About the reliability of ice cores…
Guest Post by Ferdinand Engelbeen
There have been hundreds of reactions to part 1 about the mass balance (http://wattsupwiththat.com/2010/08/05/why-the-co2-increase-is-man-made-part-1 ). Many respondents still are not convinced that the mass balance is a firm proof that the observed increase of CO2 in the atmosphere is human made. But there are more indications. Ultimately, any alternative explanation must fit all the observations. If the alternative hypothesis fails even only one of the observations, then the alternative is rejected. But before we start to look at more observations which support an anthropogenic cause, we need to address several misconceptions which fly around on the Internet, mainly on skeptic blogs… This part has a detailed look at the reliability of ice cores, which are quite important for our knowledge of the pre-industrial CO2 levels, but have been subject to a lot of critique.
Note that the ice cores only show CO2 levels back to about 800,000 years, but measurements may in the future be extended to over one million years. What is found in the ice cores is only relevant for the most recent period of our history and not for more distant geological time periods.
About the reliability of ice cores:
Some have objections to the ice core measurements, as these are regarded as the main reason for the “equilibrium” assumption of ancient CO2 levels. The only real problem in this case is the smoothing of CO2 levels. That depends on the snow accumulation rate, as it takes a lot of time to close all air bubbles in between the snow flakes. That happens at a certain depth where the pressure is high enough to transform the snow, then firn (densified snow still with open pores) into ice. The averaging happens partly because at first the firn pores are large enough to let the air in the pores and in the atmosphere exchange with each other, partly because some bubbles close early, others at a lower depth (thus contain air which is different in composition, “age”, than other already closed bubbles). The depth where this happens depends on the pressure from the layers above and the temperature of the ice. The time needed for full closure of all bubbles largely depends on the accumulation rate of snow at the place where the ice core is taken (or upstream if coring at a slope).
That makes that the average smoothing of CO2 levels is about 8 years (Law Dome 2 out of 3 ice cores, 1.2 m ice equivalent/year accumulation), some 21 years (the third Law Dome ice core, 0.6 m ice equivalent, see http://www.agu.org/pubs/crossref/1996/95JD03410.shtml unfortunately behind a pay wall…), some 570 years (Dome C, a few mm/year, see http://www.nature.com/nature/journal/v453/n7193/full/nature06949.html ) and everything in between. The Law Dome closing period of the bubbles was measured, while for Dome C one needed models to estimate the time resolution in the far past.
Thus the smaller the snowfall at a certain place, the longer it takes for the bubbles to fully close and the longer averaging one has. At the other side, the smaller the accumulation rate, the further we can look back in the past, as for the same depth of ice, there are many more years of snowfall.
The fact that the pores still are open over a long period, also means that there are differences in the age of the ice and the age of the enclosed gas. The age of the ice can be counted, as it simply is the result of ice formation from yearly snow accumulation where winter/summer snow density differences gives clearly distinguishable layers if there is sufficient accumulation. If, as depth increases, the pressure and/or flow result in layers that are near invisible, one may use several other methods like electro conduction or X-rays (see http://iopscience.iop.org/1742-6596/41/1/034/pdf/jpconf6_41_034.pdf ) to distinguish the layers/age.
Determining the gas age is not as easy. Over the years of accumulation of the snow/firn, the pressure builds up and the firn becomes more dense with decreasing pore diameter. That reduces the exchange of air in the pores with the air in the atmosphere, until the pores are too small to make any further exchange possible. If there has been considerable accumulation, as in the two fast Law Dome cores, at the depth of the first closing (about 72 meters) the ice is already 40 years old (40 layers), but the air has the average CO2 levels of less than 10 years ago, which makes the average gas age (including the average time for fully closing of all bubbles) about 30 years younger than the ice at the same depth. For the top layers, we have the advantage of direct measurements in the atmosphere for overlapping periods, which makes a comparison possible.
For cores with far less accumulation, the analysis is more problematic, as the difference increases with the reciprocal of the accumulation rate. During ice ages, there was less precipitation, thus increasing the ice age – gas age difference. The ice-gas age difference for the Vostok ice core is over 3,000 years. Be aware that the ice-gas age difference has nothing to do with the resolution of the CO2 levels, as these are in the bubbles themselves, but it makes a chronology of what happens between temperature (measured as dD and d18O proxy in the ice, see further) and CO2 levels (measured in the bubbles) more difficult to establish. But here also different techniques are used: diffusion speed is a matter of pore diameter, directly related to firn/ice density and densification speed is directly related to accumulation speed. This can be used to model the exchanges between air in the pores and the atmosphere.
The calculations to establish the gas age did fit quite well for the Law Dome ice cores, where besides ice age, the average gas age was established by measuring CO2 levels top down in the firn. That showed that the gas age at closing depth was less than 10 years old on average, but more importantly, the CO2 levels in the already fully closed bubbles and the still open pores were the same. For the low accumulation ice cores like Vostok, there is more discussion about the ice-gas age difference and different time scales were established…
The accuracy of the measurements in the three Law Dome ice cores for the same gas age is about 1.2 ppmv (1 sigma). Later works compared different ice cores for CO2 levels at the same average gas age. These show differences of only 5 ppmv, despite huge differences in average temperature (coastal -20°C, inland -40°C), salt inclusions (coastal), accumulation rate and resolution. There are a lot of overlapping periods between the ice cores, the resolution decreases with increasing length of period (from 150 years – for 2 of 3 Law Dome ice cores – to 800,000 years – Dome C), but even so, the measurements (done by different labs of different organizations) show a remarkable correspondence for the same average gas age. This is a nice indication that the CO2 levels of the ice cores indeed represent the ancient levels.
Data over the past 10,000 years of average gas age in ice cores from:
http://www.ncdc.noaa.gov/paleo/icecore/current.html
As result, for the past 150 years (Law Dome) we have accurate data with a reasonable resolution. The cores average the CO2 levels over 8 years, so any peak of 20 ppmv during one year or 2 ppmv difference sustained over 10 years would be observable. For older periods, the resolution is less and the averaging applies to the full period of resolution (about 570 years for Dome C).
The visual correlation between temperature and CO2 levels in ice cores is well known to everybody, as that was used by Al Gore and many others, although he forgot to tell his audience that the CO2 levels lagged by some 800 years during a deglaciation and many thousands of years at the onset of new glaciations:
Data from the Vostok ice core via:
The temperature is derived from dD and d18O proxies in the ice. dD means the change in the deuterium/hydrogen ratio measured in the water molecules of the ice and d18O is the change in 18O/16O ratio of the water molecules in the ice. Both heavier isotopes of hydrogen resp. oxygen increase in ratio to the lighter ones, when the ocean temperature, from where the precipitation originates, increases. Thus the change in ratio is an indication of the ocean temperature changes. For coastal ice cores, that indicates the temperature changes in the nearby Southern Ocean, while the deep inland cores receive their precipitation from the more widespread SH oceans, thus representing the temperature changes of about the whole SH. The NH ocean temperature changes are more or less represented in the Greenland ice cores, which show similar changes (over the last about 120,000 years), but with some differences in timing and more detailed extreme events (like the Younger Dryas).
There is a remarkable near-linear ratio between ice core CO2 and the temperature proxy record in the same core over 420,000 years of Vostok. Work is under way to confirm this ratio in the 800,000 years of Dome C (for the overlapping period, the CO2 levels are already confirmed similar): about 8 ppmv/°C:
Data of the Vostok ice core from NOAA, temperature proxy indication shows zero at current temperature. From:
http://www.ncdc.noaa.gov/paleo/icecore/current.html
The spread in temperature/ CO2 data, mainly at the high side, is from the long lag of CO2 levels which remain high for thousands of years at the end of a warm period, while the temperature is dropping back to a minimum. The 8 ppmv/°C is not absolutely right, because temperature at best represents a hemispheric ocean temperature, but not far off, as the pCO2 in seawater dependency of temperature shows about 16 ppmv/°C. But besides pCO2 of seawater, other land and (deep) ocean items also play a role.
This all is an indication that temperature is not the cause of the sharp increase of CO2 in the last 150 years, as that wouldn’t give more than 8 ppmv (or 16 ppmv based on ocean solubility) increase with a maximum 1°C temperature increase since the depth of the LIA, while the current increase is over 100 ppmv.
Be aware that, besides some fractionation of the smallest atoms/molecules (not of CO2), and a small fractionation of isotopes, the bubbles still reflect the ancient atmosphere as it was. Ice core CO2 thus is not a proxy but a direct measurement, be it smoothed, of what actually happened in the (far) past.
The objections of Jaworowski:
What about the objections of Jaworowski against the reliability of ice cores (http://www.warwickhughes.com/icecore/ )?
Jaworowski assumes that CO2 “leaks” via cracks in the ice, caused by the drilling and pressure release of the deep core ice. But how can they measure 180-300 ppmv levels of CO2, when the outside world is at 380 ppmv? If cracks (and drilling fluid) are found in the ice, that would show levels which were too high, compared to other neighbouring layers, never too low.
The formation of clathrates (solid forms of O2, N2 and CO2 with water at very cold temperatures and high pressure) depletes CO2 levels, according to Jaworowski. This is well known in the ice core world. Therefore they allow the ice cores to relax up to a year after drilling. Moreover: O2 and N2 clathrates would decompose first, thus escaping as first via microcracks (as Jaworowski alleges). This would lead to too high CO2 levels, not too low.
Jaworowski accuses Neftel of “arbitrary” shifting the Siple data with 83 years to match the ice core CO2 with the Mauna Loa data. But the page from Neftel’s report ( http://www.biokurs.de/treibhaus/180CO2/neftel82-85.pdf ) contains two columns in the table: the counted ice age and the calculated gas age, the latter based on porosity measurements of the firn. Jaworoski used the age of the ice, not of the air bubbles, to base his accusation on, which is quite remarkable for a specialist in these matters. CO2 is in the air, not in the ice and the average age of the gas is (much) younger than the ice where it is enclosed. Neftel even made specific remarks about the gas age, which was compared to the South Pole atmospheric data, to confirm the average age of the gas bubbles at depth:
If the 328 p.p.m. measured at a depth of 68.5 m.b.s. [note: meters below surface] is matched with the atmospheric South Pole record, the mean gas age is 10 yr, corresponding to a difference between mean gas age and ice age of 82 yr, which lies in the above estimated range. The difference is used in calculating the mean gas age for all depths.
That the CO2 concentration measured on the subsequent samples from 72.5 and 76.5 m.b.s. corresponds with the atmospheric South Pole record justifies this age determination…
This clearly indicates that Neftel based his gas age estimate on firm grounds and there is nothing arbitrary in “shifting” the data, as there was no shifting at all. Thus for the Siple ice core, the ice age – gas age difference is about 82 years (Neftel estimated 80-85 years) for an average gas age resolution of about 22 years in this case.
Many of the objections of Jaworowski were answered by Etheridge (already in 1996) by drilling three cores at Law Dome, with three drilling methods (wet and dry), using different materials for sampling, avoiding cracks and clathrates, allowing a lot of relaxation time and measuring the CO2 levels top down in firn and ice. No difference was found in CO2 levels between firn and ice at closing depth and there is an overlap of some 20 years of the ice core CO2 data with the South Pole data:
Figure from Etheridge e.a.: http://www.agu.org/pubs/crossref/1996/95JD03410.shtml
See more comment and further links about Jaworowski at:
http://www.ferdinand-engelbeen.be/klimaat/jaworowski.html
The “corrections” of J.J. Drake:
JJ Drake (http://homepage.ntlworld.com/jdrake/Questioning_Climate/userfiles/Ice-core_corrections_report_1.pdf ) claimed to have established that the CO2 levels needed a correction for the ice-gas age difference. The result of the “correction” is that the CO2 levels are much higher with little variation and the very good correlation with temperature vanished. This conflicts already with our knowledge of the influence of temperature on CO2 levels in current times…
Even so, the “correction” might be all right, but the reason he provided has no bearing in any physical relationship. He makes the basic mistake of conflating a good correlation with a causation: The error is of the kind:
A causes B and shows a good correlation.
A causes C and shows a good corelation.
Thus B causes C, because there is a good correlation between the two. But that correlation is completely spurious, as there is not the slightest physical connection between B and C.
The explanation for his observation is quite simple:
Temperature (“A”) causes the ice-gas age lag (“B”), as temperature is directly connected with humidity of the atmosphere, thus influences the amount of snowfall, thus the accumulation rate and as reciprocal the speed of closing the bubbles: higher temperature, higher snowfall, smaller ice-gas difference.
Temperature (“A”) influences CO2 levels (“C”) directly: higher temperature means higher CO2 levels.
Because the previous two results have a high correlation with temperature, that gives that the ice-gas age difference and the CO2 levels also show a high correlation, but there is no physical mechanism that shows any direct or indirect action of ice-gas age difference on CO2 levels or vice versa. It is a completely spurious correlation, without any causation involved, but both share the same cause. Any “correction” of CO2 levels found in ice cores based on the correlation with ice-gas age difference is meaningless.
Migration of CO2 in ice cores
Ice shows a thin layer of unstructured (liquid waterlike) water molecules near the surface of the air bubbles. Some CO2 may dissolve in this layer, but that is not a problem at measurement time, as measurements are made at low temperature under vacuum, effectively removing all CO2 from the opened bubbles in the crushed ice, while removing any water vapor as ice over an extra cold trap. Water in-between the ice crystals is very unlikely, as there is still the direct influence of ordered structural ice from both sides.
Migration in even the oldest cores is no real problem. The recent fuss about “migration” speed was deduced from the Siple core, based on layers where remelting occurred, something not seen in any high elevation ice core like Vostok or Dome C. It remains to be seen to what extent the Siple Dome results are applicable to other ice cores.
But if there was even the slightest migration of CO2, that would affect the ppmv/°C ratio of the above Vostok CO2/temperature graph over time: the proxy temperature indication is fixed in the ice, while CO2 is measured in the gas bubbles. If there was any substantial migration of CO2, the ratio between CO2 and temperature over warm and cold periods would fade away over the recurrent 100,000 years of time difference between the warm periods, but that is not observed.
Conclusion
The ice cores are a reliable source of knowledge of ancient atmospheres, if handled with care. The resolution heavily depends of the accumulation rate, with as result that the data measured in enclosed air bubbles are smoothed, ranging from 8 years for the past 150 years to near 600 years for the past 800,000 years.
You have still failed to answer one key point, do co2 levels at Antarctica represent the global level? I doubt it very much given the temperature of the oceans there, and recent satelite data has confirmed its not “well mixed” as was assumed. Can you comment regarding this argument? Is there any evidence that co2 levels at Antartica represent the global average at all times in history? Is they dont, they you cannot use it for mass balance without knowing its relation to global levels and at various times i.e. interglacial, and ice age. I doubt this is possible with any certainty – therefore, great uncertainty still exists.
Engelbeen states that “The spread in temperature/ CO2 data, mainly at the high side, is from the long lag of CO2 levels which remain high for thousands of years at the end of a warm period, while the temperature is dropping back to a minimum. ” In this statement, Engelbeen asserts that the data on which he is relying demonstrates that even as CO2 reaches a maximum, temperatures begin to fall. It is hard to imagine a more clear cut statement that whatever drives major climate changes in the last million plus years, it’s not CO2. Engelbeen’s other observation (not a new one either) – that increases in atmospheric CO2 concentrations lag temperature increases by 800 years – corroborates that conclusion from a somewhat different perspective. He believes that his data supports a conclusion that global temperatures begin increasing some 800 years before CO2 concentrations begin to increase. Even if we say that it is open to debate (because consensus does not rule) that human activities are increasing atmospheric CO2 concentrations, the issue is whether, and to what extent, the inquiry is really relevant if the evidence demonstrates that major climate shifts show no correlation with atmospheric CO2 concentrations.
anna v says:
August 20, 2010 at 9:48 pm
The well mixed hypothesis is absolutely necessary in order to extrapolate CO2 content of the globe in time from ice cores. As I have said before, the CO2 measurements in latitude and longitude are so few and controlled by so few people, that it is foolish to think one has measured CO2 content of the world, particularly man made CO2, that is strong over cities, as Beck’s compilations have shown.
The CO2 levels are measured by hundreds of people, from different countries working for different organisations. At some 70 places nowadays one measures “background” atmosphere + regular in-flight measurements, where there is little influence of local/regional sources and sinks and some 400 places are used to measure in/out fluxes of CO2 over land. Conclusion of this all (including the AIRS data): CO2 levels are well mixed within 2% of the range for 95% of the atmosphere within a year. Yearly averages are within 1% of the range. Only within the first 1,000 m over land, near huge sources (and sinks) there are huge diurnal and momentary variations.
Here the yearly averages for several “background” stations(cleaned from outliers, but that doesn’t change the yearly average with more than 0.1 ppmv), and one non-background station (Schauinsland), over 1,000 meters in the Black Forest (Germany):
http://www.ferdinand-engelbeen.be/klimaat/klim_img/co2_trends.jpg
The conlusion of 50 years of measurements is that CO2 is well mixed if you stay away from huge sources and sinks. For the purpose of ice cores, that doesn’t even matter, as these are at least averaging over 8 years, up to some 600 years.
And please, NO discussion of Beck’s data here.
rbateman says:
August 20, 2010 at 10:14 pm
What other gases are found in the ice cores?
Many gases are found in ice cores, in general the same as found in the atmosphere, as the ancient air bubbles simply are enclosed in ice (with some exchanges with atmospheric air during compaction of the snow via firn to ice). See for the different measurements:
http://www.ncdc.noaa.gov/paleo/icecore/current.html
Where for e.g. the Vostok ice core several other items besides CO2 are measured:
http://www.ncdc.noaa.gov/paleo/icecore/antarctica/vostok/vostok_data.html
Volcanic events are found in ice cores, mostly as dust deposits and cause trouble in the Greenland ice cores, as the acid deposits of Icelandic volcanoes react with sea salt (carbonate) deposits and make CO2 in situ. That makes that the CO2 levels from Greenland ice cores are not reliable.
Stephen Wilde says:
August 20, 2010 at 10:21 pm
“But how can they measure 180-300 ppmv levels of CO2, when the outside world is at 380 ppmv.”
Good question but there is a better one. Are the levels of CO2 in the air usually at or near 380 ppm at the drilling location at the time the drilling takes place ? We are considering very cold dry locations well away from natural CO2 sources.
K. Andersen says:
August 21, 2010 at 1:25 am
This is not entirely convincing. 380 ppmv is the average CCO2 level in the earth’s atmosphere, but it varies considerably from one location to another and may not have been the local level when the drilling was performed.
The drilling of ice cores is quite recent: some of the oldest were in the 1980’s and the most recent after 2000. CO2 levels at the South Pole were measured since 1958 (even before Mauna Loa) and increased from 320 ppmv then via 340 ppmv in 1980 to 390 ppmv today. There is very little difference in ppmv’s between stations in the whole SH, thus including all drilling places.
The measurements in the different labs, in places on land, may even have much higher CO2 levels, and I don’t think the researchers hold their breath when preparing the samples (20,000 ppmv in exhaled air)…
tty says:
August 21, 2010 at 1:25 am
It is a coincidence that those lauding stomatal-based CO2 reconstructions seem not to have read Eide & Birks 2004.
Eide, W., Birks, H. H. 2004. Stomatal frequency of Betula pubescens and Pinus sylvestris shows no proportional relationship with atmospheric CO2 concentration. Nordic Journal of Botany, 24, 327 – 339. http://dx.doi.org/10.1111/j.1756-1051.2004.tb00848.x
Of course there is the issue of exteremophiles living in the ice changing the gas composition. “Some quantitative anomalies in the greenhouse gases CO2, CH4, and N2O have been attributed to microbial metabolism (40, 42), but this issue has not been yet experimentally addressed (30). ”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC321287/
A very interesting post. Thank you Ferdinand.
Ferdinand, what is your comment on this list here;
http://c3headlines.typepad.com/.a/6a010536b58035970c0120a5e507c9970c-pi
“If there was any substantial migration of CO2, the ratio between CO2 and temperature over warm and cold periods would fade away over the recurrent 100,000 years of time difference between the warm periods, but that is not observed.”
With the different characteristics of the ice layer…some layers being created during warm periods and other being created during colder periods it is possible to create a natural forward osmosis process with the differing layers of ice in which not only the concentration of the CO2 could be preserved but in fact the CO2 concentrations could be exaggerated. In other words the concentration of CO2 could be somewhat uniform through the ice but as time passes the differing layers allows H20 molecules to move yet keep the CO2 bubbles in the same place. Over time, like 800 years of time, the slight variations in CO2 concentrations could be exaggerated.
I am not going to say “I don’t believe” because that would be the religious solution but I do know there are far too many variables in the formation of ice to trust and one cannot say for certain it’s all human.
The trapping of gas in layers of snow is a very nebulus proposition. Variations of precipitation (both type and amounts), sublimation during long periods of sunshine, intra-daily temperature variations, atmospheric pressure variations, wind velocity, drifting snow and so on. Certainty there is not. OK so does human activity put CO² into the atmosphere? well of course it does. Do the oceans put CO² into the atmosphere? well of course they do. Do sink and source rates vary over time? Of course they do. Certainty, I think not.
John Marshall says:
August 21, 2010 at 1:36 am
I don’t know where you get your information from, but I would recommend trying to find a more reliable source.
“It seems funny to me that the Vostok ice core atmospheric CO2 level graph for the past 400,000 years shows CO2 levels below that which will sustain plant life.”
Either you think that CO2 levels fell to much lower levels than they did (~180ppm) or you haven’t looked at the experimental literature on the effect of low CO2 on plants. Low CO2 reduces growth rates, makes plants more stress sensitive and favours C4 plants over C3 plants, but plants can still grow. See for example, Ward et al. 2008 http://www.as.wvu.edu/~rthomas/publications/Ward2008.pdf
Campbell et al 2005 (http://www.ingentaconnect.com/content/bsc/gcb/2005/00000011/00000011/art00008) estimate that the compensation point (the level at which growth stops) for tobacco is below 100ppm.
“This paper also assumes that the theory of Greenhouse warming due to GHG’s is correct. The laws of thermodynamics show this theory to be false so CO2 is absolutely no problem.”
Which laws of thermodynamics would those be? Certainly not the real ones.
And please, NO discussion of Beck’s data here.
Why not?
And what about the pressure in the ice?
If the alternative hypothesis fails even only one of the observations, then the alternative is rejected.
Apparently, these rules do not apply to the theory of CAGW, only to “alternative” theories.
Ferdinand:
Your long article contains many contentious assertions and ignores several issues that you and I have debated over the years.
Perhaps the most important is that you gloss over a significant problem with the ice cores: viz.
liquid water exists on all surfaces of ice – including surfaces of ice crystals – at all temperatures down to -40deg.C.
This knowledge is not new. It was first discovered by Michael Faraday in 1859. Many recent studies have confirmed this and have determined the reason for it: simply, the molecular bonds of ice vibrate so break down near ice surface.
Hence, there is a 3D matrix of liquid water throughout the ice at temperatures above -40deg.C.
And gases dissolve in liquid water so they can diffuse throughout all ice at temperatures above -40deg.C whether or not the ice experiences bulk melting. Thus, ionic diffusion of gases occurs through the ice from regions of high concentration to regions of low concentration.
Therefore, it is not possible for the ice cores to indicate any high values of CO2 that existed millennia in the past, and it is not possible for bubbles in the gas to act as sealed canisters of the gas they enclose.
This is supported by the degree of adjustment the IPCC applied to ice core indications of atmospheric CO2 to provide them with agreement with the Mauna Loa data. The IPCC set the ‘ice age/gas age’ difference at 83 years to obtain that agreement.
However, as you say in your above article, Etheridge finds much shorter ‘ice age/gas age’ differences than 83 years.
And this causes a real problem.
If the IPCC adjustment of 83 years is an indication of diffusion (which seems likely) then all the ice core data has been smoothed by diffusion in similar manner to the conduct of an 83-year running mean.
Mauna Loa data has only been accumulated since 1958 (i.e. a total of 52 years) and, therefore, the 83-year diffusional smoothing in the ice would conceal any change in the atmospheric CO2 concentration similar to that observed at Mauna Loa.
And if the 83-year diffusional smoothing has not happened then how do you explain the findings of Etheridge which you report?
Richard
Richard S Courtney says:
August 21, 2010 at 4:29 am
Thus, ionic diffusion of gases occurs through the ice from regions of high concentration to regions of low concentration.
—————–
Yes, that would explain the ~100ppm difference between glacial and interglacial ice just 100 m apart.
Ferdinand Engelbeen says:
August 21, 2010 at 2:23 am
Only within the first 1,000 m over land, near huge sources (and sinks) there are huge diurnal and momentary variations.
Most of mankind, lives and burns fuels at less than 1000 meters over land. Most of the flora is at less than 1000 meters over land.
You consider 70 stations enough , and those far away from sources?
Why then don’t we measure temperatures in 70 locations far away from heat sources, like deep ravines and caves? That would surely give us the energy content of the globe.
The conlusion of 50 years of measurements is that CO2 is well mixed if you stay away from huge sources and sinks.
So would temperature be, if you stay away from the sun. Let us then only measure temperature at night at over 1000m.
It is incredible that the assumption of going away from the sources of CO2 will give a correct measure of the CO2 volume in the atmosphere is considered so self evident.
Like measuring smoke to estimate the BTUs of a fire.
The basic assumption made in this statement “Note that the ice cores only show CO2 levels back to about 800,000 years,” is that ice cores show what the atmospheric CO2 levels were with any accuracy further than two or three thousand years into the past.
As Richard S Courtney says there is diffusion of gases within the ice and the tendency would be for that diffusion to remove variance and end with a balanced concentration of CO2 in the ice layers. This has been measured and modeled.
Thus finding that other ice cores of similar age have similar concentrations is unsurprising and does not prove that the concentration of CO2 in the atmosphere when the firn formed was the concentration now found in the bubbles in the ice or that those values matched.
Given that the base assumption is flawed – the conclusions cannot be trusted.
“Even if we are responsible for some fraction of the CO2 found in the atmosphere today, the question remains… is CO2 really responsible for climate change?”
THAT is the question. Whether the CO2 increase is man made or natural is really secondary and not all that important. Really, its a distraction…
Stephen Wilde : “Then why the absence of any irregularities in the rising CO2 slope that correspond with irregularities in human CO2 emissions ? There should be such irregularities within a steadily increasing angle of curve but neither are present.”
A good question.
I made my point earlier rather briefly. I should elaborate a bit : When I said I thought F.E. was probably correct, I was referring to his conclusion that the observed increase of CO2 in the atmosphere is (mostly) human made, not to his reasoning. I have no opinion on his reasoning, having not worked through it to fully understand it.
What I did find was that I could not get anything like a match to the CO2 increase by trying to ascribe it to warming oceans, THC volumes, etc. I was therefore unable to contradict F.E.’s conclusion, and I felt that having done the work I should admit the result.
The incredibly close correlation between temperature (T not dT) and annual change in CO2 shows incontrovertibly (to my mind) that temperature affects CO2 levels. The same applies to the long term record (CO2 lagging by a few hundred years). It is also obvious IMHO that ENSO affects CO2 levels. But all the analyses that I did led me to the conclusion that although these factors did affect CO2, they could not explain the rise in CO2 over the last several decades – that in the absence of fossil fuel emissions, CO2 levels would still have risen but not by much. It is possible of course that I missed something.
Hopefully someone will answer your question eventually. I can’t.
http://www.jaxa.jp/press/2009/10/20091030_ibuki_e.html
The variation of the scale is evident in the CO2 plot and it is not 2% but closer to 10%.
Maybe Keeling et al ( all the Scripps publications of CO2) will get to them to trim their excess.
I’m just throwing this out here: There has been much debate as to the residence time of free CO2 in the atmosphere. This uncertainty would seem to cast doubt on the hypothesis that much of the C02 increase is manmade.
Well – but what’s cause and what’s effect?
From eyesight, using a straight edge to compare graphs, I think I see the CO2-graph LAGGING the temperature-graph over time, not LEADING.
Of course, it might only be an effect of my distorted eyesight.
But it might be something different, too.
Ferdinand Engelbeen… Thanks for your explanation of ice core data. I have read very little about it, so, again, thanks.
Two questions continue to bother me about AGW.
Why do CO2 graphs over long periods, trail temperature if CO2 is the primary cause of temperature change?
Why is 390 ppm CO2 vastly more important than 20,000 to 40,000 ppm H2O when CO2 is only 20 times more “active” than H2O in the greenhouse arena?
Has there ever research been done on the possibility, that water, especially cold water – like droplets in cold clouds close to the freezing point, for example, or cold ocean surfaces – might allow different gases (Oxygen, Nitrogen, CO2) to dissolve differently in the water?
Kind of a “qualified solution”, if you will.
Because, that might alter the ways, in which research on gases dissolved / stored in water/ice is conducted today, completely.