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.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
“There is absolutely no evidence of past or present net positive feedbacks… None.”
Exactly! Except for the mountain of evidence of net positive feedbacks.
Tiny orbital changes altering solar forcing by less than 0.1 Watts/m^2 have led to swings of as much as 5C (http://en.wikipedia.org/wiki/Milankovitch_cycles). Utterly impossible without net positive feedbacks in the short term.
Robert (18:07:31),
Both George E. Smith and David Middleton have probably forgotten more about physics than you will ever learn, your being a sociologist or whatever. But I must say, your cut ‘n’ paste skillz make it easy to take realclimate propaganda and dump it here.
I’ll help you out here, by explaining the situation – without cutting and pasting what other folks say: click1, click2
See? CO2 absorbency operates on a logarithmic scale. So you can relax.
Burning all of the known reserves of fossil fuels would not double atmospheric carbon dioxide. Nor would it make the oceans acidic. And as anyone can plainly see from the links above, even a lot more CO2 would make only a negligible difference.
Just a minor note up front… several people replying to “ThinkingBeing” left my screen name in their reply – probably because that’s how the text happened to be from “ThinkingBeing’s” reply to my earlier post – but I hope folks realize that our positions are quite different.
So, now to make it even more confusing, I’m replying to:
Several points here. First, if you go back to my post, I stated right up front: “If positive feedback takes over, then how can the increase ever possibly stop? The world would continue heating, or at least hit a high point and then stay there. That’s the entire nature of a positive feedback.” A significant part of the reason I used that phrase was because of the logarithmic CO2 curve.
Now, I don’t know if all of the ‘climate scientists’ adhere to the logarithmic standpoint or if some don’t and claim a ‘runaway’ system, but I’d assume the latter since there are claims all over the place about how Venus’s atmospheric composition and temperature, far far higher than our temperatures, are because of runaway greenhouse warming from CO2.
Which segue’s right into my next point. The AGW claim is that there is a net system positive feedback occurring right now, directly or indirectly, because of CO2. That CO2 is the ‘driver,’ so to speak. In other words, that within the current system (e.g., our solar system and all of the various feedbacks within it on or off the earth), increasing CO2 is causing increasing temperatures.
That this net positive feedback will continue in the near future to the tune of somewhere between an additional 2 to what? 10 degrees? Pick your numbers, it really doesn’t matter to my point. I don’t recall seeing what those same proponents claim would happen if CO2 continued to rise beyond the upper temperature they’re predicting, but again, that’s relatively moot to the point.
That point being the same logic flaw from my original post – net system positive feedback as being described by ‘climate scientists’ is that as CO2 increases, the temperature continues to increase at least to that upper number. In which case, even if it stopped there because of the logarithmic nature, there is nothing that would be able to drop the temperature back down from that upper temperature. As the temp started to drop, you would be right back in a net positive CO2 feedback mechanism that got you there to begin with, so the temp should stay at that level (or continue higher if it isn’t a self-bounding situation, logarithmic, etc.).
The logic as its being claimed simply cannot reconcile with Earth’s history, unless some other theory is proposed for what could possibly account for temperatures to ever come down below that upper number. That theory would have to also account for how suddenly CO2 is no longer the driver of a net positive system feedback. I’ve yet to see anyone propose anything along those lines, yourself included. All that you’ve stated merely gets the temperature increase to stop once it hits an upper number that is at least several degrees warmer than present day temperatures.
So, by the current AGW theory of CO2 being the driver of a net postive system feedback, either the Earth turns into Venus (minus a teensy smidge for distance), or far back in our history we would have hit temperatures at least several degrees warmer than present day and stayed there without any mechanism to account for little ice ages or even present day temperatures.
@Robert(18:O7:31)
That’s not a feedback in the sense of the enhanced greenhouse hypothesis.
David (20:01:36)
What do you mean? If I were unclear, I am saying that small changes in solar forcings have, according the the climate record, triggered large changes in temperature, far larger than can be accounted for by the solar forcing itself. This implies that there are positive feedbacks (such as melting ice) that can and do operate on the climate system. It does not imply that GHGs are among those feedbacks; that’s a separate issue.
Do you disagree with this?
My understanding from what I have read from several sources about the 800 year lag in CO2, and ‘runaway’ warming is as follows. It is about the balance of 4 forces
1. Milankovitch cycles impose a small, 0.1 w/m^2 or so, warming/cooling cycle
2. CO2 and perhaps to a lesser extent Methane provide a warming effect but the logarithmic nature of this effect means that this tapers off. Further concentration increases provide a diminishing returns effect. And the main source of extra CO2 is release from the oceans. And the time lag of 800 years or so reflects the overturning time of the oceans currents. Surface waters may release their CO2 relatively quickly, but the real impact comes as deep water is raised to the surface and continues to supply new water to feed release. And the same process in reverse drives CO2 absorbtion during the cooling phase.
3. As warming proceeds the Albedo (Reflectivity) of the planet changes. White reflective ice is replaced by dark water, dark rock and relatively dark vegetation. And this proceeds in a very non-linear way. An Ice sheet 2 km thick can thin to 100m and the albedo hasn’t changed, Then the last 100 m goes and it is bare rock. The extent of winter sea ice remains unchanged until it has thinned enough to become weak enough to break up at the edges during the summer melt then it can decline rapidly. Vegetation takes time to fully colonise bare rock. But once the transition is complete then the albedo can’t keep changing. Vegetation, rocks and water can only be so dark. Ice can only be so white
4. Water vapour changes magnify the warming/cooling effect from all other causes. However, the amount of water in the atmosphere is governed by temperature. So unless there are other factors contributing to a temperature changes, water vapour cannot continue that change on its own.
So the sequence is something like this. In the depths of an Ice Age a Milankovitch event starts a minor warming. Ice retreat starts at the edges changing Albedo a bit, followed by some vegetation growth on the exposed ground. Methane release from melting permafrost at the margins starts to add to the warming effect. But this doesn’t show up much in the Ice Core records because its warming impact while it exists as Methane is a couple of orders of magnitude higher than CO2 molecule for molecule. So it has a bigger warming whammy briefly before it then oxidises and converts to a minor amount of CO2 that barely registers in the cores. More water vapour due to the heating magnifies the warming a bit more. CO2 starts to outgass from the oceans because at a higher temperature they can’t hold as much CO2 in solution but only slowly. A modest positive feedback has started. Then overturning of the oceans a few hundred years later starts to accelerate the effect, bringing more CO2 laden water to the surface. More warming and we start to see a real rise in CO2 in the cores. Then, after perhaps several 1000 years, the warming and the total size of the ice involved means that the collapse of the ice sheets starts to accelerate. The warming effect of CO2 is starting to taper off as the logarithmic law kicks in. Albedo change may now be a bigger driver. And Water vapour is still doing its thing, magnifying the change. Eventually the change from Ice Age to Interglacial is complete. And then the effects of Albedo change taper off radically. And CO2 may still be climbing buts its temperature impact is declining due to the logarithmic effect. And with no other things driving it, Water vapour’s contribution falls away as well. Temperatures are nearly stable although CO2 is still coming out of the oceans.
So, a positive feedback but self limiting. Not a runaway.
Then the reversal starts. Again, a reversal of the Milankovitch cycle starts the decline. With less warming from the sun, this starts to counteract the residual warming from the still rising CO2 levels which are driven by the concentration imbalance that still exists between the deep oceans and the air. So temperature rise stops even though CO2 levels keep rising for a bit. Once the cooling due to Milankovitch beats the warming due to CO2, temps start to drop. And Water vapour then changes sides and starts to magnify the cooling. And unlike the warming phase where there were long lag times before albedo change had a big impact, waiting for all the ice to melt, now more snowfalls at lower latitudes / altitudes have an immediate effect. A couple of metres of snow has the same albedo effect as 2 kilometers of ice cap. So this time albedo change leads the charge. Also, as climate cools, vegetation declines. This decomposes and releases CO2 which helps to keep CO2 levels elevated as the cooling proceeds. Eventually the cooling temps mean CO2 uptake into the oceans can increase. CO2 uptake by the oceans starts to get ahead of CO2 release from dying vegetation and CO2 levels start to drop, adding to the cooling. But it is several hundred years again before overturning of the oceans really starts to draw CO2 down into the depths and make a real impact on atmospheric concentrations. Now the big chill is on in earnest as we plunge down into the Ice Age. Lots of relatively thin ice over large areas drives temps down aided by H2O. Then as CO2 declines, the logarithmic effect works in reverse, driving the cooling even faster. So what stops the decline? Well the Milankovich effect drops away. And how far the ice can spread depends on land shapes – ice simply can’t spread too far to low latitudes over ocean. So eventually this limits ice spread no matter how cold things get. So the Albedo driver tapers off again. Then CO2 alone can’t keep driving temps lower alone and this tapers off and we are back where we started.
The depth and severity of Ices Ages seems to depend on land shape. You need at least one continent at the poles to allow major ice build up, and it seems to be that you need a major north/south continent to block east west ocean currents as a contributor as well. So our current period of glacial cycles began about 30 million years ago when Antarctica was down in the south and the Isthmus of Panama closed. A previous major glacial period during the mid Carboniferous may have started when the supecontinent of PanGaia had its lower half near the south pole and was so big that it stretched well into the northern hemisphere. And it ended when Pangaia broke up. Gondwana remained near the south but Laurasia moved north and the return of currents through the seaway in between ended that glacial period.
@Robert
“Do you agree with this?”
Maybe.
When the input of energy into the system changes, atmospheric and oceanic processes might amplify or mute those changes. There are lines of evidence to support this sort of hypothesis.
However, there is no evidence whatsoever of unremarkable changes in atmospheric CO2 causing any sort of cascading positive feedback loop.
And the rise in atmospheric CO2 over the last 5O years is wholly unremarkable. If the plant stomata data and chemical analyses are correct, it`s not even anomalous.
To me, it seems easier to imagine an ocean cooling feedback event when the cooling of a warm sea absorbs or sucks more CO2 out of the atmosphere that all natural sources can produce and lowers the greenhouse warming by one degree every time the CO2 concentration in the atmosphere is halved until the ocean has cooled to its temperature of maximum CO2 solubility.
Even in this case, however, I believe the role of CO2 would have to be secondary to some other primary forcing factor because of the logarithmic nature of the CO2 greenhouse effect.
@Spector (10:09:04) :
Since the “greenhouse” warming effect of increasing CO2 on temperature is logarithmic… The cooling effect of CO2 depletion is much greater per ppmv than the warming effect is
All other things being equal (and they never are)…
A doubling of the current CO2 level from 388 to 776 ppmv could cause maximum of 1.89 C of warming. Atmospheric and oceanic circulation would mute this warming to a large extent.
A halving of the current CO2 level from 388 to 194 ppmv could cause -1.89 C of cooling. Atmospheric and oceanic circulation would not be able to mute the cooling effect. The lower atmosphere would simply lose heat. Cooler oceans would be able to take more CO2 into solution… This would lead to accelerated cooling… Causing more CO2 to go into solution… This could actually lead to a cascading feedback loop of cooling.
However, we know from the geological record that runaway negative feedback loops haven’t happened before either.
CO2 depletion is a far greater threat to humanity than greenhouse gas emissions ever possibly could be. 2C of cooling would lead to famine on an unimaginable scale. 2C of warming would cause a lot of problems; but people can move.
RE: David Middleton (12:25:29) “… runaway negative feedback loops haven’t happened before either.”
Runaway heating or cooling are both manifestations of *positive* feedback.
An example of negative feedback would be an effect that would cause the atmosphere to cool in response to forced warming or cause it to warm in response to forced cooling. This is why negative feedback is usually used to stabilize the gain of electronic amplifiers.
“A doubling of the current CO2 level from 388 to 776 ppmv could cause maximum of 1.89 C of warming.”
If only. Actually, a doubling of CO2 is likely to cause 4+ degrees of warming, according to the very paper we are discussing.
“2C of cooling would lead to famine on an unimaginable scale. 2C of warming would cause a lot of problems; but people can move.”
I agree that any radical change in the climate is likely to be to our detriment. That being the case, the safest thing to do is to leave it as close to possible as the state we found it in (280ppm). Those are the levels that have been safe for the last 10,000 years of human history. Until we understand the climate system much better, they are the only levels that can be considered “safe” in the long run.
I like to use the analogy of a person alone on an alien spaceship who wanders into the life support control room. The room is full of buttons and levers and our traveler understands none of it. What is the only reasonable course of action we can recommend to him? Isn’t it: “Don’t touch anything”?
Practically speaking, we are going to see continued warming for our lifetimes, even if we bring CO2 down to 350ppm. The name of the game is to try and keep that warming as slow and limited as possible; to stay as close to the conditions that have been safe over the last 10,000 years.
@ur momisugly Spector (14:18:24) :
I know… But it just sounds “funny” to refer to an amplification of cooling as a “positive” feedback. Kind of like “negative economic growth” sounds funny.
Technically speaking… Negative feedback loops can’t run away at all and they happen all the time.
The endless conflict between grammar and science… ;-))
Positive feedback exacerbates an effect; negative feedback dampens it. I’m being simplistic here; feedbacks can involve time delays and very often have a frequency dependency and a frequency dependant phase shift so a feedback can in fact be negative for one part of the spectrum and positive for a different part, leading to resonance effects. This would materialize itself in oscillations, like the PDO. Which in turn leads to intermittent ica age/meltdown panics.
Dave Middleton (15:10:56) : “Kind of like ‘negative economic growth’ sounds funny.”
I am sure you have heard the phrase “vicious circle” in regard to the Great Depression. That was a classic example of a positive-feedback runaway event in the field of economics.
I want to add a PS to why the errors in the energy budget ( energy in energy out) are really unknown and could be bigger than the claimed effect of CO2 in Watts/m^2.
They treat the earth as a black body, to convert temperatures to watts/m^2
1) the earth is a gray body with emissivities from 1 to .7 of the black body constant.
2) they measure the sea surface temperature, true, so that gray body calculation in an energy balance would pass muster.
3)Have you seen anybody measuring ground temperature? Forrest canopy temperature? Sahara sand temperature? They use the temperatures 2m up from surface stations and do black body radiation? I know for sure that the temperature on sand is over 50C while the air temperature is below 40C ( try to walk on sand barefoot in greece in the summer). One can fry eggs on the sand in Sahara, but the air is what? 45C? 50C? On land it is the surface temperature that radiates according to T^4 and a gray body constant.
example. 40C in the air and 50C on the sand: there is 13.5 more flux going out for the 50C temperature. So if one budgets as if it is black body with the air temperature, that is 537watts/m^2 for 40C versus (assumed 50C) sand temperature 604 watts/m^2. Thats a lot of watts to be off, even though the Sahara is a small part of the globe and even though it is not a black but a gray body.
I have not seen 3) discussed anyplace. I can easily see systematic errors of the order of 2Watts/m^2 in the energy budget.
Hi Robert,
The point is that a 2C decrease in global temperatures would have vastly worse impacts throughout the world than a 2C increase. Which means that we have a lot more incentive to try to avoid or at least prepare for that eventuality than for a comparable warming. You went on to say:
Again, speculation. Even the levels that existed for the past 10K years are debatable. A few examples, see: http://www.sciencemag.org/cgi/content/full/286/5446/1815a where the article authors argue that historical CO2 levels may have been as high as ~360ppm. http://www.sciencemag.org/cgi/content/abstract/284/5422/1971 “well above 300ppm” Then there are the possible problems with ice cores significantly underestimating CO2 levels, and if I recall correctly, also being poor proxies for the relatively near past (holocene).
You are also making what may very well be a grossly incorrect assumption that pre-industrial levels of CO2 were 280ppm. That value is, as I understand it, highly debatable. Apparently pre-industrial CO2 levels were commonly, and likely accurately, measured well into the 400+ppm range. The 280ppm value would seem to have been from pretty heavily cherry picked data.
As to ‘…safest…leaving it in the state we found it in…’ I would strongly argue that while it may be ostensibly ‘safest’ to remain in approximately the state we are currently in – as we are currently better off now by far than in pre-industrial mini-ice-age days (your 280ppm) – it isn’t necessarily ‘better.’ I also suspect plants would argue that we’re far better off now, and would be even better yet with significantly higher CO2 levels. I’m certainly happier with warmer temps than more ice and snow myself. –grin–
Plants aside, In order to determine if we would be ‘better,’ I believe we have to do some cost/benefit type of analysis. For example, one may certainly be ‘safer’ in a completely temperature controlled padded 6ft x 6ft room with all nutritionally balanced meals delivered – but the cost sure isn’t worth it. Even ‘safety’ itself has to be defined in this sort of situation. Is a hypothetically slightly more ‘stable’ climate ‘safer’ if it comes with reduced lifespans, significantly reduced standards of living, reduced nutrition and health?
Safety cannot be the only consideration. One must consider the costs of trying to stay even at present day levels of CO2, let alone trying to actually reduce levels, if either scenario is even possible. If the costs to world standards of living, life-spans, nutrition, etc. are too high, then its surely not worth trying to halt CO2 levels on the possibility that maybe it will be somehow ‘safer’ when we’ve no idea if in reality things really would be any safer.
All of these factors mean that we had better be pretty darned sure that we base ANY decisions on good, solid, verified science. Which we very clearly do NOT have at this point in time.
Lastly, your spaceship…
Ah, but there’s a few flies in the ointment here. The more apt analogy is that our intrepid spaceman has been on the ship for awhile. He’s managed to figure out ways to take a few measurements over time, but there are flaws with his methods and the accuracy and usefulness of what he’s measured are highly questionable. Even so, he’s managed to convince himself that changes over time might mean disaster, maybe HE actually changed things, just by being there. He convinces himself that he’s got to quit burping, or its going to destroy the delicate balance of the life support system on the spaceship, that MUST be what has caused some of the values he measured over time to change. He wanders into the control room, and is just sure that SOMETHING in here MUST be able to help him sequester his burps and save the system!! So he starts messing around with the buttons and levers….. and he confines himself to a single tiny closet to try to minimize his influence on the ship. Doing something must be better than doing nothing, right? After all, he’s just trying to return things to the way it was before he started doing all that burping, and all that wandering about breathing on things, none of which the system could possibly be designed to handle.
Little does he know he’s either playing with fire or just making his own life utterly miserable, because he doesn’t have any real knowledge of the systems involved, of what his measurements mean or how they’re not accurate enough to even be meaningful.
But then of course, any really GOOD spaceship would have all those levers and buttons safety interlocked, so he can’t really hurt the system after all by acting without sufficient knowledge – we hope. Perhaps what’s really better and safer, is to keep on having the best life he can, within reason, while trying to develop the science of ‘spaceship’ which is in its infancy, until he has some solid idea of just what he’s really measuring and what the ramifications are – or aren’t.
The “peer reviewed paper” is wrong. If it was right, we would have had more warming since 1850 than the HadCRUT3 series shows.
Without positive feedbacks, a doubling of pre-industrial CO2 cannot cause more than 2C of warming. It actually can’t even cause half of that, because the net feedbacks are negative.
If mankind had never discovered fire, atmospheric CO2 would be between 330 ppmv and 390 ppmv. If you back all of the anthropogenic CO2 emissions since 1700 out of the atmosphere, you get 330 ppmv. Plant stomata data (Kurchner et al., 1995, Wagner et al., 1999, Kouwenberg, 2004, Wagner et al. 2004 and 2005, Kurchner, 2008) and chemical analyses (Beck, 2007) tell us that since the beginning of the Holocene up until the start of the instrumental record, atmospheric CO2 has routinely fluctuated between 280 and 390 ppmv. The chemical analyses point to CO2 levels in excess of 400 ppmv within the last 200 years.
If Mann and the other Hockey Stickers are correct, a reduction of atmospheric CO2 to 280 ppmv would return Earth’s climate to Little Ice Age conditions – Almost as bad as a 2C decline in global temperatures.
If the climate reconstructions that honor the low frequency component of the data are correct (Esper et al., 2003, Moberg et al., 2005 and Loehle, 2007), a reduction to 280 ppmv would have a negligible effect on the Earth’s climate.
There are no “middle ground” reconstructions. There are Hockey Sticks which suppress the low frequency signal from ice & sediment cores and boreholes… And there are reconstructions that honor the data. There is no “happy middle ground” between the two.
I personally like to use science (geology in particular) and mathematics to understand how the Earth’s climate behaved in the past to determine whether or not modern climate changes and atmospheric CO2 are anomalous. They are not anomalous.
Scientifically speaking, we are going to see a slight to moderate cooling trend over the next 2-3 decades… Then a slight to moderate warming trend over the subsequent 2-3 decades. This ~60-yr cycle will continue for the next 100 to 500 years. Then the ~1,500-year (Dansgaard-Oeschger / Bond) cycle will turn negative and the Earth will return to Little Ice Age conditions. At some point down the road, this interglacial will end and the Earth will return to Upper Pleistocene glacial conditions. At some point a bit further down the road, the Quaternary ice age will end and the Earth will return to its normal, warmer state (~22C avg. surface temp. vs. the current ~15C).
Anthropogenic CO2 emissions will not affect this process in any statistically significant manner.
Furthermore, there is no economically possible pathway to reduce the atmospheric CO2 level from 388 ppmv to 350 ppmv. An 80% reduction in CO2 emissions by 2050 (“80 by 50”) would require us to reduce our per capita CO2 emissions to levels not seen since the 1860’s… And it would only result in a 2050 CO2 level of 435 ppmv vs a “business as usual” 2050 CO2 level of 471 ppmv.
Could “80 by 50” be achieved without destroying the global economy and killing billions of people? Maybe… But the price tag would be astronomical… The High Costs of Copenhagen
A very good discussion on the differences between the “Hockey Sticks” and the correct reconstructions can be found in J. Esper et al. / Quaternary Science Reviews 24 (2005) 2164–2166
Oh… And… Esper and Moberg are not skeptics, deniers, denialists or whatever the current pejorative is…
Despite the fact that their own work devalues “impact of anthropogenic emissions”, they still accept the AGW premise.
“The “peer reviewed paper” is wrong. If it was right, we would have had more warming since 1850 than the HadCRUT3 series shows.”
Not at all: feedbacks aren’t instantaneous. We won’t know until the system reaches equilibrium exactly how much warming the CO2 increase has set us up for.
Most of your post is like that: a series of (mostly erroneous) assertions with no sources and no evidence. If you want to support the claim that there will be a cooling trend for 2-3 decades, or that anthropogenic GHGs won’t affect the climate significantly, I’d be happy to take a look. Without evidence, they are no more notable than any random claim that flies in the face of the evidence in hand: that the Earth is 10,000 years old, or cell phones cause cancer.
Citation/source please showing the net feedback lag.
Citation/source please showing evidence that anthropogenic GHGs will affect climate significantly.
@Robert (09:02:54) :
CO2 has a residence time in the atmosphere of about 5-10 years (Revelle & Suess (1957), Sundquist (1985), Segalstad (1989), Essenhigh (2009). Any warming caused by the current atmospheric CO2 and its combined feedbacks has pretty well already occurred.
Furthermore, two thirds of the data for pre-Mauna Loa Observatory CO2 levels (plant stomata and chemical analyses) show that CO2 has routinely fluctuated between 280 and 390 ppmv…
Plant SI vs Ice Core CO2
CO2 From Chemical Analyses
Even if the ice core CO2 data are correct, the Earth has not warmed in response to the increasing CO2. The Earth started to warm from the Little Ice Age in about 1600. CO2 did not start to rise until about 1860…
Moberg (2005) and Ice Core CO2
No positive feedback loops occurred during previous CO2 spikes. The Earth doesn’t all of the sudden start responding differently to atmospheric CO2 just because some of it is the result of fossil fuel burning.
The only “pipeline” in which future warming is hiding is in the oceans… And they have been losing heat content since about 2003…
NODC Ocean Heat Content Anomaly
As far as the twenty to thirty year alternating cooling and warming trends go… Just look at the HadCRUT3 in relation to the PDO phase…
HadCRUT3 vs PDO
The PDO has been negative since about 2003. Over the last 100 years, the Earth has not warmed when the PDO was negative.
The future 20-30 years of slight to moderate cooling was also predicted by Mojib Latif at the World Climate Conference last September.
The 30 or so years of cooling are on slide three of Latif’s presentation… LINK
Latif attributes the cooling to the North Atlantic Oscillation (NAO).
Here’s an enlarged version of Latif’s 30 years of cooling… LINK
Of course, the funny thing is that Latif chose to ignore the natural climate oscillations after the upcoming 30-yr cooling period, despite the fact that he attributed at least half of the prior century’s warming to those same oscillations.
For a more realistic view of the potential warming and cooling effects, I would recommend this Don Easterbrook paper…
Solar Influence on Recurring Global, Decadal, Climate Cycles Recorded by Glacial Fluctuations, Ice Cores, Sea Surface Temperatures, and Historic Measurements Over the Past Millennium
Here’s the Moberg reconstruction without the CO2…
Moberg (2005) and UAH
The MLO CO2 curve kind of obscures the temperature curve in the image from the previous post. I tied the UAH data into the end of Moberg (which he calibrated to the Hadley instrumental data).
The late 20th and early 21st centuries are no warmer than the Medieval warm period. If CO2 was 280 ppmv in the MWP (as the ice core data suggest)… The 108 ppmv rise to today’s CO2 level has made no difference at all. The current warm phase of the ~1500-yr cycle is almost exactly as warm as the prior Holocene warm phases of the ~1500-yr cycle.
The ~1500-yr cycle should be painfully obvious in the oxygen isotope-derived temperatures from the GISP2 ice core…
GISP2
@David Middleton (11:33:24)
The NOAA Graph for Ocean Heat ontent is based on the most recent paper by Levitus et al. This only deals with heat in the top 700m of the ocean. Von Scuckmann et al 2009 looks at data down to 2000m for 2003 onwards and shows heat content still rising.
(Revelle & Suess (1957), Sundquist (1985), Segalstad (1989), Essenhigh (2009) on CO2 residense time are outligher papers, not suppourted by other scientists.
@Glenn Skankey Tamblyn (13:20:35) :
If both Levitus and Von Schuckman are correct, the oceans are gaining heat from 700m to 2000m and losing heat above 700m. How could this happen if the oceans are being warmed by an atmosphere that is being subjected to an enhanced greenhouse effect?
If Revelle & Suess (1957), Sundquist (1985), Segalstad (1989) and Essenhigh (2009) are the outliers, then what, pray tell, constitutes the main body of peer-reviewed scientific literature on CO2 residence time?
The atmosphere contains about 750 Gt C.
The total annual carbon sources to the atmosphere:
Oceans: 100-115 Gt C
Decay of organic matter: 50-60 Gt C
Plant respiration: 40-50 Gt C
Fossil fuels: 5.3 Gt C
Land use: 0.6-2.6
Carbon Cycle
Total sources: 196-233 Gt C
750/196 = 3.8
750/233 = 3.2
Carbon sinks annually take up all but 3-4 years worth of the annual sources. The residence time can’t be a whole lot more than 4 years. Otherwise, CO2 would be accumulating in the atmosphere a heck of a lot faster than it currently is.
Furthermore, the total anthropogenic component is less than the margin of error of the natural sources… A lot less than the margin of error.
@David Middleton (17:21:01)
“If both Levitus and Von Schuckman are correct, the oceans are gaining heat from 700m to 2000m and losing heat above 700m. How could this happen if the oceans are being warmed by an atmosphere that is being subjected to an enhanced greenhouse effect?”
It is accepted that the last decade has seen a slowing of warming, I suggest due to a combination of factors – deep solar cycle minimum, reduced stratospheric water vapour levels, increased aerosol levels due to growth of Asia, possibly a reduced effect from the NAO. So heat flux into the top 700m layer has reduced due to these effects.
But the heat flux from 700m to lower levels is driven by the temperature gradient between these levels, not what is happening above. All that is required for this to produce the result observed is the net flux into the 700m layer from above is less than the net flux from 700 to layers below. But the total heat of the entire ensemble has increased.
So a reduction in warming, but not cooling. And all this under the conditions I have mentioned. What happens as Asia continues its attempts to clean up its aerosol emissions and we return to the next solar maximum in 5-6 years. A return of more vigorous warming?