Wednesday, 8 December 2010

Carbon Dioxide Fractionation from Air "trapped" in Ice

"Another Hockey Stick Illusion??!!??"

1300-Year History of Atmosheric CO2
- using the density of plant stomata as a proxy measurement,
- by direct analysis of air in ice cores from Antarctica (Law Dome),
- and analysis of Central Pacific air (since 1958 from 3km up Mauna Loa volcano, Hawaii)

“The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge .. the world has suffered far less from ignorance than from pretensions to knowledge. It is not skeptics or explorers but fanatics and ideologues who menace decency and progress.”
by American historian Daniel Joseph Boorstin

This work-in-progress investigates the validity of attempts by scientists to reconstruct past atmospheric CO2 concentrations using air recovered from ice sheets and glaciers. This air is considered by some to remain virtually unchanged for the decades, centuries and millennia that it is enclosed within pores that form in the ice as it is compressed. Geologist Professor Richard Alley has gone as far as referring to the ice-core record as the "Gold Standard" for determining past atmospheric CO2 content - but is it?.


Falling snow brings with it the components of the atmospheric air in which it formed and fell. As it builds up on the surface the snow's structure changes. It becomes " Firn .. partially compacted granular snow that is the intermediate stage between snow and glacial ice .. formed under the pressure of overlying snow by the processes of compaction, re-crystallization, localized melting, and the crushing of individual snowflakes. This process is thought to take a period of about one year .. " (

Initially firn has pores through which air can circulate. As it gradually builds up, pores in lower firn are compressed and the deep firn becomes fully lithified as ice, where the pores are sealed off, leaving bubbles of air. The process towards lithification takes many decades or centuries, depending upon weather conditions which vary over time and space for each individual location.


1.1 Firn Column Porosity

Firn characteristics change with depth, density increasing (see Footnote 1a of this sub-section) and porosity decreasing (Footnote 1b). Air components can move relatively freely in the firn compared with their movement in the solid ice.

The upper firn, with a density of less than 400kg/m3, is macro-porous  (porosity of around 70%) and all constituent gases plus new atmospheric air can diffuse readily within it. In the deeper firn, where the density approaches 800kg/m3, pores have been so reduced in size by compaction that the firn is meso-porous.

As the density heads towards 900kg/m3 the deepest firn gradually becomes micro-porous, with air pockets starting to form as pores start closing. This significantly restricts the movement of the air components within the deepest firn, ultimately allowing only gases with the smallest molecules to escape and continue migrating within the firn down the pressure gradient towards the surface.

In the solid ice below the firn migration of gases is restricted to hopping between defects in the crystal lattice, two such defects being interstitials and vacancies (see Para 5.5.3 of "Ice Physics", by Peter V Hobbs -

The Neils Bohr Institute Centre for Ice and Climate (see also sub-section 1.2) article referenced alongside Fig. 1 above says " .. This has two important consequences:
- The concentration of a gas species in the firn changes relative to the atmospheric concentration due to physical processes (and in case of reactive gases also chemical processes). 
- The age of the gas in an occluded air bubble is less than the age of the surrounding ice. This age difference (the so-called Δage) depends on temperature and the amount of snowfall. The value of Δage can range from a few hundred years to several thousand years .. When a density of 800 kg/m3 is reached, the pores are gradually pinched off and form bubbles in the ice. This zone is called firn-ice transition and spans about the lowest 10% of the total firn column .. ". 

From the top of an ice sheet or glacier to its base there is a gradually reducing ice porosity (see Footnotes 1b and 2 of this sub-section). As a consequence, enclosed gases experience different types of diffusion. Researchers have identified five relevant diffusion regimes; gaseous (or molecular), Knudsen, liquid, configurational and atomic (in solids). This is discussed further in Section 2.0, Footnotes 2-5.


1a) Measurements on an ice core from the West Antarctic Ice Sheet (WAIS) Divide site show the somewhat erratic (high‐resolution -light purple) but gradually (mean black line) increasing density of firn with depth.


For more on this see Fig. 1 of the source article:-
Mitchell, L. E., et al. (2015), Observing and modeling the influence of layering on bubble trapping in polar firn, J. Geophys. Res. Atmos. 120, 2558–2574, doi:10.1002/2014JD022766 (

1)b The article in 1)a refers to three zones in the firn (a porous solid), a top "convective zone", central "diffusion zone" (DZ) and lowest "lock-in zone" (LIZ).

In its 1994 document "Recommendations for the Characterisation of Porous solids" ( the International Union of Pure and Applied Chemistry (IUPAC) defined three categories of porosity in porous media, based upon the pore width:
- macro-porous (greater than 50nm)
- meso-porous (50-2nm)
- micro-porous (less than 2nm)
The last two categories fall within the commonly-used description - nanoporous (100nm or less).  

2) The IUPAC  recommendations also described different types of pore in porous media, based upon their availability to external fluids:
- "closed" (inactive to fluid flow or adsorption) as 'a' in the diagram
- "blind"(one channel opening to the outside) as 'b' and 'f',
- "through" (several channels opening to the outside) as 'c'.

Fig. 1 of the IUPAC recommendations referenced in Footnote 1.

1.2 Gold Standard or Fools Gold?

The University of Copenhagen's Neils Bohr Institute Centre for Ice and Climate proclaims that .. Air bubbles trapped in polar ice sheets reveal the composition of the atmosphere of the past. Ice cores from the large ice sheets show that the atmospheric concentration of greenhouse gases, in particular CO2 and CH4, have risen tremendously over the past 100 years compared to past natural levels .. "
This article questions the validity of that claim.

An article to which it links includes a graph purporting to show how atmospheric CO2, CH4 and temperature have fluctuated during the past 800,000 years (

The bulk of the graph is a reconstruction using measurements of air recovered from ice cores drilled at the European Project for Ice Coring in Antarctica (EPICA) Dome C site (

That air has allegedly been "trapped" within Antarctic ice for decades, centuries and millennia with its composition remaining virtually unchanged.

Conveniently spliced onto a tiny fraction at the end of the 800,000 year reconstruction is an almost vertical line connecting to much higher CO2 and CH4 measurements. made in 2009 on samples of atmospheric air. Those 2009 values appear to have been obtained from samples taken at several measurement sites set up during the last 50 years (see Footnotes 1 and 2 of this sub-section). The scary impression given is that greenhouse gases have been rising at an unprecedented rate to unprecedented heights in recent decades, forcing global temperatures to do the same.  

It is recognised that migration of atmospheric gasses within the porous solid firn causes a low-pass filtering effect on gas concentrations. The degree of filtering is specific to the particular gas and equivalent filtering appears not to have been applied to the direct air measurements spliced on the end of the graphs.    

The objective of this article is to try to better understand how the molecules of the atmospheric gases, particularly N2, O2, CO2 and CH4 move within an ice sheet or glacier. Although there are interesting questions about snow flake formation and the progressive weathering/compaction processes depicted in Fig. 1, this article focuses on what happens during the period when the Lock-in-Zone (LIZ) of the deep firn is gradually being compressed through "close-off" of channels connecting air pockets.

Aspects of this issue were discussed in the 1992 paper “Do Glaciers Tell A True Atmospheric CO2 Story?” by Z. Jaworowski, T. V. Segalstad and N. Ono, along with several subsequent papers and articles by Segalstad and Jaworowski.

In his 1997 article "Carbon cycle modelling and the residence time of natural and anthropogenic atmospheric CO2on the construction of the "Greenhouse Effect Global Warming" dogma." Dr. Segalstad commented " .. the ice core CO2 results are not representative of paleoatmospheres .. hence the CO2-ice-core-method and its results must be rejected .. " (
Dr. Jaworowski said in his 1998 paper "Ancient Atmosphere - Validity of ice records" ( QUOTE:
.. The fractionation of atmospheric gases in ice sheets was observed and discussed since the beginning of CO2 studies in ice in the 1950s .. Stauffer and Berner (1978) concluded that due to fractionation processes "the CO2 content of ancient air is neither directly preserved in the total CO2 concentration (in the ice) not in the CO2 concentration in the bubbles". Although no experimental evidence contradicting this statement has since been presented, the current opinion seems to be opposite .. In the early publications, CO2 concentrations recorded in the bubbles from pre-industrial and ancient ice were often higher than in the present atmosphere. After 1985, the high readings reported by (NEFTEL et al. 1982) from the Byrd core of 325 and 417 ppmv have disappeared without explanation (NEFTEL et al. 1988). In this latter paper the highest value reported was 290 ppmv, and the pre-industrial mean concentration was calculated at 280 ppmv, supporting carbon cycle models used for greenhouse warming predictions .. The quality of ice cores as a material for the reconstruction of the past atmospheric composition is questionable .. the air bubbles  ,, do not fulfil the absolutely essential closed system criterion .. UNQUOTE.

There have been extensive discussions about this with numerous scientists and others, including those who give their full support to the CACC doctrine (Appendix A, Note 4), initially in Dec. 2009 on the blog of science student Chris Colose following his article “Richard Alley at AGU 2009: The Biggest Control Knob”. These discussions focussed on the preferential fractionation of CO2 due to its smaller kinetic diameter but little progress was made there (see also Appendix A, Note 15).

Presently the dry atmosphere comprises the following major gaseous components in these approximate proportions,  nitrogen (N2) - 78%, oxygen (O2) - 21%, Argon (Ar) - 0.93%, carbon dioxide (CO2) - 0.04%), methane (CH4) - 0.0002% ( That is approximately the composition of the air before it is carried to the surface of ice sheets in remote places such as the Antarctic and Greenland from where the ice cores are recovered.

There is significant uncertainty about how the atoms/molecules of the atmospheric gases O2, N2, Ar, CO2 and CH4 move during the process of "close-off" of the pores in the deepest firn during its lithification towards solid ice - discussed further in Section 3.0.

Of particular concern here is the relevance of two (of several) common measures of molecular size, collision and kinetic diameters (but see Section 2.0, Footnote 1 and its para. 7) when considering what occurs as the size of pores approaches that of the individual molecules themselves. During this period of compression the firn progresses in stages from being a macro-porous medium through meso- then micro-porous to solid ice. This is an important area of Catastrophic Anthropogenic Climate Change (CACC) research that has been given inadequate attention.

The diameter of the atoms that combine to form the different gas molecules present in atmospheric air cover a narrow range of only a few Angstroms (Å), i,e, tenths of a nanometer (see Appendix A, Note 6). Researchers and designers of systems for purifying gas streams have relevant expertise in the movement of these and other gas molecules, e.g. those working on the purification of mine gas or the removal of pollutants from flue emissions. This is discussed further in Section 5 "Size-dependent Fractionation - Examples".

The results of research so far have disclosed that as far as molecular diameter is concerned, for N2, O2 Ar and CH4, there is little difference between collision and kinetic diameters at approximately 3.8Å and 3.6Å for N2, 3.5Å for O2,  3.5Å and 3.4Å for Ar and 3.8Å for CH4 respectively (see table in Section 3). On the other hand, the collision diameter for CO2 is higher than any of the others (3.9Å) but its kinetic diameter is smaller than all of the others (3.3Å). The question then is what significance does this have as far as possible preferential fractionation of CO2 during its meanderings within ice for decades, centuries and millennia before being extracted in a core and subjected to analysis (Appendix A, Notes 10 and 17)? 


1) NOAA's measurement sites are: 
- Barrow, Alaska, CO2 started in 1973, CH4 in 1986, 
- Mauna Loa, Hawaii, CO2 started in 1974, Ch4 in 1987,
- Tutuila Island, American Samoa, CO2 started in 1976, and 
- South Pole, Antarctica., starting 1975.

2) Copenhagen U's Professor Thomas Blunier is the nominated person to be contacted for more information on the topic. He has failed to respond to related E-mails inviting him to comment on the issues raised herein. Associate Professor Anders Svensson did respond briefly, providing a copy of a 2006 GRL letter "Law Dome CO2, CH4 and N2O ice core records extended to 2000 years BP" by MacFarling Meure, et al. (

Svenson said that it " .. shows the very convincing overlap there is between CO2 concentrations measured in ice cores, in firn and by direct atmospheric measurements (Fig. 1) .. "

The Law Dome ice core and firn air records: AD 1800 to Present. (top) CO 2 , (middle) CH 4 and (bottom) N 2 O. Also shown are published Law Dome records and contemporary records from Cape Grim (deseasonalized flask, archive and in situ). Thin lines are spline fits (Enting, 1987): 20 year smoothing for CO 2 and CH 4 , and 40 year smoothing for N 2 O. Uncertainties associated with ice core air samples are graphically shown, firn air uncertainties are described in text.  

(Figure 1 is a graph of Law Dome ice core and firn air record from 1800 to 2006).

Considering the inverse grading of porosity with ice depth, that overlap is hardly surprising and does not answer the questions raised herein.


Fig. 2 Illustration of the density/porosity profile of an Ice Sheet

Discussions with numerous scientists (Appendix A, Note 16) involved in ice core studies as well as with other interested individuals suggest that there is poor understanding within the paleo-climatology community of the specific issue of how the "size" (see Footnote 1 of this section) of the molecules of the different gases affects their movement through firn during the later stages of compaction. Researchers have recognised since at least 1995 that a degree of fractionation of atmospheric gases in firn does indeed take place.

At a November 1995 colloquium on ‘‘Carbon Dioxide and Climate Change’’ a paper "Gases in ice cores" was presented by researchers Bender, Sowers and Brook. They commented " .. The diffusivity of an element or compound decreases with increasing mass and increasing atomic or molecular diameter. Thus each element or compound diffuses at a different rate .. In consequence, the covariation between the composition of one gas and another (e.g., CO2 and CH4) in firn is different from their historical covariation in air .. Differential diffusivity is a first-order effect that must be taken into account when interpreting data on the concentration and isotopic composition of gases in firn air and ice cores .. ". They went on to mention two causes of fractionation  -  gravitational and thermal (

In their 2005 Earth and Planetary Science letter  "Evidence for molecular size dependent fractionation in firn air .. " Huber, Severinghouse, et al said " .. we believe that the effect of close-off fractionation is nonexistent or at least very small .. for large molecules, like Xe, Kr, N2, CO2, CH4, and N2O. This is an important confirmation for the integrity of polar ice cores as a climate archive of the ancient atmospheric composition of these gases .. ". Once again these ice core specialists choose to use collision, not kinetic diameter (see Table 2 of the letter).

Science is not about belief, but about evidence. It is not belief but only sound evidence that will confirm or refute the integrity of polar ice cores as a climate archive.

The letter's authors said in the abstract that " .. for diameters greater than about 3.6 Å the fractionation seems to be significantly smaller or even negligible .. ". They also said " .. To constrain the model, we used the CO2 firn air measurements (Fig. 1). The model was forced with atmospheric CO2 concentration since 1750 from ice core data and measurements from Point Barrow .. Modeling the CO2 profile is a good tool to adjust the parameters of the relation between diffusivity and open porosity used in the model .. ".

It appears that they used CO2 to tune their model in the belief that its relevant diameter exceeds the magic 3.6Å. Although CO2 has a collision diameter of 3.9Å (well above that magic 3.6Å) its kinetic diameter is well below at only 3.3Å. Adjusting the models parameters (frig factors?) using the profile of an atmospheric gas which has very similar collision and kinetic diameters well above that magic 3.6Å, such as CH4, could make a significant impact on their results.

As experts in the energy industry who design systems for separating gases such as O2, N2 and CO2 from natural gas (mainly CH4), it is the kinetic diameter of those molecules which is relevant, not the collision diameter preferred by ice core specialists.

As there was no worthwhile response from Copenhagen University ice core specialists Professors Blunier and Svennson (see sub-section 1.2 "Gold Standard or Fools Gold", Footnote 2) a co-worker/author was contacted. Utrecht University Professor Thomas Röckmann's research focus appears to have been on the analysis of past and present atmospheric gas isotope ratio histories for CH4, N2O and CO, not the history of atmospheric CO2. He was the primary author, with Thomas Blunier et al. of "Isotope Variations in Atmospheric Methane Over the Last Two Millenia" (*.
Professor Röckmann has looked at this article and he responded promptly but briefly.

In 2003 Professor Röckmann said that " .. Air trapped in .. firn and ice provides an important natural archive of the past atmospheric composition .. " ( He and fellow scientists (many mentioned herein) may believe that evidence in air recovered from ancient ice is the best available record of past atmospheric composition. That hardly justifies regarding it as "the Gold Standard", as suggested by Professor Alley (see Appendix A, Note 1).

That needs to be taken into consideration alongside a comment by University of Cambridge ice-core specialist Dr. Eric Wolff, FRS, Royal Society Research Professor at the University of Cambridge. Professor Wolff, an internationally recognised expert and supporter of the CACC hypothesis (see Appendix A, Note 14) leads the British Antarctic Survey team. On 2nd May 2011 Professor Wolff said “ .. I think that none of us has a definite molecular level understanding of the physical process occurring at close-off, and it would be great if someone can do the experiments in the lab to understand that better. But it won’t alter the empirical facts .. ” ( - see also Appendix A, Notes 12 and 14).
That appears to remain the current situation (see also this Section, penultimate para).

What Professor Wolff said suggests that these ice core specialists may not understand all relevant processes to the fundamental level, leaving room for misinterpretation of their research. Gas fractionation experts in the energy industry could provide ice core specialists with much-needed guidance. Sadly departed Professor Zbiniew Jaworowski, who repeatedly challenged the validity of the ice core record since 1992, said in an E-mail in June 2010 that “I am also not versatile in diffusion, and writing my paper in 1994 I was advised and enlightened by a geologist from the Norwegian oil industry, who was specializing in diffusion, a subject of great importance for oil industry. This is a highly specialized field of science. My impression is that it is a terra incognita for glaciologists” (see Appendix C).

As well as gravitational and thermal fractionation of the gases in air, further research by ice core specialists did identify a third cause of preferential fractionation arising from the difference in size of their atoms/molecules. In 2006 Severinghaus and Battle (see sub-section 4.3) reported that air withdrawn from polar firn showed systematic enrichment in the firn–ice transition region of Ne, O2 and Ar compared with N2 (a larger molecule than the other three - see the table in Section 3.0) with air from the bubbles being correspondingly depleted. Those gases appear to be preferentially excluded from the shrinking and occluding bubbles, progressively depleting the air in the bubbles and enriching the firn air over time and depth. In simple terms, the smaller molecules are squeezed out of the older (deeper) into younger (higher) levels of the ice.

They concluded that the close-off fractionation was primarily size-dependent and that a threshold diameter of 3.6Å existed, with no fractionation taking place for molecules larger than this. Note that they focused their attention on collision diameter although they did acknowledge " .. that effective diameter depends on the nature of both molecules in a collision. In our case, the relevant collisions are between a gas and a water molecule in the ice lattice, so the values given here (which were measured in pure gases) may have limited relevance .. ". As mentioned in sub-section 1.2, CO2 has a collision diameter of 3.9Å but a kinetic diameter of 3.3Å!

It is hypothesized here that the use by paleo-climatologists of collision diameter is inappropriate because the firn in an ice sheet or glacier is gradually compressed from porous through meso-/micro-porous to solid stages. The deep firn becomes a micro-porous medium (see Footnotes 2-5 of this section). Expert practitioners in the movement of individual gas molecules in meso-/micro-porous media, such as zeolites, use kinetic (not collision) diameter in their design analyses and in the models upon which they base their practical designs for gas purification systems. Such systems are used routinely in the energy and other industries, e.g. for purifying mine gas to the standard required for natural gas transmission networks and for removing pollutants from flue emissions.

In their 2003 paper "The Use of Molecular Probes for the Characterization of Nanoporous Adsorbents" ( Sing and Williams discuss the characterisation of synthetic zeolites. They list the molecular probes used for characterisation in the order of increasing kinetic (not collision) diameter - see their Table 1. They go on to comment " .. In the early work on molecular sieve zeolites the van der Waals molecular diameter was taken as the appropriate 'yardstick' for the evaluation of the pore size. By 1974, however, when Breck's book 'Zeolite Molecular Sieves' .. was published, it was considered that a more rigorously defined kinetic diameter .. should be adopted .. ". The earlier work referenced there was published in 1926, so it took 48 years for those zeolite experts to recognise that they were using a misleading measure for molecular diameter. Hopefully the ice-core experts will learn from this and won't take so long.

When (if ever) this process is properly understood by ice core specialists it could well change the way that those empirical facts to which Professor Wolff referred are interpreted.


1) It should be noted that the molecules in question here should not be regarded as hard, inert balls with a fixed diameter, however, such a simple model is adequate for a basic understanding of size-dependent fractionation of gases.

2) A sound understanding of the movement of gases like N2, O2, CO2, CH4 in porous media is fundamental within the fossil fuel industry. This well-researched part of the energy industry provides relevant knowledge for paleo-climatologists working in areas such as the analysis of ice cores.

3) Ice cores are porous crystalline structures in which porosity is graded with depth. An important form of well-researched porous material used in the energy industry are Zeolites " .. porous, crystalline alumino-silicates. Their well-defined lattice structures contains cavities and/or channel intersections connected to each other by channels (also called windows or pores) of molecular dimensions ..
In the study of a guest molecule in a zeolite, the molecular diameter is often characterized by either the minimum kinetic diameter of the molecule .. or the Lennard-Jones length constant .. or its corresponding van der Waals diameter .. 

4) Molecules should not be viewed as rigid spheres, nor should zeolite channels be viewed as rigid walls. For the case where molecular diameter is close to but still smaller than the zeolite channel diameter, molecules might experience a net attraction when passing through the channels; If molecular diameter is slightly larger than the zeolite channel diameter, molecules might experience a net repulsive force instead. If molecular diameter is much larger than channel diameter, molecules can no longer enter the zeolite due to the strong repulsive force from the channels. .. Neither zeolite channel diameter nor molecular diameter can be described by a well-defined number. The diameter of an atom, such as oxygen, is difficult to define explicitly .. 

5) There are four well-known types of diffusion: gaseous (or molecular) diffusion .., Knudsen diffusion .. , liquid diffusion .. and atomic diffusion in solids .. In porous media exposed to a gas phase, gaseous diffusion retains its characteristics so long as the pore size is much larger than the mean free path of the molecules. Molecules collide with each other after travelling an average distance equivalent to their mean free path with the average kinetic speed determined by the Maxwell-Boltzmann distribution. When the pore size is smaller than the mean free path, collisions between molecules and the wall occur more frequently than collisions among molecules themselves. The average distance traveled before collisions approximately equals the pore diameter. Knudsen diffusion results ..
For solids, an atom vibrates about its equilibrium position due to the strong bonding with neighboring atoms. The atomic vibrational mode with its frequency, v, becomes responsible for diffusion. In one unit of time, the atom makes v passes at the energy barrier presented by its neighbors, with a probability exp(-E/kT) of surmounting the barrier on each try. The jump length is often related to a, the lattice constant (Kittle, 1976) .. 
The diffusion of molecules in zeolite pores of comparable size presents us with a new diffusion regime, the "configurational regime" as coined by Weisz in 1973. As discussed in Chapter 1, the mechanism for this type of diffusion is still far from being well-understood .. 
There is no well-accepted formula for estimating the diffusivity in this regime, contrary to the four regimes discussed above where the mechanisms are well-understood and formulas are available for estimating the diffusivities ..
Qualitatively, the movement of molecules in zeolites are "bounded" by two diffusional regimes: Knudsen diffusion and solid diffusion. Molecules inside zeolites, however, are not as free as in Knudsen diffusion where the effect of the potential field of the solid surface is minimal. In zeolites, molecules can never escape completely from the potential field of the lattice since the pore size is comparable to the molecular size .. 

Footnotes 3-5 are copied from "The Diffusion Mechanism of Hydrocarbons in Zeolites" ( pages 10, 20/21, 45/46, 51/52 ).


Dr. Zbigniew Jaworowski (Appendix A, Note 5) was respected by sceptics of the Catastrophic Anthropogenic Climate Change (CAC) hypothesis for his persistent criticism of claims that air “trapped” in ice for decades, centuries and millennia provided a reliable record of past atmospheric composition. Despite the unfounded claims that his arguments had been refuted by scientists who support the CACC hypothesis, Jaworowski remained resolute in his persistent rejection of the claim that ice cores provide a “Gold Standard”.

Professor Jaworowski is not the only scientist to have questioned the validity of this “Gold Standard”. Even those who support it acknowledge mechanisms that Jaworowski argued could distort the ice-core paleo-record over time. For example, in their 1993 paper “The Ice Record of Greenhouse Gases” ( Raynaud et al. acknowledged four of the processes that Jaworowski expressed concerns about QUOTE: ..(i) .. physi .. and chemisorption of gases on the surfaces of snow and ice ..(ii) .. the separation .. of gases in the firn ..(iii) .. alteration of .. composition by formation of air hydrates .. or by drilling ..(iv) .. alteration by chemical between the gases and the ice on long time scales .. the second of which is relevant to this article.

Raynaud et al. dismissed the first concern (Appendix A, Note 13) on the basis that the ice core record for CO2 and CH4 can be made to align with the measurements made at Mauna Loa but made no mention that this can only be achieved by manufacturing an age difference between the air and the ice in which it is “trapped” (another of Jaworowski’s concerns).

They dismiss the second by referencing a 1984 comment in a “Letter to Nature” by J. Schwander and B. Stauffer on the subject of “Age difference between polar ice and the air trapped in its bubbles” ( Schwander and Stauffer said “Air entrapped in bubbles formed in cold ice has essentially the same composition as that of the atmosphere at the time of bubble formation”. Their letter did not refer to scientific papers that had been published after the scrutiny of peer review but to two other earlier “Letters to Nature”, ( and a contemporary draft paper “Atmospheric CO2 concentrations during the last glaciation” by Stauffer B. Hofer H. Oeschger H. Schwander J. and Siegenthaler U.

Based upon the claims in these references, Raynaud et al. make the assumption that “ .. the air, just before being trapped at the base of the firn column, has a composition that departs slightly from the atmosphere at the surface of the ice sheet. These effects are generally small .. of the order of 1% .. for the gravitational effect .. and can be calculated with confidence .. ”.

That comment by Stauffer, Hofer et al. about “ .. just before being trapped … ” implies a sudden transition from open firn with free diffusion of atmospheric gases to solid ice with the air trapped in bubbles but this is misleading. Neftel et al. said in their 1994 article “Historical Carbon Dioxide Record from the Siple Station Ice Core” ( for Sipple Station, West Antarctica, “ .. the duration of the close-off process was 22 years .. ” (see Appendix A, Note 3).

During that long period in which the firn, air pockets and interconnecting channels are squeezed smaller and smaller the larger air components like N2, O2, Ar, and CH4 will be trapped first, with the smaller ones like CO2, N2O, Ne, He, etc. (see the kinetic diameter sizes in the table) still being able to migrate through the slowly closing lattice.

N2      O2     Ar     CO2    CH4     Kr    Xe      Ne     CO      He      NH3 
3.8     3.5     3.5      3.9       3.8     3.7    4.0     2.8     3.7       2.6      2.6   (Å) * 
3.64  3.46   3.4      3.3       3.8     3.6   3.96   2.75   3.76      2.6      2.6   (Å) **

Cl2  HCl  C2H2 N2O  Br2  HBr  CS2  H2S  SO2  C2H4  NO   H2   H2O
 3.2    3.2     3.3      3.3       3.5     3.5    3.6     3.6     3.6       3.9      3.17   2.89  2.65    (Å) **      

* Collision Diameterfrom “Fractionation of gases in polar ice during bubble close-off: New constraints from firn air Ne, Kr and Xe observations” by Jeffrey P. Severinghaus and Mark O. Battle, Table 1 (
** Kinetic Diameter from “VUV absorbing vapours in n-perfluorocarbons” by E. Albrecht, et al. Table 3 (

In their excellent 1992 paper “Do glaciers tell a true atmospheric CO2 story?” ( Professor Jaworowski et al. discussed the flaws in the claim of an ice-core “gold standard” and many of the physical/chemical processes that distort the composition of air during its long sojourn in the ice. They also challenged the manner in which the air/ice age difference is (gu)es(s)timated in order to fit with measurements at Mauna Loa.

That paper also made reference in Fig 9 to the escape of air components towards the surface down the pressure gradient that results from the action of gravity, saying “ .. The thermal gradient and gravitational compression of snow cause upward movement of gas. Some air escapes from snow and firn back to the atmosphere .. ”. What they did not appear to recognise was that a similar process occurs in the deep firn as close-off is approached resulting in preferential fractionation of the smaller air components, particularly CO2 over the larger (and more prominent) components such as N2, O2, and Ar.

As discussed previously, Professor Eric Wolff said in 2011 “ .. I think that none of us has a definite molecular-level understanding of the physical process occurring at close-off .. ” ( Some might argue that our knowledge of processes taking place within the ice which could change the composition of the air that is eventually “trapped” in ice has improved significantly in the past decade. Although specialists in the energy industry do have significant relevant knowledge, this would seem not to be so for ice core specialists.  


This section presents a selection of some of the differing arguments presented by scientists regarding the validity of the attempted reconstruction of past atmospheric composition using air extracted from ice cores. It starts with more recent challenges to the view that these reconstructions are reliable.

4.1 Professor Murry Salby

In August 2011 atmospheric physicist Professor Murry L Salby, who at the time (Appendix A, Note 9) had been Chair of Climate at the Faculty of Science of Macquarie University, Sydney, Australia since 2008, gave a presentation to the Sydney Institute on the topic of “Global Emission of CO2: The Contribution from Natural Sources” ( In this presentation Professor Salby made a brief reference to the ice core record of past atmospheric CO2 concentration but in the subsequent Question and Answer session he made the point (at 48 minutes) that the pitfall is that people take the ice record of CO2 literally but that this is not atmospheric CO2. He said that he did not believe that it was CO2 that was in the atmosphere when that piece of snow was laid down.

Professor Salby drew a distinction between the CO2 found after only 50 years in the ice and that found after 50k years, questioning any suggestion that it remained there unchanged. He pointed out how the fluctuations found in the upper layers are progressively filtered out further down and what was measured was actually a mixture of CO2 from other levels.

Professor Salby gave much more detailed presentations on the subject of the “Relationship between Greenhouse Gases and Global Temperature” (, first at the Helmut Schmidt University, Hamburg on 18th April 2013 then at a Cambridge Centre for Climate Science (CCfCS) seminar on 22nd April 2013 ( In November 2013 he followed up with similar presentations on “Climate: What we know and what we don’t” to audiences in Edinburgh ( and London in November 2013 (see Appendix A, Note 7). In these he looked more closely at the significance of the ice core record (see Appendix A, Note 8), opining that non-conservative influences would cause past atmospheric CO2 to be significantly underestimated, so it is likely that the recent rise in CO2 is not unprecedented. He proposed a damping mechanism such as diffusion to explain an anomaly between the behaviour of CO2 in the actual atmosphere and that seen in the proxy record from the ice core, stating “Non-conservative influences inherent in the proxy record enable past atmospheric changes to be significantly UNDERESTIMATED”.

Professor Salby suggested that the ice core proxy CO2 record underestimates the fluctuations in concentration of atmospheric CO2 to an extent that increases with core depth, pointing out how diffusion, first in the firn but continuing thereafter, reduced the amplitude of fluctuations. He showed how the annual variations shown in proxy record from the firn were lower than (perhaps ½ of) the true atmospheric concentration such as those shown in the Mauna Loa record. He went on to suggest that the proxy record from much deeper in the core could be an order of magnitude lower.

It appears that this arises because of diffusion, unhindered for several decades in the firn but continuing with increasing difficulty even beneath close-off of the firn, within the “solid” ice for centuries, millennia, etc. As discussed above, this eventually leads to size-dependent preferential fractionation of the atmospheric components having the smallest molecules. It appears that the most relevant measure of molecular size under the restricted diffusion conditions within “solid” ice is kinetic diameter which for CO2 is 0.33nm. That compares with N2 (0.36), O2 (0.35), Ar (0.34) and CH4 (0.38). In other words, CO2 will continue escaping from air pockets within the ”solid” ice long after other significant gases are too large to escape, i.e. reducing the CO2 concentration in the mixture that remains trapped in the air pockets.

4.2 Professor Eric Wolff

As is to be expected, ice-core specialist and CACC-supporter Professor Eric Wolff (see Appendix A, Note 14) took exception to Professor Salby's claims and responded with a short article "Ice core measurements of trace gases". Professor Wolff presented what he saw as " ..  the main evidence that the ice core record of CO2 is a good representation of the past atmospheric concentration, and that the record is not consistent with the changes I think he believes must have occurred .. " ( Included as the second of his two most important pieces of "evidence" was that 1000-year "hockey stick" reconstruction shown at the start of this article. He opined that " .. This slide shows that CO2 rose out of what had been a very small variability in about 1830 .. It always remained in the range 170‐300 ppmv (compare the graph on the right and values in 2013 of about 395 ppmv) .. ".

Professor Wolff then goes on to opine " ..  that when the bubbles are broken open to analyse the air, one is actually measuring the concentration of CO2 in the air sample just as if it was from a flask collected from air today .. "!! He then presented his "evidence" that CO2 in ice is a good representation of CO2 in the air when the bubbles closed, based upon the research reported in the 1996 paper "Natural and anthropogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn" by Etheridge et al.

It should be noted that the Etheridge et al. paper makes no mention of size-dependent fractionation of atmospheric gases during the long period when the firn is being compacted into "solid" ice. 10 years later the paper "Evidence for molecular size dependent gas fractionation in firn air derived from noble gases, oxygen, and nitrogen measurements" by Huber et al. presented evidence of significant preferential fractionation taking place for the smaller gases He, Ne and even O2 (see Figure 8 of the paper

In their 2006 paper "Fractionation of gases in polar ice during bubble close-off: New constraints from firn air Ne, Kr and Xe observations" ( Severinghaus and Battle discussed the size-dependent fractionation of Ne, Ar and O2. Severinghaus and Battle chose to simply infer that such fractionation did not take place for CO2 (see Table 1 in the paper) despite CO2 having a smaller diameter than O2. That inference was based upon the arguments in the Etheridge et al. paper that firn air CO2 concentration was the same as air extracted from bubbles at the same depth, the assumption being made that the air pockets were completely sealed at the chosen depth.


4.3 Professor Jeffrey Severinghaus et al.

(see Appendix A, Note 18)

In their 2006 paper "Fractionation of gases in polar ice during bubble close-off: New constraints from firn air Ne, Kr and Xe observations" Severinghaus and Battle acknowledged that size-dependent preferential fractionation of atmospheric gases does take place within an ice sheet. Using ice cores from Antarctic locations at South Pole and Siple Dome they found that " .. Gas ratios in air withdrawn from polar firn (snowpack) show systematic enrichments of Ne/N2, O2/N2 and Ar/N2, in the firn–ice transition region where bubbles are closing off. Air from the bubbles in polar ice is correspondingly depleted in these ratios, after accounting for gravitational effects. Gas in the bubbles becomes fractionated during the process of bubble close-off and fractionation may continue as ice cores are stored prior to analysis ... Ne, O2 and Ar appear to be preferentially excluded from the shrinking and occluding bubbles, and these gases therefore accumulate in the residual firn air, creating a progressive enrichment with time (and depth) in firn air .. The data presented here suggests that close-off fractionation increases very non-linearly with decreasing molecular size .. The pattern of fractionation in different gases deduced from the firn air samples shows a strong inverse relationship with effective molecular diameter inferred from viscosity data, but no clear trend with molecular mass. We conclude that the close-off fractionation is primarily size-dependent .. The large atoms .. show no significant trends in the lock-in zone, .. This observation implies the existence of an effective size threshold of 3.6Å, above which molecules have a low probability of escape from the bubbles and therefore do not become significantly fractionated. This places constraints on proposed mechanisms for the size-dependent fractionation. Our data are consistent with the recent suggestion .. that the regular crystal structure of the ice lattice contains a hole 3.6Å in diameter that sharply increases the escape probability of gases smaller than this size. Our data also are consistent with the hypothesis .. that fractionation occurs because of size-dependent differential permeation of gases through the ice lattice .. no evidence for close-off fractionation is seen for molecules larger than 3.6Å" (

It is noteworthy that in their Table 1 "Molecular size and observed fractionation in firn air" the fractionation figures for O2, Ar and Ne (all of which have collision diameters of less than 3.6Å) are OBSERVED figures. On the other hand the figure of 0 shown for fractionation of CO2 (collision diameter of 3.9Å) is merely INFERRED from firn and bubble air observations reported in the 1996 paper "Natural and anthropogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn" by Etheridge et al. (

Severinghaus and Battle regard collision diameter, not the kinetic diameter, to be the relevant measure of molecular size. That measure may be relevant in the relatively open structure of the higher levels of firn, in the snow above and even in the atmosphere.  In the meso-porous to micro-porous structure of the deeper firn, as it approaches close-off and lithification into "solid" ice, it is the kinetic diameter which is relevant. The kinetic diameter of CO2 (3.3Å) is smaller than N2 (3.8Å), O2 (3.5Å), Ar (3.5Å) and CH4 (3.8Å) - see the table in Section 3.0. This implies that CO2 can continue diffusing through the micro-porous parts of the firn into higher, more porous levels well after the other gases are constrained by their size in relation to the size of the interconnecting channels between pockets of air. Also, this smaller size means that CO2 is likely to diffuse more readily within the "solid" ice after full close-off to all gases than larger gas species such as N2, O2, Ar and CH4.

In their 2006 paper "Evidence for molecular size dependent gas fractionation in firn air derived from noble gases, oxygen, and nitrogen measurements" Huber et al. reported their findings for ice cores taken from North Greenland and Devon Island, Northern Canada


4.5 Professor J. Douglas Way

(see Appendix A, Note 19)



The basic issue discussed in this article is the dynamics of the individual atoms/molecules of the air constituents N2, O2, Ar, CO2, CH4, etc. enclosed within the gradually decreasing porosity of the lowest levels of firn in ice as it is compressed towards close-off 

As mentioned in Section 1 "INTRODUCTION" researchers and designers of systems used for purifying gas streams have relevant expertise which could assist in attempts by paleo-climatologists to reconstruct past atmospheric composition..

5.1 Professor J. Douglas Way

In May 1993 Professor J. Douglas Way (Appendix A, Note 19) reported on research undertaken " .. to investigate the transport mechanism in microporous, metal oxide membranes and to examine the relationship between the microstructure of the membrane, the membrane surface chemistry, and the separation performance of the membrane .. A further objective is to use molecular dynamics to simulate the transport of penetrants in pores of molecular dimensions .. " (

Professor Way summarised his research findings as:

- 1. The permeability of gases with kinetic diameters of 2.89Å to 3.9Å were measured through microporous silica hollow fiber membranes over the temperature range 298 K to 473 K at 20 atm feed gas pressure. Permeabilities ranged from 0.01 Barrer to 1000Barrer and were inversely proportional to the kinetic diameter of the penetrant.

- 2. Linear Arrhenius plots were obtained from the permeability data and the slopes yielded activation energies ranging from 7.5 to 13.5 kcal/mole. Activation energy is proportional to the kinetic diameter of the penetrant molecule. The values of the activation energies for the hollow fiber membranes were consistent with literature data for the diffusion of hydrocarbons in zeolites.

- 3. High separation factors were obtained for O2/N2 and CO2/CH4 mixtures. The mixture separation factors for O2/N2 decreased from 11.5 at 298 K to 4.6 at 423 K. Over the same temperature range, the mixture CO2/CH4 separation factors decreased from 186 to 22.3.

- 4. The mixture separation factors for O2/N2 mixtures were up to 20% larger than the values obtained from pure gas measurements at temperatures below 373 K. A similar effect was seen for CO2/CH4 mixtures after the membrane had been heated to at least 398 K and then cooled in inert gas flow.

- 5. The differences between the mixture separation factors and the ideal gas values is attributed to a competitive adsorption effect where the more strongly interacting gases (O2, CO2) saturate the surface and block the transport of weakly interacting gases (N2, CH4)

It is noticeable that Professor Way made no mention of collision diameter in his report, only kinetic diameter.

(Fig. 6 of the report shows CO2/CH4 separation factors increasing significantly as temperature decreases, approaching 200 at a temperature of 290K. The separation factor - or selectivity - is determined by the difference in permeability of the components of interest For example, if the the permeability of CO2 is 200 times higher than CH4 then the permeate stream contains 200 times more CO2 than CH4 and the selectivity from CO2 over CH4 is 200.)



6.1 The Influence of firn air transport processes ..

October 2011 Ph.D. Thesis of Christo Buizert


Appendix A - Notes

1) Geologist Dr. Richard Alley, Evan Pugh Professor of Geosciences ( is another staunch supporter of the Catastrophic Anthropogenic Climate Change (CACC) hypothesis. Like Professor Michael Mann, originator of the (in?)famous global temperature hockey stick so enthusiastically promoted by the IPCC in its 2001 Third Assessment Report, Professor Alley hails from Penn State University. In the autumn of 2009 he gave the Bjerknes Lecture at the American Geophysical Union, giving it the title "The Biggest Control Knob: Carbon dioxide in Earth's climate history" (

Within the first 5 minutes of his somewhat over-excited presentation Dr. Alley acknowledged that as far as work on ice cores is concerned " .. I don't actually do that but I talk about it .. I teach history of the Earth's climate .. ". He then went on to claim that " .. CO2 keeps being the only explanation for a lot of what happened which is validated .. So far the only thing which really works is .. the CO2 rock-weathering thermostat .. The CO2 thermostat takes half a million years or so to work, which means it's possible to get fairly large fluctuations in temperature before this thermostat brings it back. .. How do we know CO2 in the past? Our gold standard it the ice cores. You drill and ice core. You break the bubbles. You suck the CO2 out. You measure the concentration .. We have high confidence that the ice core record really is good .. ".

Dr. Alley concludes with the opinion that " .. This story is very clearly not done but it's fairly clear where we stand now. An increasing body of science indicates that CO2 has been the most important controller of the average global climate .. ". 

2) Constructive comments are welcome from anyone who would like to help - if they shed light on the uncertainties underpinning this important aspect of paleoclimatology. Contributors are respectfully asked to avoid simply declaring that claims that the ice core record is flawed have been refuted. Such claims have been made before with links to comments such as those of Hans Oeschger, Professor of Physics, University of Bern, purporting to do the refuting. All they do is reject, not refute. If you think that they refute then please be specific about how they are supposed to do it rather than simply providing a link or mentioning a name. Too much time has already been wasted following up on such claims and finding that they were simply unsubstantiated criticisms or flawed inferences.

3) Several articles (e.g. have made reference to a 1984 paper "Age difference between polar ice and the air trapped in its bubbles" by Schwander and Stauffer claiming that the duration of the close-off process was 22 years but I haven’t been able to track down any such paper. I suspect that the reference is to this "Letter to Nature" ( Can anyone provide a link to the full letter or to a paper of that title by the same authors?

4) In 2007 I started researching the CACC doctrine being pushed by the UN and environmental activists (that our continuing use of fossil fuels will lead to catastrophic global climate change/disruption) after reading a review of propaganda booklet “Six Degrees: Our Future on a Hotter Planet” by Mark Lynas. Since then I have become increasingly interested in his concerns, especially after reading Andrew Montford’s excellent exposé “The Hockey Stick Illusion”, which set me wondering if the CO2 hockey stick might also be simply another illusion.

NB: In early 2013 there was an attempt to breath life back into the temperature "hockey stick" using one of the same questionable proxies and once again Steve McIntyre highlighted the flaws in the analysis (

5) The sad news about Dr. Zbigniew Jaworowski's death was announced on 12th Nov. 2011 ( What a tragic loss to honest science. My condolences to Dr. Jaworowski's loved ones. This reminded me that a further update to this article was long overdue.

6) For example see page 127 of "Higgs Force" by physicist Dr. Nicolas Mee (PhD in theoretical particle physics from the University of Cambridge). 

8) As a matter of interest Professor Salby also showed that the claim that the record of the declining C13/C12 isotope ratio proved that the increase in atmospheric CO2 is due to CO2 emissions from fossil fuel is questionable.

9) A month after making his presentation to Helmut Schmidt University, Hamburg in April 2013, atmospheric physicist Professor Salby was dismissed by Macquarie University, Sydney ( If the claims made by Professor Salby are correct then it seems that he was treated disgracefully by Macquarie University from the outset. He may have put himself in the firing line on 2nd August 2011 when, as Chair of Climate at its Faculty of Science, he gave the presentation to the Sydney Institute on the topic of “Global Emission of CO2: The Contribution from Natural Sources” ( That was at a time when the Australian Government, a coalition between Labour and Greens led by Julia Gillard (, was really pushing the Catastrophic Anthropogenic Climate Change (CACC) propaganda hard. More importantly, there is a lot of tax-payers money being handed out to universities for research that supports the CACC hypothesis.

As usual there are at least two sides to every story. A very different side to this one is offered in these interesting Desmogblog articles of 12th July 2013:

- "Climate Sceptic Professor Sacked From Australian University Was Banned By National Science Foundation For Deceptive Conduct" (
- "Murry Salby: Galileo? Bozo? Or P.T.Barnum?" by John Mashey (

These articles focus not on Professor Salby's scientific arguments but his previous employment as a tenured Professor at the University of Colorado-Boulder from 1988 to 2008 and his debarment from funding for three years by the National Science Foundation. They provide links to some very interesting items, including the NSF's "Report of Investigation Case Number I06090025  February 20,2009, which includes the Closeout Memorandum provided by the Office of Inspector General, Office of Investigations: " .. Our investigation determined that the subject:' submitted significantly overlapped proposals to NSF and another federal agency; received compensation from NSF awards substantially in excess of approved budget amounts; overcharged NSF awards for indirect costs on a subcontract, and failed to disclose the subcontract to NSF; received payments for effort that he documented with questionable time and effort reports; and failed to comply with his University's conflicts of interest and financial disclosure policy.
This memo, the attached Report of Investigation, and the Deputy Director's decision letters constitute the case closeout .. .
1 Dr. Murry Salby .. " (see the full report at

10) I have asked this question of numerous high-profile “disciples“ of the doctrine such as James AnnanMichael TobisWilliam Connolley, etc. but no attempt was made by any of them to answer this other than to claim that Jaworowski had been refuted years before, which appears not to be so. One of the pioneers of ice core research, Professor Claude Lorius, one of his followers and prominent IPCC supporter, Professor Richard Alley, prominent sceptics Professor Hans Oerlemans and Dr. Roy Spencer were asked if they would like to help clear up the remaining significant uncertainties when attempting to reconstruct past atmospheric CO2 concentrations from air allegedly “trapped” in ice virtually unchanged for millenia. Professor Alley was good enough to respond within a matter of hours with helpful comments and several references.

11) The thread was promptly closed by the moderator, so I contacted Professor Wolff on 20th April 2011. He responded on 26th but couldn’t post on the closed thread. Despite the thread being locked there was significant continuing interest in it, evidenced by the viewing figures so, after several requests the site admin re-opened it )apparently reluctantly) and Professor Wolff posted several very helpful comments before the thread was once again closed.

12) Anyone interested in finding out more about this discussion with Professor Wolff should read the exchanges on the Science Forum of University of Cambidge "Naked Scientists" project in the “Another Hockey Stick Illusion?” thread ( There is also another interesting set of related exchanges on another thread “What does Iain Stewart's "CO2 experiment" Demonstrate” (both of which were locked by The Naked Scientists admin team) - see also Note 16).

There is also more in the exchanges on the “Hasn’t anyone ever heard of the Medieval Warm Period?” thread

13) This concern is still held by Professor Hartmut Frank – see the comment of 28/04/2011 at 19:50 on The University of Cambridge’s Naked Science forum -

14) More about Professor Wolff can be found at and

Short clips of Professor Wolff opinions about the analysis of gases recovered from ice cores can be seen in the videos at:

Professor Wolff appears to be a staunch supporter of the CACC hypothesis. In its Sept 2006 news article "Deep ice tells long climate story" the BBC reported that at the British Associations Science Festival in Norwich Dr. Wolff said " .. My point would be that there's nothing in the ice core that gives us any cause for comfort .. There's nothing that suggests that the Earth will take care of the increase in carbon dioxide. The ice core suggests that the increase in carbon dioxide will definitely give us a climate change that will be dangerous .. Ice cores reveal the Earth's natural climate rhythm over the last 800,000 years. When carbon dioxide changed there was always an accompanying climate change. Over the last 200 years human activity has increased carbon dioxide to well outside the natural range .. scary thing .. (is) .. the rate of change now occurring in CO2 concentrations. In the core, the fastest increase seen was of the order of 30 parts per million (ppm) by volume over a period of roughly 1,000 years. The last 30 ppm of increase has occurred in just 17 years .. " (

15) In March 2010 Josh Halpern (AKA Eli Rabbitt) was asked on his "Rabett Run" blog if he could help on molecular diameter and he started a thread “How big is that molecule in the window”. He offered some basic physics and concluded “Think of this as the start of a discussion” which subsequently even involved a member of the (in)famous “hockey team’ support squad Realclimate, theoretical physicist Raymond Pierrehumbert (Raypierre). The discussion unfortunately did what the ice core experts do, obsessing on collision (Lennard-Jones) diameter, which for CO2 is larger than that of CH4, N2 and O2. This was despite the fact that Joshua had discussed briefly the smaller kinetic diameter of CO2 on another of his threads on 25th January in response to an enquiry from an “Anonymous former-chemist-mouse” (AKA Marcus) who was involved in the discussion on Chris Colose’s thread.

16) The scientists involved in these discussions include Professors Alley, Jeff Severinghaus, Michael Bender and Eric Wolff. In April 2010 the issue was raised on the Science Forum of “The Naked Scientists … a media-savvy group of physicians and researchers from Cambridge University .. ” (” under the thread title “Another Hockey Stick Illusion?” ( It was hoped that such an august body (which had previously posted a thread about Professor Wolff's activities) would be able to contribute to a better understanding of the diffusion processes taking place within ice sheets. The question asked was “why do paleo-climatologists use collision diameter in preference to kinetic diameter when considering the migration of air molecules through firn and ice?” and additional information was provided to supplement the question.

The "Naked Scientists" were unable to answer the question (Appendix A, Note 11) so Professor Wolff was contacted and postseveral very helpful comments. In his final submission on 2nd May, fter having discussed my question with Professors Alley and Severinghaus, Professor Wolff said that “.. the empirical evidence that CO2 is not fractionated on enclosure (as well as the observation that Ar is less fractionated than O2) is what led these authors to hypothesise that collision diameter was the controlling variable. So the specific answer is that they use collision diameter because this is what allows them to rationalise the data that they observe .. ”.

That aligns with the responses that had previously been given by other specialists but the argument is not persuasive. Ar being less fractionated than O2 is unsurprising  It is on the basis that the use of collision diameter rather than kinetic diameter only fits their interpretation of the data, which itself may well be flawed.

17) Techniques for extracting and analysing the air in ice cores are described in various articles, including:
- "Historical CO2 Records from the Law Dome DE08, DE08-2, and DSS Ice Cores" (,
- "A high-precision method for measurement of paleoatmospheric CO2 in small polar ice samples" ( and
- "Drilling and analysing ice cores - Sampling and analysing the gas (

18) Dr. Jeff Severinghaus is a professor of geosciences in the Geosciences Research Division at Scripps Institution of Oceanography, University of California, San Diego. His current research interests center on using trapped bubbles of gases contained in ice cores to track changes in ancient climate.(

Dr. Mark Battle is Associate Professor, Dept. of Physics and Astronomy, Bowdoin College, Brunswick, ME since 2006, studying atmospheric composition and how it changes (

19) Dr. J. Douglas Way is a Professor at the Colorado School of Mines Chemical and Biological Engineering Department, University of Colorado, Boulder, researching new materials such as metals, microporous oxides and ionic polymers for use in novel separation processes. Examples include meso-porous ceramic membranes for the separation of CO2 from nitrogen (

Appendix B - Further reading Material

1) Update on 2013-03-02 "A new method for predicting transport properties of polar firn with respect to gases on the pore space scale" by J. Freitag, U. Dobrindt and S. Kipfstuhl.

" .. Abstract: It has been claimed by those supporting the hypothesis of anthropogenic global warming (AGW) that ice core measurements prove that levels of carbon dioxide in contemporary air are much greater than prior to the industrial revolution as a result of burning earth-sourced hydrocarbons, more generally known as fossil fuels. The data analysed in this document is from the South Pole and has been reassessed in various ways. Also, the findings of the authors of the paper that published the data are highlighted. The conclusions drawn are that all gaseous species or isotopes undergo fractionation during capture into the ice sheet. This means that absolute concentrations of trapped air components are not representative of the atmosphere at the time or close to the time of their capture. It is also shown that there is divergence between the purported carbon dioxide record and the modelled oxygen record – based upon fossil fuel usage data – that occurs as the capture process completes .. .. At this juncture, it seems appropriate to mention that glaciologists, or at least some, use the collision diameter for CO2 of 3.9Å which is rather naïve value to use in such systems. It is essentially an average size attributed to a linear molecule. The dimension that should be used in this type of situation is the smallest dimension – critical or kinetic diameter – which for CO2 is around 3.3Å. By using the collision diameter and comparing it to O2 and N2 it is purported that CO2 does not fractionate by molecular sieving when air is included in ice sheets because 3.9Å is greater than the ice lattice gaps estimated to be ~3.6 Å. However, most studies of gas permeability and diffusion through membranes and porous media, outside of this climate science discipline, use the critical or kinetic diameter .. ".

Appendix C - E-mail Exchanges


From: Zbigniew Jaworowski
To: peter.ridley.....
Sent: Wed, 27 Oct 2010 20:11
Subject: Re: Preferential Fractionation of CO2 in Air "Trapped" in Ice

You may use my texts in any way of your convenience. 


From: peter.ridley...
Sent: Fri, 25 Jun 2010 17:06
Subject: Re: Preferential Fractionation of CO2 in Air 'Trapped' in Ice

Hi Professor Frank, thanks for both attachments which I can open OK. Your responses are very much appreciated. 

I had a response from Professor Jaworowski yesterday which I will be quoting from on appropriate blogs but he was unable to answer explicitly my question about the preferential diffusion of CO2, i.e:- 

is it feasible that the ice core experts like Professor Alley are incorrect in using the collision diameter of molecules rather than the kinetic diameter? Also, would the process of diffusion within the ice after total close-off (i.e. when CO2 is too large to pass through any interconnecting capillaries) that CO2 diffuses through the "solid" ice in a mainly upward direction due to , e.g. the reducing pressure at higher levels? I am not a physicist or chemist so do not sufficiently understand the various diffusion, adsorption and other fractionation effects to debate these issues from a position of knowledge. 

Severinghouse and Battle said in their ??? paper "The data presented here suggests that close-off fractionation increases very non-linearly with decreasing molecular size .. The pattern of fractionation in different gases deduced from the firn air samples shows a strong inverse relationship with effective molecular diameter inferred from viscosity data, but no clear trend with molecular mass. We conclude that the close-off fractionation is primarily size-dependent .. The large atoms .. show no significant trends in the lock-in zone, .. This observation implies the existence of an effective size threshold of 3.6Å, above which molecules have a low probability of escape from the bubbles and therefore do not become significantly fractionated. This places constraints on proposed mechanisms for the size-dependent fractionation. Our data are consistent with the recent suggestion .. that the regular crystal structure of the ice lattice contains a hole 3.6Å in diameter that sharply increases the escape probability of gases smaller than this size. Our data also are consistent with the hypothesis .. that fractionation occurs because of size-dependent differential permeation of gases through the ice lattice .. no evidence for close-off fractionation is seen for molecules larger than 3.6Å" 

SandB seem to regard the collision diameter to be relevant here not the kinetic diameter. My instinct tells me to the contrary, meaning that CO2, having a 3.3 A kinetic diameter as opposed to N2, O2 and CH4 (3.8, 3.5 and 3.8) will continue diffusing in the firn well after the other gases. Also, would not this smaller size mean that CO2 more readily diffuses within the "solid" ice after full close-off to all gases? 
Do you have any knowledge of proper research having been undertaken into what I see as this very significant area of uncertainty? 

In my opinion the ice core reconstructions produce as dubious a "hockey stick" as do the reconstructions of past global temperatures but maybe I am being overly sceptical. 


Best regards and thanks once again for your help, Pete Ridley 


From: Hartmut Frank
To: peter.ridley...
Sent: Fri, 25 Jun 2010 6:43
Subject: Re: Preferential Fractionation of CO2 in Air 'Trapped' in Ice

ATTACHMENTS: Presentation Slide; "How science makes environmental controversies worse" by Daniel Sarewitz, 2004

Dear Mr. Ridley; 

Attached I am sending you the slide once more as pdf. I hope you can open it - it is a simplified illustration of the major processes which are leading to changes of gas concentrations in the secondary bubbles (including and especially of carbon dioxide). As I have said before, if one would apply rigorous quality assurance/quality control standards as 
they are typical nowadays in analytical chemistry, the methods and results used and generated by these amateur ice-core analysts - who are mostly physicists - one would have to throw the whole data sets out. But since they are politically protected and have developed strong pressure groups including a former American Vice President, nothing can be done. I suggest to read the paper of Daniel Sarewitz "How science makes environmental controversies worse" (attached). 

In my opinion it is best just to wait until the whole story falls apart, but it will still take a while, i.e. until Schellnhuber, Al Gore and the other protagonists are fully retired. Any energy invested into this collective stupidity is wasted. 

Best wishes, Hartmut Frank 

From: Zbigniew Jaworowski .... 
To: Peter Ridley ... 
Sent: Thu, 24 Jun 2010 10:48
Subject: Re: Preferential Fractionation of CO2 in Air "Trapped" in Ice 

Dear Pete, 

I am also not versatile in diffusion, and writing my paper in 1994 I was advised and enlightened by a geologist from the Norwegian oil industry, who was specializing in diffusion, a subject of great importance for oil industry. This is a highly specialized field of science. My impression is that it is a terra incognita for glaciologists. 

Best wishes, 

From: Peter Ridley ....
To: Zbigniew Jaworowski ...
Sent: Thu, 24 Jun 2010 10:21
Subject: Re: Preferential Fractionation of CO2 in Air "Trapped" in Ice

Hi Professor Jaworowski, thanks very much for making the time to reply to my E-mail. May I assume that you, like Professor Frank, have no objection to me quoting relevant parts verbatim on the various blogs that I comment on? I will hold back on doing so for a few days but will understand that if I receive no response from you by Sunday 27th then I am at liberty to use your comment as I see appropriate .. 

Thanks once again for your efforts.

BTW, is it feasible that the ice core experts like Professor Alley are incorrect in using the collision diameter of molecules rather than the kinetic diameter? Also, would the process of diffusion within the ice after total close-off (i.e. when CO2 is too large to pass through any interconnecting capilliaries) that CO2 diffuses through the "solid" ice in a mainly upward direction due to , e.g. the reducing pressure at higher levels? I am not a physicist or chemist so do not sufficiently understand the various diffusion, adsorption and other fractionation effects to debate these issues from a position of knowledge. 

Best regards, Pete

From: Zbigniew Jaworowski ...

To: Peter Ridley ....
Sent: Wed, 23 Jun 2010 10:19
Subject: Re: Preferential Fractionation of CO2 in Air "Trapped" in Ice


Dear Pete,

Thanks for you messages. You may find my comments in the attachment.

Best wishes,


From: Hartmut Frank ...To: Peter Ridley...CC: Zbiniew Jaworowski ...; Tom Segalstad...Sent: Sat, 12 Jun 2010 12:18Subject: Re: Preferential Fractionation of CO2 in Air 'Trapped' in Ice

Dear Mr. Ridley:

.... It is a simple, undisputable fact that carbon dioxide is chemically completely different to nitrogen and oxygen. Since meteorologists and climate change researcher are almost all no chemist they have completely overlooked this fact: for physicists the various molecules are just volumes with different diameters. The preferential escape of carbon dioxide from the air bubbles within decades or even centuries of storage under increasing pressure (or rather back diffusion of nitrogen and oxygen into the secondary bubbles which are formed when the ice core is horizontally stored for a while) depends just on their completely different chemical behaviour and the slow reaction rates typically for carbon dioxide.

So Prof. Jaworowski's main argument is valid and will remain valid because it is based on simple, but hard physicochemical facts. Most of the facts can be found in the old, traditional "Gmelin's Handbook of Inorganic Chemistry” - but nobody reads such books anymore today. The facts are so basic that one cannot even start a research project on an investigation of the validity of such carbon dioxide analyses in ice cores because the referees would judge it too trivial. 

But if one would apply proper quality assurance/quality control principles, as they are common in most other areas of application of chemical-analytical methods (for instance in drug control or toxicology) the whole building of climate change would collapse because of the overlooked fault.

And so one continues because there are so many living in or from this building.

Best wishes, Hartmut Frank

PS: Attached I am sending you a slide from a presentation which I just gave a few days ago to graduate students at the Technical University in Gdansk. The times given above and below the arrows of the reaction scheme are not meant to express reaction rates but how long these processes have time to go into the one or other direction. Hartmut Frank, Prof. em., Dr.Affil. Prof., Univ. Free State, Bloemfontein, RSAEditor "Toxicological and Environmental Chemistry"Cheesefondue WorkshopsUniversity BayreuthD-95440 Bayreuth, Germany(office: Hudo-Rüdel-Str. 8, D-95445 Bayreuth)Tel +49-921-555460, Mobile: +49-152-05923690,Fax +49-921-552334... =================== 

From: Peter Ridley .... To: Zbiniew Jaworo...; Tom Segalstad...; Hartmut Frank... Sent: Fri, 11 Jun 2010 22:36 Subject: Preferential Fractionation of CO2 in Air "Trapped" in Ice  Hello Professor Jaworowski, Professor Segalstad and Professor Frank, ... I have been trying for months now to get clarification on the current status of this debate. No-one has been able to point me to any convincing research showing that the arguments offered in several papers, including:  - "Do glaciers tell a true atmospheric CO2 story? The Science of the Total Environment" 1992,  

- "Jaworowski, Z., Ancient atmosphere - validity of ice records. Environ. Sci. & Pollut. Res! 1994  
- "Ice Core Data Show No Carbon Dioxide Increase" 1997
- "CO2: The Greatest Scientific Scandal of Our Time" 2007  

are flawed.  


Reference has been made to criticism by Oeschger in 1995 ( and by Engelbeen in 2008 ( as "debubking" these arguments but there is one that I have not seen refuted. This is the preferential fractionation of CO2 which reduces the level in the deper/older "trapped" air and enhances it in shallower.younger air.  


I wonder if you can spare the time to take a look at some recent comment of mine on the blog of Mike Haulbars, currently at but previously at The attached is relevant extracts from my most recent comment.  


Thanking you in anticipation.  


Best regards, Pete Ridley


Appendix D - Updates

2020-01-16 Replaced the header graphs
2014-07-27 Updated Section 2.0 Size-Dependent Fractionation in Ice". Added sub-sections 4.3 "Professors Je2014-07-25 Changed the title of Section 4.0 from "Professor Murry Salby" to "SOME SCIENTIFIC ARGUMENTS", with sub-section 4.1 becoming "Professor Murry Salby" and added sub-section 2 "Professosr Eric Wolfe, Jeffrey Severinghaus and Mark Battle" and 4.4 "Professor J. Douglas Way".
2014-07-23 Replaced the reconstructed "Hockey Stick" with a new image from ESRL which includes Mauna Loa data (in RED) spliced onto a graph produced by Etheridge et al in 1996 (( Added further quotation to Appendix B "Further Reading Material" Item 2.
2014-07-11 Updated Section 5.0 "Size-dependent Fractionation - Examples" relating to the research by Professor J. Douglas Way into the transport mechanism in microporous, metal oxide membranes.

2014-05-23 to 31 Added:
- a paragraph in Section 1.0 on papers by Dr. Zbigniew Jaworowski,
- three paragraphs to Section 2-0 on papers by Drs. Jeff Severinghaus and Mark Battle.
- "hockey stick" graphic and Appendix A, Note 17),
- Section 6 "Fractionation in Ice - Recent Studies".
Moved discussions about exchanges with others to Appendix A, Notes 15 and 16), updated Appendix A, Note 1) and made several cosmetic alterations.
2014-05-10/11 Added Section 4.0 Professor Murry Salby and Appendix A, Notes 7-9. Also made some cosmetic changes.

2014-01-19 Added the ice lithification diagram to Section 1.0 Introduction and added Appendix C - E-mails, with references thereto. Added abstract of Jonathan Drake's article to Appendix B, ref. 2).
2013-06-13 Added to Appendix B, ref. 2) "Further reading Material" a reference to a recent related article "Breaking Ice Hockey Sticks: Can Ice be Trusted?" by Jonathan Drake.
2013-03-02 Added to Appendix B 1) "Further reading Material" a reference to a recent related article by J. Freitag et al.
2011-11-15 and 2011-12-06 Added further considerations to the body of the article and Appendix A, Note 5) on the sudden death of Professor Zbigniew Jaworowski.
2011-05-08 Additions following discussions with several specialists in this subject.


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  7. Perhaps you'd be kind enough to allow me to share a couple paragraphs of what Oeschger wrote

    Hans Oeschger’s letter to ESPR

    "The project to reconstruct the history of the greenhouse gases was conducted; it was, and is, very successful - much above expectation. The CO2 concentrations measured on the SIPLE core, Antarctica, serve as a measure of that success. They illustrate (JAWOROWSKI, Fig. 5 a, p. 168) the history of atmospheric CO2 increase since the middle of the 18th century. Another important result was the observation of low CO2 concentrations of the gases extracted from ice-age ice. The low glacial CO2 concentrations have been confirmed in ice cores with different physical and chemical properties both from Greenland and Antarctica and independently from 13C measurements on carbonate of foraminifera shells in ocean cores and, yet again, more recently in moss samples."

    "Now to the paper of JAWOROWSKI: For years he emphasizes only the difficulties of these studies, formulates the underlying assumptions which sometimcs are only partly fulfilled and criticizes the work performed hitherto in an unscrupulous manner. He does this without any appreciation for the development of expertise in this field over several decades.

    Thus he extrapolates from contamination problems in improvised pioneering experiments in the late sixties to more recent (1992) similar experiments on the Greenland ice cap for which special equipment was developed. Some of his statements are drastically wrong from the physical point of view, e.g. the statement that CO2 at 70 m depth in the ice begins to change into solid clathrates.

    Another example concerns the gas-occlusion process in firn and young ice. This process has been studied in detail theoretically and experimentally. The theory of diffusion of gases in firn and the occlusion at the firn-ice transition has been confirmed impressively by the detection of a gravitational enrichment of the heavier gases and of the heavier isotopes of a gas. This enrichment depends, in the first instance, on the depth of the firn-ice transition. It enables the reconstruction of the history of gas enclosure depth during the last glacial-interglacial cycle.

    But JAWOROWSKI maintains that the age of the ice and that of the occluded gases are the same and shifts the CO2 increase revealed from studies of the SIPLE core (Fig. 5 a) - which in the uppermost part overlaps convincingly with the atmospheric measurements by ca. 100 years back in time (assuming identical ages for the ice and the gases in the ice). Fig. 5 b speaks for itself; why should there be such a drastic increase of CO2 and of CH4 (Fig. 5 a) in the middle of the 19th century?"

  8. At 6.1.2 Ridley writes: "I ask respectfully that contributors avoid simply declaring that claims that the ice core record is flawed have been refuted. Such claims have been made before with links to comments such as those of Hans Oeschger, Professor of Physics, University of Bern, purporting to do the refuting."
    ~ ~ ~ ~ ~ ~ ~ ~ ~

    Seems to me Ferdinand Engelbeen made a pretty good effort at "JAWOROWSKI'S TAKE ON ICE CORE CO2 MEASUREMENTS"

    I have read several remarks made by Jaworoski about the ice cores. The first point that strikes me is that Jaworowski mainly refers to works written by... Jaworowski. And mostly for the period until begin 90's. Not a very strong sign of reliability of his remarks...

    While several of his remarks may influence CO2 levels measured in ice cores, if not taken properly into account, many of these problems would lead to too high measurements, not too low.
    Jaworowski has a paper on ice cores at the Warwick Huges web site [1]. Here are step by step reactions on what Jaworowski says. Follow the steps:
    Water in the ice.
    Clathrates and cracks in the ice.
    The deleting of inconvenient data.
    The arbitrary shift of air/ice data

  9. OK let me be more accurate Engelbeen put the information together, with a little help from his friends:

    [1] Zbigniew Jaworowski, M.D., Ph.D., D.Sc., March 2007. Climate Change: Incorrect information on pre-industrial CO2:

    [2] Mulvaney, R., E.W. Wolff, and K. Oates, Sulpfuric acid at grain goundaries in Antarctic ice. Nature, 1988. 331(247-249). Not directly available on the Internet.

    [3] Mulvaney et al. on H2SO4 inclusions, on the blog of Jim Easter:

    [4] Zbigniew Jaworowski, M.D., Ph.D., D.Sc., 1997, Ice Core Data Show No Carbon Dioxide Increase

    [5] On the main page of Ernst Beck's thesis about the historical CO2 measurements, "180 Years of atmospheric CO2 Gas Analysis by Chemical Methods":

    [6] Lüthi e.a., High-resolution carbon dioxide concentration record 650,000–800,000 years before present, Letters to Nature 453, 379-382 (15 May 2008):

    [7] Etheridge e.a., GRL 1996, Natural and anthropogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn:

    1. Hi Peter (citizenschallenge" Miesler,

      Thanks for contributing your 3 comments. My E-mail of 11th Jun 2010 22:36 on the subject of "Preferential Fractionation of CO2 in Air 'Trapped' in Ice" relates to what you said (see Appendix C).

      Best regards, Pete


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