I find this paper (PDF) interesting, but it still does not address the temperature/CO2 800 year time lag seen in ice core records. h/t to Leif Svalgaard – Anthony
Fossil soils constrain ancient climate sensitivity
Dana L. Royer 1
Department of Earth and Environmental Sciences, Wesleyan University, Middletown, CT 06459
Global temperatures have covaried with atmospheric carbon dioxide (CO2) over the last 450 million years of Earth’s history (1). Critically, ancient greenhouse periods provide some of the most pertinent information for anticipating how the Earth will respond to the current anthropogenic loading of greenhouse gases. Paleo-CO2 can be inferred either by proxy or by the modeling of the long-term carbon cycle.
For much of the geologic past, estimates of CO2 are consistent across methods (1). One exception is the paleosol carbonate proxy, whose CO2 estimates are often more than twice as high as coeval estimates from other methods (1). This discrepancy has led some to question the validity of the other methods and has hindered attempts to understand the linkages between paleo-CO2 and other parts of the Earth system. In this issue of PNAS, Breecker and colleagues (2) break important new ground for resolving this conflict.
The paleosol carbonate proxy for atmospheric CO2 is based on the analysis of carbonate nodules that precipitate in soils in seasonally dry to dry climates. These nodules incorporate carbon from two sources: atmospheric CO2 that diffuses directly into the soil and in situ CO2 from biological respiration. Because the stable carbon isotopic composition of these two sources is distinct, the concentration of atmospheric CO2 can be inferred if the concentration of soil CO2 and the isotopic compositions of the two sources are known (3). Atmospheric CO2 estimates scale directly with soil CO2 concentration: If the soil term is wrong by a factor of two, the inferred atmospheric CO2 will be off by a factor of two.
Estimates of soil CO2 concentration for fossil soils have been based on measurements taken during the growing season in equivalent living soils. However, Breecker et al. (2, 4) demonstrate convincingly that the window of active carbonate formation is restricted to the warmer and dryer parts of the growing season. Carbonate formation is simply not thermodynamically favorable during cooler and wetter seasons. Critically, biological productivity and respiration are low during these dry periods. As a result, soil CO2 concentration during the critical window of active carbonate formation has been overestimated in most soils by a factor of two or more (2).
What does this mean? CO2 estimates from the paleosol carbonate proxy can be cut in half (or more). Doing so snaps the paleosol-based estimates in line with most other approaches (2) (Fig. 1B) and produces the most precise view to date of Earth’s CO2 history. We are now better equipped to answer some important, basic questions. For example, what is the quantitative relationship between CO2 and temperature? That is, for every doubling of CO2, what is the long-term (103–104 years) equilibrium response of global temperature (termed here climate sensitivity)?
Most assessments of climate sensitivity for the present day hover around 3°C per CO2 doubling (5), although if the longterm waxing and waning of continental ice sheets are considered it is probably closer to 6°C (6). Less is known about climate sensitivity during ancient greenhouse periods, simply because having poles draped in forest instead of ice represents a profound rearrangement of climate feedbacks.
Records of CO2 and temperature are now sufficiently robust for placing firm minimum constraints on climate sensitivity during parts of the Cretaceous and early Paleogene (125–40 Mya), a well-known globally warm interval. Indeed, owing to the logarithmic relationship between CO2 and temperature, the geologic record is ideally suited for establishing minimum thresholds. This is because, to accommodate a declining sensitivity, other boundary conditions of the Earth system need to shift exponentially, for example, unreasonable oscillations in atmospheric CO2. Policywise, establishing a basement value for climate sensitivity is a critical step for addressing our current climate crisis (5).
With few exceptions, CO2 during the Cretaceous and early Paleogene was<1,000 ppm (2) (Fig. 1B). Global mean surface temperature is very difficult to establish for these ancient periods. However, temperature change in the tropics today scales at roughly two-thirds the global change (5, 6).
If we assume a similar relationship in the past and a climate sensitivity of 3°C perCO2 doubling, a rise in atmospheric CO2 to 1,000 ppm results in a 3.6°C warming in the tropics (relative to a 280-ppm baseline).
Given that tropical sea surface temperatures range from 27° to 29°C today, tropical temperatures exceeding 30.6°–32.6°C (red band in Fig. 1A) during the Cretaceous and early Paleogene likely correspond to a climate sensitivity >3°C. This threshold was commonly surpassed during the Cretaceous and early Paleogene (Fig. 1A). For times when CO2 was <1,000 ppm, the tropical temperature threshold for a 3°C climate sensitivity would shift to correspondingly cooler values.
Further, there is abundant evidence for flatter latitudinal temperature gradients during greenhouse periods (7, 8), meaning, again, that the tropical temperature threshold used here is probably a maximum. Together, it is clear that during the Cretaceous and Paleogene climate sensitivity commonly exceeded 3°C per CO2 doubling.
Although further work is needed, the geologic evidence (2) (Fig. 1) is most consistent with long-term, future climate change being more severe than presently anticipated (5). Also, global climate models tuned to ancient greenhouse periods commonly have emergent climate sensitivities of <3°C and they fail to simulate the shallow latitudinal temperature gradients (9). Thus even for times with little ice, there are important positive feedbacks that are presently not captured adequately in climate models. Processes for warming the high latitudes without a change in CO2 include more vigorous heat transport (10, 11), more widespread stratospheric clouds in the high latitudes (12), and climate feedbacks from polar forests (13). and their study highlights the value of a clearly resolved paleo-CO2 record. However, a limitation is that they uniformly apply a “best guess” value of 2,500 ppm for soil CO2 concentration.
They recognize this as an oversimplification and is an area for future work. Better modeling of the term, perhaps through independent proxy (14), may result in a further tightening of the paleo-CO2 record.
1. Royer DL (2006) CO2-forced climate thresholds during the Phanerozoic. Geochim Cosmochim Acta 70:5665– 5675.
2. Breecker DO, Sharp ZD, McFadden LD (2010) Atmospheric CO2 concentrations during ancient greenhouse climates were similar to those predicted for 2100 A.D. Proc Natl Acad Sci USA 107:576–580.
3. Cerling TE (1991) Carbon dioxide in the atmosphere: Evidence from Cenozoic and Mesozoic paleosols. Am J Sci 291:377–400.
4. Breecker DO, Sharp ZD, McFadden LD (2009) Seasonal bias in the formation and stable isotopic composition of pedogenic carbonate in modern soils from central New Mexico, USA. Geol Soc Am Bull 121:630–640.
5. IPCC (2007) Climate Change 2007: The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge Univ Press, Cambridge, UK).
6. Hansen J, et al. (2008) Target atmospheric CO2: Where should humanity aim? Open Atmospheric Sci J 2: 217–231.
7. Bice KL, Huber BT, Norris RD (2003) Extreme polar warmth during the Cretaceous greenhouse? Paradox of the late Turonian δ18O record at Deep Sea Drilling Project Site 511. Paleoceanography 18:1031.
8. Bijl PK, et al. (2009) Early Palaeogene temperature evolution of the southwest Pacific Ocean. Nature 461: 776–779.
9. Shellito CJ, Sloan LC, Huber M (2003) Climate model sensitivity to atmospheric CO2 levels in the Early-Middle Paleogene. Palaeogeogr Palaeoclimatol Palaeoecol 193: 113–123.
10. Korty RL, Emanuel KA, Scott JR (2008) Tropical cycloneinduced upper-ocean mixing and climate: Application to equable climates. J Clim 21:638–654.
11. Ufnar DF, González LA, Ludvigson GA, Brenner RL, Witzke BJ (2004) Evidence for increased latent heat transport during the Cretaceous (Albian) greenhouse warming. Geology 32:1049–1052.
12. Abbot DS, Tziperman E (2008) Sea ice, high-latitude convection, and equable climates. Geophys Res Lett 35:L03702.
13. Beerling DJ, Nicholas Hewitt C, Pyle JA, Raven JA (2007) Critical issues in trace gas biogeochemistry and global change. Philos Trans R Soc Lond A 365:1629–1642.
14. Retallack GJ (2009) Refining a pedogenic-carbonate CO2 paleobarometer to quantify a middle Miocene greenhouse spike. Palaeogeogr Palaeoclimatol Palaeoecol 281:57–65.
15. Bice KL, et al. (2006) A multiple proxy and model study of Cretaceous upper ocean temperatures and atmospheric CO2 concentration. Paleoceanography 21: PA2002.
16. Bornemann A, et al. (2008) Isotopic evidence for glaciation during the Cretaceous supergreenhouse. Science 319:189–192.
17. Forster A, Schouten S, Baas M, Sinninghe Damsté JS (2007) Mid-Cretaceous (Albian Santonian) sea surface temperature record of the tropical Atlantic Ocean. Geology 35:919–922.
18. Forster A, Schouten S, Moriya K, Wilson PA, Sinninghe Damsté JS (2007) Tropical warming and intermittent cooling during the Cenomanian/Turonian oceanic anoxic event 2: Sea surface temperature records from the equatorial Atlantic. Paleoceanography 22:PA1219.
19. Moriya K, Wilson PA, Friedrich O, Erbacher J, Kawahata H (2007) Testing for ice sheets during the mid-Cretaceous greenhouse using glassy foraminiferal calcite from the mid-Cenomanian tropics on Demerara Rise. Geology 35:615–618.
20. Norris RD, Bice KL, Magno EA, Wilson PA (2002) Jiggling the tropical thermostat in the Cretaceous hothouse. Geology 30:299–302.
21. Pearson PN, et al. (2001) Warm tropical sea surface temperatures in the Late Cretaceous and Eocene epochs. Nature 413:481–487.
22. Pearson PN, et al. (2007) Stable warm tropical climate through the Eocene Epoch. Geology 35:211–214.
23. Schouten S, et al. (2003) Extremely high sea-surface temperatures at low latitudes during the middle Cretaceous as revealed by archaeal membrane lipids. Geology 31:1069–1072.
24. Tripati A, et al. (2003) Tropical sea-surface temperature reconstruction for the early Paleogene using Mg/Ca ratios of planktonic foraminifera. Paleoceanography 18:1101.
25. Wagner T, et al. (2008) Rapid warming and salinity changes of Cretaceous surface waters in the subtropical North Atlantic. Geology 36:203–206.
26. Wilson PA, Norris RD (2001) Warm tropical ocean surface and global anoxia during the mid-Cretaceous period. Nature 412:425–429.
27. Wilson PA, Norris RD, Cooper MJ (2002) Testing the Cretaceous greenhouse hypothesis using glassy foraminiferal calcite from the core of the Turonian tropics on Demerara Rise. Geology 30:607–610.
28. Wilson PA, Opdyke BN (1996) Equatorial sea-surface temperatures for the Maastrichtian revealed through remarkable preservation of metastable carbonate. Geology 24:555–558.
29. Sexton PF, Wilson PA, Pearson PN (2006) Microstructural and geochemical perspectives on planktic foraminiferal preservation: “glassy” versus “frosty”. Geochem Geophys Geosyst 7:Q12P19.
30. Pagani M, Lemarchand D, Spivack A, Gaillardet J (2005) A critical evaluation of the boron isotope-pH proxy: The accuracy of ancient ocean pH estimates. Geochim Cosmochim Acta 69:953–961.
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“Thanks Robert I think we know what positive feedbacks are.”
The evidence would suggest many of you don’t. You yourself don’t seem to understand the difference between a positive feedback and an explosive change. And some of you are having trouble understanding gravity.
And on the topic of CO2 rise lagging temperature rise by 800 years. When the temperature starts to fall we have 800 years of rising CO2 and falling temperature. What makes that CO2 different from anthropic CO2? CO2 going up for 800 years while temperature falls.
Re Dave in Delaware’s CO2 release from warming water calculation:
It looks like you have made an assumption that the ocean is currently saturated with CO2, so that warming promptly results in CO@ur momisugly being “pushed” out of solution and into the atmosphere. Is the ocean “saturated” at current CO2 levels? And if not, won’t the CO2 stay in solution at near current levels until warming-induced decreased solubility results in saturation?
KW
@ur momisugly Richard (00:47:43)
@ur momisugly Robert (10:05:16)
Don’t mean to step into a minefield here but, just sayin, there might be a language issue at play, and it might be best to have a quick read here to clear things up: http://www.drroyspencer.com/2009/04/when-is-positive-feedback-really-negative-feedback/
In particular:
“climate researchers have ‘redefined’ positive feedback. We borrowed the concept from electric circuit theory, which was elucidated back in the 1940s. And, yes, all of you engineers are right…in your terms, the climate system IS dominated by negative feedback. The Earth DOES lose extra energy to outer space when it warms, which then stabilizes the climate system against perturbations.
But in the climate research world, the dividing line between ‘positive’ and ‘negative’ feedback is not whether extra energy is gained or lost with warming, but whether the increase is greater (or not) than the ‘temperature-only’ increase in infrared energy loss with warming.”
Maybe it’s not quite accurate, but I have always thought of feedbacks in the climate world as amplification (positive) or compression (negative) if that helps at all(?)
…and of course, if I’m off please set me straight 🙂
Robert (10:05:16) :
“And some of you are having trouble understanding gravity.”
Indeed we have. Nobody understands gravity – except you apparently.
Well with all this paleoproxy temperature and CO2 “data”, and Dana Royer’s assertion of a “climate Sensitivity” number of 3 deg C per doubling (that seems to be the IPCC guess); I wish the author would actually publish a plot of Temp vs Log(CO2), to demonstrate where that 3 deg C per 3X comes from; rather than simply asserting such a number and thereby implicitly endorsing the notion that T is proportional to Log (CO2), something I have yet to see demonstrated with peer reviewed data; like a graph.
My understanding is that IPCC says that 3 deg C could actually be 1 or 10 deg C. If so, the demonstration of any logarithmic; or other, mathematical function connecting those two variables would be most surprising.
Why not construct a model to fit the data, rather than try to shoe horn the data to fit a model.
If Earth’s atmosphere was inclined toward positive climate feedbacks, run away greenhouse warming would have long ago turned Earth into an uninhabitable inferno. The Earth could not have experienced ice ages in the Ordovician and mid-Mesozoic if elevated CO2 levels led to run away warming fed by positive feedback mechanisms. ..
Phanerozoic CO2 v Temp
The geological and meteorlogiocal records show that Earth’s atmosphere is dominated by negative (or neutralizing) feedback mechanisms.
The so-called greenhouse effect of water vapor, CO2, CH4 and other trace gases enable the atmosphere to retain more heat that would otherwise be possible. This keeps the Earth’s lower atmosphere about 30 to 40°C warmer than it would be without a greenhouse effect.
However, if the Earth’s atmosphere had no negative (or neutralizing) feedbacks, the greenhouse effect would make the surface temperature 100 to 140°C warmer than it currently is.
Atmospheric circulation (AKA weather) is one giant negative feedback system.
Easier said than done…
I used an equation that Bill Illis posted some time ago to do just that…
T = 2.73ln(CO2)-15.85
I then calculated a low frequency temperature trend from ice core CO2 data back to the mid-1800’s and plotted that along with HadCRUT3…
Model CO3 vs HadCRUT3
It’s not a bad fit.
If all of the warming since the mid-1800’s is the result of anthropogenic CO2, the maximum warming that could result from a doubling of pre-industrial CO2 is ~2°C.
Now… Since we know that half of the warming since the mid-1800’s is due to natural climate oscillations, solar activity and other non-anthropogenic forces… And that the other half of the warming since the mid-1800’s is due to instrumental problems, operator bias, UHI, fraud and other non-CO2 related anthropogenic activities… We’re left with no enhanced greenhouse warming.
Therefore we can conclude that the Earth’s climate is relatively insensitive to CO2 fluctuations between 275 and 4,000 ppmv.
The Spam filter may have just grabbed my last post.
[Yes. It’s posted now. ~dbs]
Just for reference, I do not believe we need fear a thermal runaway due to CO2 released from the oceans because this would require double the amount of CO2 to be released for each basic CO2 doubling-temperature step increase (nominally, I believe, one degree Celsius) before you could have a thermal run-away effect caused by CO2 released from the ocean.
“If Earth’s atmosphere was inclined toward positive climate feedbacks, run away greenhouse warming would have long ago turned Earth into an uninhabitable inferno. The Earth could not have experienced ice ages in the Ordovician and mid-Mesozoic if elevated CO2 levels led to run away warming fed by positive feedback mechanisms. ..”
Again, the problem is that you are equating the presence of positive feedback mechanisms with inevitable “runaway warming.” Those are two entirely different things. There are numerous feedbacks — some positive, some negative, some short-term, some long-term. The interplay between them is what determines the length and depth of the warming (or cooling) (plus other influences like man-made forcing, or an asteroid impact, slight changes in the earth’s orbit, etc.)
The lack of a “Venus syndrome” on Earth in no demonstrates a lack of net positive feedbacks to warming on human timescales (hundreds to thousands of years). It implies (and we have evidence of this) that over the very long term negative feedbacks move into the ascendant and return the climate system to a cooler equilibrium.
The graph doesn’t have anything labeled “paleosol carbonate proxy”. I can go look up the details, but the text should discuss what is in the graph. Or is that graph an unrelated illustration?
@Robert (11:55:51) :
Actually the lack of any evidence of past positive feedback mechanisms is what casts doubt on the model-based predictions of future positive feedback mechanisms.
The perfect example is Jimbo Hansen’s 1988 climate model. Hansen’s worst case scenario nailed the actual atmospheric CO2 trend over the next 20+ years…
Hansen CO2 Model
While the actual warming that occurred over the same period undershot Hansen’s best case scenario…
Hansen Temp Model
Hansen CO2 scenarios…
CH4 and other trace gases inexplicably stopped rising some time ago and actually followed paths closer to scenario’s B & C… But CO2 is the “Big Kahuna”. Even if CH4 has 20X the greenhouse effect of CO2. 1800 ppb is 0.46% of 390 ppm…20 X 0.46% = 9.2%. At most, CH4 accounts for only about 10% of the greenhouse effect of CO2 in Earth’s current atmosphere.
So, according to Hansen’s 1988 predictions, the global temperature anomaly should be about 90% of the way from Scenario “C” to Scenario “A”… ~0.97°C. In reality, the annual global temperature anomaly is about half of what Hansen predicted for a similar rise in CO2.
In most branches of science, when experimental results falsify the original hypothesis, scientists discard or modify the original hypothesis. In the wacky world of Warmistas the initial conditions of the experiment are simply redefined with flux adjustments.
Re:Robert (11:55:51)
So, you’re postulating +ve feedback of CO2 effects on temp in the geological short term – a few hundred or thousand years – which is then overmastered by powerful but incredibly slowly reacting -ve feedback, which forces temps down even while CO2 levels continue to climb for 800 – 1000 years or so, before CO2 concentrations follow the temp down…?
Ingenious, but do you really believe this? What turns off the strong negative feedback ie “chooses” the target temperature? Any idea what the feedback mechanisms might be? The sceptic position is simpler: CO2 has only a small effect, and the climate variations come from other sources… I dont buy your view at present, and still see the ice core cooling phase data as a “killer” for AGW via CO2.
Seems to me that a fossil soil expert has found a way to link his filed of research to AGW in order to get funding. Nothing to see here folks…
“”” David Middleton (11:46:00) :
George E. Smith (11:21:53) :
Well with all this paleoproxy temperature and CO2 “data”, and Dana Royer’s assertion of a “climate Sensitivity” number of 3 deg C per doubling (that seems to be the IPCC guess); I wish the author would actually publish a plot of Temp vs Log(CO2), to demonstrate where that 3 deg C per 3X comes from; rather than simply asserting such a number and thereby implicitly endorsing the notion that T is proportional to Log (CO2), something I have yet to see demonstrated with peer reviewed data; like a graph.
My understanding is that IPCC says that 3 deg C could actually be 1 or 10 deg C. If so, the demonstration of any logarithmic; or other, mathematical function connecting those two variables would be most surprising.
Why not construct a model to fit the data, rather than try to shoe horn the data to fit a model.
Easier said than done…
I used an equation that Bill Illis posted some time ago to do just that…
T = 2.73ln(CO2)-15.85
I then calculated a low frequency temperature trend from ice core CO2 data back to the mid-1800’s and plotted that along with HadCRUT3…
Model CO3 vs HadCRUT3
It’s not a bad fit. “””
So just how many octaves of CO2 did you cover in your plot. If mid 1800s CO2 was 280 ppm and now we haver 388.09 ppm.
That’s a ratio of 1.3857 : 1, or not even 1/2 of an octave.
So now use the same data, and assume instead a straqight line linear elationship between CO2 and temperature for that same period.
Is that fit any worse than your log function ? I somehow doubt it.
But try that same log function you gave over the roughly five octaves of CO2 going back 600 million years; and tell us if you still get a pretty good fit.
But just why are you trying to fit the data to a log function; what physical process is suggestive of it being a log function.
We know for example, that the Watts per square metre “forcing” due to surface emitted LWIR being absorbed by CO2, varies by more than a factor of ten over the earth surface, simply due to the change in surface temperature from the coldest to the hottest surface locations.
And I doubt that anyone has sampled the “climate sensitivity” value over a sufficient sample of the earth surface to even compute what a global average might be; and whay would such a value average out to produce a global logarithmic function.
Just because the sensitivity to cO2 change diminishes as you add more CO2, is no justification for saying the function must be logarithmic.
I think Anthony actually put up a Log function plot soem time ago using recent history data, and the portion of the log curve that was applicable was as linear as any drawn straight line.
Ln(1+x) =x-(x^2)/2+ …. near enough to linear given the short data range.
sorry .. this got to be a rather long answer, hope it helps
re Kwinterkorn (10:30:37) : Re Dave in Delaware’s CO2 release from warming water calculation:
It looks like you have made an assumption that the ocean is currently saturated with CO2, so that warming promptly results in CO@ur momisugly being “pushed” out of solution and into the atmosphere. Is the ocean “saturated” at current CO2 levels? And if not, won’t the CO2 stay in solution at near current levels until warming-induced decreased solubility results in saturation?
Good question -Why do I think that the oceans are at or near saturation in CO2?
Well, CO2 is highly soluble in water, and given the right conditions, the physical process to drive toward saturation should be relatively fast. There are those that claim the oceans are absorbing CO2 and others that claim the oceans are degassing CO2. I believe both are probably correct, depending on temperature and other conditions at a given location. If you read down through the chemistry information, there is much more CO2 tied up in the oceans than in the atmosphere, and I my belief is the right conditions release some CO2 to the atmosphere.
Some Air Ocean data that suggests this may be happening on a macro ocean scale. Dr Roy Spencer did a review of Sea Surface Temperature (SST) changes in comparison to Mauna Loa CO2 readings. Atmospheric CO2 Increases:Could the Ocean, Rather Than Mankind, Be the Reason? by Roy W. Spencer 1/25/2008
http://wattsupwiththat.com/2008/01/25/double-whammy-friday-roy-spencer-on-how-oceans-are-driving-co2/
He says – “The large interannual fluctuations in Mauna Loa-derived CO2 “emissions” roughly coincide with El Nino and La Nina events, which are also periods of globally-averaged warmth and coolness, respectively.”
Chemistry (and what it tells us about saturation and equilibrium)
Once CO2 dissolves into water, some stays as CO2, but most forms other ionic species, which is handy because we can then get some idea of ‘close to saturation’ from pH readings. Those pH readings suggest that even in the relatively short life times of rain drops, they absorb enough CO2 from the air to be at or near saturation. (supports the idea of relatively fast)
In sea water, there is the further complexity where the CO2 ions interact with the dissolved minerals. In fact, most of the ocean CO2 is tied up in those other ‘buffered’ entities. So if a bit of the ‘free’ CO2 is stripped out to the atmosphere, the equilibrium shifts to replace it from the plentiful ‘buffered’ species.
Here is more on CO2 in sea water, with author and link for further reading on this.
The quotes below are excerpts from http://www.seafriends.org.nz/issues/global/acid.htm
Dr J Floor Anthoni (2007)
“As CO2 dissolves in water, the water becomes mildly acidic (clean rain water has a pH=5.6) …
“This behaviour of CO2 also applies to sea water, but here the situation is much more complicated due to the buffering effect of limestone.
“CO2 ‘binds’ with water like: CO2 + H2O H2CO3 H+ + HCO3- H+ + H+ + CO32-
“In this equilibrium equation the double arrow means ‘in balance’ (equilibrium) or that the chemical reaction can move both ways.
“Of the four ‘states’ that CO2 can assume, carbondioxide CO2 is a mere 1%, bicarbonate HCO3 is 93% and carbonate CO3 8% . But the total amount of carbon dissolved in the oceans is just short of 40,000Gt (Pg) compared with less than 700Gt in the atmosphere. The sea is a massive carbon dioxide reservoir, in balance with an even more massive limestone reservoir of 40,000,000Gt carbon in marine sediments . ”
“This equation is a gross simplification of the seawater system because seawater has many more elements that are likely to play a role. One of these is Calcium (Ca2+) which ‘binds’ with CO3 like: Ca2+ + CO32- CaCO3 to form limestone as in corals and shells.”
The author goes on to show that “…the sea has a vast oversupply of calcium.”
It is difficult to conclude from an examination of the CO2-T relationships in the Eemian in the Vostok ice core that CO2 exerts any definitive positive feedback on T; the data also indicate that the increases in atmospheric CO2 concentrations caused by oceanic CO2 degassing with T increase will be of the order of 30ppmv with a 3degree C global mean surface temperature increase.
At the onset of the Eemian, atmospheric CO2 concentration increase from ~170ppmv to ~ 270ppmv, but this LAGS a T increase of 10 degrees C by ~ 800 years. Interestingly, the DeltaT-CO2 concentration relationships indicate that there is ~ 10ppmv CO2 increase per 1 degree C increase (Henry’s law gas behaviour relating to dissolved oceanic CO2). CO2 then PLATEAUS at 270ppmv, whist T then DECREASES from its maximum of 2 degrees C (above current global mean surface T’s), whilst CO2 concentrations remain at their plateau of ~ 270ppmv. CO2 concentrations then drop from their 270ppmv “plateau” to 230ppmv ~ 1000 years AFTER T drops to ~ -4 degrees C!
Where is the positive feedback signal here between rising CO2 concentrations and T’s?
The ice core data also indicate that CO2 concentrations will increase by ~ 10ppmv per 1 degree C T increase. In other words, the data indicate that a 3 degree C T increase globally should increase CO2 concentrations by ~ 30ppmv (above the anthropogenic component added).
For sources of data, go to http://www.ferdinand-engelbeen.be/klimaat/eemian.html
There are also primary data sources listed in Ferdinand Engelbeen’s descriptions, graphs of the ice core data, and a rebuttal of some criticisms of the validity of these data.
Rational Debate —
Positive feedbacks do not need to be runaway, particularly when they are logarithmic (as many/most are). Each feedback gives you less than you added to begin with, or may be bounded by some limit (such as how much ice is available to melt).
In the case of CO2, for example, you have to double CO2 to get 1 degree of warming. Each degree of warming may also add 10 ppm of CO2. So if you start at 280 ppm CO2 and double to 560 ppm CO2, you get 1 C of warming, and with that another 10 ppm of CO2. But you can see that that extra 10 ppm of warming doesn’t get you anywhere close to another 1 C of warming…. more like another 0.001 C of warming.
The biggest positive feedback in the system is H2O, which will increase with rising temperature (everyone knows it’s more humid in summer than winter), but not in a runaway fashion. You’ll get H2O that gives you another 1 C of warming, and that will in turn give you another 0.5 C of warming, which will in turn give you another 0.25 C of warming, etc. It’s a convergent series.
There are also some negative feedbacks that will counteract the positive feedbacks (like, hopefully, increased cloud formation, which will reflect sunlight before it hits the earth and warms the ground).
So, double CO2 and you get 1 C of warming from that, plus another 2-4 C of warming from all of the combined positive feedbacks and negative feedbacks, combined.
Dave wrote:
“There are those that claim the oceans are absorbing CO2 and others that claim the oceans are degassing CO2. ”
It’s fairly easy to deduce which way the arrow is pointing:
a = Mass of the atmosphere: 5 x 10^18 kg
b = Human CO2 emissions: 2.7 x 10^13kg (est. 2004)
b/a x 10^6 (to convert to ppm) = 5.4ppm/year
This is parts per million by mass, not volume, so to avoid confusion we should calculate the percent change:
5.4ppm/582ppm = 0.9% increase in CO2 per year.
But in reality what we observe is closer to half that:
388.63/386.92= 1.0044 = 0.44% increase in CO2/year
So unless the CO2 is escaping the planet somehow, about half of our emissions are going into carbon sinks, mostly the ocean.
The above commentary written by Royer is intended to publicize the implications of a research article appearing in the same issue of PNAS written by Breecker et al titled: Atmospheric CO2 concentrations during ancient greenhouse climates were similar to those predicted for A.D. 2100. That article can be obtained from co-author Sharp’s website at: http://epswww.unm.edu/facstaff/zsharp/homepage/hompage-v6_website/files/Download/breecker%20pnas.pdf
Breeker has been investigating whether the assumptions used in calculating atmospheric CO2 levels from deltaC13 isotope ratios in calcium carbonate “fossil soils”. Breeker has published one earlier paper showing that calcium carbonate is incorporated into soil at ONE site only under conditions that are warmer and drier than the average climate for the site. Applying the corrections derived for this one site to all other sites, lowers the previous estimates of atmospheric CO2 by 1.5-4.0X. According to Breeker and Royer, Breeker’s corrections bring soil-based estimates of CO2 into better agreement with other techniques. (Breeker acknowledges relying on data provided by Royer to come to this conclusion, so their analyses are not completely independent.)
The question is whether it is appropriate to apply Breeker’s correction to all other sites used to estimate CO2 levels from soil carbonate isotope ratios. A quick glance at Royer’s graph shows that numerous soil measurements made around 65 MYA give suspiciously low carbon dioxide levels when Royer’s correction is applied. So, perhaps in a fews years, Breeker’s research will have been replicated at a number of different sites under varying atmospheric concentrations of carbon dioxide by a number of different workers. Then we will know how much faith to place in the above putative change in our understanding of past atmospheric levels of carbon dioxide. Their relevance to the climate sensitivity of our current world – with polar ice caps and an isthmus of Panama – will still be questionable.
(Of course, none of this has anything to do with the first 800 years of melting at the end of the last ice age or many of the other distractions mentioned above.)
I believe there is a principle known as Henry’s Law that states “At a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.”
I think the amount of CO2 dissolved in the ocean is proportional to the CO2 concentration in the atmosphere and inversely proportional to the average temperature of the water.
@george E. Smith (13:07:16) :
I was just pointing out that you can actually derive a maximum sensitivity that is a lot less than 6 C. Any sensitivity greater than 2 C per doubling from pre-industrial levels would have caused more warming than the HadCRUT3 temperatures show. Since HadCRUT3 probably exaggerates the instrumental era warming by as much as 0.5 C… The sensitivity can’t even be 2 C.
If CO2 actually varied from 280 to 400 ppmv during pre-industrial times (and since the end of the Pleistocene) as plant stomata indices and chemical analyses suggest… The climate is almost totally insensitive to CO2 variations between about 275 ppmv and 4,000 ppmv.
There is absolutely no evidence of past or present net positive feedbacks… None.
If there were, the Earth would have already experienced run-way greenhouse warming several times from the Cambrian to the Paleogene.
If there were net positive feedbacks, HadCRUT3 would show a heck of a lot more warming over the last 150 years and the satellite data would show a steadily increasing temperature rather than no change prior to 1995 and after 2000. All of the warming in the satellite era occurred in one five year period.
“”” ThinkingBeing (14:32:28) :
Rational Debate –
Positive feedbacks do not need to be runaway, particularly when they are logarithmic (as many/most are). Each feedback gives you less than you added to begin with, or may be bounded by some limit (such as how much ice is available to melt).
In the case of CO2, for example, you have to double CO2 to get 1 degree of warming. Each degree of warming may also add 10 ppm of CO2. So if you start at 280 ppm CO2 and double to 560 ppm CO2, you get 1 C of warming, and with that another 10 ppm of CO2. But you can see that that extra 10 ppm of warming doesn’t get you anywhere close to another 1 C of warming…. more like another 0.001 C of warming. “””
Where are you getting your numbers from ? The above paper says the “Climate sensitivity” is 3 deg C per doubling, which is about what the IPCC claims. So what is the source of your 1 deg C. Spencer and Christy argue that their data shows way less than even one deg of warming per doubling.
Unfortunately the mean global temperature depends on a whole lot more factors than just CO2 abundance; for one thing CO2 is just another component of the total atmospheric GHG most of which is water. In fact, I don’t believe that for most of the earth’s atmosphere, that H2O is ever less than CO2, even over the dryest deserts. Maybe at really high altitudes, when the temperatures are way below freezing. the H2O vapor may end up less than the CO2 but then you have an even bigger problem, because all the excess H2O that is not vapor, is in the form of clouds, giving a very strong negative cooling feedback.
When a cloud passes in front of the sun, you get a shadow zone the size of the cloud, with a penumbral edge due to the 0.5 degree angular diameter of the sun; and nobody ever observed it to suddenly get warmer on the surface in that shadow zone.
On the other hand the LWIR emission form the surface; possibly diminished because of the temperature drop in the shadow, is at least a Lambertian emission pattern (for flat water) and more likely closer to isotropic for a normally rough surface; so the LWIR surface emission is a very diffuse source, compared to the 0.5 degree beam source for the incoming solar radiation.
So only a small fraction of the surface emitted LWIR, will strike that cloud, and be intercepted by water or ice absorption. The optics always favors a net cooling of the surface. Yes the atmosphere may warm due to both absorbed sunlight, and GHG intercepted LWIR (mostly H2O); but the lower mass of the warmed atmosphere layer, makes it a poor surface warmer.
And in particular, most of the returned LWIR will impinge on water (73% of the surface), and be sborbed in the top 10 microns or so. This will reult in a warmed surface film, and prompt evaporation, which conveys a whole lot of latent heat into the atmosp[here, and ultimately the higher atmosphere (where the clouds form); and that process dumps the latent heat out (around 5435 Cal/gm) plus another 80 cal/gm if it is cold enough to form ice crystals, instead of water droplets.
Doesn’t strike me as a surface warming of any major extent.
The warmists argue that the high clouds warm the surface, by absorbing LWIR, while not stopping much sunlight; so the higher the clouds the more the surface warming. Surprisingly; they say this happens, regardless of the relative humidity of the intervening air mass; so they evidently attribute all the surface warming to the LWIR returned from the clouds; but none of it comes from LWIR emitted from the water vapor warmed atmosphere. Somehow I doubt that is realistic.
The surgface temperature and relative humidity of the intervening atmosphere under those high clouds, is more likely to be the source of those clouds, and not the result of those clouds.
So I do not believe clouds are ever a positive feedback warming influence; given of course that I am talking climate, and not weather, so don’t give me that last night’s high cloud thing.
It doesn’t make any sense, that the higher and colder, and less dense that a cloud layer is, the more it warms the surface by emission of LWIR back to the surface.