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Discussion > Historic Levels of CO2

In an earlier exchange with Richard Betts he commented to the effect that CO2 levels have been steady for a long time with only minor local variances. A bit of blundering about on the web (I am no search-engine sleuth) turned up some material which appears to question that view.
Firstly this paper - - reached the conclusion: “Our results falsify the concept of relatively stabilized Holocene CO2 concentrations of 270 to 280 ppmv until the industrial revolution. SI-based CO2 reconstructions may even suggest that, during the early Holocene, atmospheric CO2concentrations that were >300 ppmv could have been the rule rather than the exception.”
Then I found this interesting, but lengthy, write-up on the history of CO2 measurement - .
It includes measurements from the 1800s which were comparable to or above today’s levels, with this comment on their likely accuracy: “CO2 readings from 1790 to 1820 should be considered interesting (and possibly approximately correct) but it is from 1820 onwards that the level of reliability increased enough for us to consider a meaningful proportion of them as a useful record of their time and place. In examining a few of the measurements taken at the time later in this article, it should be borne in mind that they are a fraction of many hundreds of thousands of independent readings taken by many scientists-several of them Nobel winners-from around 1830 to the advent of readings at Mauna Loa in 1957 by Charles Keeling.”
Lastly this post from WUWT - - reached this conclusion: “The plant stomata pretty well prove that Holocene CO2 levels have frequently been in the 300-350 ppmv range and occasionally above 400 ppmv over the last 10,000 years.” It is a long, rambling post covering a lot of other issues but the plots of stomata-derived CO2 levels are interesting, as is the explanation why the ice cores have high resolution for temperature but may not pick up decadal to century swings in CO2.
In summary, this little bit of rummaging suggests there is good evidence for historic CO2 levels being highly variable over relatively short timescales and for them matching modern levels on occasion. I have no expertise in this area nor the time to acquire it so I would very much appreciate some explanation, especially from Richard, of why this cadre of information has, apparently, been disregarded.

Sep 24, 2013 at 12:43 PM | Registered Commentermikeh

Mikeh (Hi, note oxford pub post below), if those estimates were accepted, there could be no CAGW scare. That is why they are not accepted. So each and every study which does not fit is subject to an array of criticisms. Some are too local, time-specific, not smoothed like the Mauna Loa series, subject to other influences than CO2 concentration, whatever. The warmists have managed to reduce the credibility of every study which does not suit them. How valid the criticisms are I have no way of telling. Similar criticisms of ice core CO2 do NOT undermine credibility. Of course.

Sep 24, 2013 at 12:52 PM | Registered Commenterrhoda

I agree with rhoda, the CAGW hypothesis needs 2 hockey sticks - one for temperature and one for CO2. The fact that the ice core data conflict with the chemical measurement data and the stomata data has been "hushed up" for years. There is considerable discussion on the internet about the validity of ice core methodology, with various suggestions of how it may be fatally flawed (diffusion, etc.).

Sep 24, 2013 at 1:22 PM | Unregistered CommenterRoger Longstaff

Didn't a man named Beck report on chemical measurement of CO2 in the 19th century and get values higher than those used by Climate Models.
There is this article on WUWT.
and this one

I'm sure I've seen other references but can't find them at the moment.

Sep 24, 2013 at 1:49 PM | Unregistered CommenterSandyS

Sandy, you can find Beck's work here:

Sep 24, 2013 at 2:19 PM | Unregistered CommenterRoger Longstaff

thanks for the reference. Is there any reason apart from disagreeing with the consensus why this work is ignored? It seems to me that the paper shows that CO2 was in the range 300-400ppm during the 19t century and it was more likely that:

The close relationship between temperature change and CO2 level exhibited by these results is consistent with a cause-effect relationship, but does not of itself indicate which of the two parameters is the cause and which the effect. The greenhouse hypothesis of IPCC argues for CO2 being the cause (through radiative feedback) of the temperature rise. My results are equally if not more consistent with temperature being the forcing that controls the level of CO2 in the atmospheric system. In support of this causality, ice-core data consistently shows that over climatic time scales, changes in temperature precede their parallel changes in carbon dioxide by several hundred to more than a thousand years .

Do you know if anyone has repeated the measurements using the same techniques as the 19th century researchers. It would seem a sensible thing to do taking into consideration some of the values obtained, for example Schulze, at Rostock 1863/64 which peaked at around 400ppm; and that trillions of £s are being invested in attempting to keep CO2 levels to a similar value.

Sep 24, 2013 at 4:29 PM | Unregistered CommenterSandyS


I looked into this in some detail a couple of years ago, and it was discussed here at BH, at WUWT and elsewhere. I think the data are ignored because they are an "inconvenient truth" and do not fit the consensus. I know that there are serious concerns about ice core methodology, including the fact that it gives markedly different results from the chemical and stomata data. IIRC the chemical experiments are still being performed today in chemistry undergraduate labs.

This is all from memory and I do not have time to revisit it at present. As "climate science" is at last under serious scrutiny, a fresh pair of eyes on this subject would be useful. As I have said elsewhere, I feel that one good push could bring the whole, rotten pack of cards come crashing down.

Sep 24, 2013 at 5:06 PM | Unregistered CommenterRoger Longstaff

Thanks for the various links - plenty of reading there, I am sure.

I was pretty sure this would have been covered here before, as Roger notes: I will see what I can dig up rather than covering the same ground again.

My initial impression is that, as several others have said, CO2 levels have actually shown the same type of natural variability as the real temperature records. Today's conditions are nothing out of the ordinary.

It would be very interesting to hear from Richard on this....?

Sep 24, 2013 at 5:23 PM | Registered Commentermikeh

Thanks Roger
We're back to the UK Thursday so research time will be limited. I have two threads to work on now, UK power generation and this one. If you found things on the web then I should be able to repeat that. It is good winter activity, along with my main hobby of 1\1200 scale model boats, now that I'm down to my last room requiring renovation. I sometimes wonder why there are so few people who want to find out the truth for themselves, my wife and I have come to the conclusion that we're the ones out of step with the world.

If no-one minds an interested amateur contributing then I'll continue posting what I find here; it doesn't get swamped by volume like WUWT.

Sep 24, 2013 at 7:21 PM | Unregistered CommenterSandyS

My understanding of this is that WHERE you measure CO2 is crucial in getting accurate results e.g. not in a forest, not in a town, city etc. I understand that we could only measure CO2 ppm accurately since about the 50s. there were other methods prior to that but none was accurate.

Sep 25, 2013 at 9:22 PM | Registered CommenterDung

Dung; you might take a look at the second article which I referenced. It claims CO2 was being measured accurately from the mid-1800s.

Sep 25, 2013 at 11:31 PM | Registered Commentermikeh


From memory, If you look at Beck's paper he records thousands of measurements of samples from widely diverse locations, including at sea, various altitudes, coastal areas, etc. I also seem to remember that there was an analysis of accuracy (but no time to check at present).

Sep 26, 2013 at 8:40 AM | Unregistered CommenterRoger Longstaff

I have the feeling that we are all in danger of falling into a trap set - perhaps by the climate scientists, perhaps by the warmist activists - on three separate fronts and that rather like the pea under the thimble we are being co-erced into concentrating on what those various groups want us to believe.
With 12 posts on this thread we are already unable to agree on the accuracy or otherwise of past CO2 measurements. Dung is probably right to say that there are places where you should and should not measure the stuff but surely the same argument applies here as applies to temperature and more recently to the ph levels of the oceans.
Is it possible to find any accurate measurement of any of those metrics unless you measure them at every point on the earth where they exist and at the same moment.
I'm not quite stupid enough (though it's a close run thing now and again!) to believe that that is possible or even within the realms of being theoretically practicable but the logical outcome of that impossibility is that those with the expertise (and the agenda) can virtually create whatever figures they like by choosing — and I don't necessarily mean 'cherry-picking' in the sense we usually use the phrase — where the measurements are taken and on what frequency and what is done to them thereafter in the various attempts to make them meaningful.
Where is the evidence that CO2 levels world-wide are at elevated levels compared with some arbitrary date in the past and that this represents a threat?
How we can we have any confidence in the calculated global temperature when so much of the surface of the planet and the atmosphere surrounding it and the oceans which cover 2/3 of its surface are so sparsely measured?
Exactly the same argument applies to ocean ph - only more so.

Or am I missing something obvious?

Sep 26, 2013 at 1:46 PM | Registered CommenterMike Jackson

I've often wondered why they measure CO2 from the side of a volcano which is outgassing all sorts of stuff with no relation to atmospheric concentration. You may as well measure how much your house leaks water by putting your measuring apparatus in the toilet pan.

Sep 26, 2013 at 2:17 PM | Unregistered CommenterTheBigYinJames

I think the reply is usually that CO2 is actually measured at a lot more places than Mauna Loa but if that is the case then you have to ask why Mauna Loa is always the site quoted.
And I've never heard of readings being taken from either fixed or floating buoys in mid-ocean which means that there are no readings covering (arguably from the CO2 point of view) the most important two-thirds of the planet.
And if the answer to that is that CO2 is a "well-mixed" gas so it doesn't matter where you take the readings from then can we believe that a concentration of 1:1800 is going to have dire consequences when 1:2500 obviously is not.

Sep 26, 2013 at 2:50 PM | Registered CommenterMike Jackson

Measuring CO2 at sea is not a good idea, you are in the boundary layer between a sink and the atmosphere. The balloon measurements that started in the 50s were able to get an idea of general atmospheric CO2 levels well away from possible contamination.
However I would suggest that the ice cores are an even better method which have been checked against real world observations as recently as 1980 - 2000.

Sep 26, 2013 at 2:59 PM | Registered CommenterDung

It's a well-mixed gas when they measure it, it's a local variation when somebody else measures it. I think you have to work on the data to get a general figure. Apply seasonal corrections and so on. If anybody wanted to duplicate the Beck data in place and time of day/year and compare it to the historical data there might be some mileage in that.

Dung, if an ice core from 1980 shows the 1980 ML figure, that's super. But it doesn't take away the doubt about ice cores. Isn't there a discontinuity of 80-odd years? I suspect the 280ppm for centuries story, such stability seems so unlikely.

Sep 26, 2013 at 3:40 PM | Registered Commenterrhoda

I admit to being ignorant in these matters but I fail to see why measuring anything at the interface with its sink is not a good idea. It must surely give you another perspective on how that substance behaves, no?
And I thought that ice cores had already been criticised as unreliable because the CO2 can move between the layers or something. Or was that just another make-it-up-as-you-go-along-if-the-answer-doesn't-suit? There seems to be an awful lot of them in climate science.

Sep 26, 2013 at 4:24 PM | Registered CommenterMike Jackson

"..... the ice cores are an even better method which have been checked against real world observations as recently as 1980 - 2000."

Dung, (from memory) the ice ares are no use for CO2 measurements until they have been compacted for several decades. There is no way to check the methodology IIRC.

Sep 26, 2013 at 4:37 PM | Unregistered CommenterRoger Longstaff

TheThinkingScientist, Entropicman and I just finished a long discussion in the "Speccy on AR5" thread which is currently nearing the bottom of page two of the blog. TTS was arguing about statistical methods (with EM) and I was arguing about CO2 lag. EM brought up the reliability of ice core samples for CO2 and quoted a number of papers including one from March this year. I debunked them to EM's satisfaction only today.
The 2013 paper was utter tosh in my opinion so I set about proving it.Their argument was that the CO2 trapped in the ice is of a different age to the ice surrounding it and so using the O18/O16 ratio of molecules in the ice did not date the CO2. They claimed the difference was a convenient 600 - 800 years. However I showed that the method of examining ice cores was not dependent on the ice but only on the bubbles trapped in the ice. Within each bubble is CO2 plus the O18/O16 molecules that date the CO2. They grind the ice cores at sub zero temperatures and analyse the atmospheric gases released. There is no problem with ice core dating of CO2.

Sep 26, 2013 at 7:39 PM | Registered CommenterDung


The sea like the forests (or any vegetation) will sometimes be chucking out CO2 and sometimes absorbing CO2. Depending on the time of day or the temperature the resulting CO2 levels will change dramatically.

Sep 26, 2013 at 7:51 PM | Registered CommenterDung

Roger Longstaff

As the snow layers of one year get covered by other layers from succeeding years, each layer is compressed and the resulting substance is called the "firn". The people casting doubt on the reliability of ice core records say that until the firn is compressed into ice, the air bubbles can still move about. the British Antarctic Expedition did tests. They took firn samples (and the bubbles within) from 1980 to about 2000 and checked the ice core info against real world info and it matched perfectly. For this test I do not know the methodology but they seem convinced ^.^

Sep 26, 2013 at 8:08 PM | Registered CommenterDung

Dung, do you have a reference for the 1980 - 2000 ice core analysis? That is the problem with this area, there are so many conflicting stories. When I looked into this a couple of years ago I am seem to remember that the "consensus" was that ice core data were only reliable from about 50 years ago...

Sep 26, 2013 at 10:10 PM | Unregistered CommenterRoger Longstaff


I found the info here: › BAS Research › Science Briefings‎

It is even better than I remembered since it runs from 1950 to 1990 ^.^ The general message is an alarmist one but the specific info on ice cores sort of defeats their message hehe.

Sep 27, 2013 at 12:47 AM | Registered CommenterDung


I started to read your second linked article and I followed some of the links given but the more I read, the less I was impressed.

This was at the end of one link that I followed:

This is the main problem with the historical CO2 measurements: Near all data come from sites on land, some in towns, some in (rice) fields, some in forests and grassland, or a mix of them in the main wind direction (or different for different wind directions). And near all are measured near ground 0-1 m high. For the oversight of historical measurements, it is important to know where and how was sampled and measured, including wind direction and surroundings. In this chapter we will try to compare modern measurements over land with the historical measurements, and with background measurements.

As is clear for modern measurements, the CO2 levels measured at low height over land don't give a clue about the "background" level of CO2. Therefore the influence of local sources/sinks is huge and give a (mostly positive) bias to the measurements. Here an example.

Diekirch (Luxemburg) [2], has a weather station is in a valley with forests, urbanisation and traffic in the main upwind direction. The main air intake is at about 20 m above the valley floor. The diurnal CO2 level change is heavily correlated with the buildup of an inversion layer at night, which is anti-correlated with temperatures, sunlight and wind speed. At windspeeds > 1 m/s the inversion layer is destroyed and the diurnal variation is much smaller than at low wind speeds.
Giessen in Germany [3] had a weather station which made a lot of measurements in 1939-1941 at different heights: zero, 0.5, 2 and 14 m. Some comparison here is possible.

diurnal CO2 Diekirch
Diurnal CO2 measurements compared to temperature, wind speed and sunlight in Diekirch, graph from [2]

diurnal CO2 Giessen
Diurnal CO2 measurements at Giessen, taken from [3]

The data from Giessen have an average of 462 ppmv (data in the paper are expressed in thousandth of a percent, which is 10 ppmv), with a minimum of 240 ppmv and a maximum of 680 ppmv. Variability is +/- 132 ppmv (2 sigma) at 14 m. The background level in that period was about 310 ppmv (Law Dome ice core).
Diekirch has an average of 405 ppmv and a variability of +/- 30 ppmv (sigma level not given). The background level in the time period of measurements was 376 ppmv (Mauna Loa).
From these figures, it is clear that the Giessen data have a higher average and larger variability than modern data even from a shielded valley like Diekirch. In both cases, the background level is within the variability around the average. And in both cases, the CO2 levels reach the background level at high(er) wind speeds. That points to the influence of insufficient mixing at low wind speeds and at night when there is an inversion layer.

Sep 27, 2013 at 1:29 AM | Registered CommenterDung