point which is well above atmospheric pressure. It is impossible to get any liquid carbon dioxide at pressures less than 5.11 atmospheres.”
http://www.chemguide.co.uk/physical/phaseeqia/phasediags.html
Phil you may want to shelve your indignation and simply explain what you think is correct please. Many of the people above who claim Steve is wrong propose things they are sure are correct that if true would make it IMPOSSIBLE for Mars to have any polar cap. It’s still there.
According to you there is no such thing as Solid CO2in comets either? Maybe you should re-think.
Now for the hard question, Phil. Is CO2 gonna getcha?
In other words, will CO2 cause runaway global warming and climate catastrophe? Because that is the central question, isn’t it?
Take your time.
Steven Goddard (11:09:27) :
The relative humidity in Antarctica ranges from near 0 to 100%, the high end is readily shown by clouds and snowfall, which occur in regions of 100% relative humidity. When the humidity is below 100% and the ground is about the same temperature as the air, then sublimation occurs, but at Antarctic temperatures the process is quite slow. Similarly, I can see differences during the New Hampshire winter when the air temperature is cold (0°F, ~-22°C) vs. when it’s warm but still it and objects are below freezing.
I track snow depth at home and elsewhere around New England, see http://wermenh.com/sdd/index.html , and I believe I can show some stretches of dry weather where snow depth declines faster at those warmer temperatures than the near 0°F stretches. However, some of that may be due to snow being more malleable at the warmer temperatures, and I don’t have good data to show changes due to settling vs sublimation. (However – the mechanism behind snow settling involves sublimation of and condensation of snow flakes into larger “corn snow” particles, and that does involve the effects at hand!)
The rings of Saturn are predominently ice particles, the temperatures there are so cold and the vapor pressure of ice so low that sublimation is extremely slow.
There are parts of Antarctica that are ice free, obviously Vostok is not one of them. In fact I can confidently predict that Vostok has more annual snowfall than they do sublimation. Perhaps a reader has time to verify that it does snow at Vostok and report on the typical range of annual snowfall there.
Mars does have CO2 ice in its ice caps, but I’m confident that Mars is colder than Antarctica and that it is cold enough to not sustain the partial pressure of CO2 and the vapor has to condense. Off hand I don’t know that data from Mars either. Gentle readers – help?
I don’t know. I’m disappointed you didn’t consider my frost on the windscreen analogy. I thought is was a very good way to compare an alien environment with something more familiar. BTW, for people who don’t experience freezing temperatures frequently, it works with dew also – natural dew is water the condenses at temperatures well below the boiling point. On mornings without dew, it doesn’t mean that the air is completely dry, it means merely that the ground didn’t cool below the dew point and water remained as vapor even though the air temperature was below boiling.
Now please, are you actually making a debate out of this? Maybe we could discuss also for hours whether 1+1=2?
It’s so obvious that the CO2 pressure will affect the deposition temperature I don’t really know how to say it in another way. Maybe this one: CO2 will deposit at -70 degrees whatever the CO2 pressure, in your opinion. It would all depend on the global pressure… So if one has an atmosphere with no CO2 at all, following these arguments, it should solidify anyway at -70? No molecule, but deposition? Mmmmm….
REPLY: The purpose here is to find out the true answer, we have authoritative answers from both sides. Drop the snark or find another blog to bother. – Anthony
Flanagan,
CO2 pressure affects the deposition rate. If the CO2 pressure is zero, then the rate is zero.
Hope this helps.
[Apologies in advance, but please don’t snip – Ric]
Yeah, Phil, do that. Then Steve might treat you with the same respect he treats me.
REPLY: And “what is good for the goose is good for the gander”, so it applies to everyone. Stop labeling, drop the snark. I get tired of these issues, especially from the anonymous ones. – Anthony
Really, Steven, this is basic thermodynamics. I’ve been teaching this subject for years now and, truly, there’s no other possibility here. If pp0, deposition takes place.
I think you actually confound sublimation and deposition with the solid-gas equilibrium, where the rates of these processes exactly cancel each other.
MattN (13:08:38) :
“So is the Argonne National Lab Scientist wrong?
Yes!
This is basic physical chemistry and shouldn’t be a matter for discussion.”
LMFAO!!!
Phil., bud, between an anonymous poster and an Argonne National Labs scientist, I think I’ll go with the ANL scientist.
Unless you drop you anonymity and tell us who you really are and why we should listen to you…you know, put your credentials out there for all to see…
Appeal to authority is not a part of science the truth can be found in the merits of the argument on this issue I’m right and the ANL scientist is wrong or possibly misquoted.
Steven Goddard (13:14:33) :
Again, the phase diagrams are for atmospheric pressure – not for partial pressure of the compound.
Tor the umpteenth time no!
For example, the boiling point of water is a function of atmospheric pressure – it is not a function of humidity.
Of course it’s a function of atmospheric pressure, by definition it is the temperature at which the vapor pressure is equal to the applied pressure.
The boiling point can be found from the phase diagram by finding the intersection of the applied pressure and the liquid/vapor line, you’ll find an illustration on the following site under the heading of ‘normal boiling point’.
Similarly the sublimation point is the temperature of solid CO2 at which its vapor pressure is equal to the applied pressure and can be found from the phase diagram by the intersection of the applied pressure and the solid/gas line. If you want to find the temperature at which solid CO2 will deposit from the atmosphere you look for the intersection of the CO2 partial pressure with the solid/gas line, i.e. less than -140ºC. (Just like the ‘frost point’ for water).
http://www.chemguide.co.uk/physical/phaseeqia/phasediags.html
Water boils at the same temperature in the desert and jungle.
Let’s change the subject. What’s the difference between hoar frost and snow? ;~P
REPLY: No let’s not. – Anthony
On the phase diagrams the pressure is atmospheric which is going to be somewhere in the area of one atmosphere in the Antarctic. (and is of course somewhat variable)
I have no idea how a value of 0.3 torr has anything to do with the phase diagrams for natural conditions on Earth. Please explain.
The triple point of CO2 is -56.6 deg C at a pressure of 5.11 atmospheres; that’s 3883.6 mm Hg pressure.
Below that temperature, liquid CO2 canot exist. At zero degree C you can liquify CO2 at a pressure of about 15-20 atmospheres, and solidify it at about 1000 atmospheres.
Below 56.6 deg C, solid CO2 and vapor CO2 can coexist in dynamic equilibrium. Meaning that CO2 molecules with higher than average kinetic energy escape from the surface into the vapor; while CO2 molecules from the vapor can collide with the surface and adhere; so there is a continuous sublimation/deposition process going on.
At -78.5 deg C (-109F), that equilibrium occurs at a partial pressure of CO2 of 760 mm Hg, one atmosphere. Below that pressure, there isn’t enough abundance of CO2 molecules in the vapor phase for collisions with the solid surface to occur at a fast enough rate to make up for the ones that escaped; so the solid CO2; dry ice, will continue to sublimate.
This will do two things; it will increase the CO2 in the vapor phase, and thereby increase the rate of collisions with the solid surface. Secondly the loss of dry ice will reduce the surface of the dry ice, so it will reduce the total number of CO2 molecules leaving the solid.
So the solid continues to shrink; while the vapor CO2 continues to increase (assuming a closed volume). So the sublimation rate steadily declines, while the deposition rate steadily increases. Notice that the surface area reduction also affects the deposition rate, but since the CO2 vapor pressure keeps rising, the collision rate per unit sirface area will increase, so the deposition rate increaes while the sublimation rate declines (remains constant per unit area).
Eventually with a small enough amount of dry ice, and a larger vapor abundance of CO2, the rates equalize, and a stable balance between the solid, and the vapor will persist.
In the case of the Antarctic plateau, the CO2 vapor pressure stays about constant at around 0.447 mm Hg, and that is not enough to stop continued sublimation till the temperature is about -140 deg C.
So any remaining amount of CO2 ice would be very hard to locate at -113 deg C.
REPLY: Well said, and without labeling anyone, insults, or snark being tossed. Phil. could learn a few things from you. BTW I think you meant -113 and -140 deg F – Anthony
Wondering Aloud (13:24:00) :
Phil you may want to shelve your indignation and simply explain what you think is correct please. Many of the people above who claim Steve is wrong propose things they are sure are correct that if true would make it IMPOSSIBLE for Mars to have any polar cap. It’s still there.
I’ve explained above why Mars has CO2 ice-caps, the vapor pressure of CO2 in the Martian atmosphere, ~7torr, is above the equilibrium sublimation line at the temperatures existing at the poles, about -120ºC, so it can deposit there, if the temperature increases it will sublime.
According to you there is no such thing as Solid CO2in comets either? Maybe you should re-think.
Who mentioned comets?