Thursday
Aug012013
by 
Bishop Hill
Bishop Hill A new look at the carbon dioxide budget - Part 2
Aug 1, 2013 Climate: carbon budget David Coe's post on problems with the official carbon dioxide budget generated a lot of interest and more than 100 comments. David and I have therefore decided to bring forward publication of the second part of the paper, in which he sets out a new approach to these questions.
The paper itself is attached below. For those who are interested, David is also making available the data behind the key figures: Figs 2.4 and 2.5 and Figs 2.6 and 2.7
Reader Comments (85)
David Coe
How does the variable Carbonate Compensation Depth in the oceans appear in your equations?
You must be aware that below a given depth all CaCO3 dissolves?
Martin
I didn't forget about it. I just don't know how to quantify it. The dead plants don't just magically turn into CO2. Some get eaten by bugs, some get absorbed into the ground and become future fossil fuel. In fact, curiously, it is not that important to the calibration of the equations if I regard it as a constant. Whatever value I allocate does not impact upon the estimation of the two key time constants. It simply changes the estimated net flux (which I have assumed to be absortive at the equivalent of 20ppm/yr) which in turn requires a different value for Co, the deep ocean CO2 partial pressure, in order to get the correct 280 ppm starting point on the atmospheric CO2 curve. You can see how this works by looking at the attached spreadsheets.
Sorry that this is a long single letter response.
Hans Erren
"How does the variable Carbonate Compensation Depth in the oceans appear in your equations?
You must be aware that below a given depth all CaCO3 dissolves?"
It doesn't appear. I simply postulate a mechanism for the continuous production of CO2 within the deep ocean, which happens to be endothermic thus requiring energy to be gained from that ocean. The coincidence, and I hate coincidences, is that energy at 7 x 10^17 kj/yr is virtually identical to the geothermal input via the seabed.
It occurs to me that the AGW proponents arguments about bit hiding in the deep ocean may be correct, with the exception that what is hiding down there is not heat, but CO2 :-)
David Coe--
You still have not answered my question about Figure 1.5 (or 2.1). How can it be that an input of 1 ppm CO2 can produce an increase on the order of 5-10 ppm in the atmosphere? You have also not responded to my request to produce the data on which this figure depends.
David Coe @ Aug 2, 2013 at 1:35 PM
Thank you for your response.
"Reality overcame doctrine. Nature does indeed follow the laws of physics."
I have suggested nothing unphysical. Indeed, as I pointed out above, it is the idea of tight regulation over millennia which can nevertheless be substantially affected by our relatively small perturbation which is unphysical.
It is also unphysical to assume that temperatures can drive CO2 variations while something else drives the long term behavior without any phase distortion appearing at the crossover frequency where they blend. It also runs afoul of Occam's Razor, in that the temperature accounts for both the long and the short term without needing any additional input. As Laplace would say, we have no need of the hypothesis of an additional significant driver.
"The question I am asking myself and anyone who cares to listen is - am I right or am I wrong?"
Keep watching the emissions and measured atmospheric CO2 diverge. If the emissions continue accelerating, and the CO2 continues at a steady pace, or even decelerates with decreasing temperatures, your hypothesis will be falsified. I expect that will happen, but I also expect you will have to see it for yourself to be convinced.
Aug 2, 2013 at 11:16 AM David Coe: "It is easy to envisage cold polar waters sinking into the abyssal ocean, it is not so easy to see where the waters rise gain in order to complete the circuit."
Tim Osborn may be able to answer your question more authoritatively than I, but my understanding is that major upwelling of deep ocean water occurs off the western coast of South America to form the north-flowing Humboldt current (and to a lesser extent off the western coast of southern Africa as part of the north-flowing Benguela current). In the eastern Pacific prevailing (except during El Niño events) equatorial winds push surface water westwards away from the South American coast and cold Humboldt water is continuously drawn up to the surface in response to the westward flow.
"Indeed, as I pointed out above, it is the idea of tight regulation over millennia which can nevertheless be substantially affected by our relatively small perturbation which is unphysical."
Looking back, I see I did not make that point on this thread, but on the last thread re Part 1. So, allow me to say on this thread that, in system theory, tight regulation and significant sensitivity to perturbations are generally mutually exclusive properties. Regulation and sensitivity generally vary inversely with one another, i.e., the sensitivity and complementary sensitivity functions sum to unity. An increase in one means a decrease in the other.
Aug 2, 2013 at 5:40 PM Lance Wallace
Lance, If you wish to do so, you can download data from the following:
http://cdiac.esd.ornl.gov/trends/landuse/houghton/1850-2005.txt
http://cdiac.esd.ornl.gov/ftp/ndp030/global.1751_2009.ems
http://www.esrl.noaa.gov/gmd/ccgg/trends/#mlo_data
"It is also unphysical to assume that temperatures can drive CO2 variations while something else drives the long term behavior without any phase distortion appearing at the crossover frequency where they blend."
Aug 2, 2013 at 6:40 PM Bart
That's the insight I've been waiting for.
Lance Wallace
"How can it be that an input of 1 ppm CO2 can produce an increase on the order of 5-10 ppm in the atmosphere?"
The answer comes from the control equations
atmospheric CO2 levels Ca = Cs – 1/g2.Fa (1)
sea surface CO2 levels Cs = Co – 1/g1.(Fa+ Fs) (2)
Atmospheric and sea surface CO2 levels are both proportional to the CO2 fluxes Fa and Fs. An increase in atmospheric flux of 1ppm/yr causes CO2 levels to rise by almost 10 ppm in order for the partial pressure differential between the sea surface and atmosphere to increase to a level whereby the balancing flux from the sea surface also increases by the same 1ppm/yr. This also causes CO2 levels to rise in the sea surface (equation 2) thus contributing to the so called ocean acidification. This CO2 increase comes from the deep ocean not from the anthropogenic emissions. The emissions are the catalyst for the increase. This is why the observed isotopic ratio change is six times less than it should be if the increase was due to retained emissions. Anthropogenic CO2 is not being taken up by the ocean but is necessitating a rebalancing of partial pressures in order to maintain flux equilibrium. It is a classic control action.
You should be able to get the data for the figure 2.1 from the fig 2.4 download. It is simply CO2ppm v emissions in ppm/yr.
I hope this helps.
Bart
I guess we may have to agree to differ on this one. I would dispute however your claim that CO2 increases are tailing off. Temperature might be, CO2 certainly isn't.
Coldfish
"Tim Osborn may be able to answer your question more authoritatively than I, but my understanding is that major upwelling of deep ocean water occurs off the western coast of South America to form the north-flowing Humboldt current (and to a lesser extent off the western coast of southern Africa as part of the north-flowing Benguela current). In the eastern Pacific prevailing (except during El Niño events) equatorial winds push surface water westwards away from the South American coast and cold Humboldt water is continuously drawn up to the surface in response to the westward flow."
You are almost making my point for me. Is it the contention that a uniformly cold deep ocean results from a series of localised events (assuming you can refer to large ocean tracts as local)? What encourages the waters to rise several thousand metres from the ocean bed if there is no temperature gradient?
David, this is close to what I have been thinking and playing with recently.
The only two things that I can add that are important are these
1) If you examine the dissolved organic and dissolved inorganic (DOC and DIC) gradients, you can see that they mirror each other. At the surface the DIC is denuded, being converted to DOC, by photosynthesis. Replenishment comes from below in the movement of CO2 and CH4 from the hypoxic zone.
2) Biology is all about sex and sh1t, and there is a lot of the latter. Dead organisms and excreta rain down from the oxic surface layer and begin a fall to the depths, containing DOC and DIC (mostly calcium carbonate). Some of this is intercepted on the way down being oxidized to CO2, and in the hypoxic zone oxidized to CO2 and also reduced to CH4. When it hits bottom it is either oxidized, or mineralized. The mineralization rate, over time, will match the rate that CO2 enters the biosphere through volcanic action.
The rate that dead organisms and excreta fall, called 'marine snow', is rather impressive compared with diffusion processes, about 50 meters per day:-
http://www.dtic.mil/dtic/tr/fulltext/u2/a219077.pdf
Michael Larkin: I think the concentration only matches the "calculations" because they tweaked the "residence time", claiming that CO2 emissions are resident for 50 years.
I don't think that anyone seriously believes this.
If you plug believable "residence times" into their calculations, the value resulting does not match measured values at all.
David Coe @ Aug 2, 2013 at 7:21 PM
"Temperature might be, CO2 certainly isn't."
But, that is precisely what the data show. Temperature anomaly and measured atmospheric CO2 rate of change move in lock step.
"I guess we may have to agree to differ on this one."
Eventually, the truth will out. As long as you aren't advocating authoritarian government as a response, it's OK by me.
DocMartyn
You might have just answered a problem that I have been wrestling with. I am postulating a steady CO2 flux from ocean to sea surface to atmosphere in order to balance the net absorptive fluxes in the sea surface and atmosphere. This requires the continuous generation of CO2 within the deep ocean. The twin effect is that there must also be a continuous O2 flux in the opposite direction, into the deep ocean. In order for O2 not to continuously increase there must be oxidation reactions regulating the deep ocean O2 content. I believe that you may have just suggested such a process.
Bart
I agree entirely that there is a high correlation between temperature anomaly and CO2 rate of change. Differentiate the equations generated in the part 2 above and that relationship falls automatically into place as I shall show in part 3. Yes there is a natural temperature effect but it does not explain the correlation between CO2 and rate of anthropogenic emissions. The ocean control theory provides a rational explanation for both. Please wait until Andrew posts part 3 before you dismiss me.
Martin A
Probably not. Under stable long-term climate conditions taiga and temperate woodland tend to be CO2 neutral, with net photosynthesis balanced by net respiration.
In a stable climate tundra tends to be a CO2 sink, as peat accumulates. Under present warming conditions tundra is becoming a net CO2 producer as thawing permafrost allows long frozen peat to thaw, dry and decay.
So far David Coe has failed to convince me that CO2 released from the ocean would have any direct effect on these processes. Tundra decay would not be directly affected by more CO2 (except through its warming effect). There is also the problem that under taiga and tundra conditions photosynthesis is temperature limited, not CO2 limited. Increased CO2 would therefore have no effect on the rate of phtosynthesis.
Enzyme reactions, however, have a Q10 around 2. Increasing the temperature 10C would double the rate of respiration and photosynthesis.. Even a small warming effect would significantly increase CO2 release in Winter, and both photosynthesis and respiration in Summer.
David Coe
"What encourages the waters to rise several thousand metres from the ocean bed if there is no temperature gradient?"
Resesarch the concept of mountain wave, as airflow over a mountain range creates waves of rising air at higher altitudes. Alternatively, sit by a stream and watch water rise as it flows over stones in the bed.
David,
Not a stupid question at all. But can I first turn it around? What do you expect to see in the deep ocean temperatures as evidence that the water is indeed warming and, therefore, able to rise? Perhaps some patches of warmer water in the deep ocean? Well, the warming is a slow process (the heat transfers from above and below are small), so the water will rise as it slowly warms, keeping pace with the warming. Continuing cold water input from the high latitudes undercuts the water that has warmed, replacing it as the deepest water. In this scheme you wouldn't "see" the warming because the water would be rising as it slowly warms.
This scheme, with widespread slow upwelling, is very hard to observe (trying to measure a small net vertical velocity when averaging vertical velocities over large areas of the oceans) and anyway it is too simplistic. The driving process of such a scheme was traditionally considered to be widespread downward diffusion of heat from the warmer surface oceans (which are considerably warmer than the deep oceans over much of the globe). By turbulence mostly (i.e. "eddy diffusivity"), since molecular diffusivity is very small (e.g. 10^-7 m^2/s for temperature). Often vertical eddy diffusivity was estimated to be about 10^-4 m^2/s but in the last 15 or so years it has become clear that in the interior oceans it is smaller than this, perhaps 10^-5 m^2/s. This lower value may not diffuse enough heat down to warm (and therefore buoyantly raise) the deep water at the "required" rate (i.e. the rate needed to drive an ocean overturning circulation with a strength that matches what can be estimated for the real oceans).
So how else can we drive the deep heating? One way is geothermal heating from below. This deserves wider attention than it usually gets (though it does get some -- e.g. the articles I noted in my earlier comment), which is partly what prompted me to write the first comment because, though I disagree with what you have concluded/hypothesized, it is nevertheless an interesting component. Heating from below is more efficient than differential heating at the surface in driving overturning circulations.
Other ways to drive deep heating / overturning circulation are: (i) tidal currents interacting with rough sea-bed topography generate more turbulence and in such regions the vertical eddy diffusivity will be greater than the interior ocean estimate of 10^-5 m^2/s. (ii) upwelling might be focussed more in areas such as the Southern Ocean where the vertical temperature difference between upper and deep ocean is smaller and strong winds drive stronger vertical circulation and vertical mixing.
David Coe @ Aug 2, 2013 at 10:11 PM
"Yes there is a natural temperature effect but it does not explain the correlation between CO2 and rate of anthropogenic emissions."
IMO, there is no mystery there. As I suggested previously, the "correlation" is essentially an affine similarity between effectively affine functions. Correlation is essentially trivial, but it does not imply causation.
In any case, I will look forward to your next installment, and give it a respectful hearing. If temperatures fall in the years ahead, as I expect they will, we will have the opportunity to put your hypothesis to the test.
Tim Osborn: I interpret that as a generous attempt to lend a hand with the hypothesis of another. Even if it wasn't I'm grateful for what I myself learned, thank you.
There is the iron/manganese/sulphur/nitrogen shunts. You can oxidize organic carbon to CO2 reducing iron/manganese ions and reducing sulphate and nitrite/nitrate to ammonia. These then rise up to the oxic band and are oxidized by aerobic bacteria.
In the deep ocean, if there are polar currents, there is some oxygen near the bottom.
If you look at the ice-cores you note that when it is cold, there are huge amounts of dust in the atmosphere. Dust levels change between the warm and ice ages by three orders of magnitude. High dust indicates that light flux drops, cooling the planet, but the amount of aquatic life rises due to ocean fertilization, increasing the DOC/DIC ratio. Dust could also increase the rate of mineralization of marine organic sediments. This would account for the drop in atmospheric CO2 when dust levels are high and the world is cold.
If you look at the ice-core data over the last 400K, EPICA-C is the best, you will note that the relationship between CO2 and temperature is different on cooling than it is on warming. Moreover, even though changes in temperature occur before changes in CO2, changes in dust levels (I use -Log(dust)) precede or are contemporaneous with changes in temperature.
The most important thing we can state, looking at the Keeling curve and the rate and end-point of nuclear testing derived atmospheric 14C is that the CO2 is in a dynamic relationship with an infinite sink. If the 14C were only communicating with a reservoir the size of the atmosphere, then the final steady state would be half peak height, if the (aquatic) reservoir was three times the size of the atmospheric CO2 reservoir, then the end point would be 25% of peak. The end point is now about the same as the pre-1945 level of 14C, caused by background cosmic rays hitting nitrogen atoms. The best guess is that 14CO2 is talking to a reservoir >25 times bigger than the total amount of carbon in the atmosphere and that the exchange has a half-residency time of about 13 years.
http://nzic.org.nz/CiNZ/articles/Currie_70_1.pdf
There are measurements from New Zeeland and from Austria/Switzerland that are rather informative.
Wikipedia .... in spite of all criticisms of wikipedia - this seems a useful summary of the state of knowledge (or lack thereof) regarding deep ocean currents:
Wikipedia .... in spite of all criticisms of wikipedia - this seems a useful summary of the state of knowledge (or lack thereof) regarding deep ocean currents:
Entropic Man
"Under stable long-term climate conditions taiga and temperate woodland tend to be CO2 neutral, with net photosynthesis balanced by net respiration."
This statement lies at the heart of the argument. Current climate models are based on the assumption of a zero Net Biome Production where photosynthesis is balanced by respiration (including decomposition). The assumption is both irrational and unnecessary for the following reasons.
1 Photosynthesis and respiration are different and entirely unconnected biological processes. There is absolutely no reason why they should be equal.
2 The very existence of fossil fuels is evidence of long periods, in times past, of positive net biome production, ie photosynthesis exceeding respiration. If it was positive in the past why should it be zero now?
3 In the arctic summer, a period of intense photosynthetic activity results in a decrease in atmospheric CO2 by over 20 ppm. In the winter, when temperatures have fallen below zero, CO2 levels recover at a similar rate, requiring CO2 restorative fluxes of around 60ppm/yr. It is inconceivable that these fluxes emanate from respiration and decay when everything is frozen solid. There has to be a separate and significant non biological flux to produce such a CO2 level restabilisation.
I contend that such a flux is generated by the lowering of CO2 partial pressure by the summer photosynthetic activity causing a flow of CO2 from the sea surface and oceans in order to regain equalisation of pressures. Indeed it would be most remarkable if a CO2 flow was not generated by a partial pressure differential. This concept, which requires absolutely no assumptions on the size or even sign of NBP, leads to a simple set of equations which provide solutions to every observation concerning both atmospheric CO2 and O2 including seasonal CO2 variations, interannual variations, the linear relationship between atmospheric CO2 and the rate of anthropogenic emissions, southern hemisphere seasonal O2 variations, isotopic ratio differences between the sea surface and atmosphere, isotopic ratio variations,and latitude stratification of atmospheric CO2.
I realise, however, that I am pushing against 60 years of orthodoxy and that I have an uphill battle.
Years ago studying atomic physics was a joy because of the elegence of the underlying mathematics underpinning quantum mechanics. By contrast nuclear physics was a bore. There was no maths only hand waving. I am not sure now that much has changed. We have a similar situation in climate science. Very little maths, lots of hand waving. I am trying to inject some simple phyics and maths concepts into the subject. At least then I might be able to understand it.
David Coe
1) The annual zero sum for seasonal CO2 from photosynthesis and respirationis well established empirically. Remember that the land surface is frozen permanently only at high latitudes. The UK, at 50-55N, is rarely frozen at all. Under Winter conditions the Q10 for respiration is 2. A 10C cooling will halve the rate of photosynthesis for most of the biomass. A 20C drop typical of Winter conditions South of the Taiga will still allow 25% of Summer respiration and decay.
You are mistaken that photosynthesis and respiration are independant. The biomass produced by Summer photosynthesis is the biomass respired during the Winter, The overall biomass accumulation is limited by the mineral nutrients available. In a mature ecosystem these are recycled by decay and result in similar growth from year to year.
2) Dense accumulations of fossil fuels such as coal beds took tens of millions of yesars to form, as erosion gradually liberated the nutrients necessary and volcanic activity liberated the carbon. They also formed in a climate which encouraged the swampy anaerobic conditions which preserved them. The only similar conditions today are peat bogs and tundra, both of which are becoming net CO2 releasers under modern climate change. Oil and gas accumulated from the gradual thermal breakdown of small concentrations of organic material in large volumes of rock, which then concentrated in suitable reservoirs.
3) See 1) Respiration in Winter is slower than in Summer, but continues at a greater rate than photosynthesis, 24 hours a day. No extra source of CO2 is needed to balance the numbers.
Please note that these are not assumptions. They are empirically derived, and published in the literature of which you are so dismissive. They are the orthodoxy because they work.
My sympathies if you feel deprived of precise numbers. Unfortunately this is not the clinically mathematical domain of atomic physics; it is the rather messier real world. Attempting to apply the precision of the Schrodinger Wave Equation to ecology, biogeography, oceanography and climate is inappropriate.
You can gather complete information for the behaviour of an atom. A mathematics based on sampling and statistical confidence is much more appropriate for systems about which complete information is impossible.
Entropic Man
I began to research these issues for the simple reason that, contrary to what you maintain, the orthodox views do not explain, with any degree of satisfaction, any of the observations of atmospheric CO2 and O2. It was this utter failure, a failure totally glossed over by climate science, that set me thinking about what is happening. It is simply not good enough to use the excuse that nature is too complicated to apply mathematics. If you cannot describe an event mathematically you simply do not understand it. I am afraid climate science as it exists today is simply not science but an ensemble of airy fairy ideas concocted to provide an on message narrative in support of the concept of global warming.
Tim Osborn
We appear to be on the fag end of this thread now, so I hope you get to read this response, because I have not previously thanked you for your patience in trying to inject some knowledge into me. I really do appreciate the effort, but as the man once said "I am sure that you are right, but I still don't believe you!"
In your most recent comment you provided a most lucid and credible description of a mechanism for deep sea convection, driven by geothermal heating. I have no argument with this at all. However I am not sure that deep sea convection explains the claims of the massive ocean circulations such as the thermohaline circulation. My problem lies with the thermocline.
Correct me if I am wrong, but I view the oceans as a vast body of cold water, cold for whatever reason.That water is heated from above by the sun's radiant energy. That energy penetrates no more than a few hundred metres into the ocean with most of the energy being absorbed within the first few tens of metres. This results in heating of the surface waters. Turbulent mixing promoted by wave and wind action results in this absorbed energy being mixed into a layer of water a few hundred metres deep with a reasonably constant temperature, significantly higher (up to 20 or 30 degC) than the main body of water below. The thermocline is simply the transition zone between the upper mixed layer and the deep ocean. The point is that there can be no convection from the cold deep ocean into the mixed layer. Transfer of cold water through the thermocline requires an external input of energy. We are into 2nd law territory here. I see no source of such energy. For this reason I prefer the hypothesis of chemical cooling.
As you are well aware I know naff all about ocean fluidics. I came to this subject because I realised that my theory for atmospheric CO2 control implied a constant source of CO2 generation within the deep ocean. Realising that such a CO2 source requires energy I calculated the energy required and was intrigued to find that it was almost identical to the geothermal input into the ocean. I simply put 2 + 2 together and came up with 5!
Right now people in the town of Bakewell, where I live, have concluded that I have finally lost it totally, having been seen walking the dogs in a total trance like state, complete with vacant or sometimes pained expression while I ponder these issues. Any further help you might offer to rescue a soul from this purgatory would be most welcome.
David Coe
"If you cannot describe an event mathematically you simply do not understand it."
I agree with you. It is not proper science until you do it with numbers.I was a student in the 1970s when ecology finished its transition from a descriptive qualitative science to a quantitative analytic one and got my nose thoroughly rubbed in the difference.
The problem is that we have different ideas of what constitutes a mathematical description. You are accustomed to having complete information on your atomic systems, to the limit of measuring accuracy. This allows you to completely describe your system mathematically.
When you move out of these simple systems into complex, chaotic, stochastic systems such as climate it gets harder. You have dozens of interacting variables and incomplete information on their state and behaviour. You can describe these systems mathematically, but your description is approximate and needs to include statistical measures of that uncertainty.
http://www.myphysicslab.com/pendulum2.html
To give a simplified example which illustrates the problem, look at the chaotic pendulum linked above. In theory it can be completely described mathematically. However, its state at a future time t cannot be predicted in advance, you have to run the simulation from the beginning to derive the position. If you repeat the simulation from the start under the same conditions you get the same answer.
Now build a real pendulum as close to the simulated dimensions as possible and start it from the same position, as closely as possible. None of your attempts will match the simulation because small differences in the starting conditions will cause the pendulum's real behaviour to differ from the simulation.
Climate resembles that chaotic pendulum much more than it resembles atomic theory.
You can only get a complete description mathematically with complete information, which is impossible in the real world. Godel would have recognised this problem.
You have grossly underestimated the complexity of the system you are attempting to describe, Even if your basic hypothesis is valid, which I doubt, you will need considerably more complex mathematics to describe it.
I agree with Bart. Temperature integral is proportional to the atmospheric CO2 change (accumulation). When the temperature drops, the annual CO2 change will decrease. I predict lower average annual change for the 2010s (~1.5 ppm/year) than it was in the 2000s (~2.0 ppm/year). That should make people think, especially if the anthopogenic emission keeps increasing.
I hypothesise that the seasonal global temperature cycle is driving the annual change, which is annual average temperature dependent. Different exchange coefficients for the warming and cooling phase of the seasonal (annual) cycle should be enough to do the trick - even when the temperature returns to its starting point after one cycle is over, CO2 does not. There's a net change even at constant (annualy averaged) temperatures.
Aug 5, 2013 at 8:34 AM | Edim
(1) Have I understood you correctly? You write
“Temperature integral is proportional to the atmospheric CO2 change”
Interpretation:
Global average temperature fluctuation in time is proportional to time derivative of global average atmospheric CO2 concentration
The time derivative of CO2 is easy in principle, not necessarily in practice, but what is the long term temperature trend and what is its instantaneous fluctuation? Fourier analysis can differentiate between slowly and rapidly changing components of a time series and the conjectured proportionality can be tested for each frequency. Is this OK so far?
(2) To demonstrate that T causes C, a time lag must be allowed for before correlating them at any given frequency. How does the time lag vary with frequency and is it always of the same sign?
(3) Do you have a reference to this work?
(4) If the answer is Yes, thanks in advance!
Mark Well,
If you see this you might find your questions are answered, at least in part, by Murry Salby's Hamburg lecture, if you have not already watched it:
http://www.youtube.com/watch?v=2ROw_cDKwc0
A new WUWT post very much on topic: http://wattsupwiththat.com/2013/08/31/co2-calculation-in-the-glovbal-carbon-cycle-may-be-off-due-to-a-depth-error/