[Pete Ridley (OP)]

I came across this blog while searching for detailed pictures of ice extracted from deep down an ice sheet. I have a question that has been puzzling me for over a year now and remains unanswered despite asking it of experts in the subject. My question in a nut shell to the scientists here is “why do paleo-climatologists use collision diameter in preference to kinetic diameter when considering the migration of air molecules through firn and ice”? Here is some background.

The photo shown on your “Climate Change and Ice Cores” thread (http://www.thenakedscientists.com/HTML/content/interviews/interview/643/) is a beauty as a starter because it clearly shows the air pockets which are claimed to hold air having the same composition as when it was captured from the atmosphere thousands of years ago. This sounds like a wonderful natural archive which simply has to be emptied of air which can then be analysed to provide what Professor Richard Alley refers to as “the gold standard” for exposing the ancient atmospheric make-up to – but is it?

Dr Eric Wolff from the British Antarctic Survey thinks so. When discussing the natural global warming that has occurred since the Little Ice Age (it always warms between ice ages, then cools again towards another one) he says “ .. the arguments about whether global warming is real hinge on four aspects. The first one is the physics that tells us to expect that when we get more carbon dioxide in the atmosphere it should get warmer. The second one is whether carbon dioxide has actually increased in the atmosphere, and that's what I'm best at because that's what we can see from ice cores. The third one is whether in the past that's caused climate change. And we can see in the ice cores that at least every time carbon dioxide's changed in the past, then it has warmed. So there's no counter evidence .. ”.

Let’s look at each in turn:
- physics tells us that if everything else that controls the mean global temperature remains unchanged then increasing CO2 will cause an insignificant amount of warming amounting  to about 1C for a doubling in concentration from 300 to 600ppm. The present atmospheric CO2 content is estimated (from readings on top of an extinct volcano in the “ .. exhaust plume of massive oceanic outgassing in the Eastern Equatorial Pacific .. ” - http://judithcurry.com/2011/02/26/agreeing/#) to be about 400ppm, having risen from an estimated 300ppm in 1850,
- the ice cores are only able to show us that the concentration of residual CO2 in the air bubbles reduces the lower the bubble is in the ice sheet until a depth is reached when the residual level changes relatively little around a mean value of about 280ppm (Fig 2 in http://www-das.uwyo.edu/~geerts/cwx/notes/chap01/icecore.html)
- an important piece of information about this has been withheld.   “ .. On the basis of atmospheric CO2 data obtained from the Antarctic Taylor Dome ice core and temperature data obtained from the Vostok ice core, Indermuhle et al. (2000) studied the relationship between these two parameters over the period 60,000-20,000 years BP (Before Present).  One statistical test performed on the data suggested that shifts in the air's CO2 content lagged shifts in air temperature by approximately 900 years, while a second statistical test yielded a mean lag-time of 1200 years.  Similarly, in a study of air temperature and CO2 data obtained from Dome Concordia, Antarctica for the period 22,000-9,000 BP -- which time interval includes the most recent glacial-to-interglacial transition -- Monnin et al. (2001) found that the start of the CO2 increase lagged the start of the temperature increase by 800 years.  Then, in another study of the 420,000-year Vostok ice-core record, Mudelsee (2001)  concluded that variations in atmospheric CO2 concentration lagged variations in air temperature by 1,300 to 5,000 years.  .. ” (http://www.co2science.org/articles/V6/N26/EDIT.php).

I have been researching the second of Dr. Wolff’s points for over a year now, exchanging opinions with experts in relevant fields such as Professor Alley, Professor Jeff Severinghaus, Professor Michael Bender, Professor Hartmut Frank, Professor Zbiniew Jaworowski, Dr. William Connolley (you may know him), etc. I think that is quite a balanced selection of experts and my conclusion, after reading lots and lots of relevant papers, is this. Due to its much smaller kinetic diameter, CO2 is preferentially fractionated out of the air pockets when the escape routes have reduced to a size in the lowest levels of the firn that prevents the escape of the larger N2, O2 and CH4 molecules. This results in the residual air “trapped” in pockets after close-off are depleted in CO2 while the air above is enriched. I say “trapped” because even after close-off it is still possible for further depletion in CO2 to take place due to H-bond breaking through the ice crystal lattice.

If you are interested in more of this you’ll find some on the Climate Conversation blog (http://www.climateconversation.wordshine.co.nz/2011/03/fallen-snow/#comment-46211 and http://www.climateconversation.wordshine.co.nz/2011/03/its-not-warming-you-nitwit-its-cooling/#comment-45360.

As I said before, trying to simplify science that is poorly understood is fraught with danger and the processes and drivers of the different global climates. Professor Barry Brook, previously Professor but now Director of Climate Change at Adelaide University said a couple of years ago “ .. There are a lot of uncertainties in science, and it is indeed likely that the current consensus on some points of climate science is wrong, or at least sufficiently uncertain that we don’t know anything much useful about processes or drivers. But EVERYTHING? Or even most things? Take 100 lines of evidence, discard 5 of them, and you’re still left with 95 and large risk management problem .. ” (http://bravenewclimate.com/2009/04/23/ian-plimer-heaven-and-earth/). The significant part of that comment is “we don’t know anything much useful about processes or drivers” (Please read the full comment as Professor Brook gets rather upset when readers are unable to ascertain the full context of what he said.)

It strikes me as being perhaps disingenuous to try to imply that only 5% of the science is uncertain by plucking those 100, 95 and 5 lines of evidence out of the air, but it’s a bit like what the IPCC does when trying to quantify “expert opinion”. Maybe Brook has the same attitude as Professor Stephen Schneider "To capture the public imagination, we have to offer up some scary scenarios, make simplified dramatic statements and little mention of any doubts one might have. Each of us has to decide the right balance between being effective, and being honest" (http://www.john-daly.com/schneidr.htm).

I’d be very interested to know what your opinion is of scientists being what is, in my opinion, simply dishonest. It is scientists like Schneider who make lay people like myself trust scientists even less than we trust politicians and used-car salespersons. Talking about politicians (and other power-hungry individuals), isn’t that where all of this CACC propaganda is coming from?

Best regards, Pete Ridley

[BenV]

So what's your question here Pete?

[Pete Ridley (OP)]

Hi BenV, didn't you read the first paragrapg of my comment? I asked " .. why do paleo-climatologists use collision diameter in preference to kinetic diameter when considering the migration of air molecules through firn and ice? .. " and provided some background to help the scientists here to understand what is behind my question.

Bets regards, Pete Ridley

[Jolly- Joliver]

Hi BenV, didn't you read the first paragrapg of my comment? I asked " .. why do paleo-climatologists use collision diameter in preference to kinetic diameter when considering the migration of air molecules through firn and ice? .. " and provided some background to help the scientists here to understand what is behind my question.

Bets regards, Pete Ridley

Pete would I be right in thinking that your question is how can we trust the Ice core samples, they use to base the global warming data as, it is not clear that the molecules present have arrived as they claim and think they have?

"Migration of air molecules" implies and actually suggests that Co2 in ice- can move and will move. If true how can you be sure that the Co2 levels in the ice cores are the actual levels present at the times they claim they were, and are not higher or lower for other reasons.

Would that be fair Pete, as an interpretation of what you asked? 

[Pete Ridley (OP)]

Wiybit, you have summarised reasonably well the basic question that Jaworowski et al. raised back in 1992 in their paper “Do glaciers tell a true atmospheric CO2 story?” but they covered about 20 processes that could distort the composition of residual air extracted from “sealed” pockets within ice cores. My specific question relates to only one, preferential fractionation over decades, centuries or even millennia of CO2 and other gases that have smaller kinetic diameters than do N2, O2, Ar or CH4. The researchers that I mentioned in my first comment ignore kinetic diameter and use collision diameter, which I hypothesise is not appropriate when the diameter of pores within and the channels that link ice air pockets approach the size of those smaller molecules as the ice is reaching the final stages of compression to a state where the air pockets become “closed off”.

BenV(alsler?) I’ve checked up on your background and looked up some of your previous comments. The only comment that I found of interest was your response to a question by one neilep who asked on 31/01/2008 @ 02:05:41 “So, how does a climate model get created ?...do they just use the last few hundred years of weather records and data and average it all out or is it a tad more complicated than that ?...and how accurate are they ?”

I found your response less than inspiring. “Basically, you make a weather simulator (if windspeed=x, direction=y, then Z happens - but about a millionfold more complicated) and then plug real data into it.  If the outcome of your 'simulator' consistently matches the observed changes in climate over a given timescale, you have a working climate model.  If it fails to predict what you already know to have happened, then you need to tweak your model. When your simulator can accurately predict past changes based on past data, you can assume that it may accurately predict future events based on current data.” (http://www.thenakedscientists.com/forum/index.php?topic=12826.msg352094;boardseen).

If that and your background are anything to go by you probably have nothing substantial to offer regarding migration of molecules through porous media, but I could be wrong. Your training and experience in zoology and science communications probably means that you have little more understanding than I have of molecular dynamics. Don’t take that as an insult as it isn’t meant that way. When I discussed this last June with Professor Zbiniew Jaworowski, whose 1992 paper first drew my attention to this issue, he expressed the opinion that “This is a highly specialized field of science. My impression is that it is a terra incognita for glaciologists”. Subsequently I have asked the same question of Professors Richard Alley, Jeffey Severinghaus and Michael Bender without receiving any worthwhile justification for their use of collision diameter.

One thing that you could probably help me out with is in reference to an experiment presented by the BBC’s Ian Stewart and available on U-tube (

It was linked to by climate science “expert” Professor Mike Palin, Otago University during our exchanges on the issue of CO2 fractionation a month or so ago (http://hot-topic.co.nz/the-twilight-zone/). Stewart’s attempt to persuade us through that demonstration that CO2 traps a lot of IR requires further scrutiny. I am always suspicious of anything that the BBC or its minions (like Stewart) say about climate change because of the fact that there is a possible vested interest n supporting the CACC doctrine – pension scheme investments.

I puzzled over what that demonstration really tells us. On investigation, Wikipedia (http://en.wikipedia.org/wiki/Thermographic_camera) advises that the colour picture from an infrared camera is not true but pseudo colour, where the colours represent intensity. So when Steward shows us that candle turning more and more blue what is he really demonstrating. In my humble opinion (I’m not a scientist but a retired Chartered Electrical Engineer) he may simply have verified that the candle gets colder and colder as the CO2 that he is pouring into the tube replaces the O2 upon which the candle depends to keep burning brightly (highest intensity). As most of us would expect, the O2 in the tube is depleted and the candle glows less and less brightly (getting cooler) until it goes out. Stewart’s presentation was cut short to ensure that we didn’t see it go out. Well, that’s my conspiracy theory anyway. As always I’m open to persuasion that I am wrong, so if you can repeat that experiment but this time use N2 instead of CO2 and show that the change in colour is different then I might accept that the experiment was demonstrating IR absorption by CO2 – but I’m a sceptic so I doubt that you’ll be able to because the colour change will be identical.

Best regards, Pete Ridley

[CliffordK]

Pete,

You bring up a lot of issues. 

Much like Deuterium (²H or just D) and Oxygen-18 (¹⁸O) concentrations (the standard for paleontological temperature proxies), the historic CO₂ concentrations have been driven by temperatures... 

Essentially, as ocean temperatures increase, the CO₂ partial pressure increases, and creates the effect of lowering the CO₂ solubility in the ocean, and increasing the CO₂ concentration in the atmosphere.

Obviously since the discovery of coal and fossil fuels, we've also been adding previously sequestered CO₂ into the mix.

The question is whether there is also a feedback mechanism such that increasing CO₂ concentrations cause a temperature feedback loop increasing the temperatures more.  This is hard to determine from our paleontological data.  Those that follow the Milankovitch theory for glacial/interglacial temperature changes believe that additional feedback mechanisms are necessary to cause the temperature shifts.  Those people who believe in solar output fluctuations can attribute the temperature changes to the sun without additional feedback mechanisms.

As far as migration of the bubbles.  It is quite possible that there is a local effect of migration and homogenization of the bubbles (both up and down).  But, this would be over a finite span of years.  This would lead the CO₂ (gaseous) to be found at different levels than the Deuterium (DHO) in ice.  I believe that the current theories is that the migration/homogenization occurs over a period of less than 100 years or so.  Has anybody studied Deuterated Methane or ¹⁸O as bound to carbon dioxide (C¹⁸O¹⁶O) which should have a closer association with the CO₂ concentration in the ice.  Of course, sample size might be an issue.

One of the problems with the CO₂ theories has to do with the delays.  A brief delay of CO₂ increase following the temperature increases could be easily explained by feedback mechanisms as well as the migration/homogenization of the bubbles.  Changes in the evaporation of Deuterated water may also have a quicker response to sea surface temperature changes than the release of CO₂, some from deep ocean levels.

However, as the temperature falls, the CO₂ often remains high for an additional 1000 or more years.  If the CO₂ is responsible for maintaining high temperatures, it is difficult to explain how the temperature can fall substantially before the CO₂ concentrations fall. I think this is one of the major problems with the theories of CO₂ driving paleontological temperatures.

[Pete Ridley (OP)]

Hi CliffordK (pardon my ignorance but are you one of the “experts” who responds to questions here or just a blogger like I am?), thanks for spending the time responding to my question/comment. You say “You bring up a lot of issues.” but I thought that my very first paragraph here was explicit about the one issue that I was raising as my main question, i.e. “why do paleo-climatologists use collision diameter in preference to kinetic diameter when considering the migration of air molecules through firn and ice”?

I am not asking about the causes of changes in atmospheric CO2 concentration over time or how paleoclimatologists guess at these. My interest is in the changes in composition of air that originally was collected in snow flakes from the atmosphere, carried to earth then gradually compressed into ice by falls of further snow until it became “trapped” (or “sealed”) in air pockets when the pores in those pockets and the channels connecting them approached the size of the individual air molecules.

You seem to have missed the point of my specific question completely because you make no mention of the molecular diameter of any of the different gases found in the atmosphere either now or millions of years ago. In my ignorance I was not aware that Deuterium was of interest in paleoclimatology other than as an aid to estimating how temperature changed in the past. Although thermal fractionation is a factor to be taken into consideration when looking at the extent to which the composition of the air in ice is distorted over time, this is no more relevant to my question than is gravitational fractionation.

My question is solely about size-dependent fractionation, not about any positive feedback mechanism, such as assumed by the supporters of the CACC doctrine. I am not talking about local or other “ .. migration of the bubbles .. ” but of migration of the individual molecules of the smaller air components such as CO2 after the pores in the walls of the air pockets and the channels that interconnect them have been compressed to a comparable size, too small for the larger molecules like N2, O2 and CH4 to pass through them. I obviously had not made that clear in my earlier comments or in the articles/comments to which I linked.

If that isn’t clear enough then please take a look at the animation (

but imagine that the bubble is an air pocket in an ice sheet approaching close-off, with all excepting one pore closed to all molecules (CO2 included). Imagine also that the hole size of that single pore is just larger than 0.33nm (the kinetic diameter of CO2) and that the red balls are CO2 molecules (N2, O2 and CH4 molecules present but not shown because they can’t escape but are still bouncing around inside in far larger quantities than CO2). Also imagine that the pore is not giving access to an empty space as shown but access to an equally small channel linking to another similar air pocket in a chain of such air pockets. Does that very simplified picture of the structure within the ice/firn help to clarify the basis of my main question? Does that very simplified picture of the structure within the firn/ice help to clarify the basis of my main question?

The secondary question that I put to The Naked Scientists about Ian Stewart’s experiment with a candle should be quite straight forward.

Best regards, Pete Ridley

[Jolly- Joliver]

For some reason it's not letting me quote you so I'll have to do it the old fashioned way:-

Wiybit, you have summarised reasonably well the basic question that Jaworowski et al. raised back in 1992 in their paper “Do glaciers tell a true atmospheric CO2 story?”

Thankyou Pete, I was half dreading someone moaning about asking questions.
 

but they covered about 20 processes that could distort the composition of residual air extracted from “sealed” pockets within ice cores. My specific question relates to only one, preferential fractionation over decades, centuries or even millennia of CO2 and other gases that have smaller kinetic diameters than do N2, O2, Ar or CH4.

I take it you mean, that over time CO2 moves in a different way to the other elements, potencially distorting the figures even more. Sorry to use a more common language but I find  laymans terms are eaier to understand.

The researchers than I mentioned in my first comment ignore kinetic diameter

If that is true, I do not know if it is, but if that is true, potencially all the current thinking is based on incorrect research. Are you sure they do not have a system to try and figure out where the co2 has moved from? and then compensate, although personally thinking about it, if they did that- that appears to me to be an activity in guess work.

and use collision diameter,

So is that the system they use to compensate? The gases movement, a brief search tells me:-

http://dictionary.reference.com/browse/collision+diameter
"collision diameter 
–noun Physics .
the distance between the centers of two colliding molecules when at their closest point of approach."

I suppose they are working under the idea that as ice forms the elements like Co2 collide, and therefore move into the pockets they do, in a certain way, that however does not take into consideration of movements after the fact.

I think I see your point.

which I hypothesise is not appropriate when the diameter of pores within and the channels that link ice air pockets approach the size of those smaller molecules as the ice is reaching the final stages of compression to a state where the air pockets become “closed off”.

But what does that really mean that the Co2 levels were highier than they think, as more moved upwards and escaped? or that we just cannot be sure?

[Madidus_Scientia]

Too long, didn't read

[BenV]

BenV(alsler?) I’ve checked up on your background and looked up some of your previous comments. The only comment that I found of interest was your response to a question by one neilep who asked on 31/01/2008 @ 02:05:41 “So, how does a climate model get created ?...do they just use the last few hundred years of weather records and data and average it all out or is it a tad more complicated than that ?...and how accurate are they ?”

I found your response less than inspiring. “Basically, you make a weather simulator (if windspeed=x, direction=y, then Z happens - but about a millionfold more complicated) and then plug real data into it.  If the outcome of your 'simulator' consistently matches the observed changes in climate over a given timescale, you have a working climate model.  If it fails to predict what you already know to have happened, then you need to tweak your model. When your simulator can accurately predict past changes based on past data, you can assume that it may accurately predict future events based on current data.” (http://www.thenakedscientists.com/forum/index.php?topic=12826.msg352094;boardseen).

If that and your background are anything to go by you probably have nothing substantial to offer regarding migration of molecules through porous media, but I could be wrong. Your training and experience in zoology and science communications probably means that you have little more understanding than I have of molecular dynamics. Don’t take that as an insult as it isn’t meant that way.

...

One thing that you could probably help me out with is in reference to an experiment presented by the BBC’s Ian Stewart and available on U-tube (

It was linked to by climate science “expert” Professor Mike Palin, Otago University during our exchanges on the issue of CO2 fractionation a month or so ago (http://hot-topic.co.nz/the-twilight-zone/). Stewart’s attempt to persuade us through that demonstration that CO2 traps a lot of IR requires further scrutiny. I am always suspicious of anything that the BBC or its minions (like Stewart) say about climate change because of the fact that there is a possible vested interest n supporting the CACC doctrine – pension scheme investments.

I puzzled over what that demonstration really tells us. On investigation, Wikipedia (http://en.wikipedia.org/wiki/Thermographic_camera) advises that the colour picture from an infrared camera is not true but pseudo colour, where the colours represent intensity. So when Steward shows us that candle turning more and more blue what is he really demonstrating. In my humble opinion (I’m not a scientist but a retired Chartered Electrical Engineer) he may simply have verified that the candle gets colder and colder as the CO2 that he is pouring into the tube replaces the O2 upon which the candle depends to keep burning brightly (highest intensity). As most of us would expect, the O2 in the tube is depleted and the candle glows less and less brightly (getting cooler) until it goes out. Stewart’s presentation was cut short to ensure that we didn’t see it go out. Well, that’s my conspiracy theory anyway. As always I’m open to persuasion that I am wrong, so if you can repeat that experiment but this time use N2 instead of CO2 and show that the change in colour is different then I might accept that the experiment was demonstrating IR absorption by CO2 – but I’m a sceptic so I doubt that you’ll be able to because the colour change will be identical.

Best regards, Pete Ridley

I don't recall claiming any expertise in migration of molecules through any medium, so it's no surprise you find me lacking in that arena.  My response to Neil was a general answer to a question from a lay person - not intended to inspire anyone, merely answering the question in broad, accessible terms.

I can't really comment on Ian Stewart's demonstation, as with most TV science there are lots and lots of details left out.  But I've had a look for you and have a couple of comments:

It being a false colour image is irrelevant unless someone is changing the colours throughout the experiment, or is set up to give automatically changing contrast.  It may make a small change look large, or vice versa - we can't know without the details.

Am I right in assuming that your interpretation involves having the candle inside the tube, exposed to the CO₂ he's releasing?  As far as I can tell, the tube is sealed off from the candle (there seems to be a membrane of sorts in place, but I don't know where the air is venting out.  Had he placed the candle inside the tube it certainly would have been extinguished by the CO₂ - but he's showing radiation from a candle traveling through a sealed and separated tube of CO₂.

The CO₂ conc in that tube may be ridiculously high, so there's every chance that this still doesn't really show us anything useful, but it does seem to be a good demonstration of CO₂ being opaque to IR radiation.  I think you may be wrong about replicating the experiment with nitrogen - as the vast majority of the air in that tube is nitrogen anyway, the change in the tube would be minimal, and I doubt there would be any colour change.

I don't think you should worry about bias at the BBC, it's a huge organisation and not everyone involved cares about pensions.  We broadcast on the BBC and have never had any editorial instruction from above, I suspect there are many other similar teams.

By the way, my original comment about your question was not intended to be rude - I had hoped it would act as a catalyst for you to summarise your ideas, and hopefully avoid responses like this one:

Too long, didn't read

[Pete Ridley (OP)]

Wiybit, your comment today at 12:12:30 shows that you pretty well understand my hypothesis. Let me just expand a little on it and clear up a few misunderstandings, but please bear in mind that what I describe is only one of several different process that distort the composition of air “trapped” in ice. According to Professor Hartmut Frank, these processes start from the time that the snow begins collecting air from the atmosphere.

The first point is that collision diameter seems to me to be relevant where the distance travelled by a molecule before a collision with any other molecule can occur is large compared with the size of the molecules involved. This is from the top of the ice sheet covered in highly porous fresh snow down to a level in the firn well before the eventual “close-off” of the air pockets, under which circumstances the laws of Fickian diffusion apply.

As “close-off” is approached (in the Antarctic after many decades of snow build-up) there will come a time when the space available for molecular movement is of the same order as the diameter of the molecules, where collision diameter is irrelevant and kinetic diameter becomes significant. At that level only smaller molecules will be able to move through the ice, hence air pockets will be depleted in those smaller gases. This process is recognised by the paleoclimatologists and their models take it into consideration. What they do not seem to consider is that it is the kinetic not collision diameter that is appropriate at this stage.

For many of the gases that make up the atmosphere there is little difference between collision and kinetic diameter, as seen in the listing below, but for CO2 this is not the case. Consequently, as the ice is compressed and pressure builds up in the pockets the CO2 molecules (and any smaller ones) escape from the pockets and move down the pressure gradient towards the surface, long after the larger gases like N2, O2, Ar and CH4 are trapped. Thus when the air extracted from ice cores is analysed it shows a lower concentration of CO2 than that which existed in the original atmospheric air at the time the falling snow brought it down to the ice sheet surface.

Quickly comparing collision*  v kinetic** diameter (in Å) for the molecules of atmospheric gases of interest to paleo-climatologists, N2 (3.8 v 3.6), O2 (3.5 v 3.5), Ne (2.8 v 2., CO2 (3.9 v 3.3), CO (3.7 v 3., CH4 (3.8 v 3. Ar (3.5 v 3.4), He (2.6 v 2.6), Kr (3.7 v 3.6), Xe (4.0 v 4.0).
*   From “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.
**   From “VUV absorbing vapours in n-perfluorocarbons” by E. Albrecht, et al. Table 3.

Note the difference for CO2. Also note the size of He and think of the He-filled party balloon compared with one that you and I might blow up ourselves – which stays up the longest and why?

The researchers like Severinghaus, Huber, Bender, make no mention in their papers of kinetic diameter and have concluded from their research and modelling that there is a “magic” molecular diameter of about 3.6Å above which size-dependent fractionation does not ocurr. Because they only consider collision diameter they do not bother with CO2. I have asked Severinghaus if he has run his model using kinetic diameter but had no response.

Your interpretation “ .. that as ice forms the elements like Co2 collide, and therefore move into the pockets they do, in a certain way .. “ is as I see it incorrect. The air is drawn down to the ice sheet surface within falling snow and diffuses within the firn (along with some atmospheric air from above). As the firn is compressed the air pockets develop around the air already present there.

Finally, yes (in my opinion) as far as the original past atmospheric composition is concerned it does “ .. mean that the Co2 levels were highier than they think, as more moved upwards .. ”, but only to higher levels, not necessarily “ .. and escaped ..”, if by that you meant escaped from the ice sheet into the atmosphere.

BenV, maybe I have misunderstood what The Naked Scientists are trying to do. I was under the impression that the idea was to present proper science in a manner that was understandable to lay people but nonetheless well-informed and accurate. From what I have seen the impression is given that The Naked Scientists understand the science they discuss and they happily discuss climate science. I may be mistaken here but according to your ”About Us” page “The Naked Scientists are a media-savvy group of physicians and researchers from Cambridge University who use radio, live lectures, and the Internet to strip science down to its bare essentials, and promote it to the general public (http://www.thenakedscientists.com/HTML/about-us/).

The Naked Scientists are by no means silent about climate change and I can find no admission that the subject is beyond the group’s competence. On the contrary, the blog gives the impression of fully supporting the CACC doctrine. Here’s an example relevant to the question that I raise about “Another Hockey Stick Illusion?”. In 2007 the blog posted this statement “ .. In the last 800,000 years, carbon dioxide's always ranged between 180 ppm (parts per million) in the cold periods up to 300 ppm in the very warmest times. And at the moment, it's 380 ppm. So that's already 30% higher than it's ever been. And the only possible explanation for that is human activity. There's other evidence too. We can look at the isotopic structure of the carbon and it looks like stuff that's come from fossil fuels rather than from natural systems. Also we know how much stuff we're putting into the atmosphere and all the calculations work. We're contributing to the increase .. ” (http://www.thenakedscientists.com/HTML/content/interviews/interview/643/).

The caption under that beautiful picture of apparently isolated bubbles says “Figure 1: Air bubbles fixed in ice. These can tell us how gas concentrations have changed over thousands of years.” There is no hint of uncertainty there or in the other related statements and no challenge raised about it. BTW, it would be very helpful to have some dimensions on that picture to give a hint as to whether or not there could be tiny channels of about 0.36nm or less linking those bubbles. I have given links to comments that provide much better detail via SEM reconstructions if anyone is interested.

Am I being unreasonable to expect the Naked Scientists to be able to give me a convincing answer to my question? After all, claims that past atmospheric CO2 concentrations can be determined from air “trapped” in ice for millenia are not of recent origin. Am I wrong in thinking that you are one of those Naked Scientists? Can’t the Naked Scientists get an “expert” like Dr Eric Wolff from the British Antarctic Survey to respond to it?

If I come across as being a little irritated then it could be because I have tried very hard for over a year now to get a convincing answer from such “experts” but had no success whatever. Since you were the only Naked Scientist to respond to my question I assumed that you must be the most expert among you, hence my disappointment to find to the contrary when I checked your background. If I was being unfair in my comments then I apologise and hope that you can understand my reaction.

As for Madidus_Scientia’s comment today at 12:57:20, anyone who finds my contributions “Too long, didn't read” obviously has no interest in the subject. I’m pleased to see that at least one reader thought otherwise.

If the question is too hard for The Naked Scientists to answer then just let me know and I’ll take it elsewhere, although I will be very disappointed if “ .. a media-savvy group of physicians and researchers from Cambridge University” are stumped by it.

BTW, I think that the features provided to us commenters on this blog are great – congratulations to the Web designer.

Best regards, Pete Ridley

[Jolly- Joliver]

Wiybit, your comment today at 12:12:30 shows that you pretty well understand my hypothesis. Let me just expand a little on it and clear up a few misunderstandings, but please bear in mind that what I describe is only one of several different process that distort the composition of air “trapped” in ice. According to Professor Hartmut Frank, these processes start from the time that the snow begins collecting air from the atmosphere.

Does snow collect air? i assume some particals could get trapped inside the snow flake structure, yet every flake is different and all would therefore(in theory) capture air molecules in different ways. Would there even be a way to figure an average amount captured if every snow flake is different? You would be left with possible ranges for each flake, and therefore a possible range for snow fall, I assume.

The first point is that collision diameter seems to me to be relevant where the distance travelled by a molecule before a collision with any other molecule can occur is large compared with the size of the molecules involved.

But how can you even know the starting point of a molecule? I sounds like a lot of guess work to me.

This is from the top of the ice sheet covered in highly porous fresh snow down to a level in the firn well before the eventual “close-off” of the air pockets, under which circumstances the laws of Fickian diffusion apply.

Looking it up fickian law relates to Mass Diffusivity or diffusion coefficient,
http://en.wikipedia.org/wiki/Mass_diffusivity

http://www.answers.com/topic/diffusion-coefficient

"The weight of a material, in grams, diffusing across an area of 1 square centimeter in 1 second in a unit concentration gradient. Also known as diffusivity."

looks to relate more to solids then gases.

As “close-off” is approached (in the Antarctic after many decades of snow build-up) there will come a time when the space available for molecular movement is of the same order as the diameter of the molecules, where collision diameter is irrelevant and kinetic diameter becomes significant.

I think you mean it's a multi-layered process.

 At that level only smaller molecules will be able to move through the ice, hence air pockets will be depleted in those smaller gases.

Ice is a solid isn't it, I kinda think it's like as ice forms and compacts the gases are squezzed out, and if as you are suggesting gases can move through smaller gaps, then I suppose more would be squezzed out.

Going back to the part just before this: "a multi layered process", Ice is solid and gases are gases, two different actions.

 This process is recognised by the paleoclimatologists and their models take it into consideration. What they do not seem to consider is that it is the kinetic not collision diameter that is appropriate at this stage.

but why do they ignore it? They either are ignorant of it, or for some reason feel it has no bearing, or plays to insignifcant a role to need to be accounted for. I assume again, but it sounds a bit strage for scientists to just ignore, a kinetic factor for no reason. What is the justifaction for ignoring it?

For many of the gases that make up the atmosphere there is little difference between collision and kinetic diameter, as seen in the listing below, but for CO2 this is not the case.

what is it about Co2 that makes it so different? Personally I think much of the man made co2 we have in the atmospere is comming from CO cabon monoxide, which when realesed from burning fuels etc grabs an oxygen and so forms Co2.

 Consequently, as the ice is compressed and pressure builds up in the pockets the CO2 molecules (and any smaller ones) escape from the pockets and move down the pressure gradient towards the surface, long after the larger gases like N2, O2, Ar and CH4 are trapped.

Implies Co2 is a smaller molecule, yet surely it's bigger then 02? What missing?

 Thus when the air extracted from ice cores is analysed it shows a lower concentration of CO2 than that which existed in the original atmospheric air at the time the falling snow brought it down to the ice sheet surface.

Thankyou, your saying the Co2 is/was highier then they think. Yet could it not also be the case that the cores have trapped Co2 from the ice below them? Can we trust the findings at all really?

Quickly comparing collision*  v kinetic** diameter (in Å) for the molecules of atmospheric gases of interest to paleo-climatologists, N2 (3.8 v 3.6), O2 (3.5 v 3.5), Ne (2.8 v 2., CO2 (3.9 v 3.3), CO (3.7 v 3., CH4 (3.8 v 3. Ar (3.5 v 3.4), He (2.6 v 2.6), Kr (3.7 v 3.6), Xe (4.0 v 4.0).
*   From “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.
**   From “VUV absorbing vapours in n-perfluorocarbons” by E. Albrecht, et al. Table 3.

Note the difference for CO2.

It's .6 compared to 0, 0.2 or 0.1 with the others, why does it have such variation?

Also note the size of He and think of the He-filled party balloon compared with one that you and I might blow up ourselves – which stays up the longest and why?

Strange he is lighter than Co2, yet Co2 moves more in ice, because it's smaller- fairly clear. So then why does o2 move less then Co2? O2 is O bonded with another O, so maybe the bond structure causes the 02 molecule to take up more space compared to the two double bonds of C02- what do think, that would make sense to me?(I have looked into that area a little Methanes etc)

The researchers like Severinghaus, Huber, Bender, make no mention in their papers of kinetic diameter and have concluded from their research and modelling that there is a “magic” molecular diameter of about 3.6Å above which size-dependent fractionation does not ocurr. Because they only consider collision diameter they do not bother with CO2. I have asked Severinghaus if he has run his model using kinetic diameter but had no response.

Maybe it's too complicated, and add too many varibles.

Your interpretation “ .. that as ice forms the elements like Co2 collide, and therefore move into the pockets they do, in a certain way .. “ is as I see it incorrect. The air is drawn down to the ice sheet surface within falling snow and diffuses within the firn (along with some atmospheric air from above). As the firn is compressed the air pockets develop around the air already present there.

Finally, yes (in my opinion) as far as the original past atmospheric composition is concerned it does “ .. mean that the Co2 levels were highier than they think, as more moved upwards .. ”, but only to higher levels, not necessarily “ .. and escaped ..”, if by that you meant escaped from the ice sheet into the atmosphere.

Yes, I meant escaped into the atmosphere. From what you have said I'm not sure if you could really say either way.

[Pete Ridley (OP)]

BenV, thanks for acknowledging that you aren’t competent to give an answer to that very significant but rather scientific “ .. topic in hand .. ”, the validity of attempts to reconstruct past atmospheric CO2 content from air allegedly trapped in ice. Thanks also for trying to give an answer to the other relatively simple question that I slipped in here regarding what is demonstrated by that CO2 experiment carried out by Iain Stewart. The answer you gave to that question, like my air-in-ice one, also gives a fair indication of how competent The Naked Scientists are with regard to the very important scientific debate raging presently around the Catastrophic Anthropogenic Climate Change (CACC) doctrine.

I repeat that simple “What does Iain Stewart's "CO2 experiment" Demonstrate ” question in a new post (http://www.thenakedscientists.com/forum/index.php?topic=38723.new#new) because I do not wish to distract people from the much more important scientific issue I am querying here, but wonder if The Naked Scientists up to the task. Maybe someone among your associated “ .. media-savvy group of physicians and researchers from Cambridge University .. ” can respond to this "Another Hockey Stick Illusion"? question here.

I have  tried to simplify the Ian Stewart experiment question for the benefit of people like Madidus_Scientia, although I suspect that once again it may be long for him/her and that he/she won’t be bothered reading it or my response to your answer (propagandists find it easy to persuade the gullible that black is white because many adopt a similar attitude).

Wiybit, I'll get back to you on the ponts that you raised.

Best regards, Pete Ridley

[Jolly- Joliver]

Just to assit you a bit Pete with Questions to individual posters, Using the quote opition makes it easier to see, BenV will have to read half of your last post before he'll notice the part for him.

If you use the quote option it helps to show what you are replying to. It can be a hassel multi quoting in the same post, and it is easier to just write it all out, just to say if you do put everything in one post, using something to show a change of recipient, makes it easier for others to follow.

Thanks for the reply by the way, and I agree the forum set up is pretty good.    

[Jolly- Joliver]

Wiybit, I'll get back to you on the ponts that you raised.

Yeah cool, You posted while I was writing the last post I made to you.

[BenV]

BenV, thanks for acknowledging that you aren’t competent to give an answer to that very significant but rather scientific “ .. topic in hand .. ”, the validity of attempts to reconstruct past atmospheric CO2 content from air allegedly trapped in ice. Thanks also for trying to give an answer to the other relatively simple question that I slipped in here regarding what is demonstrated by that CO2 experiment carried out by Iain Stewart. The answer you gave to that question, like my air-in-ice one, also gives a fair indication of how competent The Naked Scientists are with regard to the very important scientific debate raging presently around the Catastrophic Anthropogenic Climate Change (CACC) doctrine.

My answer to that secondary question was perfectly valid and highlighted your clear misinterpretation of the demonstration.  It would seem to suggest that I am more competent, and less biased, than yourself in the interpretation of television science demonstrations, would it not?

[BenV]

I would also like to draw question to your motives for posting in this forum - you seem far more keen to make implications about the Naked Scientists competence than to actually discuss the science in question.  You also seem keen to attack people - I personally feel attacked by your language, and your implication about Madidas can easily be seen as, at the least, impolite.

I appreciate that you may have not received an adequate answer to a question you have put to many scientists, and am pleased and honoured that you would come here to discuss it.  I'm also very sorry if no-one here can answer the question to your satisfaction either.  Perhaps if you were to email it in to the show we would have an opportunity to put it to an expert in our next climate themed show?

[Pete Ridley (OP)]

Hi Wiybit, as I have just said to rosy on my “What does Iain Stewart's "CO2 experiment" Demonstrate” post (http://www.thenakedscientists.com/forum/index.php?topic=38723.new#new), I prepare comments using Word so if you can advise me how I embed quotes from here into my word document so that when I copy it all into these blog pages they appear in the way you’d like than I’ll try to accommodate you.

In you comment today at 16:21:39 you ask “ .. Does snow collect air? .. ”. As I understand it fallen snow has a density of anything between roughly 10% and 30% that of water, so falling snow takes a lot of atmospheric air down to the top of an ice sheet. At the simplest level, that falling snow forms a very porous blanket on the ice sheet and is gradually compressed to what is referred to as firn by the paleoclimatologists, which is granular but still porous. Eventually the firn is compressed to become “solid” ice which still contains isolated pockets of air. There is a good description in Wikipedia (http://en.wikipedia.org/wiki/Snow) and there are some good SEM reconstructions at. Fig 3 of http://www.igsoc.org/journal/56/195/j09j041.pdf.

You may find it worthwhile taking a closer look at the comments and links provided during my exchanges with Richard Cumming on the Climate Conversation “Fallen Snow” thread (http://www.climateconversation.wordshine.co.nz/2011/03/fallen-snow/). In my comment of March 26, 2011 at 7:34 am I link to some excellent sets of images at http://itia.ntua.gr/hsj/45/hysj_45_03_0357.pdf which are well worth spending time on.

You ask “ .. how can you even know the starting point of a molecule? I sounds like a lot of guess work to me .. ” and I can’t argue with that. The experts call it probabilities.

Must dash as the boss is calling. This should keep you going for a little while

Best regards, Pete Ridley

[Pete Ridley (OP)]

Hi BenV, thanks for the suggestion about using (quote) and (/quote) in Word. I’ll try it now.

BenV, 15/04/2011 23:21:30 Pete, I think you should be able to put (quote) and (/quote) into your word document, but replace those brackets with square brackets. It won't say who the quote is from or when, but should at least appear...

Hi Madidus_Scientia, BenV asked

..  What do Madidus' activities on other fora have to do with the topic in hand?

so let me just explain that I have this aversion to the use of false names. It comes from having seen too many CACC disciples and followers hiding behind them and hurling insults at us deniers. I always try to find out who I am exchanging opinions with. We all have our peculiarities, don’t we.

Hi Wiybit, regarding your

15/04/2011 16:21:39 ..  I think you mean it's a multi-layered process.

I see the size-dependent fractionation and close-off processes as being “multi-layered” in space and time.

Your

… Ice is a solid isn't it, I kinda think it's like as ice forms and compacts the gases are squezzed out, and if as you are suggesting gases can move through smaller, gaps then I suppose more would be squezzed out.

is getting there. Put simply, snow is also ice but, as I said before, has a density of as low as 0.2 that of water. As it is compacted it approaches a density of about 0.9 that of water. The remaining 0.1 is air, hence 10% of an ice berg is above water.

Regarding kinetic diameter you asked

.. but why do they ignore it? They either are ignorant of it or some some reason feel it has no bearing, or plays to insignifcant a role to be accounted for. I assume, but it sounds a bit strage for scientists to just ignore, a kinetic factor for no reason. What is the justifaction for ignoring it?

. You are repeating the question that I have been putting to the paleoclimatologists for more than a year now and The Naked Scientists three days ago in my first post above. None have answered it yet. It is worth noting that experts in the field of gas purification, such as in the energy and pollutant extraction industries use kinetic, not collision, diameter. I have made this point on numerous occasions to the “experts” and none have explained why they choose to ignore the smaller kinetic diameter of CO2 compared with N2, O2 CH4 and Ar. That’s odd, don’t you think?

.. what is it about Co2 that makes it so different? Personally I think much of the man made co2 we have in the atmospere is comming from CO cabon monoxide, which when realesed from burning fuels etc grabs an oxygen and so forms Co2 ..

. I’m would expect that this “ .. media-savvy group of physicians and researchers from Cambridge University .. ” (http://www.thenakedscientists.com/HTML/about-us/) called The Naked Scientists should be able to offer a valid answer to that question. I think that you may be way off-beam with your hypothesis about CO, considering that when hydro-carbon fossil fuels are burnt the main products are H2O and CO2, with CO being comparatively minor.

.. Implies Co2 is a smaller molecule, yet surely it's bigger then 02? What missing? ..

. In this context we are talking about size in terms of volume not weight (think of a balloon).

.. could it not also be the case that the cores have trapped Co2 from the ice below them? Can we trust the findings at all really? ..

. My hyp[othesis says “Yes” to part 1 and “No” to part 2.

Regarding the difference in collision and kinetic diamter

.. Note the difference for CO2. It's .6 compared to 0, 0.2 or 0.1 with the others, why does it have such variation? ..

, again, there should be at least one of The Naked Scientists who can answer that question.

You seem to have completely missed the point of my mention of the He balloon by saying

..
Strange he is lighter than Co2, so Co2 moves more in because it's smaller fairly clear ..

. I was hoping that you’d realise that the reason the He-filled balloon collapses relatively quickly is because the balloon is a bit like those air pockets in firn – it has lots of tiny pores that are so small that He (0.26nm kinetic diameter) can escape more readily that the larger N2, O2 and Co2 molecules of the expelled air we puff into a balloon.

In saying of the scientists that I mentioned

.. Maybe it's too complicated, and add too many varibles ..

you are effectively agreeing with Professor Jaworowski, who, as I’ve already told you, said “This is a highly specialized field of science. My impression is that it is a terra incognita for glaciologists”.

Finally you said of that CO2 that escapes from the air pockets and heads down the pressure gradient towards the surface

.. Yes, I meant escaped into the atmosphere. From what you have said I'm not sure if you could really say either way .. [/quote. I ’m inclined to agree with that.

(I know, I still haven’t responded on Fickian diffusion. I need more time for that one, after all, I’m only a retired engineer).

May I just say how enjoyable it is exchanging opinions with you in the spirit of improving understanding rather than scoring points or pushing a particular doctrine. It’s a great shame that on most blogs that I get involved with it ends up simply being a battle by both sides to win an argument.

Best regards, Pete Ridley

[Pete Ridley (OP)]

.. BenV 15/04/2011 22:32:12: .. I appreciate that you may have not received an adequate answer to a question you have put to many scientists, and am pleased and honoured that you would come here to discuss it.  I'm also very sorry if no-one here can answer the question to your satisfaction either.  Perhaps if you were to email it in to the show we would have an opportunity to put it to an expert in our next climate themed show? ..

.

I am not familiar with protocol at The Naked Scientists so please can you explain why I have to raise my question about “Another Hockey Stick Illusion?” separately by E-mail in order that The Naked Scientists 

.. would have an opportunity to put it to an expert in our next climate themed show? ..

. I have already put the question to The Naked Scientists so why do I need to put it again?

Best regard, Pete Ridley