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.
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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.
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From what I see they assume that CO2 drives temperatures.
Then start interpreting.
This meas they ignore completely the 800 year lag in the ice core records.
What if they assumed that rising and falling water levels control temperature , with varying H2O proportional to the area, a much more important green house gas? Or change in areas of tropical forests, which would again change H2O.
Considering the land changes in the periods covered this is another exercise in GIGO, imho.
I find this paper (PDF) interesting, but it still does not address the temperature/CO2 800 year time lag seen in ice core records.
The paleo data is not fine-grained enough to show what follows what. The data does show that a much higher CO2-content was rather normal, and that the SST was ~5 degrees higher than today.
“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."
Wow. Who says there's no debate over AGW? There's a vitally important debate going on, only in its most important aspects it's not between "happening" and "not happening" but rather between "happening" and "Let's-recite-the-21st-Psalm happening."
Props to Mr. Watts for featuring something that directly challenges his take on the subject. I can see now why the blog wins awards.
Obviously just one paper, needs confirmation, etc., but nicely dovetails with other research. I'd like to address this point:
"it still does not address the temperature/CO2 800 year time lag seen in ice core records."
Natural cycles seem most often to start with a weak change in solar forcing. After a certain point, positive feedbacks take over, among them, very importantly, CO2.
Imagine a vase on the top of a stand. As long as you leave it alone, nothing. But push on it, even with one finger, it will tip over and then fall. Positive feedback takes over, in the form of gravity. You can see how gravity works by measuring how long the object takes to fall, just as you can measure the greenhouse effect of CO2 in the climate record, even though in both cases the initial "nudge" is different from the force being measured.
From SVOR
““The [computer model] simulations rule out (at the 95% level) zero trends [in global temperatures] for intervals of 15 yr or more, suggesting that an observed absence of warming of this duration is needed to create a discrepancy with the expected present-day warming rate.”
taken from official NOAA doc s se SVOR website
would this not automatically terminate AGW re jones statements no statistical warming since 1995?
previous:SBVOR site sorry
http://sbvor.blogspot.com/2010/02/phil-jones-proves-all-ipcc-computer.html
To my surprise, here I find myself in agreement with Mr. Svalgaard.
Most of the premises in this article are based on “proxies,” “estimates,” and “assumptions,” not at all verifiable. But the conclusions are, suddenly, “clear” and “robust” enough to “establish a basement value for climate sensitivity as a critical step for addressing our current climate crisis, policywise.”
I smell a paleofish.
Re: Leif Svalgaard (Feb 15 21:43),
I wonder if there is somebody who has calculated how much CO2 will boil out of the oceans if they were 5 degrees warmer than now .
I think it is hubris to believe that one can extract CO2 sensitivity from these paleo data, when there is water water everywhere.
Its really quite amazing what you can do when you assume the IPCC and Jim Hansen are correct. In both cases the sensitivity of CO2 is estimated based on GCM models rather than empirical data.
I wonder what results the authors would have got had they assumed different sensitivities.
Natural cycles seem most often to start with a weak change in solar forcing. After a certain point, positive feedbacks take over, among them, very importantly, CO2.
What about the fact that CO2 is less soluble in warm water? That has to be factored out along with the contribution of water vapor and clouds, which are likely to depend not only on temperature but also on ocean currents and the locations of the continents. I don’t see any indication that that was attempted. What is shown is a possible correlation, the causation part doesn’t look to be settled at all.
Looking at their nice little graph, it appears that at most points the range of CO2 values is is 600 to 700 ppm and temps range about 10C. Plus we can’t know if the CO2 is driving the temps or vice versa. I’d have to say that it’s time to change the initials from PNAS to POS.
Interesting. Quite so.
But what it tells us I am not so sure.
It does say that CO2 levels vary with temperature.
Since we do not know whether those CO2 levels led or lagged the temperature change we can say nothing beyond high CO2 levels are associated with warmer temperatures.
That is hardly controversial, if the oceans control the CO2 in the atmosphere, and given their vast bulk and huge reserves of dissolved CO2, that is more or less what we would expect to see.
Whether the CO2 levels in the atmosphere have any significant effect on global temperature is a moot point.
Even more questionable is whether burning fossil fuels can significantly affect the CO2 levels in the atmosphere: given the scale of the natural variation.
But whilst the science in this paper as to CO2 levels and temperature appear to be serious the interpretation placed on the relationship is highly dubious.
And without any foundation in either the reported data or speculative assumptions as to the magnitude of the supposed effects of changes of atmospheric CO2 on global temperatures.
In short the data, whilst possibly better than we had before, does not support the momentous conclusions placed upon it. The data only tells us what we knew before, if to a better degree of precision.
Kindest Regards
I still cannot accept the logic that non-CO2 variation kickstarts massive changes in climate but then CO2 takes over. Much like the warming from 1910 to the 1940s… we don’t know what caused it but the nexr round, oh yeah, *that* one was CO2
Don’t get me wrong, I understand the allure of “it’s a simple physics problem” but complex systems are never quite that easy. Still looks like an answer in search of a problem I think
BTW Leif, thanks for setting me straight on solar activity earlier, I hadn’t seen your post when I submitted. Good to see you around again!
“Policywise, establishing a basement value for climate sensitivity is a critical step for addressing our current climate crisis”. What crisis would that be? The crisis that has emanated from Climategate showing AGW has no foundation? A future funding crisis if nobody believes the scary projections?
Which came first: The temperature rise or the C02 released ?
What is the ultimate source of the C02 levels in play, the oceans or the planetary interior (volcanic)?
The question of volcanic activity levels releasing C02 and other gases must be answered, or we will continue to bat the oceanic ball back & forth.
Plants don’t create C02, they use it. Animals eat plants and release 02.
Geology sequesters in sediments. Limestone formations bring Calcium into the equation, and Calcium supply into question.
Oceans can hold C02 in absorbtion, but how long does it take for geology to place it out of reach of warming ocean cycles?
I think we would be better served to define the levels of vocanic activity during the Geologic Ages, then see how much the oceanic cycles work with what is in play.
The assumption is positive feedback causing sensitivity. The author quotes 3 degrees centigrade per doubling of CO2, which as about 3 times the first order rise. How can a positive feedback cause 3 times the effect, without going off to infinity? The feedback would have to be finely balanced.
If the primary effect of doubling CO2 is a 1 degree rise, and the feed back factor is x, then the second order effect is x degrees. The third order feedback is x squared, then x^3, x^4 etc
The final rise is then r = 1 + x + x^2 + x^3 + x^4 ….
Solving that gives r = 1/(1-x).
A feedback of 0.5 gives r = 2.
feedback = 2/3 gives r = 3, which is what the article assumes.
feedback = 3/4 gives r = 4
…
feedback = 9/10 gives r = 10.
So the feedback has to be very finely tuned. Less than 2/3 gives CO2 global warming is no big deal.
2/3 would be barely believable if you assumed CRU and Gistemp were gospel.
¾ would be so high the effects would already be dramatic.
9/10, we’d be fried or frozen long ago.
There is absolutely no evidence that feedback is exactly 2/3. If it was, the temperatures couldn’t have fallen since 1995, as Phil Jones now admits they have.
Polar forests instead of ice caps? Bummer, man.
Translation = We spent lots of time and money, made lots of dodgy assumptions and dont know any thing more than we did before.
I find the paper a little troubling, the issue of temperature co2 lag is V important and key to the papers conclusions. The papers assumes there is a linear relationship between co2 and temperature, which there is, but the relationship is reversed to what they assume. The relationship is due to the sea warming and then outgassing co2 and vise versa (a very well established relationship), it has not been demonstrated that co2 has had any part in past warming in any way given the large lag (see the IPCC AR4) and only climate models provide any support for this, but they based on circular reasoning as they assume co2 causes warming, hence invalid.
So I would argue the entire papers is pointless and wrong, but confusing correlation and causation they provide support for the IPCC claims of a 3 degree sensitivity but include enough get out clauses to show the results is so uncertain, its of no use whatsoever, but when sucked into the IPCC report, it can be misrepresented to mislead those who have not taken time to read or understand the paper. They also fail to mention all of the uncertainties in past paleo records.
Also the assumption that the equator has a linear relationship to temperatures globally is foolish, given the IPCC state that the poles are greatly affected by temperature change whilst the equator has remained fairly constant or cooled during previous warm periods (IPCC AR4). This again invalidates their work.
Poorly justified assumptions and reversed relationships do not equal reality! A complete waste of tax payer money!!!
However, perfect to mislead policy makers!
“it still does not address the temperature/CO2 800 year time lag seen in ice core records”
There are numerous papers that explain the lag between orbitally-forced climate change and the CO2 rise which was initiated by the warming and led to further warming. It would be far more surprising if CO2 preceded orbitally-forced climate change!
Anthony, you are to be congradgulated for staying curious. It is only old minds that are settled.
Bravo!
Fiction and fact from Sam’s almanac.
The very high temperature estimates based on TEX86 are essentially just guesses as there is no way to verify them from modern sediments. I find them very doubtful since they are never corroborated by e. g. d18O which are based on known physics.
Great, they pick one of the methods for obtaining CO2 proxies and say the other methods are wrong. If they consider consensus, should they have not discarded the method which is giving anomalous results? Of course, they would not have had preconceived ideas about global warming would they ?
Also, where does the idea of temperature increase from doubling of CO2 come from- models which have been proved to be inaccurate.
I wonder who peer reviewed this was it Mann, Jones, or Hansen who is mentioned in the references?
@Robert:
That’s reasonable. When a vase standing at a tipping point is tipped and releases such a big energy impulse it really must be possible using that energy difference to drive a perpetual motion machine.
Leif Svalgaard (21:43:28) :
‘I find this paper (PDF) interesting, but it still does not address the temperature/CO2 800 year time lag seen in ice core records.
The paleo data is not fine-grained enough to show what follows what. The data does show that a much higher CO2-content was rather normal, and that the SST was ~5 degrees higher than today.’
Or they are saying the Ice Core Data is “wrong”. There is no “lag time”.
Rabe: “That’s reasonable. When a vase standing at a tipping point is tipped and releases such a big energy impulse it really must be possible using that energy difference to drive a perpetual motion machine.”
Wow. Not content with rejecting the theory of AGW, apparently you reject the law of gravity. At least your attitude towards science is consistent.