Guest Post by David Middleton
Fingerprints are admissible evidence in criminal trials because of their uniqueness. The probability of two human beings having identical fingerprints is very low.
Measurements of δ13C depletion have often been cited as anthropogenic “fingerprints,” proving human culpability for the rise in atmospheric CO2 over the last 200 years or so…
While δ13C depletion certainly could be evidence of the Suess Effect, it is not a unique solution; therefore, not a “fingerprint.”
Examples of geologically recent δ13C depletion not of anthropogenic origin…
δ13C depletions were associated with warming events ~5,000 years ago in India, ~9,100 years ago in Poland and ~150,000 years ago in the Indian Ocean. It appears to me that δ13C depletion has been a fairly common occurrence during periods of “global warming.” It also appears that δ13C increases have occurred during periods of global cooling…
The red curve in Figure 5 is the Flinders Reef δ13C that was cited as “Human Fingerprint #1” in Skeptical Science’s The Scientific Guide to Global Warming Skepticism. The rate of δ13C depletion is quite similar to that of the lacustrine deposit on the Yucatan. The Flinders Reef data do not extend back before the Little Ice Age; so there is no way to tell if the modern depletion is an anomaly, if the δ13C was anomalously elevated during the 18th and 19th centuries and the depletion is simply a return to the norm or if δ13C is cyclical.
Is it possible that Skeptical Science’s “Human Fingerprint #1” is not due to the Suess Effect? Could it be related to the warm-up from the Little Ice Age?
References
Cook, J. et al., 2010. The Scientific Guide to Global Warming Skepticism. Skeptical Science.
Banakar V., 2005. δ13C Depleted Oceans Before the Termination 2: More Nutrient-Rich Deep-Water Formation or Light-Carbon Transfer? Indian Journal of Marine Sciences. Vol. 34(3). September 2005. pp. 249-258.
Enzel, Y. et al. High-Resolution Holocene Environmental Changes in the Thar Desert, Northwestern India. Science 284, 125 (1999); DOI: 10.1126/science.284.5411.125.
Apolinarska, K. δ18O and δ13C Isotope Investigation of the Late Glacial and Early Holocene Biogenic Carbonates from the Lake Lednica Sediments, Western Poland. Acta Geologica Polonica, Vol. 59 (2009), No. 1, pp. 111–121.
Hodell, D.A., et al., 2005. Climate change on the Yucatan Peninsula during the Little Ice Age. Quaternary Research, Vol. 63, pp. 109-121. doi:10.1016/j.yqres.2004.11.004
Pelejero, C., et al. 2005. Flinders Reef Coral Boron Isotope Data and pH Reconstruction. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2005-069. NOAA/NCDC Paleoclimatology Program, Boulder CO, USA.
FactChecker,
Murry Salby published his new textbook ‘Physics of the Atmosphere and Climate’ in Jan 2012 by Cambridge University Press. I have it and use it for reference often.
I do not know the status of his paper on the carbon cycle and the atmosphere.
John
If the IPCC centric view is correct that variation of CO2 will cause a variation of GMT, then why are those two main proxies of pre-modern (pre-instrumental) period not compatible over +800 yrs of the last +1,000 yrs?
GMT proxies show clearly visible century scale variation over more than the last +1,000 yrs. But CO2 proxies over the same period show a nearly non-variation except for the last ~100 yrs.
If GMT varies due to changes in CO2 as current IPCC climate science paradigm requires (ignoring in this discussion for the time being that proxy records show CO2 increase lagging GMT increase by ~500 to 1,000 yrs) then why doesn’t the CO2 proxy at least vary with the centennial variation of the GMT proxy? It implies both GMT and CO2 proxies cannot be right if the IPCC centric paradigm is right about CO2 variation causing GMT variation.
This question stands out from my reading of “Physics of the Atmosphere and Climate” by Murry L. Salby published Jan 2012 by Cambridge University Press.
John
Some of the discussion here questions whether the observed rise in atmospheric CO2 is anthropogenic. It undoubtedly is, and there are many lines of evidence that establish that this is the case, see Ferdinand Engelbeens’ excellent webpage on the subject http://www.ferdinand-engelbeen.be/klimaat/co2_measurements.html .
I have looked into this subject in some detail in the process of writing a rebuttal of Prof. Robert Essenhigh’s paper on the residence time of CO2, which was published by the journal, see http://pubs.acs.org/doi/abs/10.1021/ef200914u
On the Atmospheric Residence Time of Anthropogenically Sourced Carbon Dioxide
Gavin C. Cawley*
Abstract: A recent paper by Essenhigh (Essenhigh, R. H. Energy Fuels 2009, 23, 2773−2784) (hereafter ES09) concludes that the relatively short residence time of CO2 in the atmosphere (5–15 years) establishes that the long-term (≈100 year) rise in atmospheric concentration is not due to anthropogenic emissions but is instead caused by an environmental response to rising atmospheric temperature, which is attributed in ES09 to “other natural factors”. Clearly, if true, the economic and political significance of that conclusion would be self-evident and indeed most welcome. Unfortunately, however, the conclusion is false; it is straightforward to show, with considerable certainty, that the natural environment has acted as a net carbon sink throughout the industrial era, taking in significantly more carbon than it has emitted, and therefore, the observed rise in atmospheric CO2 cannot be a natural phenomenon. The carbon cycle includes exchange fluxes that constantly redistribute vast quantities of CO2 each year between the atmospheric, oceanic, and terrestrial reservoirs. As a result, the residence time, which depends upon the total volume of these fluxes, is short. However, the rate at which atmospheric concentrations rise or fall depends upon the net difference between fluxes into and out of the atmosphere, rather than their total volume, and therefore, the long-term rise is essentially independent of the residence time. The aim of this paper is to provide an accessible explanation of why the short residence time of CO2 in the atmosphere is completely consistent with the generally accepted anthropogenic origin of the observed post-industrial rise in atmospheric concentration. Furthermore, we demonstrate that the one-box model of the carbon cycle used in ES09 directly gives rise to (i) a short residence time of ≈4 years, (ii) a long adjustment time of ≈74 years, (iii) a constant airborne fraction, of ≈58%, in response to exponential growth in anthropogenic emissions, and (iv) a very low value for the expected proportion of anthropogenic CO2 in the atmosphere. This is achieved without environmental uptake ever falling below environmental emissions and, hence, is consistent with the generally accepted anthropogenic origin of the post-industrial increase in atmospheric carbon dioxide.
This paper summarises the evidence that establishes that the origin of the rise is indeed anthropogenic (Ferdinand’s web page is referenced in my article, it is strongly recommended).
The challenge to any theory of even a partially natural origin of the observed increase is to explain how the annual rise can be less than anthropogenic emissions, without contravening the principle of conservation of mass.
John Whitman says:
March 30, 2012 at 10:06 am
GMT proxies show clearly visible century scale variation over more than the last +1,000 yrs. But CO2 proxies over the same period show a nearly non-variation except for the last ~100 yrs.
Three problems: the influence of temperature on CO2 levels is rather small (~8 ppmv/°C), that is well established over very long time scales (ice ages – interglacials). On shorter time scales the ratio may be smaller (for the seasonal variations up to decennia it is 4-5 ppmv/°C). Secondly, the influence of CO2 on temperature is quite small, even if you believe the central estimate of the IPCC. A change of 8 ppmv has no detectable influence on any kind of temperature proxy… And thirdly ice cores are smoothing out the CO2 variations from 8 years averaging over the past 150 years to 560 years over the past 800,000 years, depending of snow accumulation rate and thus speed of sealing of the gas bubbles.
Despite that, one of the Law Dome ice cores shows a CO2 dip of ~6 ppmv over the MWP-LIA cooling, which again gives a ratio of ~8 ppmv/°C, if you agree with the “bathtube” reconstruction of Moberg and others (~0.8°C temperature drop between the MWP and LIA). The ratio is higher if you believe that Mann’s HS is the only truth (~32 ppmv/°C for a ~0.2°C drop in temperature), but I think that we can agree that Moberg’s work is a little more realistic…
See further:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/law_dome_1000yr.jpg
FerdiEgb says:
March 29, 2012 at 7:27 am
“Ice cores give direct measurements of the C13/C12 ratio of CO2 in trapped air. These were measured by cold crushing the ice, cryogenic freezing, distillation of CO2 and measuring with a mass spectrometer.
The d13C level in the atmosphere over the Holocene can be followed in the Taylor Dome ice core:
http://medias.obs-mip.fr/paleo/taylor/indermuehle99nat.pdf
The average variability is +/- 0.15 per mil over the Holocene, up to 1,000 years ago.”
Ferdinand, this seems to be supported only by the Antarctica ide cores and not by Greenland? Whilst from Antarctica we have only a couple of points for 100 years in Greenland ice core we have 100+, so I wonder if we do not lose a lot of natural variability using the Antarctica data for C13 as well as CO2 concentration due to the long time of about 80 years until the air is !trapped! in the antarctic ice?
climatereflections says:
March 29, 2012 at 4:04 pm
“Is this additional uptake over the last several decades reflected primarily in vegetation? Other sinks? Is it temporary?”
Would say it is not at all temporary and it is natural that it increase: the plants start to feel well:
http://www.co2science.org/data/plant_growth/plantgrowth.php
an impressive calculation was shown here at WUWT:
40 petagrams per year during ice age – plants must have been close to CO2 starvation
80 during LIA and 120 now:
http://wattsupwiththat.com/2011/11/21/carbon-on-the-uptake/
Lars P. says:
March 30, 2012 at 1:38 pm
Ferdinand, this seems to be supported only by the Antarctica ide cores and not by Greenland? Whilst from Antarctica we have only a couple of points for 100 years in Greenland ice core we have 100+, so I wonder if we do not lose a lot of natural variability using the Antarctica data for C13 as well as CO2 concentration due to the long time of about 80 years until the air is !trapped! in the antarctic ice?
The Greenland ice cores have a quite good resolution (even yearly for the ice layers). Unfortunately the CO2 and d13C levels are unreliable. There is some seasalt/carbonate dust deposit (as good as is the case for Antarctica, mainly for coastal cores), which doesn’t interfere with the CO2 levels, except when highly acidic volcanic dust from Iceland is also settled down in the ice, which frequently is the case. That increases the measured free CO2 levels in situ and probably increases the d13C levels too (I haven’t seen any figures of d13C measurements from the Greenland cores), as sea carbonate is 0-5 per mil d13C while air d13C was around -6.4 per mil…
The resolution of the ice cores heavily depends of the accumulation rate, which is very high near the coast (Law Dome, Siple Dome) with a range of 8-40 years, but as drawback that the measured time period is rather short (150-1000 years for Law Dome), as you have less ice layers when bedrock is (nearly) reached. Taylor Dome goes back several 10 kyr, but its resolution is worse (don’t know it exactly). Vostok and Dome C go back 420 kyr and 800 kyr with a resolution of some 600 years.
gavincawley says:
March 30, 2012 at 11:50 am
“It undoubtedly is, and there are many lines of evidence that establish that this is the case…”
The are many lines of evidence which are not inconsistent with the hypothesis, but that does not establish the hypothesis as true. This is sloppy logic.
“…it is straightforward to show… that the natural environment has acted as a net carbon sink throughout the industrial era, taking in significantly more carbon than it has emitted…”
In other words, through process of elimination, you have concluded that the natural environment has emitted less than it has taken in. But, process of elimination only works when you can be sure you have the full set of possibilities. This is an argumentum ad ignorantiam logical fallacy.
“The challenge to any theory of even a partially natural origin of the observed increase is to explain how the annual rise can be less than anthropogenic emissions, without contravening the principle of conservation of mass.”
Now, you’re completely off the rails. You are positing that there are no sinks in the land and the oceans, and there assuredly are.
Consistency is not proof. The eruption of a volcano is consistent with the notion that the Volcano God is angry, and demands a sacrifice. And, in earlier days when people had no knowledge of geologic processes, many cultures assented to that interpretation. It was wrong.
Lars P. says:
March 30, 2012 at 1:48 pm
climatereflections says:
March 29, 2012 at 4:04 pm
“Is this additional uptake over the last several decades reflected primarily in vegetation? Other sinks? Is it temporary?”
It is expected in the models that roughly half, more or less, of whatever goes into the atmosphere will end up in the oceans without considering any other sinks. So, again, there is consistency with the hypothesis that the rising atmospheric concentration is due to anthropogenic inputs. However, this expectation is more or less ex post facto, and we do not fundamentally know what share should end up in the oceans from basic principles.
The natural flows both in and out are huge, on the order of at least 30 times greater than the anthropogenic input flux. It does not take a lot of long term variation in the natural flows to completely swamp out the anthropogenic signal.
Bart says:
The are many lines of evidence which are not inconsistent with the hypothesis, but that does not establish the hypothesis as true. This is sloppy logic.
Besides that all observations (mass and isotopic balance in the atmosphere, isotopic balance, pH and DIC in the oceans, greeing earth) are consistent with the hypothesis, all alternative hypothesis of a natural cause of the increase are INconsistent with one or more observations.
While it is impossible to prove that a hypothesis is true, it is easy to prove that a hypothesis is false, one only need one observation which is inconsistent with the hypothesis.
For the oceans as main source, the increase in oceanic carbon mass and decreasing d13C in air and oceans are sufficient proof that the oceans are not the source. For the biosphere, the oxygen balance is sufficient proof that the biosphere is not the source. What rests are minor sources on short term, even if these may be huge sources of change on geological times.
At what point ends a hypothesis as hypothesis and do you accept that it is accepted knowledge?
Bart says:
March 30, 2012 at 5:42 pm
The natural flows both in and out are huge, on the order of at least 30 times greater than the anthropogenic input flux. It does not take a lot of long term variation in the natural flows to completely swamp out the anthropogenic signal.
As Gavin already said:
However, the rate at which atmospheric concentrations rise or fall depends upon the net difference between fluxes into and out of the atmosphere, rather than their total volume, and therefore, the long-term rise is essentially independent of the residence time.
It doesn’t matter at all that the natural flows in and out are 3 times or 30 times or 300 times the human emissions, it only matters what the difference is between the natural inflows and outflows at the end of the year. Nature as a whole is a net sink for CO2, proven at least for the past 50+ years. Even if one of the natural inflows doubled in some years and halved in other years, that doesn’t matter, as the net balance over the past 50+ years shows that in every year nature as a whole was more sink than source. The observed natural variation around the trend is about +/- 2 GtC for an increase currently around 4 GtC/yr with human emissions around 8 GtC/yr. Thus there is no sign of a swamp out, neither of huge natural variations.
Bart wrote: “The are many lines of evidence which are not inconsistent with the hypothesis, but that does not establish the hypothesis as true.”
There are lines of evidence that are inconsistent with the natural environment being a net carbon source. This means that the natural environment must therefore be a net carbon sink and hence is opposing the arise in atmospheric CO2. We know that the rise is of anthropogenic origin because the observation is consistent with that hypothesis, but inconsistent with the hypothesis of a natural origin.
“In other words, through process of elimination, you have concluded that the natural environment has emitted less than it has taken in. But, process of elimination only works when you can be sure you have the full set of possibilities. “
No, it is not a process of elimination, it is a logical deduction. If we assume conservation of mass (i.e. the annual increase in atmospheric CO2 is the difference between the total flux of carbon into the atmosphere minus the total flux of carbon out of the atmosphere) and that there are only anthropogenic emissions and natural emissions and uptake (i.e. the carbon cycle is essentially a closed system), then the observation that the annual rise being less than annual anthropogenic emissions means that total natural emissions must be less than total natural uptake.
To disprove this deduction, it would be necessary to either disprove the assumptions (which seem rather solid to me) or show that the observations were incorrect (which seems rather unlikely as the difference between annual increase and annual anthropogenic emissions is small compared to the uncertainties in either measurement).
“Now, you’re completely off the rails. You are positing that there are no sinks in the land and the oceans, and there assuredly are.”
No, quite the reverse, the mass balance analysis shows that the sum of all natural sinks (on land and ocean) have been stronger for at least the last 50 years than the sum of all natural sources.
“Consistency is not proof.”
I fully agree, however inconsistency does constitute disproof (contingent on the assumptions made and on the uncertainty of the observations). In this case the observations are consistent with an anthropogenic cause, but inconsistent with a natural cause, therefore we can be quite sure that the rise is of purely anthropogenic origin.
The attribution of increases in atmospheric CO2 since ~1850 to man’s burning of fossil fuel is said by the IPCC centric scientists ( in FAR, SAR, AR3 and AR4) to be unequivocally established by a construction (from earlier proxies and recently measurements) of two concurrent opposing trends in the composition of the atmosphere. Those two concurrent opposing constructed trends in atmospheric composition (which the IPCC scientists say is the fingerprint of mankind’s effect on atmospheric composition) are the decline in the relative concentration of atmospheric carbon 13 (parts per thousand referred against a standard value of C13 concentration) and the increase of volume mixing ratio (ppmv) of atmospheric CO2.
If either of these opposing trends is shown not to be primarily driven by man’s activities then the IPCC’s anthropogenic case is significantly weakened to the state of being refuted.
There are large uncertainties in the produced amounts from natural sources of CO2 which have the same carbon 13 concentration as CO2 from man’s burning of fossil fuels. Until these uncertainties are reduced by further research then the IPCC’s anthropogenic case for changes in the composition of the atmosphere then the IPCC’s case is based on ignorance of those natural sources.
Significant funds need to be timely diverted to the natural sources of atmospheric carbon away from the IPCC centric scientist’s/institution’s bias and myopic focus on fossil fuel burning.
This would allow a more respectable independence in the science, some overdue advance toward balance and certainly some restoration of the declining trust in climate science which has been caused directly and entirely by the IPCC.
John
John Whitman The IPCC mention several lines of evidence that establish that the rise in atmospheric CO2 is of anthropogenic origin. See section 1.2.5 of the FAR on page 14. These include the mass balance argument:
“Since the start of atmospheric monitoring in 1958, the annual atmospheric increase has been smaller each year than the fossil CO2 input. Thus oceans and biota together must have been a global sink rather than a source during all these years”
I suspect that the reason the IPCC reports do not devote a great deal of space to this particular question is simply because the evidence is conclusive and can be checked by anybody that wishes to do so. This really is one of the sort of arguments that Prof. Singer urges sceptics to drop in order to strengthen their position.
It is true that there are large uncertainties in our best estimates of the natural fluxes into and out of the atmosphere. However this is not relevant to the mass balance argument as the mass balance argument is used to infer the difference between total natural emissions and total natural uptake, which is equal to the difference between the annual increase in atmospheric CO2 and annual anthropogenic emissions. Both of these are known with more than sufficient accuracy for there to be considerable certainty in the conclusion.
FerdiEgb says:
March 31, 2012 at 12:42 am
“For the oceans as main source, the increase in oceanic carbon mass and decreasing d13C in air and oceans are sufficient proof that the oceans are not the source.”
No, it isn’t. This is a dynamic system, and you are using static models.
“At what point ends a hypothesis as hypothesis and do you accept that it is accepted knowledge?”
When it stops assuming the answer before it is proven, and starts relying on confirmational data.
“It doesn’t matter at all that the natural flows in and out are 3 times or 30 times or 300 times the human emissions, it only matters what the difference is between the natural inflows and outflows at the end of the year.”
Wrong. Wrong, wrong, wrong, wrong, wrong. We’ve been over this too many times for me to have any hope that you will get it, but it is stunningly bad logic.
gavincawley says:
March 31, 2012 at 4:09 am
“We know that the rise is of anthropogenic origin because the observation is consistent with that hypothesis, but inconsistent with the hypothesis of a natural origin.”
With your concept of what “natural sources” can do tied in a straightjacket of a priori baseless assumptions.
“…then the observation that the annual rise being less than annual anthropogenic emissions means that total natural emissions must be less than total natural uptake.”
NO!!!! It does not mean that at all. You are assuming the sinks do not expand due to an increase in atmospheric partial pressure. They do. You are wrong.
You guys… you do not even realize you are heading down the same path that led church leaders of old to proclaim that the Sun revolved around the Earth, or the ancient shamans to believe that the Volcano God had to be appeased. In each case, those guys thought they were basing their beliefs on the best available evidence, too. Your arguments are mind-numbingly flaccid, and you do not even realize it. This is not to say that you may not be right, but if so, only in the sense that a stopped clock may be right twice a day. Your arguments are not conclusive in any way, shape, or form.
I’m done with this thread. We’ve said all there is to say. Further lack of response on my part should not be taken as evidence of acquiescence. We will know the truth as the data record of reliable measurements increases. In the meantime, it is rather a moot point, since temperatures are not increasing in line with the AGW hypothesis anyway.
Let’s take the combined natural sources of atmospheric CO2 to be on the order of 150 CtC/yr and the anthropogenic source to be on the order of 6 CtC/yr. What is the uncertainty in the amount of the natural 150 CtC/yr CO2 production that has the same net carbon 13 conc as CO2 from burning fossil fuels? Is it’s production uncertainty higher than the total of mankind’s production? It appears to be the case. So the IPCC’s argument about anthropogenic caused changes in atmospheric composition is based fundamentally on a very incomplete quantitative knowledge of the natural carbon cycle.
We need much more of the independent vehicle of skeptical science to counter the grossly overfunded myopic CAGWism of the IPCC. In other words, we need to restore the more open scientific process that preceded the manipulation by the UN to create the completely political body that is the IPCC.
John
Bottom line: This is a dynamic system, and you guys are doing static analysis. And, you are assuming greater precision in the quantification of natural fluxes than actually exist, and when anthropogenic influx is less than 3% of natural fluxes, you do not need a lot of error to destroy the conclusion.
This is all elementary to someone who analyzes dynamical systems every day. You guys apparently lack the tools to address this problem rigorously.
Bart writes “With your concept of what “natural sources” can do tied in a straightjacket of a priori baseless assumptions.”
No, the mass balance argument makes no assumptions about the nature of the sources or sinks. It is away of inferring something we can’t directly measure (the difference between total natural emissions and total natural uptake) from two quantities that we can directly measure, namely anthropogenic emissions and the annual rise in atmospheric CO2. I would be happy to go through the argument with you step by step if you like and you can point out the step where the error in the argument appears.
“NO!!!! It does not mean that at all. You are assuming the sinks do not expand due to an increase in atmospheric partial pressure. They do. You are wrong.
No, this is not correct, the mass balance argument makes no such assumption. Furthermore in my paper I use a one-box model of the carbon cycle very similar to that used by Essenhigh, where the flux out of the atmosphere is proportional to the atmospheric CO2 concentration (starting on page 5508). Thus my analysis explicitly includes the expansion of the sinks.
John Whitman As I pointed out, the conclusion that the rise in atmospheric CO2 is based on a number of lines of evidence. The mass balance argument is the most elementary of these, and only relies on observations with uncertainties not nearly low enough to cast any doubt on the conclusion. While you may not be convinced of isotopic evidence due to observational uncertainties, you cannot dismiss the conclusion without addressing other arguments that demonstrate that the observed rise is not a natural phenomenon.
I would recommend that you read the very clear explanation of the mass balance argument on Ferdinand Engelbeen’s web page .
Bart wrote “Bottom line: This is a dynamic system, and you guys are doing static analysis.”
This incorrect, in my paper I discuss a simple one-box model of the carbon cycle, which is a dynamical system described by a differential equation. It is not a static analysis.
“And, you are assuming greater precision in the quantification of natural fluxes than actually exist”
The mass balance argument does not require any knowledge of the magnitudes of the natural fluxes, hence the uncertainty of our best estimates of them is irrelevant. The mass balance argument relies only on knowledge of anthropogenic emissions and of atmospheric concentrations, both of which are known with more than adequate certainty for the purposes of the mass balance analysis.
“and when anthropogenic influx is less than 3% of natural fluxes, you do not need a lot of error to destroy the conclusion.”
This is incorrect, as has been pointed out earlier in the thread, the rate of increase in atmospheric CO2 depends on the difference between total uptake and total emissions, not the magnitude of the fluxes themselves, and anthropogenic emissions are large compared to the difference between total natural emissions and total natural uptake.
However, the mass balance argument does not depend on our knowledge of the magnitude of the natural fluxes, so this objection is irrelevant.
Bart says:
March 31, 2012 at 9:56 am
Bottom line: This is a dynamic system, and you guys are doing static analysis. And, you are assuming greater precision in the quantification of natural fluxes than actually exist, and when anthropogenic influx is less than 3% of natural fluxes, you do not need a lot of error to destroy the conclusion.
Bart, again (for others, as you have an idee-fixe about the dynamics of the system), we don’t need to quantify any dynamics of any of the natural fluxes involved, as that doesn’t tell us anything about what the cause of the increase in the atmosphere is. Only the difference between all natural inflows and all natural outflows together is important. And that is quite exactly known and was negative (more sink than source) at least over the past 50+ years.
The dynamics of the difference is important, and based on observations, the variability of the difference is only halve what humans add as emissions, around the trend which is about halve the emissions. Even taken into account the error margins of the emissions estimates and the measurement error of the CO2 levels, the natural variability in difference is only 1.5% of the total in or outflows. Thus there is no reason to assume that some natural variability may be larger than the human emissions, that is proven wrong for the past 50+ years.
John Whitman says:
March 31, 2012 at 9:54 am
What is the uncertainty in the amount of the natural 150 CtC/yr CO2 production that has the same net carbon 13 conc as CO2 from burning fossil fuels?
There are only rough estimates of the CO2 production from natural sources with a low 13C/12C ratio. That are mainly vegetation decay/burning and natural “fossil” carbon from methane and oil leaks and coal or peat burning.
That may be important if there were huge natural disasters in the recent past, but that is not the case, taking into account that the measured increase in CO2 and decrease in d13C is the equivalent of burning down 1/3rd of all land vegetation (!).
Even if there was some extra natural supply from low 13C sources, the total d13C decrease caused by all human use of fossil fuels is high enough to have caused a threefold drop in d13C as what is observed, Thus any extra source must have a higher d13C level than the atmosphere, not a lower one. And not a source, but a replacement, as an extra source in mass would give an increase in the atmosphere higher than the human emissions, not lower. As both the ocean surface and the biosphere have a limited storage capacity and most of what is absorbed in one season returns in the next, mainly the deep oceans are responsible for most of the high d13C exchange.
One can calculate how much carbon with the deep oceans need to be exchanged to get the right d13C drop in the atmosphere:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/deep_ocean_air_zero.jpg
The deviation until 1960 might be caused by the biosphere (as a net source), which is not taken into account in this calculation.
FerdiEgb,
Hey, I noticed you shortened your handle here at WUWT!
NOTE: Let’s use of the multi-proxy reconstruction of GMT during the last two millennia from Moberg et al (2005) and judiciously ignore Mann’s much more problematical AGW-marketing oriented reconstruction.
The observed (proxy plus measurement) increase in atmospheric CO2 in the twentieth century was about 80 ppmv. The part of the atmospheric CO2 increase which could be considered as resulting from the temperature rebound from the LIA over the same period roughly 55 ppmv. So, if those figures are reasonable then we have, in the twentieth century, about 50% of the atmospheric CO2 increase being naturally the result of that part of the LIA temperature rebound that occurred in the twentieth century.
So I find little to support the idea that increases in CO2 release to the atmosphere from a naturally occurring increased temperature of land and sea are insignificant when compared to anthropogenic releases of CO2 during the twentieth century.
I am using as a reference and an educational guide the textbook ‘Physics of the Atmosphere and Climate’ by Murry L. Salby (published Jan 2012 by Cambridge University Press). I have found it to most informative.
John
John Whitman If you use the Law dome CO2 data to extend the mass balance analysis back prior to to the start of the Mauna Loa record, it still shows that the annual rise in atmospheric CO2 was less than total anthropogenic emissions (land use change + fossil fuel) going back at least as far as 1840 (see figures 4 and 5 of my paper). This indicates that the natural environment has been a net carbon sink going back at least as far as that, and hence has been opposing the observed rise rather than causing it. This contradicts the hypothesis that the rise is partly due to a rebound from the LIA.
The airborne fraction (the ratio of the rise in CO2 and cumulative anthropogenic emissions) has stayed pretty much constant at about 0.45 going right back to the 1840s. It would be quite a coincidence if a rebound from the LIA caused an increase in atmospheric CO2 that was in so close a relationship to anthropogenic emissions!
I would be interested to see Prof. Salby’s paper, so if anyone can tell me the identity of the journal or news about likely publication date I would be grateful. I did send him a pre-print of my paper, but I recieved no response.