# Calculating atmospheric CO2 levels from ice cores **URL:** \ **Category:** Factual Questions\ **Created:** [May 21, 2008, 11:53am UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086 "2008-05-21T11:53:10Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [May 21, 2008, 11:53am UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/1 "2008-05-21T11:53:10Z")
Can I have a fact-check, please, Bob? I’ve just read [this](http://www.anenglishmanscastle.com/archives/005788.html) which questions the accuracy of historical CO2 levels as measured by ice cores. I don’t have access to the paper it cites. Can someone please fact-check this? I rather doubt it’s disputing the measured CO2 levels - that would be absurd - but rather the atmospheric CO2 calculated from those measurements. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [May 21, 2008, 9:17pm UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/2 "2008-05-21T21:17:06Z")
I think that it does not matter that the bubbles inside the ice can exchange CO2 with the ice itself. According to Fick’s law there is a partitioning of various solutions in multiphase systems like this, which depends on the chemical potential or fugacity (these are essentially the same thing). The point is that if there is an equilibrium of CO2 concentration in ice and in water and in air when the samples formed, then what’s in the bubbles will continue to represent the concentration at the time of formation, unless the entire system can effectively exchange CO2 with newer systems. So, if you left that ice core out in the freezer warehouse long enough, its CO2 levels will change. But, then, it will sublime away, too. By the way, fugacity seems to be one of the most inconsistently understood and defined concepts in the chemical engineering world. I would up having to get multiple professors talking with one another to negotiate a concensus definition when getting patents for sorbent systems. Perhaps this innocent thread will now death spiral into a debate about fugacity? ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [May 21, 2008, 10:57pm UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/3 "2008-05-21T22:57:24Z")
I’m not entirely sure I understand that. You’re saying that they can caulclate how much of each atmospheric gas migrates from the bubbles to the ice for a given temperature and pressure? And from that they can calculate what the atmospheric concentrations would have been? How long does it take for this to change when the extracted ice core is stored under different temperature and pressure? ---
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [May 27, 2008, 12:54am UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/4 "2008-05-27T00:54:34Z")
This is a good question, so I think I’ll give it a bump. If no one answers by tomorrow, I’ll see if I can’t dig out the original paper cited in the OP and give it a read - I should caution that I’m not a chemist, so it would probably be best if someone else interpreted it, but I can give it a shot if no one else does. ---
**Author:** ![Fubaya](https://avatars.discourse-cdn.com/v4/letter/f/c2a13f/32.png) [@Fubaya](https://boards.straightdope.com/u/Fubaya)\ **Post date:** [May 27, 2008, 7:48am UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/5 "2008-05-27T07:48:21Z")
I never replied because this is circumstantial and doesn’t factually answer the OP, but this should get you going in the right direction. Or if you’re like me, it may be enough to conclude there’s really nothing valid enough in what that blog link says to put any more effort into it. The paper he quotes is co-authored by “Stauffer, B” in 1977. I did a little searching for his name (aka Bernhard Stauffer from Climate and Environmental Physics of the University of Bern) and, among other things, [found](http://www.copernicus.org/EGU/awards/medallists/_2006/hans_oeschger.html): > [@](#): > > In collaboration with colleagues from the University of Bern, he developed a method to measure the concentration of trace gases of small ice samples. This was a major experimental challenge for various reasons. The dry extraction system was based on a needle crusher and proved to this date to be a reliable tool in avoiding the contamination of gas samples on which the content of carbon dioxide, the most important greenhouse gas after water vapor, was to be measured. Using this device, Stauffer was leading the effort which resulted in the first determination of the concentration of CO2 during the last ice age. This is arguably one of the most important results in paleoclimate research because it defines the range of natural variability of CO2 in the climate system. So this guy pretty much **invented** the method for reading CO2 accurately from ice cores. He’s also written/cowritten some papers about CO2 levels. I’d suggest [Atmospheric CO2 Concentrations over the Last Glacial Termination](http://www.sciencemag.org/cgi/content/full/sci;291/5501/112?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=%28Bernhard+AND+Stauffer%29&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT). Follow the footnotes to other papers like “[Processes affecting the CO2 concentrations measured in Greenland ice](http://www.blackwell-synergy.com/links/doi/10.1034%2Fj.1600-0889.47.issue4.6.x)” and others. It seems pretty clear that the scientists know what they’re doing. Here is what annoys me. The blog in the OP posted a small blog entry quoting a 30 year old abstract and claiming it “takes the legs out from under the whole global warming theory” but never bothered to really learn anything about the subject they were talking about or even make an attempt to see if anything new had happened in the last 30 years. They just selectively find a sentence that they like and proclaim global warming to be dead. ---
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [May 28, 2008, 4:45am UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/6 "2008-05-28T04:45:03Z")
Thanks for replying, **Fubaya** , I wouldn’t want to go it alone. 🙂 Anyway, the confluence of three factors bothers me about the quote cited in the OP: [ul]1. The quote comes only from the abstract.[/ul] [ul]2. The work cited is rather old (1978).[/ul] [ul]3. The issue of the journal the paper is in is apparently not available online.[/ul] (I should note that neither #2 nor #3 would be enough by themselves to make me suspicious, but the combination of them together gets me there.) For the first issue, it’s unusual to see just the abstract from the article quoted. For any readers (I know many people reading this are, so my apologies) unfamiliar with scientific writing, the abstract is a very short summary of the work, its central point, and its significance. It’s just the “hook” to get you to read the paper, really. The details are what’s really significant, and they’re inside the paper, not in the abstract usually. So why didn’t the blogger quote some significant phrase from the “meat” of the paper? I don’t know, but I shouldn’t even have to ask the question - that’s why it’s suspicious. For the second issue, it’s not necessarily bad that the paper is old. However, the authors have published much more recent work. I was able to download Bernhard Stauffer’s “Atmospheric CO[sub]2[/sub] concentrations over the last glacial termination.” From Vol. 291, issue 5501 of _Science_ in 2001. > [@B. Stauffer and co-authors](#): > > The ice core record from Vostok, Antarctica, covering the past 420,000 years, shows increases of the CO[sub]2[/sub] concentration between 80 and 100 ppmv for each of the past four glacial terminations (5). The increase during the last termination is well established on the basis of various polar ice cores from both hemispheres (6-10). However, not all ice cores are well suited to investigate the details of such an increase. Some CO[sub]2[/sub] records, especially those from Greenland ice cores, are compromised by the production of CO[sub]2[/sub] by chemical reactions between impurities in the ice (11-13). Ice cores from Antarctica are less affected, but a small amount of in situ CO[sub]2[/sub] production by chemical reactions cannot be excluded for all Antarctic ice cores and all climatic periods (14,15). CO[sub]2[/sub] records from Vostok and Taylor Dome are thought to be the most accurate (5, 10, 16). However, the time resolution of these two records is too low to provide a history of CO[sub]2[/sub] changes that shows the detailed evolution of atmospheric CO[sub]2[/sub] over the last glacial termination. > > Here, we present a record from the Dome Concordia (Dome C), Antarctica (75°06’S, 123°24’E), ice core drilled in the frame of the European Project for Ice Coring in Antarctica (EPICA) during the field season 1998-99. This does not sound like the work of someone who thinks: > [@http://www.anenglishmanscastle.com/archives/005788.html](#): > > If I interpret the abstract correctly it means that CO2 concentrations in trapped air bubbles are not related to the original concentration, but probably more related to the temperature and pressure of the ice. Instead, it sounds like someone who has a definite opinion that Antarctic ice cores are better than Greenland ice cores for determining ancient CO[sub]2[/sub] concentrations - which is almost completely the opposite of saying the air bubbles are not related to the original concentrations. For the third issue, my access may be different from that of others operating at an institution with a different subscription, but [http://www.ingentaconnect.com](http://www.ingentaconnect.com) tells me that only recent issues of the _Journal of Glaciology_ are available online: > [@](#): > > 33 issues are available electronically > … [From] > · Volume 54 > · Number 184, January 2008 > … [To] > Volume 46 > · Number 155, December 2000 > · Number 154, June 2000 > · Number 153, March 2000 > · Number 152, January 2000 And now that I read the post completely, it seems that **An Englishman’s Castle** hasn’t even read the article attached to the abstract himself: > [@http://www.anenglishmanscastle.com/archives/005788.html](#): > > I have not yet managed to get a copy of the presentation. I have to go with **Fubaya** ’s assessment: this is an ideological opposition to global warming that has taken the trouble to _look_ scientific, without any of the actual _reading_ of sources to see if the science says what he thinks it does. Very intellectually dishonest. ---
**Author:** ![Fubaya](https://avatars.discourse-cdn.com/v4/letter/f/c2a13f/32.png) [@Fubaya](https://boards.straightdope.com/u/Fubaya)\ **Post date:** [May 28, 2008, 5:43am UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/7 "2008-05-28T05:43:59Z")
[QUOTE=wevets] Instead, it sounds like someone who has a definite opinion that Antarctic ice cores are better than Greenland ice cores for determining ancient CO[sub]2[/sub] concentrations - which is almost completely the opposite of saying the air bubbles are not related to the original concentrations. [/QUOTE] I am entertaining the thought that the paper from the 70s may still be accurate. Maybe he (or they-- his name just stuck out) found that bubbles didn’t work back in the 70s, but later found a better way to get samples. I only skimmed some of the papers but I didn’t see any mention of bubbles and I don’t really understand how they get CO2 now, but I don’t feel like going any deeper. I’m actually pretty interested in ice cores but I’ll put my money on the science dudes without attempting to learn all the technical methods behind CO2 extraction. Speaking of taking the legs out from under the whole global warming theory… Flipping through radio channels today, I heard Rush Limbaugh say that Mars has 95 times as much CO2 as earth, so it should be extremely hot, but the “global warming wackos” don’t want you to know that Mars is a cold planet. Even now, hours later, I literally cannot form words to describe how insanely stupid that is. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [May 28, 2008, 7:24am UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/8 "2008-05-28T07:24:58Z")
[QUOTE=wevets] I have to go with **Fubaya** ’s assessment: this is an ideological opposition to global warming that has taken the trouble to _look_ scientific, without any of the actual _reading_ of sources to see if the science says what he thinks it does. Very intellectually dishonest. [/QUOTE] Thanks. ---
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [May 30, 2008, 1:47pm UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/9 "2008-05-30T13:47:32Z")
> [@Fubaya](#): > > I am entertaining the thought that the paper from the 70s may still be accurate. Maybe he (or they-- his name just stuck out) found that bubbles didn’t work back in the 70s, but later found a better way to get samples. I only skimmed some of the papers but I didn’t see any mention of bubbles and I don’t really understand how they get CO2 now, but I don’t feel like going any deeper. I agree that it’s possible, but at the end of the abstract there’s a hint: > [@](#): > > The CO2 content of ancient air is directly preserved neither in > the total CO2 concentration nor in the CO2 concentration in the > bubbles. Possibly the CO2 content of ancient air may at least be > estimated if the solubility and the diffusion constant of CO2 in > ice are known as a function of temperature. It’s also possible that instead of finding an alternative to bubbles we now know what the solubility and diffusion constants of CO[sub]2[/sub] in ice are as a function of temperature, correct? Hopefully he’s published some methodological work that follows up on this and is more recent than 1978. I’ll see if I can dig any up. I hope you don’t mind, **Quartz** , we may have answered your question, but I’m still interested in the topic. 🙂 ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [May 30, 2008, 2:49pm UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/10 "2008-05-30T14:49:57Z")
[QUOTE=wevets] I hope you don’t mind, **Quartz** , we may have answered your question, but I’m still interested in the topic. 🙂 [/QUOTE] No problem; it can be very interesting when someone says, “Hang on a moment…” ---
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [May 30, 2008, 7:41pm UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/11 "2008-05-30T19:41:49Z")
[QUOTE=Quartz] No problem; it can be very interesting when someone says, “Hang on a moment…” [/QUOTE] Sadly, for me often a “moment” can mean days to weeks. 😉 However, in this case I overlooked something I should have checked. The article cited above has a methodological appendix: [http://www.sciencemag.org/cgi/content/full/291/5501/112/DC1](http://www.sciencemag.org/cgi/content/full/291/5501/112/DC1) > [@B. Stauffer and co-authors](#): > > For CO2 measurements, each sample (of size 2.5 cm by 2.5 cm by 1.5 cm) is cracked in an evacuated and cooled (-30°C) needle cracker. The air from opened bubbles expands into a laser absorption cell. The CO2 concentration of the gas in the absorption cell is measured by tuning an infrared laser six times over the absorption line of a vibration-rotation transition of the CO2 molecule. Reference gas from the Scripps Institution of Oceanography at 251.7 ppmv is used for the calibration of each measurement. Control measurements are routinely (after about five measurements) performed by using other reference gases from the Scripps Institution of Oceanography at 321.06 and 342.03 ppmv to check the linearity of the system. The linearity of the measurement technique for CO2 concentrations lower than the calibration reference gas can be checked indirectly by generating control measurements at lower pressure, generating similar absorption line depths than for measurements with lower CO2 concentrations. Measurements on bubble-free single-crystal ice samples, to which reference gas is added and which are cracked afterward, yield a reproducibility of ±1.5 ppmv. > > For the methane measurements, an ice sample (~40 g) is melted under vacuum and then refrozen from the bottom with an alcohol bath at -25°C. The methane concentration on the gas is measured with a gas chromatograph. The external precision from replicate and blank measurements is 10 ppmv (1s). For additional information see (1). > > Possible Artifacts Produced in the Ice > > Most chemical impurities in the ice show large variations over short depth intervals corresponding to one or several annual layers [annual layer thickness at Dome Concordia (Dome C) is ~10 to 20 mm in the considered depth interval]. If there is a production of CO2 in the ice matrix, we expect a scatter of the samples in a depth interval that cannot be explained by the analytical uncertainty (±1.5 ppmv). A c2 test yields agreement of the standard deviations with the analytical uncertainty. A detailed analysis of the Ca2+ record [continuous flow analysis with a resolution of 10 mm (2)], which is a qualitative indicator of the carbonate concentration, shows variations between 10 to 30 parts per billion per weight (ppbw). These variations correspond to a CO2 production potential of 60 to 180 ppmv (3). Our CO2 measurements performed with a similar depth resolution do not show variations that are correlated significantly with the Ca2+ variations. On the other hand, the concentration of H2O2, a likely oxidant, is below the detection limit (\<1 ppbw) in the Dome C ice core, and therefore, no oxidation of organic matter by H2O2 is expected. Results from the Vostok (4) and Taylor Dome (5) ice cores are in agreement with this record within the analytical uncertainties (the time resolution of these records allows only to confirm the gross features). CO2 measurements from the Byrd ice core (6-8) are about 5 to 10 ppmv higher, especially on samples older than 18 ka. The reason for these deviations is still unclear. Apart from these systematic deviations, the general trend of the Byrd values is in agreement with the new measurements from the Dome C ice core. > > Assumptions Made on the Link Between Deuterium Content in the Ice and Southern Ocean Temperature > > Strong climatic connections could exist between Antarctica and the Southern Ocean (SO), as the SO could export latent and sensible heat to Antarctica. Similarities between temperature reconstructions in Vostok and reconstructions of the SO sea surface temperature (SST) by deep sea sediment core records (9, 10) and fossil Antarctic diatoms (11) were found at least for the long-term features. The Dome C temperature reconstruction based on stable isotopes measurements is very similar to the record of Vostok, so it can be expected that the Dome C temperature is an indicator for the SO SST. It is not clear without ambiguity if structures on shorter time scales such as the Antarctic Cold Reversal (ACR) were also a SO SST signal. Some SST temperature reconstructions on deep sea sediment core records (9) and fossil Antarctic diatoms (11) show a distinct ACR, but on other cores (10, 11), the ACR cannot be recognized. Short-lived peaks in Antarctic isotope records could, in principle, be due to temporary coolings of the evaporation sites of the deposits associated with cold conditions in the Northern Hemisphere (12). > > Procedure for Determining the Correlation Coefficient Between the CO2 and dD Records > > In order to compare the CO2 and temperature records, we carried out the following procedure. We calculated the correlation coefficient of the CO2 and dD records using the mean values of 11 dD data points (corresponding to a time interval of 200 to 500 years) to every corresponding CO2 data point. This procedure was chosen in order to take into account the fact that the enclosure process of air into ice causes a natural averaging of the CO2 record corresponding to ~10% of the gas-ice age difference and, therefore, a single CO2 value represents a time interval of 200 to 500 years. In order to estimate possible leads or lags, we shifted the CO2 record in steps of 10 years and calculated the correlation coefficient between CO2 and dD after each step. The CO[sub]2[/sub] being measured does indeed come from air bubbles in the ice core. There are sources of uncertainty in that production of CO[sub]2[/sub] can occur in the air bubble under certain conditions - measurements of calcium and hydrogen peroxide can help determine how great production of CO[sub]2[/sub] in a given core might be. Syncing the record with other cores and with diatom deposits from that time period allows the establishment of common events which are atmospheric, rather than local to the air bubble since its deposition in the ice. There may be more in the rest of Stauffer’s work that describes how the problem from the 1978 paper was addressed, but this does give us some ideas of modern methodology. ---
**Author:** ![intention](https://avatars.discourse-cdn.com/v4/letter/i/e95f7d/32.png) [@intention](https://boards.straightdope.com/u/intention)\ **Post date:** [May 30, 2008, 8:35pm UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/12 "2008-05-30T20:35:52Z")
I too was curious about this work. The oddity to me is that the relationship between (air age - ice age) and CO2 should exist at all, I don’t see the mechanism … w. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [May 30, 2008, 8:45pm UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/13 "2008-05-30T20:45:40Z")
The problem with basing any predictions from ice samples is that there aren’t any ice samples in the middle of the Atlantic Ocean. Greenland is subject to North American weather patterns and does not represent the planet as a whole. ---
**Author:** ![Fubaya](https://avatars.discourse-cdn.com/v4/letter/f/c2a13f/32.png) [@Fubaya](https://boards.straightdope.com/u/Fubaya)\ **Post date:** [May 31, 2008, 5:13am UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/14 "2008-05-31T05:13:49Z")
[QUOTE=Magiver] The problem with basing any predictions from ice samples is that there aren’t any ice samples in the middle of the Atlantic Ocean. Greenland is subject to North American weather patterns and does not represent the planet as a whole. [/QUOTE] Not sure what you mean by predictions, but CO2 levels would be the same in Greenland as in the rest of the world. But they know that whatever weather/climate information they get from ice cores is only good for that area. It’s just another piece of the puzzle. If, for example, you find that Greenland was much warmer at a certain time and data from around the world for the same time period shows sea levels were higher, tropical plant fossils were farther north, and Foraminifera from oceanic core samples show warmer ocean currents, you can figure out the global climate during that period. ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [May 31, 2008, 5:27am UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/15 "2008-05-31T05:27:44Z")
[QUOTE=Magiver] The problem with basing any predictions from ice samples is that there aren’t any ice samples in the middle of the Atlantic Ocean. Greenland is subject to North American weather patterns and does not represent the planet as a whole. [/QUOTE] The data used in things like the UN report are based on mutliple studies which use different original sources like ice, tree rings, coral, sediments, etc. > **[Paleoclimatology](https://en.wikipedia.org/wiki/Paleoclimatology)** > > Paleoclimatology (British spelling, palaeoclimatology) is the scientific study of climates predating the invention of meteorological instruments, when no direct, artificial measurement data were available. As instrumental records only span a tiny part of Earth's history, the reconstruction of ancient climate is important to understand natural variation and the evolution of the current climate. > Paleoclimatology uses a variety of proxy methods from Earth and life sciences to obtain data previous... ---
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [May 31, 2008, 2:37pm UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/16 "2008-05-31T14:37:22Z")
[QUOTE=intention] The oddity to me is that the relationship between (air age - ice age) and CO2 should exist at all, I don’t see the mechanism … [/QUOTE] My WAG is that the mechanism is that when a specific parcel of ice is added onto a glacier, it is frozen either as snow compressed by the weight of other snow and ice on top of it, thus incorporating air that was between snowflakes into the ice as air bubbles, or as melted snow on the surface of the glacier that then freezes as ice, which would also incorporate air bubbles. The air trapped at the time of freezing is then sequestered further and further away from the atmosphere as the glacier grows. If the glacier shrinks, the air bubble is released to the atmosphere and we’ll never find it in an ice core. If the above is true, the air should be frozen at the same time the ice does (since the ice is the only thing keeping it from escaping to the atmosphere,) and its CO[sub]2[/sub] content should be at least that of the atmosphere at the time of freezing. Creation of CO[sub]2[/sub] through chemical reactions in the ice is possible and mentioned above in the portions of the article that I quoted. Breaking down CO[sub]2[/sub] in the ice is extremely unlikely due to the combination of the low free energy state of CO[sub]2[/sub] and low temperatures inside ice. I’m operating off memory for that, so I’m pretty confident a search of the relevant literature will turn up minor corrections to my explanation - hopefully no major corrections though. 😉 ---
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [May 31, 2008, 2:49pm UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/17 "2008-05-31T14:49:56Z")
[QUOTE=Magiver] The problem with basing any predictions from ice samples is that there aren’t any ice samples in the middle of the Atlantic Ocean. [/quote] I’m afraid that I am completely confused by this question, **Magiver**. What predictions are based on ice samples? As far as I know, none. 😕 You may be thinking about how ice samples are used to quantify paleoclimates, that’s what the work discussed above in the thread deals with. Note the title: “Atmospheric CO2 concentrations over the **last glacial termination** ”, Stauffer and his co-authors are talking about thousands of years in the past - out to 420,000 years **ago** in the paper cited, not into the future. > [@](#): > > Greenland is subject to North American weather patterns and does not represent the planet as a whole. This is also unclear to me. Who ever said Greenland represented the planet as a whole? The papers we’re looking at discuss the methods of extracting air from ice and measuring its CO[sub]2[/sub] content. CO[sub]2[/sub] is pretty well mixed in the atmosphere and will not be very different in Greenland vs. Antarctica (although there will be small differences.) **Sage Rat** alludes to a different methodology, that of constructing a paleoclimate over the entire planet using multiple sources. To this point, all the papers discussed here have only been presenting one source, not an entire paleoclimate. ---
**Author:** ![intention](https://avatars.discourse-cdn.com/v4/letter/i/e95f7d/32.png) [@intention](https://boards.straightdope.com/u/intention)\ **Post date:** [June 1, 2008, 12:01am UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/18 "2008-06-01T00:01:08Z")
OK, some further research. I downloaded the Vostok data, and the relationship between (ice-age minus air-age) is quite strong, especially in the older samples (R^2 = 0.87, older half of dataset, and 0.82, full dataset). The reason for this is rooted in a 1991 paper by Barnola which spelled out a formula for calculating how long it takes for the ice bubbles in the firn to close completely. This formula uses the temperature, inter alia, to calculate the closeout date. Since the CO2 content is related to the temperature, and the closeout date is a function of the temperature, they are related. What I haven’t found out is what they used as a proxy for the temperature in say 276,000BC … my research continues. I will report back if I find anything else. The oddity is that the Vostok (ice-age minus air-age) data is much more closely related to Vostok CO2 levels than to the Vostok ∂O18 levels, which are usually taken as a temperature proxy. Curious. Perhaps they used CO2 levels as a temperature proxy in some fashion, dunno. w. ---
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [June 3, 2008, 2:43am UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/19 "2008-06-03T02:43:07Z")
[QUOTE=intention] What I haven’t found out is what they used as a proxy for the temperature in say 276,000BC … my research continues. [/quote] From what I understand the ratio of heavy to light isotopes is used to determine temperature in ice cores. If you can, for example, relate δ[sup]18[/sup]O values to temperature, is it possible to relate [sup]14[/sup]CO[sub]2[/sub] or C[sup]18[/sup]O-O values to temperature? > [@intention](#): > > The oddity is that the Vostok (ice-age minus air-age) data is much more closely related to Vostok CO2 levels than to the Vostok ∂O18 levels, which are usually taken as a temperature proxy. Could you elaborate on how it is more closely related? Thanks, 🙂 ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [June 3, 2008, 3:16am UTC](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086/20 "2008-06-03T03:16:54Z")
[QUOTE=wevets] I’m afraid that I am completely confused by this question, **Magiver**. What predictions are based on ice samples? [/QUOTE] I was under the impression that global warming predictions were linked to CO2 levels and that ice samples were prevalent in this research. My mistake. Carry on. [Next page](https://boards.straightdope.com/t/calculating-atmospheric-co2-levels-from-ice-cores/450086.md?page=2)