A couple of days ago WUWT carried a story, talking about intense cold in Antarctica, carbon dioxide, and the icecap of Mars. This one passage stirred up a significant debate:
According to Weather Underground, Vostok, Antarctica is forecast to reach -113F on Friday. That is four degrees below the freezing point of CO2 and would cause dry (CO2) ice to freeze directly out of the air.
It seemed (at the time) a reasonable statement. The freezing point of CO2 is -109.3 degrees Fahrenheit (-78.5 degrees C). There’s been mentions of this supposed phenomenon of CO2 freezing out of the air before on other blogs and websites. One of the best examples was even an entry in the website “ask a scientist” where the question of CO2 freezing out of the air was posed, and the answer from an Argonne National Laboratory scientist seemed to indicate that CO2 could indeed precipitate as a solid from the air if the temperature was low enough at Earth’s south polar ice cap, specifically at Vostok Station, which holds the record for the lowest surface temperature recorded on Earth at −89.2°C (−128.6°F)
Certainly, at least some of the carbon dioxide in the atmosphere at the poles does freeze out during the winter. However, there is not enough frozen out to accumulate to any extent at the present.
David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory
So, it seemed possible. But as WUWT commenters soon pointed out, temperature is only part of the equation needed to deposit CO2 as a solid from the free atmosphere at that temperature.
Soon we were discussing gas laws, phase diagrams, and partial pressures. The debate mainly centered on whether or not this phase diagram for carbon dioxide applied to 1 atmosphere of pressure of pure CO2 versus simply 1 atmosphere of pressure independent of the purity of the gas.
The author of the post, Steven Goddard wrote in comments:
The phase diagram shows unambiguously that the equilibrium state of CO2 at one atmosphere at 113F is solid. The freezing point of CO2 is -109F at 1 atmosphere.
The PDF referenced doesn’t translate well to the blog size format, but this less detailed phase diagram for CO2 does fit and was mentioned in comments also:
Since many of us know from experience that with ice, be it water ice or CO2 (dry) ice, that a phase change can occur directly from solid to gas (sublimation). It seemed reasonable to conclude that the reverse could be possible, going from a gas to a solid as long as the temperature was below the “triple point” of CO2 as well as the freezing point at 1ATM.
The freezing point/sublimation point of CO2 at 1ATM is at -78.5C (-109.3F). In the situation described in the forecast for Vostok station, the temperature was forecast to reach below the freezing point for CO2 at -80.5 C (-113F ). It seemed reasonable then to concludes that CO2 would freeze right out of the air, much like frost does from water vapor. Plus we had a statement from a scientist at a National Laboratory saying it was possible also. What’s not to like?
One small detail: partial pressure.
The concentration of CO2 in the free atmosphere is very small. Thus the partial pressure of CO2 in the atmosphere is about 0.0004 atmospheres. But wait there’s more. Vostok station is at a high elevation, 3288 meters above sea level (10,787 feet) and the atmosphere is thinner. Thus the partial pressure of CO2 is even lower.
Commenter George E. Smith summed it up pretty well with this paragraph:
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.
Basically, there are so few CO2 molecules in the free atmosphere, sublimation rules over deposition as a solid. Yes some CO2 may deposit on a surface at at -80.5 C (-113F ), but it would quickly sublimate back into the free atmosphere, and thus accumulation would not occur.
Meanwhile WUWT reader Ric Werme had written to Dr. David Cook of Argonne National Lab to ask about his original opinion he wrote for “ask a scientist” web site. Ric reports he responded with this:
Ric,
You are correct. In my attempts at being simplistic I made a mistake in my answer to “Freezing CO2″ on the Ask-A-Scientist page. -57 C is the boiling point of CO2. The freezing point of CO2 at atmospheric pressure is -78.5 C (-109.3 F). If the temperature reaches -113 F at Vostok, Antarctica, some carbon dioxide might freeze out of the air, assuming that the carbon dioxide vapor pressure drops to its saturation vapor pressure.
The vapor pressure must reach the saturation vapor pressure for dew or frost to form. This happens at the dew point or frost point temperature, which is dependent on atmospheric pressure and the absolute amount of vapor in the air. As atmospheric temperature increases, the dew/frost point temperature increases. As atmospheric pressure increases, the vapor pressure increases. At very low temperatures, the dew/frost point temperature is very low.
When the temperature of the surface (whether grass or a car window) is below freezing, frost will usually form instead of dew, although water can be super-cooled and not produce dew, fog, or clouds in some cases. Surfaces on the Earth cool off sooner than the air, so dew/frost will normally form on them before fog (water or ice) forms in the air.
The temperature being at “freezing” or below does not imply that frost will form on surfaces or in the air. The vapor pressure must be high enough (saturation vapor pressure) and the temperature low enough (the frost point temperature) for frost to form.
So it seems, Dr. Cook (and our own Steve Goddard) made the basic and simple error of not taking vapor pressure into account. Given our human experience with the everyday freezing of water, we don’t often think about it. I didn’t catch it either initially, nor did some WUWT commenters.
It does demonstrate though, how little CO2 there is in our atmosphere, we can’t even precipitate it to solid under any natural condition of earth.
But, even with the debate apparently settled, the CO2 freezing question was still all in the realm of opinions and phase diagrams. Some people really wanted to see some empirical proof. Some thoughts on experiments were tossed about.
Enter WUWT reader Dr. Thomas Thatcher of the University of Rochester who had not only an idea for an experiment, but the means with which to carry it out. He had a lab freezer which would “maintains -80˚C (-112˚F) in my lab, and it can be set as low as -86˚C (-122˚F).”.
He proposed that he could use that freezer to do a test with dry ice:
The argument, as far as I can tell, is that at the atmospheric partial pressure of CO2, dry ice at -113F will sublimate faster than it forms (which may be different than how a pure CO2 atmosphere would behave). I am in a position to test this, as described above.
…
Based on the arguments presented here, the two postulated outcomes are,
1) significant loss of mass, as the sublimation rate exceeds the deposition rate
2) no change, or negligible gain in mass.
(I suspect that any gain in mass will evaporate on the short walk from the freezer to the balance.)
It’s admittedly an imperfect experiment. But I expect the outcome will be rather obvious; the dry ice will be gone in the morning. We’ll see.
He conducted his experiment overnight between Thursday and Friday, and writes:
The freezer is a VWR brand ultralow temperature upright freezer, similar to models shown here.
http://www.vwrsp.com/catalog/product/index.cgi?catalog_number=14230-120&inE=1&highlight=14230-120
It is set to -86C, the temperature typically rises 1-3C when opened, and recovers in about 30 minutes. (Factory temperature calibration was NIST-traceable but it has not been recalibrated since it was installed here.) The samples were loaded at 4:30 pm and removed at 9:30 am, so the freezer will have been largely undisturbed during that time.
The interior is mostly filled with stainless steel racks that hold cardboard boxes for storing biological samples. I placed the test samples in two boxes on the bottom shelf at the rear of the freezer, the coldest zone and closest to the temperature probe.
One sample was placed in an open box with extra holes cut to allow air circulation. The other sample was placed in small zip top plastic bag inside a cardboard box. The samples were weighed by difference before being placed in the freezer and after removal in the morning. Additional weighings were taken to estimate the amount of sublimation during the weighing procedure and the amount of water that might condense on the boxes, but these amounts proved insignificant next to the overall results.
The samples were placed in the freezer at 4:30pm (reading -82C) and removed at 10:00am (reading -83C).
Open container, start weight 36.5g dry ice, end weight 0g, amount sublimated 100%.
Zip-top bag, start weight 27.6g dry ice, end weight 25.3g, amount sublimated 8.3%
Proving, I think, that CO2 will freeze and remain frozen at below -78.5C if the partial pressure of CO2 is near 1 ATM, but the CO2 will rapidly sublimate is the partial pressure of CO2 is near atmospheric normal.
And he concludes:
Bottom line, 40g of dry ice placed in an open container at -82C completely sublimated overnight, while 27g of dry ice placed in a zip top bag retained 90% of its mass. This proves two things, first, that the temperature of the freezer did not exceed -78.5C for any appreciable period of time, and second that yes indeed, the partial pressure of CO2 is the key to the problem.
Best of all, he sent photos of the experiment he conducted:
Thanks to everyone who participated in the debate, including Ric Werme for his correspondence help and especially Tom Thatcher for conducting the experiment and taking photos.
We all learned something, we had a little fun, some online yelling occurred, and some egos were bruised. Overall though it was worthwhile that this myth of “CO2 snow at Vostok station” was finally put to rest.
Yeah, hate to say this guys but this is a downer… I have to say that the science on this is fairly established… However I applaud the fact that someone went through the trouble to experiment, simply because science is established does not mean that real world experimentation is not warranted or smiled on when it is done.
Tom Thatcher (13:56:18) :
@ur momisuglypkatt, probably water ice. In our lab we also have large dewars of liquid nitrogen (-196C, I think). When we draw off the liquid nitrogen, frost forms on the steel transfer hose. I would expect that as long as that hose gets below -140C, some of the frost will be CO2. The problem is that most of it will be water ice and it will be difficult to measure the CO2 fraction without special equipment.
Boiling Point of nitrogen @ur momisugly 1 atm: -320.5°F. Definitely could be some frozen CO2 there. We were also taught in the navy that the “water” on the hose was a no-no. It’s actually liquid oxygen (boiling point of -297.3°F). We used the LN2 for freeze seals on pipes that could not be isolated.
Andy
Somewhere way back up in the middle of the 100+ comments, I think it was Anthony who made an oblique reference to comparing the results of cooling water to cooling of CO2, since we are all familiar with dew and frost forming from water as the temperature drops. Recall, if you will, that the dew point is where, sort of by definition, the water vapor content is maximum (100%), and can’t go any higher. Since CO2 content is less than 0.01%, the comparison fails. Frost point comparison suffers the same fate. All just another way of illustrating that the partial pressure is the controlling factor.
What country are you in? My experience in the US is that nothing like what you describe (proper educational system) is taught in our schools any longer. So I take exception to your dismissal of the experiment as unnecessary, since no social science, fine arts or other non-science graduates understand the concept of partial pressure, and as illustrated here, apparently many science graduates missed that lesson also.
Squidly (08:06:36) :
Aughh! Please, not soon. That was rather stressful, especially since I thought we had settled the issue in February. One good thing, this article will be easier to find.
Hmm. Let me save that February link here.
http://wattsupwiththat.com/2009/02/04/snow-job-in-antarctica-digging-out-the-data-source/
KBK (10:00:08) :
> It seems that Dr. Cook still has some misconceptions
Yeah, the first paragraph especially suffers from not realizing how little CO2 we’re talking about. I sent a reply to explain that a bit better (and referred to 140F where I should’ve said -140C) so I didn’t clear things up very well.
If he had participated in the debate here I think he would have worded the first paragraph more clearly, but the big thing is he readily admitted his mistake. Not all scientists in this sordid field would do that.
I figure I can “appeal to authority” and reference his “Ric, You are correct” for all future debates here. 🙂
Here we have an example of real science taking place. Hypotheses were formed; theoretical calculations were made; experiments were devised and executed; reality was better understood; and not one dime of government money was expended! Let’s have more science!
Hu McCulloch on Climate Audit, date December 19 2008.
(It’s so good to see that Climat Audit and WUWT combine and cooperate so well).
57
reply and
paste link Hu McCulloch:
December 19th, 2008 at 7:07 pm
Re Geoff Sherrington, #47,
Is it relevant that a block of dry ice has a surface temperature of -109.3 degrees Fahrenheit (-78.5 degrees C)? (Wiki). Dry ice is solid carbon dioxide.
In the Antarctic, Vostok is recorded a a lowest -129°F (-89°C) on July 21, 1983.
That bothered me too, since it would seem that it would snow CO2 on a cold day in Vostok, perhaps skewing the ice core CO2 readings.
But in fact, the -78.5 °C temperature only applies when the partial pressure of CO2 is 1 atmosphere. When there is only .00028 or .00038 atmosphere of CO2, the freezing temperature is much, much lower.
Jeremy (13:42:45) :
On one hand, I fully agree with you, it is just high school chemistry and physics. Several people posted notes that the answer was in the phase diagram and left shaking their heads at the controversy.
When you get right down to it, Tom’s experiment merely qualitatively verified two points on the phase diagram and that pahse diagram is clearly “settled science.”
On the other hand, the CO2 frost idea is a concept that people had trouble wrapping their heads around. Heck, I had trouble myself in February until I came up with my frost on the windshield analogy, whereupon it became “crystal clear” (sorry).
Ultimately, the debate served as a teaching experience for a diverse audience ranging from people who hadn’t been exposed to all this, people who had but forgotten most of it, several who were quite familiar with it, and a few who should have been but weren’t. More people know about phase diagrams today then they did a week ago. This blog has made the world a better place this week. Cool.
Ric Werme,
Well said. Science is also about teaching. Jack Eddy certainly thought it was a worthwhile part of science. Also our own much loved Leif must feel that it is worth his time to help those of us, like me, who are science-challenged. Thanks to all who through questions, information, explanations, experiments and challenges make this a place of learning and joy.
Mike
I knew that we didnt have CO2 snow at the poles but I didn’t know why so I was looking for phase diagram specifics and even the simple diagram above is just what I needed. Notice at -120 C the pressure can be much lower,(Mars?) and at -150 it can be very low. The shape of the curve down there was important because it explains solid CO2 existing in various places in the solar system and why we see the stuff forming on our liquid Nitrogen lines.
I think what some of the people jumping all over Steve etc. are missing is these examples. I knew that atmospheric pressure affected boiling point but that partial pressure should have been the thing controlling solid-gas equilibrium. But I also knew there were conditions where solid CO2 could form that at first glance are not that wildly different than the Antarctic, but 40 or 50 C is a pretty big difference.
Are phase diagrams based on theory or observation? A telling point may be that the latter is true.
[wry]
It’s quite obvious that Dr. Thomas Thatcher is in the employ of “Big Oil” due to the raw material composition of the plastic bag.
Sorry folks, but the U.N. has plans to stop this sort of science…
Achim Steiner, UN Under-Secretary-General and UN Environment Program Executive Director would now like to have a word with Dr. Thomas Thatcher specifically about his plastic bags. The U.N. of course cannot allow such experiments to be done in the future as that would allow “unfair” competition with computer models.
The U.N. would also argue that such models do not use plastic bags and are thus “environmentally superior.” Oh, also please ignore:
http://wattsupwiththat.com/2009/01/21/meet-deep-black-the-met-office-supercarbon-footprint-climate-computer/#more-5216
[/wry]
@Ric Werme (19:38:46) :
“When you get right down to it, Tom’s experiment merely qualitatively verified two points on the phase diagram and that pahse diagram is clearly “settled science.” “
Ric, you are so right that CO2 “snow” is all in the phase diagram. That level of science is absolutely settled.
That is why I, and the other chemical engineers with whom I work and otherwise associate, know for a fact that there is zero correlation between CO2 in the atmosphere, and global air temperatures.
Just as the CO2 phase diagram is solid science, so too are the principles of cause-and-effect for process control. Engineers take one look at the steadily rising CO2 levels, and the global air temperatures that sometimes rise, sometimes fall, and sometimes stay fairly constant, and know instantly that AGW is all very Bad Science (BS).
What Anthony has shown on WUWT regarding negative water vapor feedback seals the deal.
“crosspatch (15:39:41) :
Atmospheric pressure really isn’t the issue. The issue is how much CO2 is in the atmosphere. An easier way of thinking about it is to pretend that CO2 is water. If we pretend CO2 is water than Earth’s atmosphere is very “dry”. It has extremely little CO2. Mars has a very “wet” atmosphere or a lot of CO2 by proportion to the total gasses.”
Excellent very simple very clear. Thank you
Jari (15:50:44) :
I hope to have definitive answer on that soon. It’s taking a while to get my refrigerator up the side of Mount Everest.
I believe I was the first to suggest an experiment. After about 100 posts of argy bargy which didn’t look like it was going to settle anything.
As the drag racers say ” when the clutch drops, the bs stops”.
I’ll run the results past my software guy tomorrow.
rephelan: please don’t call a troll anyone who doesn’t share your vision! As I said, I was right about the CO2 thing from the beginning, and the link I give to the French site is about the NCEP/NCAR reanalysis which is in my sense a pretty cool global temperature indicator.
About the study linking level of education to climate skepticism, it’s not my fault, I didn’t do the survey myself you know. You also forgot to mention my never-ending references to the Mercer paper of 1978 on antarctic ice shelves :0)
And I also (some time ago) gave rather unknown references to papers showing a direct, satellite-based measurement of the greenhouse effect when a “debate” was raging about the fact it was a “hoax”.
Flanagan,
Let’s cut to the chase, shall we? Do you believe that a rise in CO2 will cause runaway global warming and climate catastrophe? And if so, exactly where do you think this tipping point will occur?
“Are phase diagrams based on theory or observation?” Oh, better yet, they are based on controlled experiments, backed up by well established theory, principally Gibbs’ Phase Rule.
Things happen so fast on this site that most issues are resolved before I think to comment. But I may have something to contribute as follows.
An equilibrium vapour pressure occurs when the condensation rate equals the evaporation rate. If there is insufficient material all of it will evaporate before this pressure, a partial pressure, is reached. The equilibrium points define the lines on the P-T phase diagram. There is no unique condensation point except for the triple point, which is the point where solid, liquid, and gas are in equilibrium. The important relationship for vapour pressure , whether gas-solid or gas-liquid, can be derived from the Clausius-Clapeyron equation as
P = Po exp(-L/RT)
where L is the molar latent heat, R is the gas constant, and Po is a characteristic pressure. This is not an exact relationship but gives you the basic idea of the P-T dependence.
The melting of a solid to liquid is more complicated. There is still a pressure dependence, but it is the pressure exerted on the solid externally.
Boiling is a non-equilibrium phenomenon. Eventually all the liquid will evaporate as the external atmosphere will not be close to the required partial pressure of the vapour concerned.
To understand the dependence on the total atmospheric pressure of all gases, consider the physical process of boiling. Inside the liquid a bubble of gas has nucleated at an impurity, usually at the bottom of the container (pot or beaker). The bubble contains only the vapour of the liquid concerned, but it will only be stable or grow in size if the internal vapour pressure is equal to or greater than the local hydrostatic pressure, which in turn is equal to the total external atmospheric pressure plus the effect of the liquid depth (usually small). This is why the boiling point depends on atmospheric pressure and why quoted condensation temperatures are referenced to one standard atmosphere. The internal, bubble, vapour pressure is still given by the Clausius-Clapeyron equation. There is a similar process for sublimation, but it is easier to describe boiling.
I hope that this is a useful contribution, but if not I had fun writing it. Some what off topic, but it would be nice if you had a printer format option, as some topics deserve to be read at leisure. Cheers.
William:
Simply highlight the text or article of interest, copy and paste to Wordpad or almost any word processing program and print. Read at leisure.
Flanagan (02:58:27) :
“….About the study linking level of education to climate skepticism, it’s not my fault, I didn’t do the survey myself you know….”
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Sheesh. Even when denying you are any kind of a troll, you still can’t resist indulging in trollish behavior. Your statement above certainly implies that the paper I referred to
How Citizens Integrate Information without Ideological Cues: Local Weather and Americans’ Beliefs about Global Warming by Patrick J. Egan and Megan Mullin
Said what you claimed for it. Let’s check the record. On April 30th in the Mad Dogs and Englishmen thread you wrote:
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Flanagan (14:08:29) :
By the way, another intersting study
http://politics.as.nyu.edu/docs/IO/4819/egan_mullin.pdf
people tend to belief in global warming as a function of their local temperature. In cold and temperate places, those supporting global waming are the ones with the highest level of education, whose opinion is relatively constant whatever the local temperatures.
I made some snarkish comment about getting some integrity and your defender Tom P challenged me on that. I then submitted on May 2 a more detailed response, as follows:
Tom P (02:40:34) :
rephelan,
I don’t know why you are questioning Flanagan’s integrity. The lower plot of figure 6 in the Egan and Mullin paper shows precisely what he states:
“…people tend to belief in global warming as a function of their local temperature. In cold and temperate places, those supporting global waming are the ones with the highest level of education, whose opinion is relatively constant whatever the local temperatures.”
Perhaps I was too hasty in criticizing Flanagan’s integrity. There is an equal probability that neither you nor Flanagan can interpret a graph. The paper itself was concerned with the influence of non-ideological information on perceptions of global warming. The non-ideological information in question was the local weather. The chart referenced showed that the weather, either hotter or colder, had almost no effect on changing the perceptions of the more educated and had the greatest effect on changing the perceptions of the least educated. The chart does NOT show that more educated people believe in global warming and less educated do not. The authors own legend for that graph should have given you a clue:
“Figures show predicted probabilities of agreeing there is evidence for global warming when local temperature is much hotter than normal (at the 95th percentile, or 14.7°F above normal) and much cooler than normal (at the 5th percentile, 4.3°F below normal).”
The conclusion of the paper, as presented in the abstract, was:
“Our results suggest that when politically relevant information is conveyed without ideological cues, political sophistication may prohibit the integration of this information into political beliefs regardless of the direction of one’s predispositions. “
The bottom line is that whether you are an alarmist or denialist, political sophistication (defined by the authors as either high education or ideological commitment to a party) tends to leave your position on AGW unmoved in the face of your perception of the weather.
Whether Flanagan has an integrity issue or literacy issue, neither choice looks particularly good for Flanagan….
===============================================
Neither you nor Tom P followed up on that and today you are still implying that your interpretation of the paper was correct. You are a troll not because you disagree with me, rather you are a troll because your presentations are dishonest. I can’t speak to anything you may have gotten correct or were accurate about because I simply haven’t seen them. I for one, will not be bothering to check out anything you suggest. Your credibility is nil.
Paul Coppin (04:47:36) : “Now, I’ve never bothered to pursue this, but my chem profs back in the ’60s used to insist that water never sublimated. That while vapour production looked like sublimation, there was actually a 3 point phase change from ice >water>vapor, and there wasn’t in fact a true two-point change to gaseous phase directly from solid state. Maybe some active physical chemists can update me.”
I used to live in Denver. Some mornings, all the accumulated snow would suddenly be gone, even though the temperatures had been below 32°F overnight. I always assumed the snöw had sublimated. Hmm. Maybe not. Any opinions based on theory?
Smokey: sorry, but this is not the topic at all… I wouldn’t like to be accused of trolling!
rephelan: though you are also widely digressing I thought I could simply copy and paste the rest of the sentence you mention from the abstract:
“In this study, we identify one piece of information that is devoid of ideological content and to which Americans are exposed at random—their local weather—and show that it leads a significant share of the public to reassess its beliefs about the evidence for global warming. This effect is much stronger for the less educated and those with weak partisan ties, and virtually non‐existent for the most educated and most partisan citizens.”
and further in the text (yes, usually people read the entire text)
“By matching geocoded survey data to local weather records, we find a significant relationship between local weather and beliefs about global warming.”
“Is there solid evidence that the average temperature on earth has been getting warmer over the past few decades, or not?” Americans’ responses to this question were largely in the affirmative: […] 74% of respondents agreed that the earth is getting warmer.”
which, combined with
“Local weather affects those with the least education significantly but those with the most education not at all”
and the result of Figure 5b showing that 0% of post-graduate people are influenced by the local weather leads to, in any sense, self-evident conclusions.
Flanagan,
You seem to be missing rephelan’s point. He agrees the article was linking lack of education with the influence weather has on people’s perceptions. What he doesn’t agree with is your original comment that people with lower education seem to be skeptics.
Indeed, based on your premise, I guess we can conclude something about Al Gore and his gang opening the windows to let in the heat during Hansen’s famous 1988 testimony.
Who were the “lower educated” that Gore and his cronies were trying to influence?