About the reliability of ice cores…
Guest Post by Ferdinand Engelbeen
There have been hundreds of reactions to part 1 about the mass balance (http://wattsupwiththat.com/2010/08/05/why-the-co2-increase-is-man-made-part-1 ). Many respondents still are not convinced that the mass balance is a firm proof that the observed increase of CO2 in the atmosphere is human made. But there are more indications. Ultimately, any alternative explanation must fit all the observations. If the alternative hypothesis fails even only one of the observations, then the alternative is rejected. But before we start to look at more observations which support an anthropogenic cause, we need to address several misconceptions which fly around on the Internet, mainly on skeptic blogs… This part has a detailed look at the reliability of ice cores, which are quite important for our knowledge of the pre-industrial CO2 levels, but have been subject to a lot of critique.
Note that the ice cores only show CO2 levels back to about 800,000 years, but measurements may in the future be extended to over one million years. What is found in the ice cores is only relevant for the most recent period of our history and not for more distant geological time periods.
About the reliability of ice cores:
Some have objections to the ice core measurements, as these are regarded as the main reason for the “equilibrium” assumption of ancient CO2 levels. The only real problem in this case is the smoothing of CO2 levels. That depends on the snow accumulation rate, as it takes a lot of time to close all air bubbles in between the snow flakes. That happens at a certain depth where the pressure is high enough to transform the snow, then firn (densified snow still with open pores) into ice. The averaging happens partly because at first the firn pores are large enough to let the air in the pores and in the atmosphere exchange with each other, partly because some bubbles close early, others at a lower depth (thus contain air which is different in composition, “age”, than other already closed bubbles). The depth where this happens depends on the pressure from the layers above and the temperature of the ice. The time needed for full closure of all bubbles largely depends on the accumulation rate of snow at the place where the ice core is taken (or upstream if coring at a slope).
That makes that the average smoothing of CO2 levels is about 8 years (Law Dome 2 out of 3 ice cores, 1.2 m ice equivalent/year accumulation), some 21 years (the third Law Dome ice core, 0.6 m ice equivalent, see http://www.agu.org/pubs/crossref/1996/95JD03410.shtml unfortunately behind a pay wall…), some 570 years (Dome C, a few mm/year, see http://www.nature.com/nature/journal/v453/n7193/full/nature06949.html ) and everything in between. The Law Dome closing period of the bubbles was measured, while for Dome C one needed models to estimate the time resolution in the far past.
Thus the smaller the snowfall at a certain place, the longer it takes for the bubbles to fully close and the longer averaging one has. At the other side, the smaller the accumulation rate, the further we can look back in the past, as for the same depth of ice, there are many more years of snowfall.
The fact that the pores still are open over a long period, also means that there are differences in the age of the ice and the age of the enclosed gas. The age of the ice can be counted, as it simply is the result of ice formation from yearly snow accumulation where winter/summer snow density differences gives clearly distinguishable layers if there is sufficient accumulation. If, as depth increases, the pressure and/or flow result in layers that are near invisible, one may use several other methods like electro conduction or X-rays (see http://iopscience.iop.org/1742-6596/41/1/034/pdf/jpconf6_41_034.pdf ) to distinguish the layers/age.
Determining the gas age is not as easy. Over the years of accumulation of the snow/firn, the pressure builds up and the firn becomes more dense with decreasing pore diameter. That reduces the exchange of air in the pores with the air in the atmosphere, until the pores are too small to make any further exchange possible. If there has been considerable accumulation, as in the two fast Law Dome cores, at the depth of the first closing (about 72 meters) the ice is already 40 years old (40 layers), but the air has the average CO2 levels of less than 10 years ago, which makes the average gas age (including the average time for fully closing of all bubbles) about 30 years younger than the ice at the same depth. For the top layers, we have the advantage of direct measurements in the atmosphere for overlapping periods, which makes a comparison possible.
For cores with far less accumulation, the analysis is more problematic, as the difference increases with the reciprocal of the accumulation rate. During ice ages, there was less precipitation, thus increasing the ice age – gas age difference. The ice-gas age difference for the Vostok ice core is over 3,000 years. Be aware that the ice-gas age difference has nothing to do with the resolution of the CO2 levels, as these are in the bubbles themselves, but it makes a chronology of what happens between temperature (measured as dD and d18O proxy in the ice, see further) and CO2 levels (measured in the bubbles) more difficult to establish. But here also different techniques are used: diffusion speed is a matter of pore diameter, directly related to firn/ice density and densification speed is directly related to accumulation speed. This can be used to model the exchanges between air in the pores and the atmosphere.
The calculations to establish the gas age did fit quite well for the Law Dome ice cores, where besides ice age, the average gas age was established by measuring CO2 levels top down in the firn. That showed that the gas age at closing depth was less than 10 years old on average, but more importantly, the CO2 levels in the already fully closed bubbles and the still open pores were the same. For the low accumulation ice cores like Vostok, there is more discussion about the ice-gas age difference and different time scales were established…
The accuracy of the measurements in the three Law Dome ice cores for the same gas age is about 1.2 ppmv (1 sigma). Later works compared different ice cores for CO2 levels at the same average gas age. These show differences of only 5 ppmv, despite huge differences in average temperature (coastal -20°C, inland -40°C), salt inclusions (coastal), accumulation rate and resolution. There are a lot of overlapping periods between the ice cores, the resolution decreases with increasing length of period (from 150 years – for 2 of 3 Law Dome ice cores – to 800,000 years – Dome C), but even so, the measurements (done by different labs of different organizations) show a remarkable correspondence for the same average gas age. This is a nice indication that the CO2 levels of the ice cores indeed represent the ancient levels.
Data over the past 10,000 years of average gas age in ice cores from:
http://www.ncdc.noaa.gov/paleo/icecore/current.html
As result, for the past 150 years (Law Dome) we have accurate data with a reasonable resolution. The cores average the CO2 levels over 8 years, so any peak of 20 ppmv during one year or 2 ppmv difference sustained over 10 years would be observable. For older periods, the resolution is less and the averaging applies to the full period of resolution (about 570 years for Dome C).
The visual correlation between temperature and CO2 levels in ice cores is well known to everybody, as that was used by Al Gore and many others, although he forgot to tell his audience that the CO2 levels lagged by some 800 years during a deglaciation and many thousands of years at the onset of new glaciations:
Data from the Vostok ice core via:
The temperature is derived from dD and d18O proxies in the ice. dD means the change in the deuterium/hydrogen ratio measured in the water molecules of the ice and d18O is the change in 18O/16O ratio of the water molecules in the ice. Both heavier isotopes of hydrogen resp. oxygen increase in ratio to the lighter ones, when the ocean temperature, from where the precipitation originates, increases. Thus the change in ratio is an indication of the ocean temperature changes. For coastal ice cores, that indicates the temperature changes in the nearby Southern Ocean, while the deep inland cores receive their precipitation from the more widespread SH oceans, thus representing the temperature changes of about the whole SH. The NH ocean temperature changes are more or less represented in the Greenland ice cores, which show similar changes (over the last about 120,000 years), but with some differences in timing and more detailed extreme events (like the Younger Dryas).
There is a remarkable near-linear ratio between ice core CO2 and the temperature proxy record in the same core over 420,000 years of Vostok. Work is under way to confirm this ratio in the 800,000 years of Dome C (for the overlapping period, the CO2 levels are already confirmed similar): about 8 ppmv/°C:
Data of the Vostok ice core from NOAA, temperature proxy indication shows zero at current temperature. From:
http://www.ncdc.noaa.gov/paleo/icecore/current.html
The spread in temperature/ CO2 data, mainly at the high side, is from the long lag of CO2 levels which remain high for thousands of years at the end of a warm period, while the temperature is dropping back to a minimum. The 8 ppmv/°C is not absolutely right, because temperature at best represents a hemispheric ocean temperature, but not far off, as the pCO2 in seawater dependency of temperature shows about 16 ppmv/°C. But besides pCO2 of seawater, other land and (deep) ocean items also play a role.
This all is an indication that temperature is not the cause of the sharp increase of CO2 in the last 150 years, as that wouldn’t give more than 8 ppmv (or 16 ppmv based on ocean solubility) increase with a maximum 1°C temperature increase since the depth of the LIA, while the current increase is over 100 ppmv.
Be aware that, besides some fractionation of the smallest atoms/molecules (not of CO2), and a small fractionation of isotopes, the bubbles still reflect the ancient atmosphere as it was. Ice core CO2 thus is not a proxy but a direct measurement, be it smoothed, of what actually happened in the (far) past.
The objections of Jaworowski:
What about the objections of Jaworowski against the reliability of ice cores (http://www.warwickhughes.com/icecore/ )?
Jaworowski assumes that CO2 “leaks” via cracks in the ice, caused by the drilling and pressure release of the deep core ice. But how can they measure 180-300 ppmv levels of CO2, when the outside world is at 380 ppmv? If cracks (and drilling fluid) are found in the ice, that would show levels which were too high, compared to other neighbouring layers, never too low.
The formation of clathrates (solid forms of O2, N2 and CO2 with water at very cold temperatures and high pressure) depletes CO2 levels, according to Jaworowski. This is well known in the ice core world. Therefore they allow the ice cores to relax up to a year after drilling. Moreover: O2 and N2 clathrates would decompose first, thus escaping as first via microcracks (as Jaworowski alleges). This would lead to too high CO2 levels, not too low.
Jaworowski accuses Neftel of “arbitrary” shifting the Siple data with 83 years to match the ice core CO2 with the Mauna Loa data. But the page from Neftel’s report ( http://www.biokurs.de/treibhaus/180CO2/neftel82-85.pdf ) contains two columns in the table: the counted ice age and the calculated gas age, the latter based on porosity measurements of the firn. Jaworoski used the age of the ice, not of the air bubbles, to base his accusation on, which is quite remarkable for a specialist in these matters. CO2 is in the air, not in the ice and the average age of the gas is (much) younger than the ice where it is enclosed. Neftel even made specific remarks about the gas age, which was compared to the South Pole atmospheric data, to confirm the average age of the gas bubbles at depth:
If the 328 p.p.m. measured at a depth of 68.5 m.b.s. [note: meters below surface] is matched with the atmospheric South Pole record, the mean gas age is 10 yr, corresponding to a difference between mean gas age and ice age of 82 yr, which lies in the above estimated range. The difference is used in calculating the mean gas age for all depths.
That the CO2 concentration measured on the subsequent samples from 72.5 and 76.5 m.b.s. corresponds with the atmospheric South Pole record justifies this age determination…
This clearly indicates that Neftel based his gas age estimate on firm grounds and there is nothing arbitrary in “shifting” the data, as there was no shifting at all. Thus for the Siple ice core, the ice age – gas age difference is about 82 years (Neftel estimated 80-85 years) for an average gas age resolution of about 22 years in this case.
Many of the objections of Jaworowski were answered by Etheridge (already in 1996) by drilling three cores at Law Dome, with three drilling methods (wet and dry), using different materials for sampling, avoiding cracks and clathrates, allowing a lot of relaxation time and measuring the CO2 levels top down in firn and ice. No difference was found in CO2 levels between firn and ice at closing depth and there is an overlap of some 20 years of the ice core CO2 data with the South Pole data:
Figure from Etheridge e.a.: http://www.agu.org/pubs/crossref/1996/95JD03410.shtml
See more comment and further links about Jaworowski at:
http://www.ferdinand-engelbeen.be/klimaat/jaworowski.html
The “corrections” of J.J. Drake:
JJ Drake (http://homepage.ntlworld.com/jdrake/Questioning_Climate/userfiles/Ice-core_corrections_report_1.pdf ) claimed to have established that the CO2 levels needed a correction for the ice-gas age difference. The result of the “correction” is that the CO2 levels are much higher with little variation and the very good correlation with temperature vanished. This conflicts already with our knowledge of the influence of temperature on CO2 levels in current times…
Even so, the “correction” might be all right, but the reason he provided has no bearing in any physical relationship. He makes the basic mistake of conflating a good correlation with a causation: The error is of the kind:
A causes B and shows a good correlation.
A causes C and shows a good corelation.
Thus B causes C, because there is a good correlation between the two. But that correlation is completely spurious, as there is not the slightest physical connection between B and C.
The explanation for his observation is quite simple:
Temperature (“A”) causes the ice-gas age lag (“B”), as temperature is directly connected with humidity of the atmosphere, thus influences the amount of snowfall, thus the accumulation rate and as reciprocal the speed of closing the bubbles: higher temperature, higher snowfall, smaller ice-gas difference.
Temperature (“A”) influences CO2 levels (“C”) directly: higher temperature means higher CO2 levels.
Because the previous two results have a high correlation with temperature, that gives that the ice-gas age difference and the CO2 levels also show a high correlation, but there is no physical mechanism that shows any direct or indirect action of ice-gas age difference on CO2 levels or vice versa. It is a completely spurious correlation, without any causation involved, but both share the same cause. Any “correction” of CO2 levels found in ice cores based on the correlation with ice-gas age difference is meaningless.
Migration of CO2 in ice cores
Ice shows a thin layer of unstructured (liquid waterlike) water molecules near the surface of the air bubbles. Some CO2 may dissolve in this layer, but that is not a problem at measurement time, as measurements are made at low temperature under vacuum, effectively removing all CO2 from the opened bubbles in the crushed ice, while removing any water vapor as ice over an extra cold trap. Water in-between the ice crystals is very unlikely, as there is still the direct influence of ordered structural ice from both sides.
Migration in even the oldest cores is no real problem. The recent fuss about “migration” speed was deduced from the Siple core, based on layers where remelting occurred, something not seen in any high elevation ice core like Vostok or Dome C. It remains to be seen to what extent the Siple Dome results are applicable to other ice cores.
But if there was even the slightest migration of CO2, that would affect the ppmv/°C ratio of the above Vostok CO2/temperature graph over time: the proxy temperature indication is fixed in the ice, while CO2 is measured in the gas bubbles. If there was any substantial migration of CO2, the ratio between CO2 and temperature over warm and cold periods would fade away over the recurrent 100,000 years of time difference between the warm periods, but that is not observed.
Conclusion
The ice cores are a reliable source of knowledge of ancient atmospheres, if handled with care. The resolution heavily depends of the accumulation rate, with as result that the data measured in enclosed air bubbles are smoothed, ranging from 8 years for the past 150 years to near 600 years for the past 800,000 years.
Fred H. Haynie says:
August 23, 2010 at 1:05 pm
The finding of C14 at depths older than its detectable limits strongly suggests that this has occurred.
———-
Reference please. Or retract.
Richard S Courtney says:
August 23, 2010 at 6:14 am
No! It does not. Please read what I wrote and dispute it if you want to. But merely ignoring it and making an unfounded assertion instead does nothing for your credibility (and it is an annoying habit of yours).
I have responded to it, but you simply left it out (an annoying habit of yours):
Every time there was a warm period, one sees higher CO2 levels in the record than over cold periods. That may be caused by retained levels without much migration or by (much) higher levels in the past with migration. All warm periods in the Vostok ice core show about the same CO2 levels, as do the cold periods. And the ratio between the warm/cold periods remains about the same with the ratio of temperature between warm/cold periods.
As we have 4 (nowadays 8) periods, each 100,000 years apart, in the first case, we have no problems. In the second case, each migration period towards the past needs a doubling of the extra amount of CO2 to fulfill the decay rate which is supposed to show the current difference between the warm and cold periods (and the same ratio compared to the temperature proxy). Thus 8 times the migrating quantity for period 4 over the previous warm period in the Vostok core. Then we have period 5-8 in the Dome C record which are substantially lower than period 1-4, but even then, nothing points to a systematic reduction in level. That means that period 8 needs 8 times the migrating quantity to fulfill the migration speed of period 6. And that all without filling the cold periods too much (as these should pick up the migrating CO2).
As I said, very unlikely.
———————–
“Here you make again the same mistake: the liquid-like layer is only at the ice-air surface, not in between the ice crystals, as quite different forces come into play. That is clearly seen under scanning electron microscope and X-ray diffraction.”
You are plain wrong.
Scanning electron microscopy (SEM) cannot do it because it lacks the needed resolution.
Transmission electron microscopy (TEM) cannot do it because the transmission samples need to be too thin for the analysis.
Scanning transmission electron microscopy (STEM) cannot do it for the same reason as TEM.
X-ray diffraction (XRD) is ambiguous because the diffraction comes from near the surface of the solid.
But atomic force microscopy (ATF) suggests the effect exists between ice crystals.
And nuclear magnetic resonance (NMR) indicates that the liquid effect exists on the surfaces of ice crystals in the bulk:
e.g. ref.
VI Kvlividze et al. Surf.Sci. 44 60 (1974)
And
Y Mizuno et al. J. Phys. (France) Colloque C1 48 511 (1987)
Very impressive and I believe you for the methods used…
But by looking for the last reference, I found an old one back, where I lost the reference of (very readable, about the behaviour of the ice surface):
http://people.virginia.edu/~lz2n/mse305/ice-skating-PhysicsToday05.pdf
Indeed different methods which show the thickness of the liquid layer on the ice-air surface, but nothing about water like structures in between the crystals. Moreover, no liquid layers below 30-35 C (thus no liquid layers at Vostok, except for impurities).
The abstract of the last reference too only looks at the quasi liquid (at air) surface of ice, nothing about intercrystalline water.
And the abstract of the first reference makes it quite clear:
The NMR spectra of finely dispersed ice were investigated. It is shown that the narrow NMR signal from the ice is caused by the mobile water molecules on the ice-gas and ice-teflon interfaces.
Thus where is all that water in between the ice crystals gone?
—————
Then you completely fail to understand what I wrote when you say to me:
“Here you are mixing two different mechanisms: an equilibrium between air CO2 and dissolved CO2 and the migration of dissolved CO2 from higher levels to lower levels via intercrystalline water or veins (if that/these exist).”
Maybe I have expressed myself not that clear, but I suppose that you see that I have understood what you wrote, as you need increasing CO2 levels as start condition further back in time to end with the current rather similar CO2 levels over warm vs. cold periods, if there was substantial migration. See the item at the beginning.
——————-
Then you add more unfounded insults to Jaworowski (because you do not like what he says but cannot dispute it?) as though that affected the validity of his work one jot.
And if people do read the paper by Neftel et al. then they will be able to check the data and see Jaworowski’s claim is correct (whatever interpretation anybody wants to put on his text).
If you really think that Jaworowski is correct by accusing Neftel of “arbitrarily” shifting the data with 83 years then there is no hope left. He writes literally
An ad hoc assumption, not supported by any factual evidence, while it is clear from about all available scientific literature and simple logic, that there is a difference between the age of ice and the age of the enclosed air, for the simple reason that firn is an open system until the permeability is low enough to prevent further exchanges with the air above it.
One can discuss that it was 70 years or 90 years difference between the ice age and the gas age for the Siple Dome ice core, but as Neftel did compare his measurements at closing depth with the South Pole measurements and for two other depths, there is little doubt that he was right and Jaworowski just is talking nonsense, “not supported by any factual evidence”.
Richard Telford:
Your message to me at August 23, 2010 at 1:47 pm begins by saying:
“It is unclear what magnitude and frequency of variation you believe there should have been in atmospheric CO2 concentrations. Instead you spread (or rather diffuse) doubt and uncertainty, this time about the potential for diffusion to corrupt the CO2 record in ice cores. This stratagem makes it difficult to demonstrate inconsistencies in your beliefs.”
That is offensive and untrue so I have not bothered to read any more of your post.
1.
If anything I wrote is unclear to you then state it and ask for a clarification.
2.
I do not “believe” anything about this subject. On the contrary, if you had read my posts here then you would know that I think the ice core data is incapable of providing definitive knowledge of past atmospheric CO2 concentrations.
3.
I do not know what variations should be in past atmospheric concentrations but I suspect (n.b. NOT “believe”) they should be similar to the indications of stomata data.
4.
I do not “spread (or rather diffuse) doubt and uncertainty” but I do promote and practice proper scientific scepticism (which your posts lack).
5.
The “potential for diffusion to corrupt the CO2 record in ice cores” is a scientific fact (read the posts and link provided by Jim at August 23, 2010 at 10:26 am and August 23, 2010 at 12:30 pm).
6.
I have no “stratagem”.
7.
There are no “inconsistencies in [my] beliefs” and my beliefs are not relevant to any discussion on this thread.
If you post a reasonable comment to me then I will read it, but I have only read the first paragraph of your post at August 23, 2010 at 1:47 pm and I have no intention of reading any more of it. As my response shows, that pargaraph is offensive, insulting and untrue drivel. No sensible person would bother to read any more of such stuff.
Richard
George E. Smith says:
August 23, 2010 at 9:49 am
Well The very first thing that I noticed in Ferdinand Engelbeen’s graphs of CO2 and temperature is that they are plotted on different “pages”. That’s very odd for plotting scientific data, where the idea is to expose important features of the information. It a text book they would put the two graphs on difefrnet pages so you can’t really compare them.
George, this was just an illustration of the comparibility of the graphs. The important one is the one below it: the rather linear ratio between CO2 and temperature. And you have obviously not read what I wrote above the CO2-temperature graph:
The visual correlation between temperature and CO2 levels in ice cores is well known to everybody, as that was used by Al Gore and many others, although he forgot to tell his audience that the CO2 levels lagged by some 800 years during a deglaciation and many thousands of years at the onset of new glaciations:
Thus before you accuse somebody, first read what he says.
Engelbeen implies that it takes about 40 years of compaction of the snow to get good samples of the entombed atmosphere, so why does the latest data say the CO2 is 280 ppm when it hasn’t had that measured value in actual atmospheric measurements since virtually th4e dawn of “climate science.”
Again you haven’t read what was said in the introduction: The Law Dome needs 40 years of compaction of the snow, but the air still is in open contact with the atmosphere and is only 7 years older than the open air at closing depth. Thus the CO2 levels digged in 1990 contains air from around 1980 and show levels of 335 ppmv, the same CO2 levels measured at the South Pole. Because the South Pole measurements started before 1960, there is an about 20 years overlap between the South Pole data and the Law Dome ice core data.
Further, indeed ice cores are averaging the CO2 data, depending of the amount of snowfall at the drilling site: more snowfall, faster compaction and less averaging of the CO2 data. The averaging is between 8 years (Law Dome) and some 600 years (Dome C). The fastest accumulating ice cores do record any peak of 20 ppmv, lasting one year or any increase of CO2 of 2 ppmv lasting some 10 years. But not farther than some 150 years back in time. The resolution becomes worse, the farther you go back.
Ferdinand:
I am replying to your post at August 23, 2010 at 3:21 pm .
You have replied to my complaining that you had not addressed my argument by your asserting:
“I have responded to it, but you simply left it out (an annoying habit of yours):”
OK. Where did you reply to the argument that I actually made?
I have read all your comments more than once and I fail to see it.
Then you repeat your assertions that completely ignore my argument (again).
You say;
“Every time there was a warm period, one sees higher CO2 levels in the record than over cold periods. That may be caused by retained levels without much migration or by (much) higher levels in the past with migration. All warm periods in the Vostok ice core show about the same CO2 levels, as do the cold periods. And the ratio between the warm/cold periods remains about the same with the ratio of temperature between warm/cold periods.”
Yes!
As I explained – and you again ignore or fail to understand – that is what one would expect to see as a result of the quasi-equilibrium I said could be expected to result from diffusion. So, it is NOT supporting evidence for your assertions.
Then you say;
“As we have 4 (nowadays 8) periods, each 100,000 years apart, in the first case, we have no problems. In the second case, each migration period towards the past needs a doubling of the extra amount of CO2 to fulfill the decay rate which is supposed to show the current difference between the warm and cold periods (and the same ratio compared to the temperature proxy). etc.”
No! It does not. I again ask you to read what I wrote. You have again ignored it completely.
Your claim that this is “very unlikely” is true of what you say concerning your imagined “doubling of the extra amount of CO2 to fulfill the decay rate” but is not – repeat, NOT – true of the probable quasi-equilibrium that I described.
We can swap references and our interpretations of them for ever, but the fact is that the liquid layer DOES exist between the ice crystals and this DOES enable diffusion. Please see the posts from Jim at at August 23, 2010 at 10:26 am and August 23, 2010 at 12:30 pm which demonstrate that leading ice core analysts agree it exists and that diffusion occurs at an unknown rate through it.
And you conclude by dismissing Jawarowski’s correct statement concerning the IPCC ice age/gas age difference with yet another ad hom. This does you no credit.
Richard
Jim says:
August 23, 2010 at 12:30 pm
***********
But they apparently did have reason to conclude that there is migration of CO2. From the quote: “We estimate the permeation coefficient for CO2 in ice is ∼4 x 10-21 mol m-1 s-1 Pa-1 at -23°C in the top 287m (corresponding to 2.74 kyr). Smoothing of the CO2 record by diffusion at this depth/age is one or two orders of magnitude smaller than the smoothing in the firn. However, simulations for depths of ∼930-950 m (∼60-70 kyr) indicate that smoothing of the CO2 record by diffusion in deep ice is comparable to smoothing in the firn. “
Thanks Jim for this quote. Thus quantitatively:
The smoothing of the CO2 data from the Siple Dome ice core was estimated (based on firn densification at closing depth) to be around 23 years.
The deepest layers (representing air of 60-70 kyr ago), then would show a spread of around 46 years, but the younger parts are hardly affected.
That means that one need to be cautious about the resolution of the “warmer” ice cores. And in this case also about the accuracy of the CO2 measurements, as the ice core also shows CO2 peaks of about 20 ppmv, probably from the presence of remelt layers.
Richard S Courtney says:
August 23, 2010 at 4:17 pm
To repeat your argument:
Eventually, a quasi-equilibrium of the gas in each bubble will be achieved. This quasi-equilibrium will result from
(a) the rate of the migration through the 3-dimensional matrix of the liquid phase on the surfaces of the ice crystals
and
(b) the initial concentration (so, partial pressure) of the gas in the bubbles.
At which I responded:
“but I don’t see any reason that the migration via water should stop, before all levels are equal everywhere (including the remaining CO2 levels in the air part). Only the speed will reduce with the concentration differences.”
Your quasi-equilibrium is a false one, as the leveling simply will go on as long as there are differences in CO2 levels, if there was any migration at all. What we see in reality is differences in CO2 levels which are about equal over 4 periods of each 100,000 years.
The only way to obtain the same CO2 levels in warm periods today if there was migration, is by increasing levels at start condition, for each period huge enough to show about the current (pre-industrial) CO2 level with the migration speed. As the migration speed depends of the concentration differences and the concentration difference reduce over time, one need a doubling of the initial quantities for each period back in time.
Richard S Courtney says:
August 23, 2010 at 4:17 pm
Forgot to add:
Other types of diffusion (e.g. via liquid in ice grain boundaries or veins) may also be important but their influence has not been quantified.”
As the whole investigation showed, this seems all about diffusion through the ice itself, although I don’t see a physical explanation how that can happen through the ice matrix. But they exclude liquid in ice grain boundaries or veins for what they have done.
There may be some, but all the references I have found only show ice-air waterlike layers, without any reference to intercrystalline water. And definitively not below -30 to -35 C, while Vostok is average -40 C.
“There is evidence that liquid water is present in pure ice down to temperatures
of around — 13°C, the approximate temperature at which the liquid-like signal
in NMR spectroscopy falls below the limit of detection (Bell et al, 1971,
Kvlividze et al, 191 A). Of course, these experiments give no indication of where
the water may be found but, following the work of Nye and Mae (1972), it
seems likely that the NMR liquid signal originates at the grain boundaries of
the ice. Nye and Frank (1973) have advanced thermodynamic arguments which
indicate that any water present as bulk liquid in equilibrium with the solid must
be found at triple junctions which form interconnecting networks in the ice. A
thin liquid-like layer may also exist at free surfaces (Fletcher, 1968) and possibly
even at grain boundaries.”
http://www.google.com/url?sa=t&source=web&cd=10&ved=0CDsQFjAJ&url=http%3A%2F%2Fiahs.info%2Fredbooks%2Fa118%2Fiahs_118_0263.pdf&rct=j&q=water%20between%20ice%20grains&ei=GyFzTLvCPIGclgehn_U_&usg=AFQjCNGfWXkRDIeRMCuqrRA7N6vYh3QFfw&cad=rja
Ferdinand I would like to preface my remarks with a sincere appreciation for your diligent responses to the blogs,” I may not agree with what you say but I will defend with my life your right to say it”
There is obviously a great extent of research papers on both sides of this debate and one can cherry pick the papers to “ prove” either argument thus the debate continues ad nausem.
However returning to the mathematics of the mass balance which is not subject to the above bias.
I think the critical oversight you make with your rusty knowledge of process calculations is that exchanges will occur with respect to quantities of natural and anthropogenic carbon in between the air, ocean and land in the ratio that exists in the sources.
Thus if the air contains 80% natural and 20% anthropogenic carbon the land and the ocean will absorb the carbon in that ratio. So in the case of 150 GT ( it is a lot more but we will use your number) the sinks absorb 30 GT of anthropogenic carbon. However they only emit the ratio of the N to A carbon that they contain i.e. for oceans 900 to 18 and for land 2300 to 101 per IPCC AR4 page 515. Thus there is a large imbalance of carbon absorption in the land and oceans verses emissions by human plus reemission from the land and ocean if we use your assertion of the anthropogenic content of the atmosphere.
Frankly your argument against this relatively simple mathematical analysis is as distorted as your responses to so many valid arguments, 40 year half life, give me a break that is pure smoke and mirrors IPCC double speak.
Once again let me quote from the IPCC 4th AR page 446 Box 6.2.
“ Ice core records show that atmospheric CO2 varied in the range 180 to 300 ppm over the glacial-interglacial cycles of the last 650 kyr … The quantitative and mechanistic explanation of these CO2 variations remains one of the major unsolved questions in climate research”
That is because it never happened. The ice core data is substantially flawed.
Jim says:
August 23, 2010 at 6:37 pm
“There is evidence that liquid water is present in pure ice down to temperatures
of around — 13°C, the approximate temperature at which the liquid-like signal
in NMR spectroscopy falls below the limit of detection (Bell et al, 1971,
Kvlividze et al, 191 A). Of course, these experiments give no indication of where
the water may be found but, following the work of Nye and Mae (1972), it
seems likely that the NMR liquid signal originates at the grain boundaries of
the ice. Nye and Frank (1973) have advanced thermodynamic arguments which
indicate that any water present as bulk liquid in equilibrium with the solid must
be found at triple junctions which form interconnecting networks in the ice. A
thin liquid-like layer may also exist at free surfaces (Fletcher, 1968) and possibly
even at grain boundaries.”
Thanks for the link! It shows that water is mainly found at the triple points, which are isolated parts in the ice. To sustain migration of CO2 via water one need water with a sufficient layer thickness at the grain boundaries to let CO2 or (bi)carbonate ions pass the ice. And that is what I haven’t found yet.
And temperature is of course important, at -13°C, the water layer at the ice-air border is much thicker than at -23°C (Siple ice core) and completely absent at Vostok (-40°C)…
The Siple core shows an extra 23 years smoothing after some 60,000 years of migration, but also problems due to remelted layers. If we assume the same migration speed at Vostok (in fact much less, due to much colder temperatures, no remelt), that would give an increase to about 650 years averaging for the CO2 levels, compared to the estimated 600 years now, after 100,000 years of migration, 700 after 200 kyr, 750 after 300 kyr and 800 after 400 kyr (I know, that is linear, while it is not, but so what). And that would be (hardly) visible as an increased smoothing for each period further back in time.
No big deal, as a transition from cold to warm needed some 5000 years and back is over 10000 years. And that doesn’t change the average, only the resolution gets worse.
Ferdinand:
This is a brief initial response to your comment at August 23, 2010 at 5:01 pm because I have to leave for a business appointment. I will provide a full answer when I return this evening.
Thankyou for your clarification that demonstrates your misunderstanding. It says:
“At which I responded:
“but I don’t see any reason that the migration via water should stop, before all levels are equal everywhere (including the remaining CO2 levels in the air part). Only the speed will reduce with the concentration differences.”
Your quasi-equilibrium is a false one, as the leveling simply will go on as long as there are differences in CO2 levels, if there was any migration at all. What we see in reality is differences in CO2 levels which are about equal over 4 periods of each 100,000 years.”
That is so removed from reality that it is no wonder I failed to recognize that you had tried to address my explanation!
It is plain wrong that “the leveling simply will go on as long as there are differences in CO2 levels”. The “leveling” will reduce to almost nothing when the partial pressure gradient at the tip of the diffusing agent becomes very small.
As an illustration, I point out that this reduction of diffusion rate is why steel can be used as reinforcement in concrete. Iron oxide is about four times larger than the oxidised iron. So, if steel rusts it breaks the concrete. (Many people have seen a concrete fence post that has been destroyed by rusting of its internal steel reinforcement that is close to the post’s surface). But if the concrete’s steel reinforcement is about 10 cm or more from the concrete surface then the steel does not rust. This is because the diffusion rate decreases to almost nothing when the partial pressure gradient at the tip of the diffusing oxygen becomes very small, and the partial pressure gradient reduces with distance from the high partial pressure at the concrete surface.
The same effect must occur with diffusion of CO2 through ice crystal boundaries.
Must rush now so will read the rest of your posting when I get back.
Richard
Barry Moore says:
August 23, 2010 at 7:34 pm
Ferdinand I would like to preface my remarks with a sincere appreciation for your diligent responses to the blogs,” I may not agree with what you say but I will defend with my life your right to say it”
Thanks!
Thus if the air contains 80% natural and 20% anthropogenic carbon the land and the ocean will absorb the carbon in that ratio. So in the case of 150 GT ( it is a lot more but we will use your number) the sinks absorb 30 GT of anthropogenic carbon.
Agreed.
However they only emit the ratio of the N to A carbon that they contain i.e. for oceans 900 to 18 and for land 2300 to 101 per IPCC AR4 page 515. Thus there is a large imbalance of carbon absorption in the land and oceans verses emissions by human plus reemission from the land and ocean if we use your assertion of the anthropogenic content of the atmosphere.
Agreed, but if you use the more realistic figures, anthropogenic CO2 (aCO2) is less than 10% of the atmosphere and supply and removal of aCO2 are more or less in balance (a slight increase, because aCO2 emissions still are increasing).
Frankly your argument against this relatively simple mathematical analysis is as distorted as your responses to so many valid arguments, 40 year half life, give me a break that is pure smoke and mirrors IPCC double speak.
The error you and many before you make, is to make a distinction between the origin of the molecules in the atmosphere and the origin of the increase in total mass of CO2 in the atmosphere.
The origin of the type of molecules in the atmosphere is governed by two items: the supply of aCO2 and the refresh rate. For the sake of clarity, let’s assume that all aCO2 has a red color.
Thus at year one: 8 GtC red CO2 enters the atmosphere and the fraction of red color increases from zero to 0.01. Total mass in the atmosphere increases from 800 to 808 GtC. Independent of the red color, a stream of 150 GtC nCO2 enters the atmosphere and 154 GtC (n + a)CO2 leaves the atmosphere. Net result: an increase of total mass from 800 to 804 GtC CO2 and an increase of 0.08 in red fraction, or 6.5 GtC red CO2 (some 20% removed by the refresh rate). I hope we may say that the increase in mass may be fully attributed to the addition of aCO2, as the other flows are a net sink, even if the fraction aCO2 is less than 1% by now.
Year two: same scenario: 8 GtC red CO2 in, 150 GtC nCO2 in (not completely right: part of aCO2 returns back from other reservoirs, but let’s have it clear), 154 GtC mix out, again removing 20% of the red CO2, total mass increases to 808 GtC, of which some 11 GtC or 0.015 fraction is red CO2. But still the full increase is caused by the 8 GtC injection, as the balance between natural inputs and natural outputs is negative.
Thus at last, for at least the past 50 years, the fraction of aCO2 increases slowly in the atmosphere until as much aCO2 is removed as is injected, to reach at maximum less than 10% nowadays. Thus the red colored aCO2 increases the redness of the atmosphere, but slowly until an equilibrium is reached.
But the full increase is attributable to the injection of aCO2, as nature was a net sink all over the years.
The refresh rate of 150 GtC doesn’t change the total mass in the atmosphere, it only governs how much red CO2 resides there, it is only the imbalance which adds or removes CO2 from the total mass in the atmosphere.
The near 40 years half life time is not from the IPCC (which uses a set of much shorter and much longer decay times) but from a known (C)AGW skeptic: Peter Dietze, see: http://www.john-daly.com/carbon.htm
Ferdinand:
I am back and have now read all your post at August 23, 2010 at 5:01 pm and the subsequent posts.
Jim seems to have covered all that matters in his contributions (I do not know who ‘Jim’ is but I brook that he knows more about ice core analysis than yourself).
I only now write
(a) to show I am not ignoring your points
and
(b) to make sure that I completely refute one of your mistaken assertions.
You assert in your post at August 23, 2010 at 5:01 pm :
“The only way to obtain the same CO2 levels in warm periods today if there was migration, is by increasing levels at start condition, for each period huge enough to show about the current (pre-industrial) CO2 level with the migration speed.”
No!
This is a complete misunderstanding on your part.
If diffusion through a matrix operated like that then all steel-reinforced structures would fall down in less than 10 years (please see my explanation of this in my post at August 24, 2010 at 1:45 am).
A quasi-equilibrium becomes established in the manner I explained at August 22, 2010 at 4:24 pm. And the result would be – as I there explained – exactly what we see in the ice cores.
Some here doubt your knowledge of mass balance analyses. I know your writings here demonstrate your lack of knowledge of materials science.
Richard
One thing that ice core data tells us is that the process rates upon which “climatetology” of the earth is calculated has never been “more or less in balance”. The rates of change for different processes vary within and between processes. The ice core data shows us that both internal and external forces and their interactions cause these rates to change in cycles. The problem we have with the ice core data, in trying to establish cause and effect, are the limitations with respect to accuracy and time resolution. The CO2 data is probably the most limited.
Thanks, Ferdinand, for your patience. I’m not easy to convince, but find your analysis convincing. And right up front you state that this has nothing to do with the “CO2 is causing runaway warming” mantra.
This topic really should be a formal paper, but it prb’ly wouldn’t be accepted unless you put the obligatory “we’re all doomed” or equivalent as the last sentence.
Richard S Courtney says:
August 24, 2010 at 5:59 am
OK, I have no problem to assume that the oxydation of steel in concrete shows little migration of oxygen in the deeper layers (although some 50 year old bridges needed to be renewed here, due to “concrete rot”, be it probably from adding CaCl2 for fast hardening in the past).
But let us look at the probability and the results of a similar mechanism in ice cores.
In my opinion, the ice core matrix is more closed than a concrete matrix, but nevertheless, let’s go on.
A quasi-equilibrium becomes established in the manner I explained at August 22, 2010 at 4:24 pm. And the result would be – as I there explained – exactly what we see in the ice cores.
That is what I doubt: assuming that the CO2 levels in a warm period were substantially higher than observed today, that should migrate from the higher levels to the lower, thus spread over a longer period, until the higher level is at the quasi-equilibrium.
A relative concrete example: assume that the CO2 levels in the atmosphere in the previous warm period, the Eemian, were the same as today (temperatures were somewhat higher than in this period), then migration would spread the 390 ppmv CO2 levels over a longer period, until the quasi-equilibrium of 290 ppmv is reached. Indeed there is a long tail of high CO2 levels in the Eemian, while temperature (and CH4) is falling (see
http://www.ferdinand-engelbeen.be/klimaat/eemian.html for a graph of the Eemian).
But I don’t see a reason why the migration doesn’t go back in time (or in this case: further down the ice): the CO2 levels before the rise in temperature are very low (190 ppmv) and follow temperature with some 800 years lag when temperature goes up. With a two-sided migration of an extra 100 ppmv during 10,000 years, CO2 levels should preceed the temperature rise with thousands of years. A one-way migration seems very unrealistic to me, the more that the levels before the rise in temperature are lower than after the cooling down.
Next the warming from the LGM (last glacial maximum) until the Holocene optimum (again somewhat warmer than the current warm period: North Pole largely icefree at least in summer): CO2 levels follow the temperature increase with a lag of again some 800 years, see:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/epica5.gif
with thanks to André Van den Berg who provided the graph.
Once the warm period would have been reached, the CO2 levels would increase over the quasi-equilibrium level and should spread two-way. Back: nothing to see. Forward: an small increase since about 4000 years, but rapid since about 160 years. But if the real CO2 levels in the ice indeed were 390 ppmv in the past 10,000 years, where is all that CO2 gone?
Think about this as a probability and how it would affect the CO2 ice core data. Let’s assume that under the weight of all the ice above it, the ice at depths acts as an amorphous mass like glass and flows ever so slowly under the pressure. At some point in depth and time, bubbles would no longer exist. Where do the highly compressed and cooled gases go, by what mechanism, and how fast?
Fred H. Haynie says:
August 24, 2010 at 10:25 am
Think about this as a probability and how it would affect the CO2 ice core data. Let’s assume that under the weight of all the ice above it, the ice at depths acts as an amorphous mass like glass and flows ever so slowly under the pressure. At some point in depth and time, bubbles would no longer exist. Where do the highly compressed and cooled gases go, by what mechanism, and how fast?
Under sufficient pressure, and low temperatures, all air molecules disappear as clathrates. When the ice cores are retreeved, they are stored at normal pressure at low temperatures (below -20°C) mostly under the surface on site for up to a year. This allows the ice to expand again, reforming gas bubbles from the clathrates. This is called relaxation of the ice.
Measurements are done under vacuum while crushing the ice. Eventually surviving clathrates decompose rapidely under vacuum.
Ferdinand,
With all this that you know has occured you still expect the concentrations in the reformed bubbles to be the same as when it was first trapped? How much carbon in some form is retained in the ice when the bubbles are formed and when the ice is crushed?
Mike Jonas says:
August 23, 2010 at 6:45 am
Sorry, there was too much traffic and I had only a limited time to respond in last days…
Temperature in the last 50 years has risen about 0.55 deg C [http://data.giss.nasa.gov/gistemp/graphs/]. If the relationship is linear (I doubt it is, but it is probably the best available assumption) then without human emissions, CO2 levels would have gone up (8 * 0.55 / 1) = 4.4ppm.
CO2 concentrations (Mauna Loa) have gone up from 319ppm in 1960 to 390ppm now [http://www.co2now.org/]. That’s an increase of 71ppm in the last 50 years.
4.4ppm is 6% of 71ppm.
So the increase due to human emissions is 94%, not 100%.
Well, the increase in temperature certainly added more CO2 to the total natural input flows, but it didn’t add to the increase, as the total natural outflows were larger…
In the same way, one can look at all natural inputs as contributing to the increase, like the permanent oceanic releases near the equator (also temperature controlled), which may be a factor 5 larger than the human emissions, but then forget that at the other side of the world more CO2 is removed near the poles.
Even for one-way additions like volcanic vents: there are also one-way CO2 sinks like rock weathering and carbonate deposits in the oceans by coccoliths. In all cases the inputs are more than compensated by the outputs.
One can discuss if a lower sink rate (thanks to an increase in temperature, gigantic forest fires,…) also is a form of “addition”, but that is rather academic…
But in fact this is a discussion for part 1 (but I didn’t look there for a while)…
Fred H. Haynie says:
August 24, 2010 at 12:35 pm
With all this that you know has occured you still expect the concentrations in the reformed bubbles to be the same as when it was first trapped? How much carbon in some form is retained in the ice when the bubbles are formed and when the ice is crushed?
With the crushing technique, less than 80% of the air (including CO2) is recovered, but that doesn’t change the composition, the remainder is in bubbles which didn’t crush.
But one does regularly measurements (especially for isotope compositions, to be sure that no fractionation takes place) where all ice is sublimated under vacuum and water and air cryogenically removed. Recuperation of CO2 >99%. Similar results for CO2 levels as in the previous method. See page 6 of:
http://courses.washington.edu/proxies/GHG.pdf
winterkorn says:
August 21, 2010 at 9:07 am
The old saw that extraordinary claims require extraordinary proof should have a couple of corollaries:
1. claims that run counter to common sense require extraordinary proof
2. claims that support secondary gain for the presenter require extraordinary proof.
In the case of atmospheric CO2 and human emissions #1 above is partly invoked (I am not invoking #2 in this posting; I do not think it is an issue here). If it is true that human CO2 production is only 4% of total production, then common sense indicates that a relatively small change in the other 96% (which must be biological, for the most part) could overwhelm any human change. For example a few percent change in CO2 production from the huge reservoirs of biologically available carbon (rotting vegetation, peat, coal, oil seeps, etc) could produce big changes in the overall flows in the Earth’s CO2 cycle.
The huge increases in CO2 during some interglacials in the past came from somewhere, as yet not known with certainty.
So long as these sorts of issues remain, the truth about effects of human production of CO2 should be considered as in some doubt.
Sorry for the delay in reaction…
Well point 2 is no problem: I am not badly paid by a (until now) solid pension fund.
About point 1:
That can be used the other way out too: If the human emissions are double the observed increase in the atmosphere, then claims that run counter to common sense, like that humans are not responsible, require extraordinary proof…
But your question is quite simply answered: the observed variability of the natural carbon balance is about +/- 2 GtC around the trend. That can be seen as the variability in the increase in the atmosphere, because the emissions show far less variability. The main driver of the variability is (ocean) temperature, which influences the sink rate of the oceans and opposite the growth rate of vegetation. As these two are opposite influences, the net effect is quite small (about 4 ppmv/°C), despite the huge fluxes involved.
The huge differences over glacials/interglacials have mainly the same sources, but additional: ice sheet building, at the cost of vegetation area and changes in (deep) ocean flows. Not all details are known, but the effect is: some 8 ppmv/°C between warm and cold periods. By far not enough to explain the current 100+ ppmv rise for 1°C rise in temperature since the LIA.
Bart says:
August 21, 2010 at 12:44 pm
you do not see any broad correlation between human inputs and actual CO2 measurements. I have done the analysis. There are no discernible overlapping periodicities between human production and the measurements.
Mike Jonas says:
August 22, 2010 at 8:06 am
You might be interested in these graphs, which might indicate that changes in CO2 concentration are driven by tropical temperatures, with quite rapid mixing across the hemispheres.
http://members.westnet.com.au/jonas1/CO2NorthAndSouth.pdf
And some others with similar remarks…
There is a quite good correlation between (ocean) temperature and increase rate in the atmosphere, far less between temperature and increase of CO2 in the atmosphere. Many, warmers and skeptics alike, agree on that.
But what you are doing is looking at the derivative of the trend, where most of the trend (caused by the relative constant emissions) is removed and temperature is the dominant driver of the variability. But a derivative of a trend doesn’t say anything about the cause of the trend itself…
Thus please have a look at the accumulation in the atmosphere and the accumulated emissions, not the year-by-year emissions and increase in the atmosphere:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/acc_co2_1900_2004.jpg
and compare that with the influence of temperature:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/temp_co2_1900_2004.jpg