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.
“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). ”
Small pores allowing gas to migrate? This sounds like good conditions for reverse osmosis or ultra high filtration. I see no convincing data or study that shows that the gas bubbles are not interacting with their surroundings.
Richard Telford:
At August 23, 2010 at 3:26 am you say to me:
“Basically you mean you cannot be bothered to spend thirty seconds on google (try ice CO2 diffusion), or better still ISI, to find out what is known about the diffusion rates of CO2. Is ignorance that bliss?”
No!
That is not “what I mean” (as I suspect you know well).
Read what I wrote. The reduction of CO2 concentration in a bubble cannot be determined simplistically because it is determined by the mass flow through the very thin layers on the surface of ice crystals. And it is forced by the initial concentrations in the bubble and they are not known.
Determination of the matter would require a laboratory study lasting decades.
Richard
anna v says:
August 22, 2010 at 10:07 pm
design aims in accuracy for IBUKI:
http://directory.eoportal.org/presentations/330/7450.html
Thanks for the link!
It is quite normal that they find huge differences over land, as that is where the largest sources and sinks are situated, but the satellite shows rather large differences over the oceans, even between adjacent area’s. And that is strange, as that isn’t seen in ocean ships surveys:
http://www.esrl.noaa.gov/gmd/ccgg/iadv/ and have a look at the Western Pacific cruise data: not more than 3 ppmv around the trend, including the seasonal variation.
Further, about CO2 measurements:
Similarly, for CO2 the objective is to measure the amount of CO2 circulating in the atmosphere, from 0 meters to the stratosphere. To say that sitting far away from sources and sampling the air in 70 locations justifies the estimate of the tons of CO2 circulating is as ridiculous as saying that sampling the energy in 70 remote locations away from heat sources can estimate the energy radiated by the globe.
It is simple physics after all.
The amounts of CO2 circulating are of interest for defining the fine details of the carbon cycle, but have little interest for “global” CO2 levels and its evolution.
But if the Japanese satellite can give the exact total column CO2 for all parts of the globe, that will be excellent.
Meanwhile, why make it yourself difficult if you can measure something that approaches “global” CO2 levels within a few ppmv, just by averaging a few stations? What happens local/regional over land will be readily mixed in within a few days to a few weeks for the near-ground stations and within a few months in the altitude stations…
Mike Jonas says:
August 23, 2010 at 4:40 am
Dead wrong. If we accept that temperatures have risen over the last 50 years, then the level of CO2 would have risen even without human emissions. Therefore less than 100% of the increase is caused by humans.
The levels would have risen absent human emissions with less than 8 ppmv since the LIA (16 ppmv, if one looks at the ocean’s solubility of CO2 only). But because humans have emitted about double the increase, nature as a whole was a net sink over the past 50 years, despite the temperature increase. A net sink doesn’t contribute to an increase…
Hoppy says:
August 23, 2010 at 5:03 am
Small pores allowing gas to migrate? This sounds like good conditions for reverse osmosis or ultra high filtration. I see no convincing data or study that shows that the gas bubbles are not interacting with their surroundings.
I was waiting for this reaction, as I was wondering too. But for reverse osmosis and ultra high filtration, one needs a substantial pressure difference, which is not present in adjacent layers. The study of Etheridge ( http://www.agu.org/pubs/crossref/1996/95JD03410.shtml unfortunately behind a paywall) did what you asked: looking at the composition of several players top down in firn and in ice over the transition zone. Besides some gravitational fractionation of the different isotopes (for which is corrected), there are no problems found and the gas composition at closing depth is about 10 years older in composition (for CO2 levels) than in the atmosphere. Gas composition in already closed bubbles and still open pores was the same. Except for some fractionation of the smallest molecules/atoms as recent investigations showed (not of CO2).
richard telford says:
August 22, 2010 at 12:56 pm
“2. Also my opinion: average levels over land where plants grow are some 30-50 ppmv higher than “background”.”
–
Dubious. Perhaps under a forest canopy. If CO2 levels were this much higher over land, it would suggest that the land was a huge source of CO2.
OK, a little more complicated than could be told in one sentence…
At night, under an inversion layer (as is often the case with low wind speed), levels get skyhigh (even hundreds of ppmv over background) for the first several hundred meters of air (depends of the height of the inversion layer). That is caused by plant respiration and soil bacteria. At first sunlight, plants start absorbing CO2 and levels start falling. This goes on until currently some 50 ppmv below background levels.
But as the sun is shining and/or temperature increases and/or wind comes up, the inversion layer breaks away and the lower air layers are better mixed with “background” air, which makes that the minimum CO2 level doesn’t drop further. That makes that the average CO2 level over land in general is higher than background, and that plants at least at the beginning of the day can profit from higher CO2 levels.
In how far that is comparable with times of 180 ppmv CO2 remains an open question, I suppose that the plants slow down with their CO2 intake when the levels drop too far, but still may have some periods during the morning where they have sufficient CO2 available.
Ferdinand Engelbeen says:
August 23, 2010 at 5:25 am
underwater vents?
Plimer has said that the CO2 output just from the vents in the island of Milos in Greece represent 2% of the world (volcanic ?)output, or something like that. I am curious to see if Milos shows up, once a final map is given, that can be magnified. There seems to be a red spot in the vicinity of Greece, but the resolution is poor.
http://www.mannkal.org/downloads/environment/profpilmer.pdf
Considering that the number of underwater vents is not known, I have heard numbers like 200 000, a scenario where the chaotic motions of the magma are increasingly venting CO2, coinciding with the exit from the little ice age, cannot be dismissed without further study, for example.
Ferdinand:
In your reply to me at August 23, 2010 at 3:53 am you assert:
“The main force is the difference in CO2 levels. That is for all ice cores which go far enough back in time, the difference of CO2 levels between warm and cold periods, as I explained in my message. Pressure differences are of interest, as these may help to establish migration speed. But that showed very little migration and is of no interest for the circumstances in the Vostok ice core. Of more interest is that the Vostok ice core CO2 measurements show no measurable flattening over time, neither on itself, nor in ratio with the temperature variations. This points to an extremely low migration speed.”
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).
Then you follow that with:
“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)
And you assert:
“Agreed, but no measurable changes observed over 4 periods of each 100,000 years longer…”
True, but since the starting conditions are not known it is a physical impossibility to measure any changes from them.
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).”
No! The two effects interact (they do not “mix”) to provide the eventual – and resulting – quasi-equilibrium. Please read what I wrote.
And you say to me:
“Your reasoning is theoretically possible, but very unlikely.”
“Very unlikely”? Prove it!
I say the mechanisms are certain to occur but the magnitude of their effect is not known but could – probably would – provide the resulting alteration to CO2 entrained in the bubbles that I describe.
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.
Importantly, I advised people to read references to papers by Friedli et al. and Neftel et al. that Jaworowski cited but you asserted were by Jaworowski. Now you say what amounts to “Jaworowski cites himself elsewhere”, but so what?
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).
Richard
Richard S Courtney says:
August 23, 2010 at 5:21 am
Determination of the matter would require a laboratory study lasting decades.
————-
Is is a coincidence that this is exactly what your coal mining friends would wish for? Decades of uncertainty while some hypothetical problem is solved to your satisfaction. Fortunately, you have already answered the problem: if the diffusion rate takes decades to measure, it must be small enough to be ignored.
Ferdinand Engelbeen : “because humans have emitted about double the increase, nature as a whole was a net sink over the past 50 years, despite the temperature increase”
True.
Ferdinand Engelbeen : “A net sink doesn’t contribute to an increase”
Well that’s missing the point. You are addressing the “with-human-emissions” situation. We’re talking about what nature would have done if there had not been the human emissions. The answer is very simple – the oceans would have been net emitters of CO2. We can argue about whether the amount they would have emitted is significant, but the very simple mathematical fact is that the amount of the observed increase due to human emissions is less than 100%.
OK, let’s do some sums.
You say that “The levels would have risen absent human emissions with less than 8 ppmv since the LIA“. You mention the possibility of 16ppm, but let’s use 8ppm. In that period, the temperature rose about 1 deg C. [http://www.physicalgeography.net/fundamentals/7x.html “During the Little Ice Age, the average annual temperature of the Northern Hemisphere was about 1.0 degree Celsius lower than today.“]. Maybe the global temperature went up by less, because there is more ocean in the S hemisphere, but let’s use 1 deg C as the global increase.
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%.
And there are enough unknowns that I doubt anyone can guarantee that the figure is not even less.
Ernst Beck says:
August 22, 2010 at 6:04 am
So glad you could make it to the party… thank you.
Ferdinand Engelbeen says:
August 23, 2010 at 5:33 am
But because humans have emitted about double the increase, nature as a whole was a net sink over the past 50 years, despite the temperature increase.
I guess this claim is based upon your claims in your Part One paper… and Part One would be supported by your Part Two paper… sounds like a circular argument to me… suppose it just goes to prove that blinkered animals have a tendancy to walk around in circles…
Ferdinand Engelbeen,
You look busy with responding to many commenters. Thank you for taking the time for your response to my comment.
Sincerely, I was not implying, by my context statement, that you would/could/should write an article on CO2 influence on temperature. It was not my intent to imply that. I do not think I did.
Regarding what you call “[my] conspiracy theory of WUWT slowly changing into a (C)AGW propaganda machine”, my context statement was to give my view of why we are discussing CO2 in this post. My context statement is not an endorsement of the context, only stating that the context exists. It certainly did not and is not intended to be the view of WUWT/Anthony.
I do not understand how the C-word (conspiracy) came up.
John
Ferdinand,
Certainly reverse osmosis requires high pressure differential to achieve any kind of productive rate. But I believe it will still proceed even at zero delta P (random molecular motion) and would have some affect if given enough time. Say 8 years.
Richard Telford:
You assert:
“if the diffusion rate takes decades to measure, it must be small enough to be ignored.”
No, (sigh) not over millennia.
Richard
Moderator,
My recent (within last 1 hour) comment to Ferdinand Engelbeen may have gone to the nether regions of spam, etc. Can you check?
John
REPLY: fixed, Anthony
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.
Notice how quite by accident, the vertical size of the excursions on the two graphs are about equal; and the time scales look reasonably similar too.
So the only reason you would NOT draw moth plots on exactly the same piece of paper, is if you wanted to deliberately hide the only useful information that is on these graphs which is the time relationship beytween these two variables.
But just as Al Gor failed to hide the truth in his book; so do has ferdinand failed to hide the fact that the Temperature changes precede the CO2 changes.
One other little problem is that Ferdiand’s CO2 graph says the popresent CO2 level is 285 ppm whereas other world locations say it is about 390.
Also just looking at the two graphs one would conclude that the two variables are linearly related; there’s no evidence that they are logarithmically related; as the late Dr Stephen Schneider claimed in promulgating his “Climate Sensitivity” theory that the temperature changes proportionately with the logarithm of the CO2.
Ferdinand says that the theory relies on the assumption of a well mixed atmosphere so that CO2 is the same everywhere.
Well NOAA publishes pole to pole three dimensional graphs of CO2 in the atmosphere which show that the CO2 isn’t even approximately well mixed in the atmosphere.
At the north pole and throughour almost the entire Arctic, the annual cyclic change in CO2 has a peak to peak amplitude of 18 ppm (out of 390) which is a huge variation in such a short time, but at the south pole it is only about 1 ppm, and it goes the opposite way from the north pole. So Vostok ice core cO2 can hardly be considered representative of global CO2 since the well mixed assumption isn’t valid.
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.”
Just looking at the slow CO2 decay compared to the Temperature fall that causes the CO2 decline, confirms that the Temperature must be the driving signal; not the other way round.
And let’s not forget that when you have a slow sampling process such as Englebeen describes (40 years or more to collect a sample of the atmosphere), the fact that the sample time is not instantaneous, means that the frequency response of the measuring system is degraded.
As an old hand at designing sampling oscilloscope circuitry back when they first appeared in the early 1960s, I know that the frequency response of a sampled data system depends on the width of the sampling pulse or more specifically on how long it takes to shut off the sampling gate.
The result of limiting the frequency response of a sampled data system with a slwo samplign gate is that the fastest shortest lived peak values are integrated out.
So the fact that ice cores don’t seem to show CO2 levels ever going above 280 ppm, is just a natural consequence of the slow shutoff of the ice sampling gate. The transient response of the system simply isn’t fast enough to capture the real tops of the upward spikes in the CO2 signal; so if there had been peak values as high as 390 ppm; that would never be recorded by the ice core sampling system.
All of which says nothing about whether humans caused the current levels (maybe they did) but who cares, since clearly the ice core peak values clearly aren’t accurate, and CO2 isn’t the Temperature driving force anyway; even though Ferdinand Englebeen tried to hide that from us.
Richard S Courtney says:
August 23, 2010 at 8:36 am
Richard Telford:
You assert:
“if the diffusion rate takes decades to measure, it must be small enough to be ignored.”
No, (sigh) not over millennia.
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You don’t have millennia to diffuse away late Holocene variability of the type that Beck imagines.
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Richard S Courtney says:
August 23, 2010 at 5:21 am
Determination of the matter would require a laboratory study lasting decades.
Richard
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But you might be able to measure the migration of CO2 through a thin slice of ice in months or less.
“One common assumption in interpreting ice-core CO2 records is that diffusion in the ice does not affect the concentration profile. However, this assumption remains untested because the extremely small CO2 diffusion coefficient in ice has not been accurately determined in the laboratory. In this study we take advantage of high levels of CO2 associated with refrozen layers in an ice core from Siple Dome, Antarctica, to study CO2 diffusion rates. We use noble gases (Xe/Ar and Kr/Ar), electrical conductivity and Ca2+ ion concentrations to show that substantial CO2 diffusion may occur in ice on timescales of thousands of years. 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. 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.”
http://cat.inist.fr/?aModele=afficheN&cpsidt=20841572
Richard Telford:
Your post at August 23, 2010 at 10:11 am is disingenuous or ill-advised.
In response to my comment concerning diffusion processes in ice that is cored to obtain samples that indicate atmospheric CO2 concentrations over hundreds of thousands of years you asserted:
“if the diffusion rate takes decades to measure, it must be small enough to be ignored.”
And at August 23, 2010 at 8:36 am I replied to that by saying:
“No, (sigh) not over millennia.”
Your post at August 23, 2010 at 10:11 am responds to that saying;
“You don’t have millennia to diffuse away late Holocene variability of the type that Beck imagines.”
Please explain what relevance – if any – that has to anything I have written.
Richard
Jim:
Thankyou for your useful comments at August 23, 2010 at 10:19 am and at August 23, 2010 at 10:26 am.
Your first says;
“But you might be able to measure the migration of CO2 through a thin slice of ice in months or less.”
I agree that you might, but I doubt it. Indeed, it is surprising that this has not been quantified if it is so simple to measure it.
This lack of quantification is confirmed by the quotation you provide (with a link to its source) in your second post. It includes this statement:
” 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.”
Also, that quotation agrees the existence of “liquid in ice grain boundaries” that Ferdinand denies.
Richard
George E. Smith says:
August 23, 2010 at 9:49 am
At the north pole and throughour almost the entire Arctic, the annual cyclic change in CO2 has a peak to peak amplitude of 18 ppm (out of 390) which is a huge variation in such a short time, but at the south pole it is only about 1 ppm, and it goes the opposite way from the north pole. So Vostok ice core cO2 can hardly be considered representative of global CO2 since the well mixed assumption isn’t valid.
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So Vostok cannot capture seasonal variability in atmospheric CO2 concentrations because the atmosphere is not well mixed on these time tables. Big deal. Did anybody ever claim that it could? CO2 is well mixed on the relevant timescales. Compare the CO2 concentration curves from South Pole and Mauna Loa.
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Richard S Courtney says:
August 23, 2010 at 11:13 am
This lack of quantification is confirmed by the quotation you provide (with a link to its source) in your second post. It includes this statement:
” 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.”
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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. “
Molecular diffusion in, and flow of ice under pressure is not trivial even within a century. Check out my analysis of the high resolution Greenland isotope depletion data at http://www.kidswincom.net/climate.pdf. It is hard for me to believe that air bubbles exist under the pressure of 3000m of highly compressed ice. The bubbles most likely form during the decompression of “climatization”. Also, during that time, present day air can diffuse into the microcracks that form as the bubbles form and the ice expands. The measured air age is then an average of a mixture which varies with depth. The finding of C14 at depths older than its detectable limits strongly suggests that this has occurred.
Richard Courtney
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.
Some possible belief you might wish to adopt:
1) The glacial-interglacial difference in CO2 concentration recorded at Vostok etc is smaller than it should be because diffusion has blurred the peaks and troughs. The problem is that this would imply that glacial values were even lower than 180ppm.
2) The Holocene should have large high-frequency variations in CO2, as purported by Beck. If these are century scale then the Law Dome should detect them, unless the diffusion rate is massive, in which case the older glacial-interglacial curves would also be affected (sub-180ppm – poor plants). If the variation is decadal in scale, then the ice cores would have difficulty in recording it, but it is also difficult to think of a plausible physical mechanism that would produce large changes in CO2 concentration on a short timescales. Except of course for burning fossil fuel.
I hope your coal mining friends appreciate your efforts on their behalf.