Guest Post by David Middleton
In my first guest post (CO2: Ice Cores vs. Plant Stomata), we discussed the merits of ice cores vs. plant stomata as paleo-CO2 measurements. One of the key stomata papers I cited was Thomas van Hoof’s “Atmospheric CO2 during the 13th century AD: reconciliation of data from ice core measurements and stomatal frequency analysis.” Van Hoof and his coauthors demonstrated that the Antarctic ice cores only reflected the low-frequency component of the CO2 “signal”…
It is well known that diffusion processes within the firn layer and the gradual enclosure of the air in the lock-in-zone of the ice lead to a reduced signal of the original atmospheric variability and may obscure high-frequency variations (e.g. Trudinger et al., 2003).
This “diffusion process” is primarily a function of snow accumulation rate. The higher the accumulation rate, the less diffusion and the higher frequency resolution. Compaction effects due to burial can also add to the diffusion process. Dr. Van Hoof’s paper presented strong correlative evidence that the plant stomata chronologies were capable of recording a much higher frequency CO2 signal than the ice cores. I was curious about whether or not any evidence of the diffusion effect on CO2 resolution could be identified in the ice cores through the correlation of CO2 mixing ratios and snow accumulation rates. NOAA’s paleoclimatology library does not include any accumulation rate data for Antarctic ice cores with published CO2 chronologies; but the accumulation rate can by approximated by calculating a sample rate.
I used data from two Antarctic ice cores (Law and Taylor Domes) over most of the Holocene (11 kya to the early 20th century) to compare the sample rate to the CO2 mixing ratio. The sample rates were calculated by simply dividing the sample depth interval by the ice age interval:
sr = [(zn – zn+1) / (tn – tn+1)]
Where sr = sample rate (m/yr), z = sample depth (m) and t = ice age (yr)
I then plotted the CO2 mixing ratio against the sample rate. Not surprisingly, there is an extremely strong correlation between the sample rate and the CO2 mixing ratio throughout the Holocene…
This makes it very clear that the low CO2 values in the Antarctic ice cores during the Holocene could easily be the result of diffusion and do not constitute valid evidence of a stable pre-industrial atmospheric CO2 level of ~275 ppmv.
References
Etheridge, D.M., L.P. Steele, R.L. Langenfelds, R.J. Francey, J.-M. Barnola, and V.I. Morgan. 1996. Natural and anthropogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn. Journal of Geophysical Research 101:4115-4128.
Indermühle A., T.F. Stocker, F. Joos, H. Fischer, H.J. Smith, M. Wahlen, B. Deck, D. Mastroianni, J. Tschumi, T. Blunier, R. Meyer, B. Stauffer, 1999, Holocene carbon-cycle dynamics based on CO2 trapped in ice at Taylor Dome, Antarctica. Nature 398, 121-126.
Van Hoof, T.B., K.A. Kaspers, F. Wagner, R.S.W. van de Wal, W. Kürchner, H. Vissher, 2005. Atmospheric CO2 during the 13th century AD: reconciliation of data from ice core measurements and stomatal frequency analysis. Tellus (2005), 57B, 351–355.
Wouldn’t diffusion be easy enough to measure in a laboratory environment? I can see using a press and snow in a container with sides made of a gas-permeable substance. Slowly compact 10 feet of snow and measure CO2 in the cores after a certain amount of time to see if its an accurate representation of atmospheric CO2 one year ago.
Prezakly. There is little or no chance that spikes would be preserved. And the baseline error is necessarily downward.
First – I’m not sure I understand ‘sampling rate’. Is this a proxy for the thickness of the annual ice layers? On the subject of diffusion, I understand you are talking about movement of CO2 in as-yet porous, unconsoldidated ice over multi decades. As a Precambrian geologist, I’m familiar with a much more aggressive form of diffusion – that of elements, like K, Na, Si, Al, etc. through solid rock! For example, a sequence of pillow lavas (when lava erupts on the ocean floor it shoots out soft ‘toffee blobs’ into the seawater that pile up layer-upon-layer) of basaltic composition (black Mg-Fe silicates) of Archean Age in the Lake of the Woods area of Manitoba-Ontario have been partly altered from the pillow edges inwards to a more granitic composition (grey-pink coloration) by diffusion of alkali-alumina-silica solutions that replace the pre-existing material but preserve the pillow structure. A more familiar example is fossilized wood where entire tree trunks have been replaced by silicates with no trace of the original wood. Even dinosaur bones are no longer of the original calcium phospate composition but rather have been replaced by (I believe – I’m not a paleontologist) silicate material. Regarding the ice cores, I have always believed that the relativel uniformity of CO2 is due to the more aggressive form of diffusion along crystal boundaries driven by high pressure. Moreover, one of the characteristics of the ‘invading’ solution is its reactivity with the solid medium and CO2 does react with H2O.
Any geochemists out there? I hate to wake up the ‘Granitizationists’ like Doris Reynolds (1899 -1985) whom I met at Bedford College, London in the 1960s -are there are any of you left these days who believe all rocks are formed by pervasive diffusion of a endless soup of mobile elements? Now is the time to be helpful.
http://www.britannica.com/EBchecked/topic/241716/granitization
Piers Corbyn says “you aint seen nothing yet”. This guy can save lots of lives and keep us much safer that the current crop of forcasters.
Just a casual thought — ice is an unusual solid being less dense than liquid water — I wonder if ice might be slightly CO2 repulsive such that the CO2 concentrations observed in deep ancient ice could actually tend to be less than the average of the CO2 concentrations when freshly formed … Does anyone know?
Spector;
Don’t think so, but the bubbles have a thin cold-water “pressure” film, and cold water aggressively dissolves CO2. IMO, that would tend to transport it out of there.
For a view from the other side I recently came across this article:
http://www.sciencedaily.com/releases/2009/10/091008152242.htm
She says her method of determining CO2 levels by looking at the ratio of calcium/boron in marine algae corresponds well with the ice core records.
I emailed her recently regarding what I consider to be some errors or flaws in her statements/reasoning, but, if I receive a response, I wouldn’t post any such correspondence without her permission.
Is the pattern of CO2 concentration versus depth/age the same in other ice cores? Does the CO2 level out at the same concentration? Is this what the warmers are relying on as evidence of a lower and stable pre-industrial CO2 concentration?
Maybe there is another explanation. What about biological processes? Is there any cyanobacteria which is photosynthesizing in the firn zone? Or maybe something to do with phase changes from gas to liquid and back to gas during burial/compression and sampling/decompression?
Spector says:
January 1, 2011 at 6:10 pm
Yes. The experiment, CO2 diffusion in ice, has been performed at Scripps in 2008, demonstrating unequivocally that CO2 does indeed diffuse through ice at a rate that would be significant over years or decades timeframe, much less millenia or megayears, and initial concentrations will decrease if they are higher than the current ambient concentrations:
“CO2 diffusion in polar ice : observations from naturally formed CO2 spikes in the Siple Dome (Antarctica) ice core
Auteur(s) / Author(s)
AHN Jinho (1 2) ; HEADLY Melissa (1) ; WAHLEN Martin (1) ; BROOK Edward J. (2) ; MAYEWSKI Paul A. (3) ; TAYLOR Kendrick C. (4)
Journal of Glaciology ISSN 0022-1430 CODEN JOGLAO
Source / Source
2008, vol. 54, no187, pp. 685-695 [11 page(s) (article)] (1 p.1/2)”
I had been posting about CO2 diffusion for some time at WUWT and elsewhere, but nobody has put together what this means, until now, to my knowledge. Fick’s Laws of diffusion govern diffusion of gases and solids in gases liquids and solids. The Second Law states that diffusion occurs from high to low concentration, and is directly proportional to change of initial concentration, and inversely with time.
What this means is that 600 ppm in a bubble in ice with 300 ppm outside will deplete CO2 in the bubble until the outside concentration approaching 300 ppm is asymptotically reached. A concentration of 1200 ppm will diffuse twice as fast as 600, 2400 ppm 4 times as fast, etc. Twice the age, conversely, will have twice the time for diffusion, so old cores will be nearer outside equilibrium level.
Practically, then, no old ice core can give an accurate result for ancient conditions using the traditional CO2 bubble gas chromatography method, and the result will be worse the higher the initial concentration of CO2 that existed in the past, and even worse the longer the residence time in the core. Old, high CO2 cores will be nowhere near the initial condition. So if we had tens of thousands of CO2 ppm in the past, ice core CO2 methodology would never show it.
This is intuitively obvious to me, since the extreme size of dinosaurs 100 Mya required high CO2, parts per thousand, for plants to grow to supply them with food,; said plants could then generate the high oxygen levels the dinosaurs needed to maintain their metabolism at such high levels.
I would think that the leaf stomata method, since it is static and not dynamic as is the CO2 sampling method, should be the method of choice until a better proxy comes along. Moreover, the CO2 method should be discarded completely for anything but current atmospheric conditions.
One cannot deduce a past static state using a dynamic conditions method.
Gary Pearse is correct to be skeptical about the fidelity of gas-bubble contents in millenial ice to the atmosphere at the time of inclusion. Honestly, can anyone really believe that atmosphere entrained among snow crystals during snowfall will remain unchanged for hundreds/thousands of years while those snow crystals slowly get transformed to firn and then to ice (multiple H20 phase changes)?
Oxygen isotopes in the ice are not such a problem because the water molocules remain the same in ice (regardless of transformations). CO2 as a trace contaminant in the gas phase of the ice-air mixture is much more susceptible to diffusion/conduction/convection processes that would tend to smooth out “spikey” variations over time.
I think CO2 concentration values in ice core are largely meaningless due to thermodynamic “smoothing” issues (above).
Modern CO2 concentration values in the atmosphere are largely governed by ocean heat content and biologic uptake/decay.
Human effects on CO2 are trivial and mostly immaterial regarding “global temperatures”, whatever they may be. Humans greatest effect on atmospheric temperatures is in “urban heat islands” due to land-use changes.
But not enough to create any “global” changes, except in unrealistic computer models of “climate change”.
Ah, Dave…I just looked at the Law Dome data ( ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/law/law_co2.txt ) and I notice a little bit of a pattern in time…like the only data above 300 ppm is that dated after 1900 and, in fact, the data is not a scattering of points centered around a higher value…It is simply the march of CO2 levels upward in the last 100 years or so. The plot that you made completely obscures the very strong, steady dependence of the CO2 level on the mean air age in the Law Dome data! Since the Taylor core has such a low accumulation rate, it doesn’t have any data points in the post-industrial era!
I know you really really want to prove your incorrect preconceptions but this post is frankly ridiculous!
Jim Cole says:
January 1, 2011 at 7:21 pm
Hear, hear!
Well said. Anyone that has ever thought that CO2 can be “trapped” in ice is not appreciating molecular movement and thermodynamics.
OT
I musing a little bit, please indulge me.
We could end all this anti-constitution talk with just one nuke exploding somewhere in the world. All markets would crash and these constitution haters will come running back to mama constitution in a New York minute when they start getting cracked on the head by Homeland Security’s jack booted thugs soon thereafter.
The complete and total economic collapse of the USA is a bit more subtle, but has an absolute certainty of 100% happening. No one is sure of the timetable except those who really pull the strings. How much longer can the Federal Reserve kick the can down the road? By May 2011 we will need an answer. QE3, Yes? If No we got 6 months, if yes, six months more, tops till, May 2012, notwithstanding a collapse of Europe happening before, then all bets are off. The markets will front run the collapse. They seem to be starting to do that already. Buy Silver and Gold.
Either way, we should all be uniting to get the Jack Booted Thug of Homeland Security out of our lives before the inevitable happens. I’d prefer to see The Department of Homeland Security abolished now.
bubbagyro says:
Here’s a copy of that paper, so that we are all on the same page: http://ns.geocraft.com/WVFossils/Reference_Docs/CO2_diffusion_in_polar_ice_2008.pdf Reading that paper does not seem to lead to the conclusions you draw. In particular, they note:
(1) “Smoothing of the CO2 record by diffusion is one to two orders of magnitude smaller than the smoothing by diffusion in the firn at the depth of 287m (gas age = 2.74 kyr BP) in the Siple Dome ice, and so does not degrade the record.”
(2) At depths where the ice age is tens of thousands of years (they use 80,000 years as an example), the diffusion may be comparable to the diffusion in firn and hence it may have “an impact on the smoothing of CO2 records on a decadal scale”. However, they admit that “there are no decadal CO2 data for
ice that is 80 kyr old”. Hence, it would seem that their conclusion about smoothing is, at least at the moment, basically academic.
(3) They also note factors that make the diffusion less of an issue for other ice cores: “Ice cores from colder sites than Siple Dome would experience slower CO2 diffusion in deep ice. The formation of clathrate ice (bubble-free ice) at depths from 500 to 1200m (25–65 kyr) at other Antarctic cold-drilling sites (Vostok, Dome Fuji and EPICA Dome C) is expected to result in highly reduced gas diffusion (Salamatin and others, 1998).”
Perhaps your misreading of the paper stems from the fact that you are reversing how the timescales work. You seem to think their talk about what happens on years to decades mean much more diffusion will happen over longer times. However, what they are doing is looking at 80,000 year old ice and saying, “The amount of diffusion in this ice might be enough for the CO2 to migrate enough to smooth out the CO2 data over a time period of years to a decade or so.” Do you understand the difference?
OT
Something that has always puzzled me about the US Civil War. It seems to highly organized to have not been staged? We fell for the Civil War. Everything the Civil War accomplished could have been accomplished by legislation. Every other country in the world did it that way. What else won’t we fall for? I count 33% of the population woken up in recent years. I wouldn’t worry yourself too much about it. It only took 8% of the population of the US in 1776 to beat the British and win us a country. And what a great country.
“What a Country!” TV Spot from WPIX-11
Gary Pearse – look for granitisation processes in
http://www.ellistonresearch.com.au/Verification%20Reports.pdf
This is yet another example of experts looking down long noses at an emergent theory, without being able to answer the awkward questions posed to the mainstram hypotheses. Theory developed with Prof S Warren Carey, a giant among geologists, also shunned by the establisment (until they found him likely to be correct about plate tectonics).
Then if you are so inclined, read about ice/gas age gaps at
http://homepage.ntlworld.com/jdrake/Questioning_Climate/_sgg/m5m1_1.htm
The World Wide Web took over the vastness of the US Empire years ago. When are they going to see that?
Spector says: January 1, 2011 at 6:10 pm – “Does anyone know?”
Short answer, no.
First one has to assume that isotope fractionation happened, with the common explanation being that ocean evaporation leaves behind some heavier isotopes. That’s ok, sort of. Then you make a quantitative relationship (which is really not ok, sort of loose).
Then you have to assume that these isotopically anomalous air packets find their way over the miles of ice to sites like Vostok and the South Pole, which are very cold and very dry. Snow seldom forms. (Expressed as “low accumulation rate”). It’s plausible, from watching movies of the strong winds at these places, that what accumulates also includes windblown ice particles of unknown isotopic history or origin. Next, you assign your isotopic temperature reconstruction to the location of the ice core, rather than the postulated ocean evaporation source a thousand or more miles away, ignoring the stong wind mixing effect.
Then you have to get your time line right, which raises awkward questions. If the Vostok hole, estimated older than 700,000 years, is deepened until there is no longer ice (but a lake or rock) – then what was the climate like 700,000 years ago before the ice was put in place? Some say the older ice was squeezed sideways into the oceans, but I think they are having a guess. If so, they are returning the isotopically anamlous ice back to the sea, so we have the makings of a mixed system where present day isotopic fractionation figures are partially determined by the amount of ice remelted to the oceans.
It is amusing to work through the convolutions of logic (often without the benefit of measurement or experiment) that are created to explain the awkward.
There is a lot of prior discussion on this blog and on CA. More questions than answers.
Interesting info on the Thorium fuel. Needs more advertising and pushing, I feel, especially with the woodentops in parliament.
.
Archie, could you also do an analysis of hydrogen as a ‘fuel’. We have a mayor of London and several influential parliamentarians who think that hydrogen is the way forward. I have been trying to tell them for some time that:
a. Hydrogen is not a fuel, it is a ‘battery’, an energy storage medium. And since the original fuel source is mostly coal and oil, hydrogen is effectively a fossil fuel.
b. Hydrogen is perhaps the most inefficient ‘battery’ we have. I estimate the losses being so great, that a hydrogen-fuelled car will do just 1/3 the mpg of a traditional fossil-fuelled car.
These truths need to be broadcast widely in the media, as there is a body of opinion that is pushing us towards hydrogen as a ‘fuel’. In reports recently I saw Boeing, GM and BMW all pushing the lie that hydrogen is ‘100% clean, with only water from the exhaust’ – while quietly ignoring the fact that the electricity to create the hydrogen was fossil fuelled.
There is also a chemical process that generates hydrogen through a reduction process, but again the true fuel for this process is oil. But again the calculations that I made on this process – after you have liquified the hydrogen, stored it, and then passed it back through a fuel cell – showed that it was less than half as efficient as a diesel car or truck. In other words, the ‘clean hydrogen’ actually emits twice the CO2 and noxious gasses as a standard diesel car. Plus, the added complexities and equipment mean the fuel will be four times the cost.
Thanks.
RE: bubbagyro January 1, 2011 at 6:56 pm –
What this means is that 600 ppm in a bubble in ice with 300 ppm outside will deplete CO2 in the bubble until the outside concentration approaching 300 ppm is asymptotically reached.
But, what about a 300 ppm bubble forming in an atmosphere of 600 ppm? The comment is silent on this point.
Should we expect the behavior to by symetric? There are forces that argue against symetry.
First, there is size and mass of of the CO2 molecule compared to N2 and O2. During compression and closing of the bubble, the molecular sieve effects could be come important in a Physical sense. Second, the Chemical effects of solubility at the ice crystal surface during forming of the ice bubble may enhance or counter act the physical molecular sieve.
Third, what about the snow_to_ice accumulation rates with a 300 ppm bubble in a 600 ppm atmosphere versus a 600 ppm bubble in a 300 ppm atmosphere? Does anyone believe they are the same? Up to a couple of years ago, IPCC would certainly propose much less snow in a 600 ppm environment (dare we say “none”) than a 300 ppm atmosphere. Today, with England snow covered and Ireland’s water pipes bursting, it would not surprise me if they suddenly claim more snow at 600 ppm than at 300 ppm – somehow. I guess the IPCC would say the matter is only academic because according the the ice cores, [CO2] has never been as high as 600 ppm and the physical inability of ice to preserve 600 ppm spikes in a 300 ppm average is unproven. But an experiment showing this inability might be easy and inexpensive to perform.
Fourth, to the suggestion of an experiment that snow should be compressed into ice to analyze the potential diffusion. The compression by mechanical means would tell us very little. It has to be compression by snow accumulation. So you can start off with a steady accumulation of snow, but very the atmosphere in [CO2] over time and see if the forced [CO2] is preserved in the bubbles. Rate of accumulation would be a critical variable: could a 1 yr test represent a 100 year natural accumulation?
While it could be done, more rigorous tests would be to vary the atmosphere above the snow in temperature and pressure as you accumulate snow. In the course of forming an ice bubble (50 to 500 years) the atmospheric pressure possibly changes by at least 20 mbar weekly from weather systems. That would be 2500 to 25000 kneadings of the entire firn gas column as the column is degassing during compression. It is not much of a pressure change, but repeated thousands of times during the formation of the ice bubbles, is it insignificant factor in the bubble’s composition?
bubbagyro says: January 1, 2011 at 6:56 pm
Yes. The experiment, CO2 diffusion in ice, has been performed at Scripps in 2008, demonstrating unequivocally that CO2 does indeed diffuse through ice at a rate that would be significant over years or decades timeframe, much less millenia or megayears, and initial concentrations will decrease if they are higher than the current ambient concentrations:
I think you are slightly mis-interpreting the results. The abstract states
That seems to state that the diffusion is about as significant as smoothing when the ice originally compacts. So for recent ice, the effect is small. For moderately old ice, the effect is predicted to be similar to other smoothing. For really old ice, the smoothing presumable would be more than the smoothing due to compaction (which I have typically heard to be about 100 years). So it is quite possible that the oldest ice samples are smoothed over 1000 years or so. But that still gives some very useful data.
This seems to me to be another classic case of experts in one discipline not consulting wide enuf with other disciplines. The issues over at CA demonstrate the folly of not using the correct statistical methods, and O’Donnell et al demonstrate the problems of geophysicists likewise not consulting with statiticians. I was originally a physical chemist, and the issue of ice core veracity has always troubled me.
I guess my question is why don’t these ice core people talk to the physical chemistry people.
Nigel Calder in ‘Magic Universe’ (Oxford, 2003 pages 110-112) describes the mismatch between ice-core CO2 concentration and that revealed by stomata/cm2 in preserved birch leaves. The leaves can form well definined annual layers over thousands of years. The stomata count is itself digital, so even partially decayed leaves yield useful information (unlike CO2 level in ice bubbles, subject as that is to diffusion etc).
This work was dismissed by the IPCC because it “conflicted with the ice-core data”.
This is not explained very well.
Is David proposing that CO2 is being removed from the snow by diffusion but N2 and O2 do not diffuse out of the snow thereby altering the ratio?
I am going to make a wild guess that the relative diffusion rates of gasses in ice are known. So what are they. My intuition says that CO2 would be slower as the molecule is bigger and this is the opposite if what is leopard.
bubbagyro says
————
This is intuitively obvious to me, since the extreme size of dinosaurs 100 Mya required high CO2, parts per thousand, for plants to grow to supply them with food,; said plants could then generate the high oxygen levels the dinosaurs needed to maintain their metabolism at such high levels
————
There would never be enough CO2 in the air to allow photosynthesis to ellevate O2 by a significant amount.