Press Release: Landsat 8 helps unveil the coldest place on Earth
SAN FRANCISCO, CA—Scientists recently recorded the lowest temperatures on Earth at a desolate and remote ice plateau in East Antarctica, trumping a record set in 1983 and uncovering a new puzzle about the ice-covered continent.
Ted Scambos, lead scientist at the National Snow and Ice Data Center (NSIDC), and his team found temperatures from −92 to −94 degrees Celsius (−134 to −137 degrees Fahrenheit) in a 1,000-kilometer long swath on the highest section of the East Antarctic ice divide.
The measurements were made between 2003 and 2013 by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on board NASA’s Aqua satellite and during the 2013 Southern Hemisphere winter by Landsat 8, a new satellite launched early this year by NASA and the U.S. Geological Survey.
“I’ve never been in conditions that cold and I hope I never am,” Scambos said. “I am told that every breath is painful and you have to be extremely careful not to freeze part of your throat or lungs when inhaling.”
The record temperatures are several degrees colder than the previous record of −89.2 degrees Celsius (−128.6 degrees Fahrenheit) measured on July 21, 1983 at the Vostok Research Station in East Antarctica. They are far colder than the lowest recorded temperature in the United States, measured at −62 degrees Celsius (−79.6 degrees Fahrenheit) in Alaska, in northern Asia at -68 degrees Celsius (−90.4 degrees Fahrenheit), or even at the summit of the Greenland Ice Sheet at -75 degrees Celsius (−103 degrees Fahrenheit).
Scambos said the record temperatures were found in several 5 by 10 kilometer (3 by 6 mile) pockets where the topography forms small hollows of a few meters deep (2 to 4 meters, or 6 to 13 feet). These hollows are present just off the ice ridge that runs between Dome Argus and Dome Fuji—the ice dome summits of the East Antarctic Ice Sheet. Antarctic bases sit on each of the sites and are generally not occupied during Antarctic winters.
Under clear winter skies in these areas, cold air forms near the snow surface. Because the cold air is denser than the air above it, it begins to move downhill. The air collects in the nearby hollows and chills still further, if conditions are favorable.
“The record-breaking conditions seem to happen when a wind pattern or an atmospheric pressure gradient tries to move the air back uphill, pushing against the air that was sliding down,” Scambos said. “This allows the air in the low hollows to remain there longer and cool even further under the clear, extremely dry sky conditions,” Scambos said. “When the cold air lingers in these pockets it reaches ultra-low temperatures.”
“Any gardener knows that clear skies and dry air in spring or winter lead to the coldest temperatures at night,” Scambos said. “The thing is, here in the United States and most of Canada, we don’t get a night that lasts three or four or six months long for things to really chill down under extended clear sky conditions.”
Centuries-old ice cracks
Scambos and his team spotted the record low temperatures while working on a related study on unusual cracks on East Antarctica’s ice surface that he suspects are several hundred years old.
“The cracks are probably thermal cracks—the temperature gets so low in winter that the upper layer of the snow actually shrinks to the point that the surface cracks in order to accommodate the cold and the reduction in volume,” Scambos said. “That led us to wonder what the temperature range was. So, we started hunting for the coldest places using data from three satellite sensors.”
More than 30 years of data from the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA Polar Orbiting Environmental Satellite (POES) series gave Scambos a good perspective on what the pattern of low temperatures looked like across Antarctica.
“Landsat 8 is still a new sensor, but preliminary work shows its ability to map the cold pockets in detail,” Scambos said. “It’s showing how even small hummocks stick up through the cold air.”
Scambos suspected they would find one area that got extremely cold. Instead they found a large strip at high altitude where several spots regularly reach record low temperatures. Furthermore, dozens of these extremely cold areas reached about the same minimum temperatures of −92 to −94 degrees Celsius (−134 to −137 degrees Fahrenheit) on most years.
“This is like saying that on the coldest day of the year a whole strip of land from International Falls, Minnesota to Duluth, Minnesota to Great Falls, Montana reached the exact same temperature, and more than once,” Scambos said. “And that’s a little odd.”
—Credit: Ted Scambos, National Snow and Ice Data Center
The scientists suspect that a layer in the atmosphere above the ice plateau reaches a certain minimum temperature and is preventing the ice plateau’s surface from getting any colder.
A physical limit
“There seems to be a physical limit to how cold it can get in this high plateau area and how much heat can escape,” Scambos said. Although an extremely cold place, Antarctica’s surface radiates heat or energy out into space, especially when the atmosphere is dry and free of clouds.
“The levels of carbon dioxide, nitrogen oxide, traces of water vapor and other gases in the air may impose a more or less uniform limit on how much heat can radiate from the surface,” Scambos said.
Scambos and his team will continue to refine their map of Earth’s coldest places using Landsat 8 data. “It’s a remarkable satellite and we’ve repeatedly been impressed with how well it works, not just for mapping temperature but for mapping crops and forests and glaciers all over the world,” Scambos said.
“The uses for Landsat 8 data are broad and diverse,” said James Irons, Landsat 8 project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “And Scambos’ work is an example of some of the intriguing science that can be done using Landsat 8.”
In the longer term, Scambos and his team will try to design weather stations and set them up in the area where the record temperatures occur to confirm the data from Landsat 8 and MODIS. Currently, most of the automated weather stations in the vicinity do not work properly in the dead of winter.
“The research bases there don’t have people that stay through the winter to make temperature measurements,” Scambos said. “We will need to investigate electronics that can survive those temperatures.”
wbrozek says:
December 10, 2013 at 8:27 am
I thought that one reason that the poles would warm more than the rest of the globe is because there are so few water vapor molecules to compete with the CO2 in terms of absorbing and re-radiating certain wavelengths of radiation. It does not look like the CO2 is really that potent.
I initially thought the same thing but I don’t think this helps. The troposphere is non-existent at this location. Hence, the atmosphere above the surface is really the stratosphere. And, AGW predicts cooling of the stratosphere.
It’s been so cold that the dog had to be chiseled off the lamp post.
It’s bee so cold that warmist words at the AGU froze in midair and had to put them in a frying pan to thaw so we hear what they were talking about.
Several comments. Space is not at “3 K”. Space has no temperature, it is a vacuum. Its RADIATIVE temperature is 3 K, which means that anything unheated that is warmer than this will radiate energy away until it reaches equilibrium with this temperature.
On the other hand, vacuum itself is an “insulator” in the sense that it completely blocks three out of four heat transfer mechanisms: conduction, convection and (assuming a sealed satellite) latent heat — it loses heat ONLY through radiation. Exposed to night sky at a vacuum far from any star, objects cool towards 3 K but they cool more and more slowly the colder they get and it can take a very long time for a large object with a small surface to volume ration to cool. Brown dwarf stars, for example, have no mechanism for producing heat (other than very slow gravitational collapse, perhaps) but will still be “hot” tens of billions of years from now, long after our sun will have burned out and exploded.
Satellites can be kept warm quite easily, as they are exposed to direct sunlight which (close to the Earth) has a radiance of ~1400 W/m^2. This is large enough that the problem can easily be not heating up too much in direct sunlight, as the cooling rate from the shadow side of a satellite will be much smaller than the heating rate. However, both sunlight and LWIR are easily reflected from shiny metal foil. Hence the invention of “space blankets” — metal coated mylar. Interpose one between the satellite and the sun and it blocks (most of) the heat gain, reflecting the energy without itself heating up much. Interpose one between the satellite and the rest of space and it blocks (most of) the heat loss by reflecting outgoing LWIR back to the satellite. Mount the reflectors on movable shrouds, and you can regulate the temperature of the satellite to stay cool in direct sun or retain heat when one is e.g. in the Earth’s shadow or on a foray through the solar system that takes it first close to the sun and then out into the outer darkness. Up close to the sun, one may even need “radiator” panels — panels shielded from the sun and designed (high surface to volume ratio) to efficiently radiate heat away, perhaps from a compressed fluid as part of an active refrigeration cycle.
As long as such a satellite is sufficiently close to the sun, solar panels can perform the dual function of providing electrical energy and blocking/reflecting sunlight from the satellite body proper, and one may even need a shielded radiator as noted to keep the satellite cool. Out among the outer planets, where sunlight is weak and nothing changes fast, a satellite needs an internal power supply and needs to conserve the heat it produces. IIRC, satellites destined for the long dark often carry radioisotope (thermal) generators that have very long lifetimes. Basically, things like Plutonium Oxide are mixed up at a subcritical size that produces enough heat from alpha decay that it actually glows a dull red, then surrounded by a solid state thermocouple that directly generates electricity as the heat flows from this heat source to actively cooled surrounding coolant gas. The satellite conserves as much of the waste heat as it needs to to keep the electronics (which also release heat on their own in operation) happy and radiates the rest away.
Second — regarding the “pegging” of the temperatures close to -100 C — it is worth noting that the sublimation temperature of CO_2 at 1 atmosphere is considerably warmer than this — around -79 C. Up on the plateau the air pressure will be something less than 1 atm (although I didn’t see what it is in the article above) and so the gas-solid coexistence temperature is likely to be very close to the observed temperature. I wouldn’t be surprised at all if the cause of the consistent “clipping” of the temperature is that CO_2 is misting out of the atmosphere at that temperature in these pockets, accumulating as CO_2 “snow” that further accretes CO_2 frost on the surfaces. There is an infinite supply of CO_2 (replenished rapidly by diffusion) and so latent heat clips the temperature unless/until the atmosphere is completely stripped of CO_2 (which never happens).
This could easily be tested, of course. Simply grab a sample of the surrounding surface snow after the temperature has held steady at the CO_2 freezing point for a week or two and measure its CO_2 concentration when it melts.
It is at least plausible that this process “clips” the Earth’s low temperature during glacial eras, and is one of the processes responsible for the dip of atmospheric CO_2 to near the extinction levels of at least some plants during the Wisconsin. It could also easily be a major factor in the rapid warm up during the initial stages of interglacials — as soon as high arctic and antarctic reservoirs warm up enough to fail to re-freeze CO_2 in the long winter night, the active GHE could easily provide rapid positive feedback and reduce the CO_2 deposition zones, releasing massive amounts of CO_2 to the atmosphere extremely rapidly (but not until well after the warming was underway elsewhere, as this is likely to be relevant only inside the arctic circle or VERY high up — Greenland, Antarctica, and perhaps parts of Alaska and Siberia).
Of course, this opens up a lot of questions. The upper troposphere is around -80C, which would be cold enough to deposit CO_2 if it were at 1 atm, but is safely too warm at a couple tenths of a bar over most of the Earth. However, if the polar circulations alter and trap cold, inverted air over deposition cells such as the ones below, the troposphere can further cool, extending the depth of the deposition layer and conceivably actually starting to deplete the atmosphere of CO_2 locally. Note that it doesn’t even have to fall to the surface — all the CO_2 has to do is start to clump — stick together when one CO_2 molecule collides with another — and even microscopic flecks of solid CO_2 so small that they never have time to fall out are removed from the GHG equation as the clumps no longer have the same spectrum as isolated CO_2 molecules. Polar cooling could well be nonlinear once atmospheric temperatures reach the deposition point, at which point the atmosphere becomes unstable if it is not well-mixed.
Ordinarily, of course, it is quite stable. The tropopause is where the atmosphere inverts, with a warmer stratosphere over a coolest tropopause atop a DALR from the surface. But when the surface itself becomes very cold, instabilities can easily form and this is one of them that is at least plausible, although before I believed too much in my own prose I’d want to see a measurement of increased CO_2 deposition in the surface snow of the cold zones and/or direct measurements of atmospheric deposition in the air immediately above them. But this too could be a contributor to the relatively rapid END of interglacials. If periods of deposition are interspersed with periods of heavy snowfall, concentrated CO_2 could get systematically locked up in increasing glacial ice even if it re-sublimates as the falling snow warms it back up above the deposition point.
rgb
The problem is the batteries: no battery works below -50°C and heating costs a lot of energy. Solar cells don’t give help during 6 months of darkness and wind energy only helps when there is wind, which in general is not the case for the coldest periods.
It’s times like this that Plutonium can be your best friend. Nothing like a gentle PuOxide fire to keep your toes toasty and gear powered up for the next few thousand years.
Shame about that pesky alpha radiation, though. Fortunately, it is pretty easy to shield.
rgb
It can not be the levels in itself that sets the limit. It can only be the combination of the gasses and that they are as cold as the surface.
“The levels of carbon dioxide, nitrogen oxide, traces of water vapor and other gases in the air may impose a more or less uniform limit on how much heat can radiate from the surface,” Scambos said.
He should know the connection, so how can it be that he does not spell it out correctly.
rgb,
Why are you referring to total and not partial pressure?
I initially thought the same thing but I don’t think this helps. The troposphere is non-existent at this location. Hence, the atmosphere above the surface is really the stratosphere. And, AGW predicts cooling of the stratosphere.
This is vastly oversimplified. It is true that the atmosphere is often inverted over peak surface cold, so that the atmosphere is warmer above the ground than the ground is, but that isn’t quite the same thing as saying that there is no troposphere, and it certainly has nothing to do with AGW predictions of cooling of the “stratosphere” if you choose to call the inverted troposphere the stratosphere.
The question of cooling arises when the troposphere, that is effectively opaque to in-band LWIR from ground level up to within a km or so of the tropopause, becomes transparent to in-band LWIR as the absolute density of GHG molecules falls below the levels required to keep the mean free path of upward-directed LWIR photons smaller than the distance to infinity. Near the ground the mean free path is order meters and in-band photons “diffuse” around in the gas, directed down (back to Earth) almost as often as they are directed up, ascending in a random walk of increasing stride as they go up to where the GHGs are less dense.
In the actual stratosphere, most upward-directed LWIR photons escape. Oxygen and Nitrogen don’t have much bandwidth in the relevant blackbody regime, so they do not contribute much to radiative cooling, but (especially) CO_2 and Ozone and water vapor do and as they are heated by collisions with O_2 and N_2 (cooling the O_2 and N_2 in the process) they radiate away a lot of the heat. Hence cooling.
In the lower atmosphere — whatever you want to name it — this does not happen. Sure, O_2 and N_2 collide with CO_2 near the surface, but the LWIR the CO_2 radiates away has an even chance of being returned to the surface and has to diffuse all the way to the tropopause before it has a good chance of being radiated away from the Earth. The plain old GHE still works, in other words, as long as the mean free path of the relevant in-band photons is smaller than the optical depth of the atmosphere overhead.
rgb
Thanks everyone for your efforts to set the chemistry record straight on whether that cold weather could cause significant solidifying of CO2. I didn’t realize it was the *partial* pressure that mattered, but I knew pressure would make the difference.
The bulk of the atmosphere (N2 and O2) is the surface insulator and thus the real GHG (air). The radiatively active gases, especially water vapor are atmospheric ‘coolants’ or ‘radiators’. H20 is also a very effective surface ‘coolant’ or ‘evaporator’.
H2O, sorry..
No, I think the coldest temperature ever recorded on the planet is IN MY CLASSROOM RIGHT THIS MINUTE.
Or at least it seems like it…
I posted a link to this story on the book of faces last night and oh, my…it was not appreciated very much by a certain subset of those on my list of friends. They just do not want to hear about this, or the recovery of ice in the north, or cold temps anywhere at all, actually.
It tastes sweet to me, though.
ClimateForAll says:
I agree–factor it in. Of interest is that the coldest temps are between -134 and -137–isn’t that the same for the highest temps ever recorded? between +134 and +139?
Kinda of a balance there don’t ya think?
Last week, while Alberta was struggling with lows in the -30C’s, some dimwit started spreading the rumor that Alberta currently had the lowest temperatures on the planet. I seriously wonder what planet these people live on. It was laughably easy to find many places far colder than we were.
And STILL some refused to believe it.
rgb,
Why are you referring to total and not partial pressure?
Because I’m not certain which one is relevant in this context. Bear in mind that the last chemistry class I took was in 1974 and Richard Nixon was (IIRC) still president:-)
At the molecular level one is balancing nucleation and growth. Colder means that when two CO_2 molecules hit and stick together they have a longer lifetime stuck. Higher pressure means that they have a better chance of losing their surplus energy when they first collide, because energy has to be conserved and the collision is inelastic (meaning there is leftover energy when they are stuck that has to be lost as “heat”). It cannot easily be lost via radiation as the lifetimes are too long. It can (and in general will) be lost in molecular collisions with the surroundings, but those collisions don’t have to be with CO_2 molecules, they can be with anything.
So yes the probability of a CO_2 molecule encountering another CO_2 molecule definitely increases with partial pressure, the probability of two CO_2 molecules that collide and stick together will remain stuck increases with increasing absolute pressure/density and decreasing temperature of the surrounding gas. The same thing happens with water vapor — water vapor is constantly nucleating tiny droplets consisting of more than one water molecule, but these droplets have a finite lifetime because the surface to volume ratio isn’t favorable when the relative humidity is less than 100%. One thing that I think may be de facto neglected in climate science is that molecules that are stuck together in these finite-lifetime nucleations are pulled out of the effective GHG concentration. That is, the mean concentration may be unchanged, but if 50% of the molecules are stuck to other molecules then one’s assumptions about mean free path and the molecular bands involved are no longer correct.
The question then is: what is the lifetime of a microcrystal of solid CO_2 in the atmosphere and how does it scale with particle size, absolute pressure, partial pressure, and temperature? I don’t know the answers to any of these questions, but I do know that large blocks of CO_2 are comparatively stable when they are cooled well below -78 C even in 1 atmosphere air with only a tiny CO_2 concentration, just as large blocks of ice — like glaciers — are comparatively stable to sublimation losses at 1 atmosphere even when the air above has almost no humidity at all as long as the temperature is well below the freezing point. I also know that even when the humidity is well below 100%, a cold night can cause water vapor in the upper atmosphere to deposit out directly into ice crystals, causing rings around the moon and so on. I suspect that the equations for nucleation and growth of those crystals are quite different from those for the formation of water droplets.
Finally, I’m not at all certain that this process would be relevant in the upper atmosphere — the whole point there is that absolute CO_2 density there becomes so low that collisions of any sort with other CO_2 molecules is probably pretty unlikely. But at the surface of the snow, one has all of those lovely ice-crystal corners with high polarizability and strong local fields that can nucleate CO_2 deposition as easily as the deposition of additional water molecules. That is, the local conditions may strongly favor growth even of very small CO_2 crystals because they can get a boost from polar molecule water ice. And of course other aerosols in the air can conceivably do the same thing that they do for water vapor and water ice crystals — form a growth-favoring nucleation site for microcrystalline CO_2 deposition once the temperatures are sufficiently below the freezing point at 1 atmosphere absolute pressure.
But all of this is pure speculation on my part, of course. However, I like it as an explanation for the apparent temperature clipping better than some unknown atmospheric radiative clipping that produces a sharp temperature. Constant temperature during a period of nominal energy loss smacks of latent heat and phase transition. So what in the atmosphere is undergoing a phase transition around -100C? Not O_2. Not N_2. Not Argon (all of them far colder to the liquid transition, let alone the solid transition). Not even Ozone. Only CO_2, of the substantive components of the atmosphere. So it isn’t a completely insane speculation. Otherwise, good luck with coming up with some sort of radiative-physics-wu magic that permits the surface to cool to “exactly” -93C plus or minus one degree but then stops working. Latent heat can easily explain why it stops working — at that temperature all of the lost heat converts gaseous CO_2 to solid CO_2, warming the surrounding air to maintain the temperature. What else can?
(And yes, “what else can” doesn’t imply that there isn’t anything else that might be able to do the job and isn’t itself an argument for the hypothesis. It is, however, a genuine question that requires an answer at some point. In the meantime, it would be SO easy to test empirically with a sample of the surface snow, the atmosphere immediately above the surface snow, and a bit of hardware that it is scarcely worth arguing about the hypothesis on molecular chemistry grounds in the meantime…:-)
rgb
@RGBatDuke – “Bear in mind that the last chemistry class I took was in 1974 and Richard Nixon was (IIRC) still president:-)”
That depends. Did you take it in the spring or fall? 😉
Very interesting perspective; I thought this part bore repeating. And thank you for making the that very informative post.
.
Spring:-) The next to last chemistry class I ever took was in the fall of 1973. The US got out of the Viet Nam War on my 18th birthday that year, which was good from my point of view as my draft number was 55 and I was not thrilled at the prospect of involuntary servitude in an unwinnable war that was maintained (as the “CAGW of the day”) as a way of transferring large amounts of money from taxpayer pockets into the pockets of the “military-industrial complex”. I’ve read that $0.50 of every dollar spent on the Viet Nam war was stolen, diverted, used as payoffs in inflated contracts, or otherwise vanished into thin air. Pickings are slim for the MIC these days (although they still feast every decade or so on things like the Iraq war) and I suspect that they’ve diversified into the global warming business. One also wonders whether or not Carbon Trading can be used as a scheme to launder money. Oh, wait, of course it can, and already is being so used. Probably not yet competing with barbershops and restaurants at the end of the universe, but anything implemented non-uniformly across an international community with little to no oversight and with the nominal purpose of transferring money from haves to have nots has infinite potential for transforming billions of dollars in e.g. drug money into nice, clean carbon trading profits (or for that matter, into tax write off losses that similarly result in nice clean money).
The pirates of one generation are often the wealthy entrepreneurs and upstanding citizens of the next, once they manage to wash their sins away in the blood of the lamb at the local cash-only laundromat. Off topic, sure, but perhaps not so much as all that.
rgb
@RGBatDuke – you got a year on me. But then of course they ended the draft after 1974. As my number that year was 310 that year, I was less “concerned” than you. But alas the fall of 74 was also the last Chemistry class I took. So you think Taking Chemistry is cause for presidents resigning? 😉
rgbatduke, it really is just the partial pressure that matters. Water will condense or frost out as long as the partial pressure in the diluent gas is greater than the vapor pressure of the liquid or solid phase. At the interface there will be a continuous exchange of molecules as some sublime, others frost out.
With CO2, the same equilibrium statistics will apply. If you had a bag full of pure CO2, yes it would freeze- but the same CO2 diluted to 400 ppm will not produce any frost. The partial pressure of CO2 is not high enough to allow frost to form, just as air with partial pressure of water below the vapor pressure will not form frost.
To put numbers on it:
http://www.wolframalpha.com/input/?i=vapor+pressure+of+co2+at+136K
Vapor pressure of CO at 136K: 931uBar
On the Antarctic plateau at ~2km altitude, the atmospheric pressure is about 0.8 Bar, so
Partial pressure of CO2: 800,000 uBar x 400e-6 = 320 uBar
So even at 136K. air is very “dry” with respect to CO2 and no condensation can occur.
I got the notice by email through my Digg account. Here’s what it said in my email:
http://i1103.photobucket.com/albums/g480/FrankLeeMeiDere/ScreenHunter_01Dec101438.jpg
Note the little subhead above the main title saying, “Yes, Global Warming is still real.”
Glad they cleared that up.
So there we have it; at what partial pressure (at the temperature given above) and then translating that to xxx ppm on that plateau could we expect to see CO2 ‘frost’ appearing?
.
Prof Sir David King, when he was the UK ‘government scientist’, predicted that by 2100 “the only habitable continent will be Anarctica.”
In reality they are setting up new thermometers in that plateau so they can claim warming next year and get the $$$.
Seems like some are not convinced that it is CO2 partial pressure that matters in condensation from the vapor phase.
N2 and O2 molecules cannot condense into CO2 dry ice, no matter how many of them are present.
For a small volume of “dry ice” the volume and molecule count goes as the cube of diameter. which establishes how many molecules there are at the high energy end of the M-B distribution, to be able to sublime off the surface. The collection of atmospheric CO2 molecules, depends on the surface area, not the volume.
So the smaller the volume of a dry ice flake, the faster it will sublime, and the slower it will accumulate new CO2 from the atmosphere. So in theory, there is a maximum size that a dry ice blob can grow to at some Temperature below the triple point. I’m guessing that the size is likely too small to be visible.
So even at 136K. air is very “dry” with respect to CO2 and no condensation can occur.
Well, maybe, for pure CO_2 with little to no other gas present, such as in the atmosphere of mars (where dry ice snowfall has recently been observed at just 14x the partial pressure of CO_2 on Earth) and where the adiabatic heating produced by the phase transition limits the temperature drop precisely they way I suggest might happen above in Antarctica. But just as aerosols modulate the critical dynamics of nucleation and growth of water droplets, so might they modulate the critical dynamics of nucleation and growth of CO_2 microcrystals.
Note well I’m not talking about the falling out of huge amounts of CO_2 snow. I’m talking about the possibility that — just as frost lines forms preferentially and at partial pressures too low to actually support “snow” on defects (e.g. scratches) in a cold surface because the local electrochemistry causes surface adsorption potentials to be lowered enough to permit nucleation and limited growth — it may be that snow and ice crystals themselves produce a similarly favorable “defect rich” environment that can collect CO_2 deposition in air where direct deposition is unstable. It would certainly explain the apparently “fixed” lowest temperature, but hey, the observations so far are nearly anecdotal in scope and it may be that in five years they’ll observe a much broader range of lowest temperatures.
I’ve done a fair amount of work simulating critical phenomena, and the big questions are what is the size distribution function and mean lifetime of microparticle condensates that are ALWAYS forming and breaking up in a gas, as functions of the temperature and partial pressure and composition of any background gas, not whether or not one has reached a macroscopic critical point or a critical size where droplet growth is favored over decay (as is the relevant case for water droplet condensation into clouds). The presence of bare ions of any sort in the atmosphere is enough to shift the distributions significantly for polar water — I have no good feel for what non-polar CO_2 will do. However, I think it is safe to say that the critical temperature you suggest above is a lower bound, and probably doesn’t take into account any sort of heterogeneous surface chemistry that might favor deposition. Note well that there has been a recent paper suggesting that we sequester solid CO_2 in the Antarctic because a block of solid CO_2 has a very, very long lifetime at -90 C and 1 atmosphere — that was the entire point of their argument.
Either way, I certainly won’t argue — perhaps the hypothesis is implausible and there is some other reason the temperatures are clipping or none at all (because the clipping is an anecdotal accident, not a real effect). It would still be so easy to check experimentally, though. Well, easy if you allow for the fact that one has to travel a long ways and work in extremely dangerous conditions to take the samples in the first place…;-)
But for all that, it is a lot simpler than travelling to Mars. And wouldn’t it be cool if we could observe spontaneous CO_2 deposition on Earth, catalyzed by surface chemistry or aerosol chemistry to be sure, but even so it would have a potentially large impact on our perceptions of things like the Ordovician-Silurian transition, when an ice age occurred with Mars-like CO_2 partial pressures in the Earth’s atmosphere.
rgb
“Oh Oh… Its worse than we thought. A new record low – the ice age is coming. We are all going to freeze, and starve, and the ocean is going to rise, after turning into three mile thick glaciers, and wipe our New York city. This is a clear sign that global warming has stopped stopping and has started again with a vengeance. The increase in CO2 emissions by mann is causing this cold spot in the antarctic, just like the models will predict after we tweak a few of the algorithms” — Dr Chick. Little, Senior Climate Seance Holder, Penn State
About Dr. Little – This Nobel prize winning peer of Dr Mann is acknowledged by every one I asked in Penn State’s physics dept staff lounge at 4 am last night as the worlds best climate grant writer. His work with tree rings is legendary in his own mind, and the cause of many laws suits against jealous deniers who don’t understand that consensus means the debate is over..