NOTE: This post is the second in the series from Dr. Roy Spencer of the National Space Science and Technology Center at University of Alabama, Huntsville. The first, made last Friday, was called Atmospheric CO2 Increases: Could the Ocean, Rather Than Mankind, Be the Reason?
Due to the high interest and debate his first post has generated, Dr. Spencer asked me to make this second one, and I’m happy to oblige.
Here is part2 of Dr. Spencer’s essay on CO2 without any editing or commentary on my part.
(Side note: Previously, I erroneously reported that Dr. Spencer was out of the country. Not so. That was my mistake and a confusion with an email autoresponse from another person named “Roy”. Hence this new update.)
More CO2 Peculiarities: The C13/C12 Isotope Ratio
Roy W. Spencer
January 28, 2008
In my previous post, I showed evidence for the possibility that there is a natural component to the rise in concentration of CO2 in the atmosphere. Briefly, the inter-annual co-variability in Southern Hemisphere SST and Mauna Loa CO2 was more than large enough to explain the long-term trend in CO2. Of course, some portion of the Mauna Loa increase must be anthropogenic, but it is not clear that it is entirely so.
Well, now I’m going to provide what appears to be further evidence that there could be a substantial natural source of the long-term increase in CO2.
One of the purported signatures of anthropogenic CO2 is the carbon isotope ratio, C13/C12. The “natural” C13 content of CO2 is just over 1.1%. In contrast, the C13 content of the CO2 produced by burning of fossil fuels is claimed to be slightly smaller – just under 1.1%.
The concentration of C13 isn’t reported directly, it is given as “dC13”, which is computed as:
“dC13 = 1000* {([C13/C12]sample / [C13/C12]std ) – 1
The plot of the monthly averages of this index from Mauna Loa is shown in Fig. 1.
Now, as we burn fossil fuels, the ratio of C13 to C12 is going down. From what I can find digging around on the Internet, some people think this is the signature of anthropogenic emissions. But if you examine the above equation, you will see that the C13 index that is reported can go down not only from decreasing C13 content, but also from an increasing C12 content (the other 98.9% of the CO2).
If we convert the data in Fig. 1 into C13 content, we find that the C13 content of the atmosphere is increasing (Fig. 2).
So, as the CO2 content of the atmosphere has increased, so has the C13 content…which, of course, makes sense when one realizes that fossil-fuel CO2 has only very slightly less C13 than “natural” CO2 (about 2.6% less in relative terms). If you add more CO2, whether from a natural or anthropogenic source, you are going to add more C13.
The question is: how does the rate of increase in C13 compare to the CO2 increase from natural versus anthropogenic sources?
First, lets look at the C13 versus C12 for the linear trend portion of these data (Fig. 3).
The slope of this line (1.0952%) represents the ratio of C13 variability to C12 variability associated with the trend signals. When we compare this to what is to be expected from pure fossil CO2 (1.0945%), it is very close indeed: 97.5% of the way from “natural” C13 content (1.12372%) to the fossil content.
At this point, one might say, “There it is! The anthropogenic signal!”. But, alas, the story doesn’t end there.
If we remove the trend from the data to look at the inter-annual signals in CO2 and C13, we get the curves shown in Figures 4 and 5.
Note the strong similarity – the C13 variations very closely follow the C12 variations, which again (as in my previous post) are related to SST variations (e.g. the strong signal during the 1997-98 El Nino event).
Now, when we look at the ratio of these inter-annual signals like we did from the trends in Fig. 3, we get the relationship seen in Fig. 6.
Significantly, note that the ratio of C13 variability to CO2 variability is EXACTLY THE SAME as that seen in the trends!
BOTTOM LINE: If the C13/C12 relationship during NATURAL inter-annual variability is the same as that found for the trends, how can people claim that the trend signal is MANMADE??
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Raven,
I have a background in process technology (some time ago…) and was 17 years trouble shooter for chemical processes (later cahnged the job to process automation). The makes that I was quite good in eliminating non-causes, based on evidence to get the real cause of mechanical and/or chemical and/or control problems in the factory.
About non-causes (of general interest)
Based on evidence:
– the oceans are not the cause of the increase in the atmosphere, as their d13C content is too high (even including the fractionation that Paul Dennis mentioned). And the d13C level decreases in the oceans everywhere, even in places where deep ocean upwelling is common (thus CO2 goes from the atmosphere into the oceans).
– vegetation is not the cause of the increase in the atmosphere, as there is a deficiency in oxygen use from fossil fuel burning, thus vegetation is a net sink.
What rests are the emissions…
About the process side (of interest for you)
If you look at the CO2 variations, then one can say that temperature has had a pre-industrial surprisingly linear effect on CO2 levels (even if a lot of underlying processes are far from linear). But that temperature is not the main driver of the current increase (whatever the non-existing source), as the increase (over 50 years) in temperature is much too small and temperature variations only have en effect on increase speed, but not on the increase. Temperature modulates the sink speed, mainly into the oceans, not the fact that the oceans are a near constant net sink…
If you look at the emissions and increase in the atmosphere over the past 50 years, that is a simple equilibrium process, where the increase of the emissions in % of total is quite constant over the past 50 years and is followed by a constant increase in % of the atmosphere.
Thus dCO2atm/dCO2emiss is quite constant, less year by year, but increasingly constant over more years.
If you backcalculate (based on the past 50 years) what the CO2 level was at the start of the emissions, then you end at about 280 ppmv, the figure that was found in ice core bubbles of some 150 years ago. That was the old equilibrium, only influenced by temperature variations (about 10 ppmv/°C).
Thus the basic equilibrium was at about 280 ppmv. Together with the fact that there is a current disequilibrium between natural sources and sinks (of average -3.5 GtC/yr of the atmosphere), that means that if you don’t emit today, that tomorrow the CO2 levels would start to sink (if temperatures stay constant, as is the case in the past 7 years), probably to the old equilibrium of 280 ppmv + 10 ppmv from the LIA-current temperature increase. But it will take quite a lot of time (the current sink rate is 3.5 GtC/yr, still 200 GtC to go, but the sink rate decreases with falling CO2 levels…).
Ferdinand,
Ok, I think I’ve got what you’re driving at. Is there a way to demonstrate that fact to their satisfaction?
Raven
Ooooh. Hmmm.
So it could be sort of deeper a springboard effect then?
In which the amount of CO2 from the ocean depends on the 730-to-38K (or the lesser amount in the upper ocean layers) ratio as it tries to come into balance, and 6.3 is simply lost in the wash?
Where the 6.3 just pushes the sinks a tiny bit deeper but it’s not significant to the balance? Because the sinks are not fixed in size (but why or even how could they be)?
An equation where the smaller rates of exchange are not the drivers but the much larger amounts in the sinks themselves?
Ferdinand,
What you seem to be saying is the planet does have feedback mechanisms that regulate the amount of CO2 in the atmosphere and that these feedback mechanisms would keep the CO2 levels at the set point of 280 ppm even after experiencing a huge anthropogenic perturbation.
So how do we know the set point is fixed at 280 ppm? What would happen if this set point changed for some unknown reason? Wouldn’t it follow that the CO2 levels would increase to the new set point and the human contribution would either cause the climate to reach the new equilibrium faster or simply reduce the contribution required from the natural sources?
I realize I am out on a limb with the ‘unknown reason’ but I would like determine whether the current observations could be explained if someone developed a plausible natural explanation for a changing CO2 set point?
P.S., I respect Ferdinand’s expertise, and if the DoE theory is right, then so is he. I also want so acknowledge that he has said that he doesn not necessarily thing CO2 has the effect that some say it has.
But I find this interesting even if over my head, and I have an abiding belief that the basic premises (though not the full arguments) can be boiled down to common vernacular that would fit on one side of a postcard, so that a layman can get his mind around it.
Ferdinand,
Humans have altered the biosphere with deforestation, intensive agriculture and urbanization. These actions could perturb the carbon cycle and cause a change in the natural CO2 set point.
Here is a paper with data that shows how CO2 levels have varied with human population in the past. http://courses.eas.ualberta.ca/eas457/Ruddiman2003.pdf
Figure 7 is the most interesting for this discussion. It shows CO2 level drops are correlated with disease outbreaks.
This paper demonstrates that the idea that humans could alter the carbon cycle without burning fossil fuels has some support by the data.
A rising CO2 set point caused by human induced changes to the carbon cycle could be the true cause of the rising levels in the atmosphere today and it is possible that eliminating fossil fuel use would not actually reduce CO2 levels – especially if bio-fuels use leads to more intensive agriculture.
Good Article –
By the way, the ocean is a good source of CO2 as the Earth’s temperature increases, because the solubility decreases.
And the carbonate created by crustacea and plankton is a good source of C13 (as well as O16, over any O18)
and I think the case is pretty well closed.
Possible influences on C12/C3 ratios:
The Hadcrut SST data with the Folland and Parker corrections removed shows a steady increase from 1910 of .14 deg/decade, a minor excursion around 1939 and a resumption of .14 deg/decade up to present.
1. Warming oceans are more stable. The nutrient levels in the surface layers fall. Plankton switch from C3 to C4 metabolism (yes, can happen) or C4 plants, which do not need zinc or chromium, outcompete their compatriots. The C4 process is less discriminating between C12 and C13 (and 14), so the biological pump takes more heavy isotopes into the deep water.
2. Methane is stored as clathrates at low temperature very deep: a tiny warming will increase the ability of methanophages to metabolise the methane, bubbling off CO2 which reflects the isotopic composition of the clathrates — organic, ie low in the heavier isotopes.
3. Ancient peat deposits are warmed in the high Arctic — methanophages eat the methane before it is outgassed (methane levels have not shown the uptick which was expected as the peats recover from the suppressive effects of acid rain). The excreted CO2 is, obviously, isotopically light.
4. Plant populations in warming tundra are more C4/CAM types, pulling down more C13. (I’ve only seen one reference to this, so it should be checked, not taken on trust.)
5. Increased dustiness of the North Atlantic means that diatoms, normally silica limited, can outcompete calcareous phytos. The biological pull down is reduced. I don’t know what this will do to ratios as that will depend on the metabolic processes of the two populations.
6. Wind engagement with the surface is reduced by oil and surfactant pollution — less mixing, less nutrient, see number 1. An interesting test for this would be to find CO2, isotope, wind data and SSTs for the North Atlantic during the period 1935 to 1950. I have one graph — I have lost its provenance — which shows a CO2 blip from 39-45, HADCRUT minus F&P) shows the temperature anomaly, and page 19 at
http://aerosols.lanl.gov/conf2006/talks/files/Volz.pdf
shows a curious wind notch. It’s the Kriegesmarine effect in my opinion, but I digress.
2,3 and 5 will alter the oxygen signal. Dusty volcanoes with ejecta high in leachates rich in zinc or chromium should, if 1 is correct, leave an isotopic signal as C3 plants are preferentially fertilised.
I am suspicious of arguments which boil down to ‘we’ve looked at everything else so it must be…’ What they are really saying is ‘it must be if we haven’t forgotten something or something’s not yet been measured. The CO2 budget always looks like that to me — the C3/C4 versatility wasn’t even known when the Suess effect was confidently put forward as the great proof of anthropogenic CO2 rise.
JF
Raven,
The Ruddiman paper is talking about +/- 5 ppmv caused by the bubonic plague, as forests reoccupied abandoned farms. Although possible, this coincides with colder temperatures around 500 AD and 1500 AD. This makes it difficult to know the real partitioning between temperature effects and reforestration/destruction effects. Anyway, after the end of the plague effects and/or temperature effect, we see that the CO2 levels reached the old values again (thus indicating that the setpoint didn’t change).
Since 1850, CO2 increased about 100 ppmv, of which a large part is from fossil fuel burning. Another part is from deforestration, as mainly the underground root system is diminished from trees towards agricuture. That gives a temporarely increase of CO2 in the atmosphere of a few years, as long as the deforestration goes on, which is quite uncertain (more forests in the high latitudes, more forest destruction in the low latitudes). Both a mature forest and continuous agriculture are carbon neutral, if one makes the balance over (a) decade(s).
A further comment on figure 9 of Ruddiman: He plots the expected CO2 level based on insolation / temperature, but that wasn’t true for the previous warm(er) interglacial, the Eemian. While temperatures (and methane) levels decreased about 9°C, the CO2 levels remained constant at about 270 ppmv during 20,000 years, only dropping 40 ppmv after the lowest temperatures were reached (without measurable influence on temperature, probably within the accuracy of the ice core temperature proxy measurements). Thus after an interglacial, CO2 levels remain high and lag the insolation/temperature drop with many thousands of years.
See: http://www.ferdinand-engelbeen.be/klimaat/eemian.html
have an abiding belief that the basic premises (though not the full arguments) can be boiled down to common vernacular that would fit on one side of a postcard, so that a layman can get his mind around it.
Well, Evan, one can only hope, although this discussion has been truly enlightening, even absent any meaningful math and physics skills on my part. And I kind of came away with the same reaction you have, that Ferdinand does an excellent job of explaining why most of the increase of atmospheric CO2 is man-made, but that increased atmospheric CO2 is not necessarily, in and of itself, a bad thing, as long as it doesn’t cause runaway GH warming (which it does not appear to have done). If you’re still monitoring this thread, Ferdinand, have I got that about right?
Raven (or Ferdinand, or anyone), do you know if anyone has ever done serious calculations to determine the amount of CO2 attributable to human exhalation and what percentage it is of total human emissions? Since 1850 the world population has gone from 1.2 billion to 6.6 billion, a 450% increase. It seems to me that that would have some measurable effect.
And a single unchecked forest fire does the same thing. What’s your point? how about reforestation? You’re acting as if the “biosphere” is some single thing that is reliant upon extremely specific conditions.
CO2 natural set point?? What’s that exactly?
Ferdinand,
You said:
“Anyway, after the end of the plague effects and/or temperature effect, we see that the CO2 levels reached the old values again (thus indicating that the setpoint didn’t change).”
The only thing that bothers me about your response is the argument that we must assume that the set point has not changed unless we can find some reason to explain why it should have changed. This is a reasonable argument but it is only an assumption – not a statement of fact.
Is there any way to deduce the real set point today from the data without making assumptions about what might cause it to change?
Jeff in Seattle (08:55:09) says:
“CO2 natural set point?? What’s that exactly?”
If humans stopped emitting tomorrow the CO2 levels would drop because sinks would exceed sources. However, it is reasonable to assume that the CO2 levels would not drop to zero and would level off at some natural set point.
I am arguing that we don’t know what that set point really is today and we can’t accurately infer it from historical data because there has never been 6.5 billion people on the planet before. If that set point is higher today then that could explain some or all of the increase in CO2 levels.
This argument still presumes that humans are the cause of the rise but proposes a different mechanism which would require a different policy response if we wish to reduce CO2 levels.
Raven,
My opinion (yes, not more than an opinion) that the old setpoint still is valid and we probably might go back to the old setpoint, if we stop all anthro emissions, is based on the fact that back-calculation of the cumulative emissions/atmospheric CO2 trend line to its origin is around 280 ppmv. See:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/emissions.gif
Note: the emissions accumulation in the graph is from 1959 on, for 1850-1958 one need to add 36 ppmv CO2 (from 76 GtC) to the accumulation. Backcalculating to zero emissions gives a 20 ppmv lower result than the 1959 atmospheric CO2 content, or about 295 ppmv.
This includes a small temperature gradient of about 10 ppmv in the same period…
If there was an increase in setpoint by any external cause, then the straight correspondence between cumulative emissions and atmospheric CO2 level (R^2=0.9988) would be an upgoing curve.
That doesn’t say that the setpoint didn’t change, it did, because of the emissions. The difference between the CO2 partial pressure (pCO2) of the atmosphere and average oceans is only 7 ppmv in average (not 100 ppmv as one might expect). That is because the upper oceans increased in CO2 content too. That does influence the net sink speed, which is now about 2 GtC/7 ppmv.
The first year after emissions stopped, the oceans would absorb the 2GtC, as the difference in pCO2 atmosphere/oceans still is 7 ppmv. But the year after that, the pCO2 difference dropped to 6 ppmv (assuming constant pCO2 in the upper oceans), thus the absorption would be reduced to 1.7 GtC, etc…
Lucky, there is a second cycle involved, as the upper oceans upwelling – sink flow is about 100 GtC (compared to the 1000 GtC present in the upper oceans), plus an about 6 GtC sink, due to the drop out of dead algues from the ocean surface into the deep oceans…
A few people, more knowledged than me, have calculated that the half-life time of the excess CO2 (thus above 290 ppmv) is somewhere between 30-40 years. The IPCC gives much longer times, but that aren’t half-life times…
Stan Needham
Indeed, even if humans are near fully responsible for the recent increase in CO2, that doesn’t say anything about the influence of CO2 on temperature.
Even not from the past: in all ice cores, CO2 lags temperature changes with hundreds to thousands of years. But as there is most of the time an overlap, climate modellers can claim that CO2 is “helping” the temperature increase/decrease as positive feedback/forcing. But there is one period in time, the end of the Eemian, that there was no overlap, and temperatures were already at minimum before CO2 levels started to decrease. The subsequent 40 ppmv drop had no measurable effect on temperature, see:
http://www.ferdinand-engelbeen.be/klimaat/eemian.html
Further, if CO2 caused more warming (outside the accuracy of the measurements), that should be visible in high accumulation ice cores (like Dome C). But it is not, see:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/epica5.gif
With thanks to André van den Berg, who made this nice graph.
About human/animal CO2. This plays no role at all, as it all is from food which has sequestered CO2 from the atmosphere before eaten. The only difference is that the return to the atmosphere is somewhat delayed: instead of rotting on the field, now it is eaten, or frozen/canned, or accumulated in eaten animals first…
What counts from humans is the area of forests that were converted to fields, as the root system of fields is less than from forests.
Raven, considering that insect respiration accounts for more CO2 annually than all the human industrial CO2, I doubt anything would drop.
Sure, there haven’t been 6.5 billion people on the planet before, as far as we know. But there have been billions of other CO2-emitting creatures for a billion years or more. We know in the past that CO2 was 10 times higher and life thrived like no other times in geological history. So explain again why CO2 is bad?
Julian Flood,
A lot of interesting things you come up with. But hard to quantify.
Some remarks:
1. Warming oceans are more stable.
This is right, but if the about 1°C warming is enough to make a difference is questionable. There is little evidence for less turnover of the oceans (after the alarming THC shutdown messages af a few years ago). And the increase of reported algue blooms seems to contradict the fertiliser deficiency (at least near river discharges).
2., 3. and 4. Methane from clathrates and tundra.
The maximum level of CH4 during the peak warmth of the Eemian (average 2-3°C above current) was about 700 ppbv, for temperatures which were about 7°C warmer in the high altitude tundra than current. Today, methane leveled out at 1800 ppbv (Barrow) and 1900 ppbv (Mauna Loa). Thus mainly man-made and adding to the decrease of d13C…
See: http://www.gxnu.edu.cn/IGCP379/1997/part33.htm
and http://www.esrl.noaa.gov/gmd/ccgg/insitu.html
5. Increased dustiness of the North Atlantic?
Seems to me that the 1930’s Mid-West US dust storms should have had more influence on North Atlantic d13C changes with the prevailing W/SW winds.
But d13C changes are decreasing continuously in the 1930’s, until now, as well as in the atmosphere as in the oceans surface.
See: http://www.ferdinand-engelbeen.be/klimaat/klim_img/sponges.gif
In Europe we have incidentaly Sahara sand deposits, and Mongolean desert storms can be visible up to Arizona…
6. One of the coralline sponges of Bermuda is mainly influenced by the North Atlantic gyre (the other one by the S/N oceanic backstream), there seems to be a cluster around 1940 of halted d13 decrease in the (ice core) air d13C measurements, see the sponges graph in 5. The Law Dome ice core (with very high accumulation) also shows a about 1 ppmv peak around 1940 and decline after that, see:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/law_dome_co2.jpg
But that is within the accuracy of the ice core CO2 measurements.
If that is the result of the Kriegsmarine effect or natural fluctuation or reduced industrial activity, or the sum of all three, that is a big question…
Further, the huge Pinatubo eruption of 1992 didn’t leave a CO2 signal (because the temperature drop had more influence), neither a d13C signal. But there was a remarkable extra decrease in the period 1987-1992, especially at the high North near-tundra locations Barrow and Alert.
See: http://www.ferdinand-engelbeen.be/klimaat/klim_img/d13c_trends.jpg I have no direct explanation for that.
That wind has a profound influence on CO2 sinks and d13C/oceanic life is sure, as can be seen in the mainly NAO influenced uptake in the North Atlantic ocean (Gruber ea.):
http://www.sciencemag.org/cgi/content/full/298/5602/2374
And a lot about trace elements in the oceans from Gruber and Sarmiento:
http://www.atmos.ucla.edu/~gruber/publication/pdf_files/gruber_thesea_02.pdf
Well, we’re only talking about time, then here. With the above reasoning, burning of fossil fuels is then just returning the CO2 that was sequestered millions of years ago back into the cycle. It’s neither bad, good, nor indifferent.
I’m sure the planet’s plants would love the CO2 levels to be a good 5 or 6 times higher than they are now, like they are artificially in actual production greenhouses.
Ferdinand Engelbeen (12:18:36) says:
“If there was an increase in setpoint by any external cause, then the straight correspondence between cumulative emissions and atmospheric CO2 level (R^2=0.9988) would be an upgoing curve.”
Thanks – this point settles the issue for me. There is no reason to believe that a changing set point would exactly follow the human emission pattern.
Jeff in Seattle (14:28:30) :
“Sure, there haven’t been 6.5 billion people on the planet before, as far as we know. But there have been billions of other CO2-emitting creatures for a billion years or more.”
Humans are the only creatures who are able alter the environment on a large scale.
However, I think you misunderstand my point. I was simply brainstorming and looking for any rational explaination other that fossil fuel burning that could explain the rise in CO2 levels. I am now in agreement with Ferdinand that the data only supports the hypothesis that the CO2 levels are the result of fossil fuel emissions and that Roy Spenser is probably wasting his time on this issue.
That said, I also agree with you that rising CO2 levels are not necessarily bad no matter what the reason for the rise.
About human/animal CO2. This plays no role at all, as it all is from food which has sequestered CO2 from the atmosphere before eaten.
While, as I said before, I’m not a scientist, I have, over the last 5 or 6 years, read hundreds of papers and articles about this subject. This is the first time I have ever seen a statement such as the above quote, Ferdinand. Do you have a link to a scientific paper or even a news article that says that CO2 exhaled by humans comes from the food they eat? Are you saying, in effect, that If I fast for say 3 or 4 days, that I no longer exhale CO2? Somehow I don’t think we’re talking about the same thing.
Stan Needham,
All food we eat is directly or indirectly (via meat) from plants. All plants incorporate CO2 taken from the atmosphere, from a few days ago to a few years ago. We use that food directly or indirectly (via fat reserves) to provide energy and building materials for all body functions. The waste of this process is water and CO2. Thus all exhaled CO2 was a few days to years ago sequestered from the atmosphere… Even if you fast a few days, you are using fat/energy/carbon eaten in the period before. If all fat reserves are gone, then you start to use other (building) materials, until that is gone…
Some simple cycle can be found here:
http://www.windows.ucar.edu/tour/link=/earth/Water/co2_cycle.html&edu=high
The total cycle CO2 – plants (- animals) – humans – CO2 is “carbon-neutral”.
The 13C/12C ratio in animal/human meat/bones has the same low value as from the food we eat. This can be used to determine what food was used in the past by animals and humans. See:
http://uf.ilb.uni-bonn.de/versuchsgueter/Gut_Rengen/en/Forschung/Forschungsliste/index.html
Jeff-in-Seattle,
Indeed it is a matter of time span.
By definition, if the time span is within a few decades, the cycle of carbon sequestering – release is considered to be “carbon neutral”, as that doesn’t change the CO2 level over the full cycle.
That is the case for food and wood.
Fossil fuels are not “carbon neutral”, because using them today increases current CO2 levels (regardless if that is a good or bad thing).
There are a few border problems here:
– burning wood from a 600-years old oak house is considered “carbon neutral”
– burning 600 years old peat is considered “fossil”, thus “not carbon-neutral”
But as the first is a very tiny part of the overall CO2 cycle, that doesn’t have much influence.
With a risk for duplication (one comment disappeared in cyberspace…):
Stan Needham:
Plants have incorporated CO2 from the atmosphere. All animal food comes from plants, either directly or indirectly (via other animals). Thus all food contains atmospheric CO2 from a few days to a few years ago.
Animals use food directly or indirectly (from fat reserves) to supply energy and building blocks, necessary for the functioning of the body. The waste prducts are water and CO2 and other products. If you fast a few days, you will use your fat reserves as energy/carbon source.
Some simple carbon cycle is here:
http://www.windows.ucar.edu/tour/link=/earth/Water/co2_cycle.html&edu=high
Thus all together, one can say that the carbon cycle from CO2-plants(-animals)-humans-CO2 is quite fast and this cycle is “carbon neutral”, as that doesn’t alter the amount of CO2 in the atmosphere over a short time span.
Animal/human meat/bones show the same 13C/12C ratio as the food that was eaten. This can be used to determine the type of food the animals have eaten during their lifetime. See:
http://uf.ilb.uni-bonn.de/versuchsgueter/Gut_Rengen/en/Forschung/Forschungsliste/index.html
Jeff in Seattle,
Indeed it is a question of definition of the time period.
Food and wood are by definition “carbon neutral”, as the carbon cycle is relative short (up to a few decades) and over that time span have no influence on CO2 levels in the atmosphere.
Fossil fuels are not “carbon neutral”, as the sequestering happened hundreds (peat) to millions of years ago (coal, oil, gas), and increase the current atmospheric CO2 level (no matter if that is good or bad)…
Re: Ferdinand Engelbeen (14:24:53)
Copied and saved, thank you. That should keep me occupied for a few days…
Pinatubo: do you know if this was a nutrient rich volcano? Some eruptions seem to have very little leachable nutrients of the kind which phytos need to make the C3 pathways.
JF
Evan Jones + Gary Gulrud:
“Well, I mentioned very early on (in the previous thread) that the DoE lists the oceans as a net sink (around minus 2 BMTC/year).
But would seem to be the very point that Dr. Spenser is disputing”.
“I had Ecology too but I think my physics, math and chemistry prepared me better for this study. You didn’t mention why you think the deep ocean is lagging in CO2 uptake, but in any event, Dr. Spencer is simply stating that one particular argument in support of AGW is invalid. You haven’t addressed that issue and the remainder of your discussion does not seem to pertain”.
Well, I had not read your mention, Evan (sorry about that) but of course, this is indeed the point that Spencer disputes. My wondering stems from the fact that Spencer seems totally unaware of any of the countless studies which have actually bothered to sort out in excruciating detail that there is no coherent way the oceans could possibly be a source of the atmospheric co2 rise – like the mentioned ones of Sarmiento or Sabine and coworkers. If you – and you, Gary – go and read those papers, all the claims and questions that Spencers makes/raises are already debunked/answered, including the deep ocean lag (and actually, they already were long before those two studies were published).
It is always fine when researchers take a look at the original sources of the basic stuff that is thought to have been settled long ago – sometimes they do find features that have been overlooked by followers taking basics for granted. But surely, to debunk basic textbook facts really requires a lot of thorough studies and meticulous work adressing an awful lot of work carried out by thousands of other scientists through decades or even centuries. As far as I can see, Spencer is nowhere near this point – has just seems to have wondered a little over some very basic things and went and wrote this without bothering to check whether anybody before him had written something about this.
To put it bluntly, his course bears much more resemblance to an overconfident undergraduate student preparing for an exam, who halfway through his textbook starts to wonder about what he has read so far – and then, instead of reading the rest of the book (in which it is revealed that all his questions have been asked and answered decades ago) goes on to claim that he has made a groundbreaking insight that will henceforth shake all scientific inquiry and Civilisation As We Know It. All this writing of Spencers is exactly like that, and there is just none of his claims that have not been done to death countless times before.
Now Dr. Spencer sure is no amateur nor an overconfident undergraduate, but either he must be amazingly ignorant of some basics he really should know better, he must be capable of an extraordinary level of self-delusion, or hest must be deliberately misleading. He undeniably does have a somewhat dubious record of making frankly absurd scientific claims (both about climate science and about evolution) that noone with his background or skill could possibly not know were dead wrong. I am struggling to believe that Spencer as an atmospheric physicist/meterologist could really be unaware of the enormous body of research that exists on the field.
Honestly, I am mostly inclined to believe that this is a deliberate intent of blowing smoke from Dr. Spencer, which is disgraceful for anyone, but only more so for a scientist which often make tacit allegations against most of his collegues for the very same thing.
If Spencer really intends to write this up as a paper, then I will be really surprised if the reviewers do not send this back immediately asking for Spencer to check up on the basics before submitting such things.
Jeff:
“Well, we’re only talking about time, then here. With the above reasoning, burning of fossil fuels is then just returning the CO2 that was sequestered millions of years ago back into the cycle. It’s neither bad, good, nor indifferent”.
Well, it sure is not indifferent, but whether it is good or bad cannot be adressed just by stating that it “just” returns the carbon sequestered millions of years ago. You are right that a co2 level of 7000 ppm as in the Carboniferous is perfectly “natural” (as would the then higher temperatures of 10-12 degrees be), but this hardly is reassuring. Exaggeration eases understanding – It is a bit like saying that if the oxygen were disappearing slowly from the current atmosphere, then it would just be back to perfectly natural conditions like those in them good olden days four billion years before present……… 🙂
“I’m sure the planet’s plants would love the CO2 levels to be a good 5 or 6 times higher than they are now, like they are artificially in actual production greenhouses”.
Well, I am not so sure. Are you aware of the “Liebig law of minimum”? It states that the growth of plants is not limited by the total sum of resources, but by the scarcest resource.
http://en.wikipedia.org/wiki/Liebig%27s_law_of_the_minimum
In actual production greenhouses, all conditions can be controlled to the point of near-perfection with respect to light, nutrients in the soil and water, and thus extra co2 can further enhance growth. Under field conditions, things are rarely like that, and water, soil quality and access to sunlight are by far the limiting factors of most ecosystems. There is not too much reason to believe that extra co2 will have much positive effect on the wild flora – and actually, the associated warming is more likely to damage the forest ecosystems most places in the tropics.
This is, admittedly, a bit different for some crop plants. Many plants have a C3-metabolism which is sensitive to co2 limitation, and they can be expected to respond positively to co2 enrichment. However, some of the most important crops worldwide (maize, sorghum and sugarcane) are c4 plants which are more likely to be effected adversely.
See
http://en.wikipedia.org/wiki/C3_carbon_fixation
http://en.wikipedia.org/wiki/C4_carbon_fixation
There are not too many field experiments with several controlled factors, but one of the pioneering works studying the effect of co2 enrichment together with other growth factors is Shaw et al.
http://www.sciencemag.org/cgi/content/full/298/5600/1987
They did find that co2 enrichment alone could have a positive influence – but when they added and varied other factors (precipitation, nutrient presence and temperature) that will likely change with increased co2/warming too, thay actually found that co2 enrichment decreased nutrient uptake in the roots, decreasing growth too.
This is not to say that the last word has been said on this subject – but there is certainly no compelling reasons for handwaving optimism about how co2 will benefit plants, either
I should ask Dr. Spencer and others to read the speach of Pieter Tans at the CO2 conference ( http://www.co2conference.org/agenda.asp ), November 2007, in Hawai, at the 50th anniversary of the Mauna Loa observatory CO2 measurements:
http://www.co2conference.org/pdfs/tans.pdf
It contains a lot of answers about CO2 and d13C variations and origins…