“As with CO2, the radiative effects of water vapor depend on the fractional change rather than the absolute change.” — But how is it actually calculated? Is there a simplified expression for the forcing from a given change in water vapor at a given altitude?
[Response: Thanks. Fixed in the text, will fix the figure.--eric]
[Response: Ack, thanks for the corrected spelling. The mis-spelling is due to me (which I picked up from a bad transliteration years ago and have been using ever since). I have been using the Kombayashi spelling for a long time in articles, and this is the first time anybody picked up on the correct spelling; I hope I haven't done too much damage to the fellow's name by using the "h" spelling in my climate book; I'll fix that in the second edition, since the thing is coming out of the presses right now. Star Trek fans have a tendency to say "Kobayashi" (as in "Kobayashi Maru,") but I at least managed to weed out all of those. --raypierre]
Great Post! I learned a lot. It’s interesting that “Observations and models support a roughly 7% increase in specific humidity per degree warming, consistent with scaling of the Clausius-Clapeyron relation” works out so well despite the actual mechanisms being much more complex.
This, I think, is a key insight:
“In general, evaporation and precipitation go up much less rapidly than the water vapor content, resulting in an increase of the mean residence time of water vapor in the atmosphere. This has strong implications for circulation patterns…..”
Strong implications, indeed. It seems to me that’s where the early climate change disruptions will occur – more from changing weather patterns than the temperatures that cause them.
Lastly, Chris, you just let the cat out of the bag! What will the deniers make of:
In conclusion, water vapor is the dominant feedback on our planet
…. after having invested so much rhetoric to the effect that climate scientists ignore the most important greenhouse gas ?
Does the Ssfc term include near IR? On the Planck curve there is a significant amount radation of near IR just beyond the end of the visible red. Explanation of greenhouse effect usually mentions only visible light.
Is the radiation absorbed by the water droplets and cause heating of clouds?
What is the portion of water vapor transported directly from surface water by the mechanical force of the wind into the air as compared to simple evaporation? How is thus taken into account when calculating water vapor feedback? A stong wind suchas Northeaster moves larges quanities of ocean surface water onto and into the land.
What is the fate of the hot CO2and HO2 deposited in the stratopshere by really big jets? For example, a Boeing 747 takes off with 346,000 US gallons of fuel for a long international flight. Do these gases stay above the tropopause? If they do, would this lead to extra heating of the stratosphere? Or do the aerosol particles from the exhast cause cooling?
There can be no runaway greenhouse effect because in polar regions the temperature drops to low values very fast after the sun drops below the horizon. By mid to Nov the ice become at lets about 3 ft thick which allows the start of the ice road trucking season. I have been “Ice Road Trucking” on the History Channel. The amount of truck traffic on the Dalton highway at ca -30 to -40 deg C is amazing.
Comment by Harold Pierce Jr — 2 Nov 2010 @ 1:15 PM
It’s been out for a couple of weeks, and I may have missed citations of it here, but even so it’s worth citing again:
Andrew A. Lacis, Gavin A. Schmidt, David Rind, and Reto A. Ruedy, 2010: Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature. Science 15 October 2010: 356-359.
This differentiates clearly between forcing and internal feedbacks and quantifies the effects of the two quite nicely. Those results, with explanations such as the one here, may just help people understand all this better.
[Response: This short note provides a convenient and concise summary of the essentials of water vapor feedback, but it should be recognized that there is nothing there that hasn't been said already innumerable times in various review articles on water vapor feedback, or other prior publications. In particular, the result that the Earth turns Snowball if you take out all the CO2 was published earlier by Voigt and Marotzke. See Voigt A and Marotzke J 2009: The transition from the present-day climate to a modern Snowball Earth. Climate Dynamics DOI 10.1007/s00382-009-0633-5 . Still, given all the confusion surrounding these issues they bear repeating. --raypierre]
Thanks for the spelling note Kooiti– That actually wasn’t a typo, I picked up that spelling from what other authors have written, so apparently the mistake has found its way into the literature as well. I’ve read Ingersoll’s original 1969 paper but not the one by Komabayasi, so thanks for the reference.
So you expect people to believe what climate scientist when you can’t even understand that positive feedback = runway system.
It doesn’t mater if the positive feedback is 10x the input or .01x the input. Here is a really simple example take you bank account pretend that it gets paid 1% interest in a hundred years your bank account will still be increasing. Just like if instead of 1% it was a 101%. All that changes is the rate of change.
Now you claim that with out CO2 the earth would be really cold but CO2 alone wouldn’t warm the earth enough to support the current temps. Then it follows that adding more CO2 must have a negative feedback otherwise the planet would have long ago entered into a Venus like state.
[Response: Please try reading again, but this time without thinking that you know the answer already. Hint: positive feedback in the climate sense is not what you have assumed. - gavin]
Here let me show a case for you. Assume T0 = 0 and an input of one and 10% feedback
T1 = 0 input of 1
T2 = 1 input is now 1 + .1
T3 = 2.1 input is now 1 + .21
T4 = 3.21 input is now 1 + .321
Repeat until the system equals the temperature of the sun.
[Response: If you read the post, you will see that this is *not* how this is defined for climate purposes. Rather than assume that a whole field is stupid, try and consider the possibility that terms could be defined differently in different fields. - gavin]
The description is not completely right, but the very first sentence is on-target and addresses your confusion. I’ve even defined the reference system based on the Stefan-Boltzmann law in both of my posts by which climatoolgists define the “sign” of feedbacks. I’m not sure you’re reading any of this.
Spenceer @13 — From your Wikipedia link: “Electronic amplification devices may have positive feedback signal paths intentionally added …”
Now I do indeed understand linear systems theory and the correct formula, even in Chris Colose’s good expostion, is
R = (g/(1-f))F
where R is the response, g is the forward, or open loop gain, f is the feedback, constrained to be in the open interval (-1,+1) to avoid runaway or oscillation and F is the input, called a forcing in climatology. The feedback is called positive when greater than zero (imagine that!).
Here is a correctly done example in which g=1, f=1/2 and F=1:
R = (1/(1-1/2))*1 = 2
which can otherwise be understood as starting with a response of 1 and then the feedback adds a half to that and then another half of half and so on. One has
1 + 1/2 + 1/4 + 1/8 + … = 2
And, by the way, you couldn’t have read the Wikipedia article very carefully, it is clear.
Comment by David B. Benson — 2 Nov 2010 @ 10:07 PM
Oh dear. I must learn to pause before submitting comment.
The feedback f is only constrained to be less than one; any negative amount is ok.
Comment by David B. Benson — 2 Nov 2010 @ 10:21 PM
Thank you. Bookmarked as thermodynamics to be read again and studied. I remember as Maxwell-Boltzmann from 46 years ago. How did Stefan replace Maxwell?
I think it’s worth another comment on the Lacis et al. paper in Science, and also the related Schmidt et al paper in JGR. They both tie very much into this post. I encourage everyone to read them (they are both pretty easy reads) here and here. I also summarized their results at here on my blog.
I agree with Ray Pierrehumbert that there is nothing physically “new” or inherently surprising in the results, but in science if you don’t write it down it doesn’t count. Thus far, there has been a very weak effort to partitition the greenhouse effect by the fractional contribution between H2O, CO2, etc, and also to detail the effects of a zero ppm CO2 experiment in terms of the collapse of the water vapor greenhouse effect. I’m not sure the detailed partitioning is a very interesting scientific question, but there’s a lot of nuances behind the structure of the greenhouse effect which are still not well appreciated outside of specific expertise.
The quantiative partitioning of the terrestrial greenhouse effect shows that the contribution between various agents to the longwave absorption in the atmosphere is about 50% due to water vapor, 25% to clouds, 20% to CO2, and the rest to ozone, methane, nitrous oxide, etc. Amongst other things, this puts to rest common fallacies which claim water vapor swamps the CO2 effect. A more important implication however is that several popular claims which still show up in basic textbooks or internet descriptions, such as “water vapor is the most important greenhouse gas” or “the greenhouse effect means the surface temperature is 33 K hotter than it would be” are missing out on key feedback processes that make the respective claims meaningless.
In particular, it is CO2 (and the other non-consensable gases at Earthlike conditions) which provide the supporting framework by which the condensable component of the greenhouse effect is allowed to operate. Removing the non-condensable gases and the corresponding temperaure reduction demands that you lose most of the water vapor effect as well, further lowering temperatures, and it also means the surface albedo grows to make the total planetary albedo well in excess of the modern day 30%. Neglecting the shortwave feedback effect from the “33 K difference” relative to the modern emission temperature actually underestimates how important the trace molecules are to the climate of the Earth.
CO2 is also the most readily available forcing agent to change both fast and of sufficient magnituide to matter. Solar changes are either too small or too slow. Changes in solar distribution (e.g., Milankovitch) are slow on anthropogenic timeframes, but can probably best be served as pacemakers of climate on glacial-interglacial timescales, losing resolution or importance on geologic timeframes (particularly in ice-absent climates); CO2 (particularly as a feedback via silicate weathering) modulates Earth’s temperature, yet one can still see snowball-like planets and PETM-like situations on the way, and even these events are intimately linked to the optical characteristics of the atmosphere. There’s no way to cut corners around the physical demands of atmospheric radiative transfer, or no reason to suspect human modulation to those physics will suddenly not matter.
“In 1872, Boltzmann …. wrote an equation …. today referred to as the Maxwell-Boltzmann distribution, since Maxwell had derived a similar equation.”
“Stefan-Boltzmann law … established experimentally by Jožef Stefan in 1879. Boltzmann, who was Stefan’s student, successfully derived the law from theoretical considerations in 1884.”
… “the foundations of classical statistical mechanics…. applicable to the many phenomena that do not require quantum statistics and provide a remarkable insight into the meaning of temperature.”
However in Sweden the “sceptics” managed to get in to one of the bigger newspapers saying it showed that climate sensitivity is 0.6 C. Now that is not what it say but anyway… I think it would be grate with a post on what this kind of studies could tell us about climate sensitivity and the problems with them.
Spencer, you are taking a literal engineering view about the issue of positive feedback.
Sure engineers learn about the meaning of positive and negative feedbacks in closed loop systems, that is hardly appropriate in this context.
Language is flexible and a term in one field of endeavour can have a different meaning in a different endeavour.
It is possible that since climate science uses the term, dictionaries need to be updated to reflect a modern use. Language evolves, so there should be no reason for an update.
How do we turn this into a positive feedback system? Simply change the sign of beta. Then: A’ = A/(1-beta.A)
Note that if beta.A is less than 1, we still get (in the ideal case) a stable amplifier whose output does not go to infinity, but whose gain is greater than amplifier without feedback. (In practice, A tends to vary from circuit to circuit, and introducing positive feedback just amplifies the differences, so we don’t do this.)
But this seems to me to be what the climate guys are talking about with positive feedbacks. You get a bigger change in the temperature than you would expect without the feedback, but you don’t get a runaway.
Spencer wrote in comment 13: Here let me show a case for you. Assume T0 = 0 and an input of one and 10% feedback
T1 = 0 input of 1
T2 = 1 input is now 1 + .1
T3 = 2.1 input is now 1 + .21
T4 = 3.21 input is now 1 + .321
That should have read:
Here let me show a case for you. Assume T0 = 0 and at T1 there is an input of one and 10% feedback
T0 = input of 0
T1 = 0 input of 1
T2 = 1 input is now 1 + 0.1 = 1.1
T3 = 2 input is now 1.1 + 0.01 = 1.11
T4 = 3 input is now 1.1 + 0.001 = 1.111
Tn = n input is now 10/9
Tn+1 n+1 input is now 10/9
#14 is incoherent anyway, due to ambiguous formatting–you can’t reliably distinguish between ‘waldo’ and ‘wally,’ for one thing. Moreover, the unattributed “he” abounds, meaning you often can’t tell if Gavin, McKittrick or for that matter, Santa Claus, is the intended subject. Possibly it makes some kind of sense if you have already read the papers referred to, but as it is it is practically undecipherable, IMO.
I have a question for Chris – is it correct to say (and this is based on a post by Lubos Motl) that if you expand Stefan’s Law, at 192K, the quadratic term is equal to the linear term. Therefore, (and this is my opinion), at up to 20K rise, the linear feedback relationship can still be used and since burning up all fossil fuels will not cause anywhere near that range of increase, the Zaliapin/Ghil result is more of an academic curiosity that prevents the blow-up to infinity?
18, Chris Colose: I think it’s worth another comment on the Lacis et al. paper in Science, and also the related Schmidt et al paper in JGR. They both tie very much into this post. I encourage everyone to read them (they are both pretty easy reads) here and here. I also summarized their results at here on my blog.
I agree with Ray Pierrehumbert that there is nothing physically “new” or inherently surprising in the results, but in science if you don’t write it down it doesn’t count.
That’s well worded. I may be off-topic in asking this, but does the model used in Lacis et al provide an estimate to the lag time (“thermal inertia”) in the atmosphere system? This question can be rephrased in different ways. How long before (90% of) the full temperature effect of the CO2 accumulation to date will be experienced? For a bolus of 100ppm (say), how long before the system reaches its steady state?
I am a bioengineer, studying algae sequestration of carbon with the University of Illinois.
This is the problem: dissolution of atmospheric carbon dioxide occurs at the interface of atmosphere and seawater, so the drop in alkalinity & pH is greatest closest to the interface. This is also where the bulk of photosynthesis and planktonic grazing occurs.
Research is showing that calcifying phytoplankton such as coccolithophores are being inhibited by the dissolution of carbon dioxide into this interface. These phytoplankton are the foundation of the ocean’s food web, and as they are impacted, so are other important species including antarctic krill. http://www.abc.net.au/news/stories/2010/10/13/3037651.htm
Dr. David (!) Archer seems to get this, he has a solid background in ocean biochemistry. I recommend his book “The Long Thaw” highly.
My primary concern at this time isn’t increasing temperatures but collapse of the food web in the oceans. If this happens, we better get used to eating jellyfish (a line stolen from a colleague of mine).
Re 30 (Septic Matthew), 32 (Hank Roberts), and thermal inertia. An important paper by Susan Solomon et al in last week’s PNAS explores this issue in some detail. Among the conclusions is that thermal inertia in the ocean becomes increasingly important as both the magnitude and the duration of a forcing increase, and can extend the temperature effects of a perturbation (e.g. a CO2 increase) for a very long interval after the perturbation itself has ended. The link is Persistence of Climate Change
32, Hank Roberts, If the modeling used by Lacis et al can provide the information that it provided (CO2 as control knob), it’s at least worth asking if it can provide the information that I asked for in my post.
33, Fred Moolton, thanks for the link, but I was requesting a quantitative estimate of the “time to steady state”, what in linear systems theory would be the “relaxation time” after a pulse input (but this is a question in non-linear systems theory, so analytical solutions are probably not available.)
Climate models display many interesting nonlinear phenomena …. the application of numerical techniques from dynamical systems theory (bifurcation analysis, attractor reconstruction, etc.) has shown to be very fruitful. In this symposium, we want to bring together experts on the numerical techniques used in the analysis of nonlinear dynamical systems and climate physicists….”
To continue. Figure 2 of Lacis et al (cited above) shows that, after zeroing out all non-condensing GHGs, the temperature has adjusted about 95% of the way toward its asymptotic value. Is that a reasonable estimate of the time to wait before 95% of the full effects of CO2 accumulation to date have occurred?
The Lacis paper looks like it runs a model out to year 50, achieving a drop in temperature of some 35 C in that time, but this can’t really be an equilibrium response and the paper doesn’t go into the detail required to interrogate Septic’s question thoroughly.
Isaac Held recently gave a talk in Wisconsin on the topic of how one could usefully decompose the evolution of the surface response to global warming by a fast component (which is proportional to the radiative forcing) and a slower component which reflects the response of the deep ocean. Right now, the response to increasing CO2 has been dominated by the fast component, with relatively small influence from the slow component (but which grows in time). This also emphasizes the utility of the transient climate response for timescales relevant to the 21st century. In fact, the two timescale components have different spatial structures (e.g., less relative warming in the Southern Ocean at first, and a reduction in the land-ocean warming ratio over the slower timescales); it follows that the changing relative magnitude of these two components actually introduces time-dependence into the strength of the climate sensitivity.
What’s more, forcings, even short-lived ones, have remnants that lurk in the climate system on long timescales. Signatures of Tambora or Pinatubo for example are still existent in the deep ocean. The literature on volcanic responses has been pretty weird about making this clear though (see e.g., Stenchikov et al 2009)
elspi @28 — Post in haste, repent at liesure. (Referring to my prior two back-to-back comment). Regarding the infinite series, it only converges in the open interval (-1,+1) as you state. However, read on.
earlier, I didn’t write down quite the right equation. For response R with forward (open loop) gain g, feedback f and forcing F, in the s-plane one has
R = Fg/(1-gf)
If g=1 then the formula is, of course, just
R = F/(1-f)
Now this equation is readily solved for any rational functions F and f, but only has physical significance when the roots lie in the right hand portion of the s-plane, including the imaginary axis as a limiting case. Stated more simply, f is bounded above by +1. But the feedback can be as negative as may be. For example, if f = -1000 then R is approximately 0.001F. The simple infinite summation doesn’t apply for f less than or equal to -1 and of course one can check everything in the time domain using convolution, but viewing this small point in the s-plane is much the easier.
Apologies to all for not having been more careful the first time around.
“… Until the new description of seawater is widely adopted, ocean models will continue to assume that the heat content of seawater is proportional to a particular temperature variable called ‘potential temperature’.
“The new description allows scientists to calculate the errors involved by using this approximation while also presenting a much more accurate measure of the heat content of seawater ….
“The difference is mostly less than 1 degree C at the sea surface, but it is important to correct for these biases in ocean models….”
[Response: This is an improvement in theory, but for it to be an improvement in practice needs all of the ocean codes to track carbonate and other ions as well as salt, which figure in the density equation. NB. the GISS-E-R model already uses enthalpy as the state variable and so had more-accurate-than-standard thermodynamics anyway. - gavin]
Isotopious @39 — I have been fiddling with a two resevoir (two box) model.
The first resevoir represents the atmosphere and that portion of the ocean, the upper few meters, which is at the “same” temperature as the bottom of the atmosphere just above it due to the mixing via wave action. Since I only have data with yearly averages available, I fix the time constant of the response of this resevoir to be one year.
The second resevoir represents the so-called mixed layer of the ocean, your nominally 700 meters. This resevoir has a characteristic time of 30 years as I am under the impression that is what happens in ModelE.
The parameter estimation program determines the sizes of these two resevoirs by best fit to GISTEMP using the annualized globalized total forcings from 1880 CE through 2003 CE available on the GISS website. The fit is quite impressive once a fraction of the SOI, with a 7 month lag, is subtracted from GISTEMP.
Yeah I have often heard a few meters of the surface ocean is equal to the entire atmosphere with respect to heat content, so the upper ocean (700m) has somewhere near a thousand times the heat content of the entire atmosphere (but I have no idea, this is a guess)… What I would like is a better estimation, since I have not been able to find it anywhere (I can only find anomalies which tell me nothing about the total).
Then of course we line up the heat content and compare them with each other.
The literature on volcanic responses has been pretty weird about making this clear though
Pretty weird? As in, not making it clear at all?
to others, I was referring to this paper, referenced earlier in the thread: Andrew A. Lacis, Gavin A. Schmidt, David Rind, and Reto A. Ruedy, 2010: Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature. Science 15 October 2010: 356-359.
In Figure 2 it looks like the temperature response to removal of greenhouse gases is 95% of the way to equilibrium after 20 years or so. I left the “after 2 years or so” out of my post that Chris Colose responded to. Sorry.
This thermodynamic law says that the saturation pressure increases nearly exponentially with temperature (1)
It is given in approximate form as
e(s,T)=A exp(-B/T) (2)
Also agreed. My quibble is that some people might incorrectly think you have said the same thing twice. (1) and (2) need to be reversed.
It would be clearer to have started with the approximation (2) (Boltzmann or Arrhenius) * and then stated that this behaves like a growing exponential over a limited range of T. This would make it clear that there are two approximations involved
(39) IIRC the specific heat of the atmosphere per unit mass is roughly the same as for water. A layer of water roughly 10M thick contains about as much mass as the atmosphere, therefore the thermal inertia of a 700M layer of water is circa seventy times that of the atmosphere. Of course we don’t just heat up the water uniforming as in raising a block of water 700Mdeep uniformly by 1C, the surface responds much quicker than the deeper layers.
I probably disagree with that statement. No time to check. Anyway it might be safer to regard them as different. From a modern standpoint, and on the theoretical side, Boltzmann never got as far as Planck’s law and SB is its integral.
> In Figure 2 it looks like the temperature response
> to removal of greenhouse gases
In the model, removed instantaneously, starting from pre-industrial level
> is 95% of the way to equilibrium
In the model, where it’s snowing, temperature falling, humidity dropping
> after 20 years or so
with zero greenhouse gases the equilibrium is below the freezing point of that “condensable greenhouse gas” water vapor — so that greenhouse gas also goes very low, and hello Slushball Earth
Earth reaches equilibrium far more slowly than that after greenhouse gases double from preindustrial rates. Not even close.
That isn’t how fast the world reaches a very different equilibrium after doubling greenhouse gases, either from natural (PETM) or human action.
Clarification. Boltzmann , the theorist did of course provide the underpinning to Stefan’s equation. But he did ordinary thermodynamics as well as statistical physics and he must have used the former not the latter otherwise he might have encountered the so called ultra-violet catastrophe which was solved by Planck. But I have not gone back to see how he did it.
For Harold Pierce: the NIR bands of water vapor and, to a lesser extent, CO2 are combination (excitation of multiple different vibrational modes simultaneously) and overtones (excitation of two or more quanta in a single mode) bands. They are very, very weak, and the average distance any photon goes before being absorbed is ~km, not the ~10m in the thermal IR. Still, there is a path length of several km in the atmosphere and thus when you look at the absorption of the solar spectrum you can clearly see these bands. Since the 300K radiation is essentially zilch in the NIR, the light that is absorbed is that from the sun
While light can be absorbed at these frequencies, the emission from the excited molecules remains completely in the thermal IR because the energy in the multiquantum excitation is rapidly converted to thermal motion of the surrounding atmosphere by collisions. Re excitation to anything but the lowest vibrational and rotational levels is energetically the only thing that occurs as a practical matter. So what this represents is a mechanism for converting sunlight to thermal IR in the atmosphere rather than at the surface and the greenhouse effect proceeds as usual.
Septic Matthew @53 — The deep ocean is vast so to actually reach something close to equilibrium requires on the order or a millennium and maybe a bit more. One of the papers on Dr. Hanson’s website has a graph of a long run of ModelE with the temperature still slightly increasins after 1300 model years following a 2xCO2 slug injection.
Comment by David B. Benson — 3 Nov 2010 @ 10:02 PM
56, David B. Benson. Thank you. I’ll seek out the paper.
“Keeling & Bacastow (1977) predicted that it would take at least 10,000 years for atmospheric CO2 to return to preindustrial levels. Walker & Kasting (1992) reached a similar conclusion but extended the duration of the long tail to hundreds of thousands of years. Broecker & Takahashi (1978) described the neutralization reaction with CaCO3. Many other carbon cycle models of a variety of configurations and resolutions have found the same result (Sundquist 1990, Caldeira & Kasting 1993, Archer 2005, Lenton & Britton 2006, Montenegro et al. 2007, Ridgwell & Hargreaves 2007, Tyrrell et al. 2007). The mean lifetime of the elevated CO2 concentration of the atmosphere resulting from fossil fuel combustion has been calculated to be tens of thousands of years (Archer et al. 1997), not at all similar to the 50- to 100-year lifetime calculated using the linear approximation based on fluxes immediately following a release of CO2 to the atmosphere. Clearly, the linear approximation, using a single characteristic timescale for the removal of CO2 from the atmosphere, is a poor representation of the way the carbon cycle works.”
“As the globe warms from anthropogenic forcing”
Do you mean that if the globe warms for other reasons, for instance sun irradiance variation, or GHG coming from other sources than human, the water vapor feedback should no longer be the strongest amplifier of global temperature change ?
(That is what your sentence strongly suggests).
[Response: No. Water vapour feedback is always the dominant feedback regardless of why the climate is changing. - gavin]
Comment by Pierre Allemand — 4 Nov 2010 @ 12:54 AM
Re #5 Harold Pierce.
What is the portion of water vapor transported directly from surface water by the mechanical force of the wind into the air as compared to simple evaporation?
Do you mean by the creation of small droplets which then evaporate? OR by the action of wind in removing the saturated water vapour close to the surface of the water. I should expect that the latter to be a major part of normal evaporation without being ‘simple’ as far as I know.
Iso 45: Yeah I have often heard a few meters of the surface ocean is equal to the entire atmosphere with respect to heat content, so the upper ocean (700m) has somewhere near a thousand times the heat content of the entire atmosphere (but I have no idea, this is a guess)… What I would like is a better estimation, since I have not been able to find it anywhere (I can only find anomalies which tell me nothing about the total).
BPL: Heat content H = m cp T where H is in Joules, mass m in kilograms, specific heat capacity at constant pressure cp is in K/J/kg, and temperature T is in kelvins.
For the atmosphere, m = 5.14e18 kg, cp = 1007 K/J/kg, T = 250 K (on average), so H = 1.29e24 Joules.
For the ocean, the mass of the upper layer m = A d rho where A is the ocean’s area (5.10e14 square meters x 0.708 = 3.61e14 square meters), d is the depth in meters, and rho the density in kg/m^3. Seawater cp is about 3,900 J/K/kg (less than the freshwater value of 4184 due to impurities). Seawater rho is about 1,025 kg/m^3. T is about 289 K at the surface. So the top 1 m has H = 4.17e23 J. The equivalent depth for the same heat content as the atmosphere would then be 3.1 meters.
Anyone: I have a detailed question/clarification from the post (actually Hansen’s referenced article) which says,
“For f = 3-4 the response time of the surface temperature to a heating perturbation is of order 100 years, if the perturbation is sufficiently small that it does not alter the rate of heat exchange with the deeper ocean.
The climate sensitivity we have inferred is larger than that stated in the Carbon Dioxide Assessment Committee report (CDAC, 1983). Their result is based on the empirical temperature increase in the past 130 years, but their analysis did not account for the dependence of the ocean response time on climate sensitivity. Their choice of a fixed 15 year response time biased their result to low sensitivities.
I read this to say that some of the heat (and temperature) added to the atmosphere (presumably not including the non-radiative heat added from the sea) will eventually transfer to the sea as it moves toward surface level equilibrium, and 63% (e^-1 factor) of the total of that some will transfer to the sea in 100 years. Am I reading this correctly?
What I was really wanted to know is if NIR goes thru water droplets in clouds. Even tho these absorptions are weak the conc of water is ca 1000x the gas phase.
ATTN: Geoff @ 60
When wind sweeps across water, the water vapor just above the liquid will be swept into the air but the surface will cool. The wind molecules and atoms have tremendous momentum that can be transferred to the light water molecules by collision., i.e., these molecules are like “molecular sandbasters” and strong winds from a hurricane can blow land structures to bits.
An everyday example is the use of commpressed air to clean surfaces materials. In the same way the wind can “clean” the surface by removing water molecules by mechanical action.
Consider a rack of pool balls as liquid water and the cue ball as an argon atom (at. wt. = 39 g/mole vs OH2, FW = 18 g/mole.). On the break. the stongly struck cue ball causes the balls to scatter all over the table.
Comment by Harold Pierce Jr — 4 Nov 2010 @ 1:46 PM
Hank, depending how they are counted, my reference is given in the 5th (?) paragraph of this post by Colose. My quote is in the 3rd and 2nd para. from the end of the Hansen, et al paper (actually the summary). The full paper I think is the same that you list. I’m looking for just a yes or no to my question #62. If “no”, unless the explanation is very simple (which I would appreciate), I can do further digging.
BPL @61 I was going to question your use of Cp for the change in heat to warm the atmosphere, but I came up with a simple argument in the following case:
(1) The gas is a perfect gas, i.e. the kinetic energy is 3/2kT.
(2) The gravitaional field is uniform.
(3) The temperature is uniform.
Then the scale height is kT(g/m) (where g is gravitational field and m is the molecular mass).
So this yields an energy partition of 1kT gravitational potential energy per molecule, and 3/2kT for the kinetic energy, which is the same as the perfect gas heat capacity 95/2kT.
I don’t know how to generalize this to non-perfect case, and variable temperature (but a uniform change with temperature, and multi-species etc. but I am convinced it will generalize.
Perhaps the argument about winds and evaporation is more relevant to the hurricane situation. At some windspeed/sea state the lower layers of the atmosphere/upper layer of the sea becomes a sort of wind whipped foam. Supposedly the evaporation rate goes up significantly. I think this is what lets hurricanes get so strong, as the evaporation rate is no longer limited by a small sea surface area, but has the huge area of the foam region to work with.
Still a little unclear. Are you suggesting a new mechanism or reporting on an exotic one which we should know about? i.e. “forced evaporation” say. If so we should need see (a) some calculations (b) some experiments.
As for (a), the height of the energy barrier which a liquid molecule needs to achieve in order to escape can probably be estimated from the value of the constant B in the lead article above (approximate version of Clausius Clapeyron). You could start by comparing the typical energy received by a collision between an individual liquid molecule and one in the blast of wind.
But that might be far too simple.
Help! Hope this is not too OT, but I’m in this environmental anthropology listserve discussion (with hundreds of participants) & this came up — the ideas of David Routledge — see http://rutledge.caltech.edu/ (esp slide 49 of the PowerPoint).
Seems to me he’s leaving out all the feedbacks — including albedo & methane/carbon from melting permafrost and hydrates.
Also (but what do I know) is he using the log function in a mistaken way (slide 48)? Seems there was something about that on RealClimate some time ago.
No, I don’t think he’s leaving out feedbacks. The slides seem to imply that he’s going with the IPCC projection of 3C per doubling of CO2.
His point seems to be (I just went through it very quickly) that production will peak and reserves will run out, and therefore CO2 levels will never get high enough to reach 2C, and temperatures will begin to fall after 2064.
He also seems to think that CO2 emissions won’t grow substantially beyond today.
I think the key slide is #38.
I’ll leave it to others to discuss the veracity of (or holes in) his claims.
Lynn Vincentnathan now @70 — Professor Rutledge (note the spelling) appears to know what he is about although his conclusions are certainly at variance with others who have looked into the question of fossil carbon depletion. I am uncertain whether he has recently considered unconventional sources such as tar sands but when I read his article a few years ago he had not. Dr. Hanson (possibly with others) has written on just that matter; the paper(s) are available from his website.
I have looked at the question of what we can expect based on both conventional and unconventional fossil fuels. The conventional fuels (oil, natural gas, coal) could take us as high as 700-800 ppmv, while the unconventional (tar sands, oil shale, etc.) could take us as high as 1000-1200 ppmv. So we’re looking at something a bit over 2 doublings–most likely 6 degrees by century’s end. Rutledge is ignoring not just unconventional fuels, but exponential growth in energy demand.
What is more, if fossil fuels were so finite, it would be all the more essential to develop alternative energy–just as it is to combat climate change.
Lynn and Bob,
There may be some confusion. Lynn talked about carbon feedbacks which can of course not be included in sensitivity so Rutledge may be using the standard 3C/doubling while ignoring the carbon feedbacks (emissions from permafrost melt and so on) as well as the slow feedbacks such as the albedo change from the shrikage of ice-sheets (not sea ice) which are (so far as I know) poorly quantified and not included in the regular definition of sensitivity.
Comment by Anonymous Coward — 5 Nov 2010 @ 8:35 PM
Re: raypierre’s reply to my comment (#3)
Excuse me for digressing into a non-scientific issue of spelling of name of persons. “si” vs. “shi” is a problem of multiple transliteration systems of the Japanese language. Simply speaking, both are correct expressions of the same Japanese sound. It seems that majority of Japanese who write their names in English use “shi”. Users of “si” were not so few in the middle 20th century among physical scientists. Syukuro Manabe, who was a classmate of Makoto Komabayasi, and Sigekata Syono, the professor of meteorology who taught them, were among them. I notice that many Japanese scientists refer to “M. Komabayashi”, and we need to tolerate this kind of variability.
Great post. However, you seem to assert that a runaway greenhouse effect will only occur in the far distant future, and will not happen due to anthropogenic activities. This is in contrast to Jim Hansen, who believes that a runaway greenhouse effect is not only possible, but almost certain if we burn all the coal & oil (especially that locked up in the tar sands and tar shale):
Is there any recent peer-reviewed literature that tackles this question, taking into account Hansen’s fears regarding slow feedbacks and the unprecedented rate at which we’re burning fossil fuels (plus a possible massive methane hydrate outgassing)? If not, it could be worth a future posting to remind us about the arguments for and against a runaway greenhouse on earth.
Hank, thanks. Sounds reasonable. I take it to mean that of the total potential heat transferable from the atmosphere to the ocean, about 63% is expected to actually transfer within 10-20 years, or a few hundred years, or within some time in between.
> I take it to mean … 63% …
> within 10-20 years, or a few hundred years,
Maybe more than half and less than all;
More than ten years, less than a thousand years.
It’s fudge to attribute your precise numbers to an _old_ paper
It’s a paper about _uncertainty_.
You can look up citing papers to see what’s new since the 1980s.
I say it’s herring.
Dear “Septic”: thank you for pointing out what we know already.
Clouds are probably the biggest source of uncertainty in predicting climate change. But even taking that uncertainty into account, we can still produce effective models. It will be nice to reduce that uncertainty, but you keep implying in a really unsubtle way that clouds will overturn established science – and that’s just your own private fantasy.
But don’t rely on me waffling on. Try actually reading the source you linked to:
The IPCC reported in 2007 that it projects the Earth’s average temperature to be about 1.8 to 4 degrees Celsius higher by the end of the century than it was in 1900–a rapid rate of increase compared to observed rates of increase in the Earth’s recent history. Scientists could probably narrow down the Earth’s projected temperature range further if they better understood the relationships between clouds and climate as well as other factors, such as the amount of greenhouse gases that will be pumped into the atmosphere by 2100.
“Given the estimated size of fossil fuel reservoirs (figure 6b), the chief implication is that we, humanity, cannot release to the atmosphere all, or even most, fossil fuel CO2. To do so would guarantee dramatic climate change, yielding a different planet than the one on which civilization developed and for which extensive physical infrastructure has been built.
Estimated oil and gas reservoirs (figure 6b), with only modest further use of coal, are sufficient to bring atmospheric CO2 to approximately 450–475 ppm limit of the alternative scenario (Kharecha & Hansen 2007). Given the convenience of liquid and gas fuels, it seems likely that readily available oil and gas reservoirs will be exploited. Thus, attainment of the alternative scenario implies the need to phase out coal use, except where the CO2 is captured and sequestered, and to impose the same constraint on development of unconventional fossil fuels.”
Could I suggest a couple of minor improvements:
(a) The quantity lambda is the inverse of the derivative of the Stefan-Boltzmann law, at least if you assume the usual form, radiation proportional to the fourth power of absolute temperature (the text reads as if lambda is the derivative).
(b) Figure (2) would be much more comprehensible if you pointed out that the a’s are the coefficients of quadratic non-linearities, e.g. a caption to the effect that Figure 2 shows the behavior of linear feedback moderated by a quadratic non-linearity. The a=0 curve corresponds to the linear theory.
Zaliapin and Ghil’s equation 9 might be a useful addition
Zaliapin and Ghil seem to be arguing that linear feed-back is inappropriate, and that the rapid changes of sensitivity near f=1 result from a flawed analysis. Their non-linear theory places the earth’s climate close to a bifurcation point, and the climate sensitivity is then very sensitive to exact location (Their figure 5).
I’d appreciate some expert comment on this.
Hank: To be clear, I was talking about initiating a runaway greenhouse if we burned all the fossil fuels
Dave (86): I hope raypierre can chime in on this since we had some private exchange on the f=1 limit prior to this being published, but a key point I believe is that it corresponds to a bifurcation (between stable/unstable states) rather than a runaway. The system can equilibriate to a new (hotter, for a positive radiative forcing) state if the OLR rises with T on the other side of the bifurcation point, although information is lost at the bifurcation on precisely where this equilibrium point is.
[Response: This is getting pretty esoteric, but the 'bifurcation' stuff has it's own critics, notably Roe and Baker who've written a commentary on this, which I think is published. I'll look it up and post it here.--eric]
[Response: I don't think it's esoteric. It's very basic stuff -- no more than realizing that linearization is only the first term in a Taylor series. When f=1, that doesn't tell you that you get a runaway. It only tells you that you need more terms in the series to see what happens. It also means that you can't tell what lies beyond f=1 by any local analysis. The misunderstanding of f=1 is one of the many points the original Roe and Baker article was confused about. I'm giving plenary address on bifurcation and climate sensitivity at the S.I.A.M Snowbird meeting in the Spring, and perhaps as a run-up to that I'll do an RC primer on bifurcations. On the matter of the runaway greenhouse, the main reason CO2 can't generally trigger a runaway is that you need a certain threshold absorbed solar radiation to sustain a runaway, which is determined ultimately by water vapor opacity alone, which dominates in a true runaway state because it gets so hot that water vapor is most of the atmosphere. Adding CO2 doesn't significantly change the amount of solar absorption. There is one exotic case (explained in Chapter 4 of my book, on sale December, available for pre-order now!) in which you have enough solar absorption for a runaway, but there's a "barrier" between a stable climate state and the runaway state. This can happen when you have a mixture of N2 and water vapor, for example. Adding CO2 can eliminate the barrier and trigger the runaway. But you still need to exceed the threshold solar absorption to get the runaway and the Earth is in an orbit where it's safe from that. BIG CAVEAT: This is all based on clear-sky physics. The net effect of clouds on the runaway threshold is a BIG QUESTION (tm). Another thing I will discuss in the S.I.A.M. talk. --raypierre]
Hansen’s claim regarding the possibility of a runaway H2O greenhouse at the current stage of our star’s evolution. We have requested several times the RC staff to state whether we can safely summarily dismiss these claims (as I suspect we can). Hansen’s stature makes this more difficult than it should be I think. This is the first frank response I’ve read from anyone who writes RC articles. Thank you Chris!
Comment by Anonymous Coward — 6 Nov 2010 @ 8:01 PM
The lack of evidence means you can’t summarily dismiss, this not being a court of law.
Hansen in that book review linked above is quoted saying there isn’t enough evidence available to make a scientific conclusion, and then as stating his personal opinion that it’s possible if every bit of carbon is burned fast.
Those aren’t inconsistent statements.
I recall — vaguely — one paper, some decades ago, that suggested the upper atmosphere could lose enough hydrogen, removing water from the biosphere, to cause a runaway.
But this is a “what’s the worst thing you can imagine” question, not something about which you get people writing much in the journals.
It would be really, really stupid to burn all the carbon fast.
It would be stupid to do it as fuel.
It would be stupid to allow big asteroid strikes.
It would be stupid in any imaginable way.
You can be sure it would set off a methane clathrate event.
You can be sure the oceans would go anoxic.
Those things have happened before.
Earth has recovered.
Burn all the carbon?
Forget whether you end up with — or without — a Venus result.
Even the least worst result wastes a good planet for the foreseeable future.
ON MODELING AND INTERPRETING THE ECONOMICS OF CATASTROPHIC CLIMATE CHANGE
Martin L. Weitzman*
With climate change as prototype example, this paper analyzes the implications of structural uncertainty for the economics of low- probability, high-impact catastrophes…. the economic consequences of fat-tailed structural uncertainty (along with unsureness about high-temperature damages) can readily outweigh the effects of discounting in climate-change policy analysis.
Mentioned at RC before http://www.google.com/search?q=site%3Arealclimate.org+Weitzman
Hansen’s narrative in his book Storms of My Grandchildren (2009) does suggest that burning all coal may result in a runaway greenhouse situation somewhat like Venus. But I did not find his estimate of probability of its occurrence. I understand that the scenario was mentioned as precaution rather than projection. I know that we can only tell a subjective order-of-magnitude guess about the probability. But I thought just such a thing is necessary in order to use it as a piece of science-based discussion. I might have failed to catch some of his words. Also, I had just read Stephen Schneider’s Science as Contact Sport, so I might be too harsh as an “uncertainty cop”.
On the other hand, the quotation by Hank Roberts (#85) from the article by Hansen et al. (2007) in Philosophical Transactions of the Royal Society, “dramatic climate change, yielding a different planet than the one on which civilization developed…” does not necessary mean the runaway greenhouse situation (which, I suppose, that all the ocean eventually evaporates).
I think that the state without continental ice sheets (even in East Antarctica) and the present state are different regimes of the planetary climate. (I remember some geologists call them hothouse and icehouse regimes though I do not remember an exact quotation.) And I subjectively think that probability that fossil fuel combustion triggers a transition to another regime with no return is not negligible, though I think that the transition must take many thousands of years. I guess (just guess) that the reviewers of the Phil. Trans. article interpreted the paragraph in question like that, rather than complete loss of the ocean.
Since people have been curious about Hansen’s statements…
To be fair, quite a lot of uncertainty exists in precisely what conditions get you across the SKI limit, particularly with cloud feedbacks in a moist atmosphere (to which virtually nothing is known). But there’s work that concludes that it is rather insensitive to the CO2 concentration of the atmosphere. In fact, Kasting and Ackerman (1986) show that at some 100 bars of CO2 in the atmosphere, the surface temperature, although at several hundred degrees C, is not in a “runaway greenhouse point” (i.e., liquid water is still stable at the surface). The oceans provide a couple hundred bars of atmosphere-equivalent vapor, and in the limit of strong water vapor feedback can dilute any other infrared absorbing components. You can make CO2 more important by throwing several hundred bars of it in the air, or making the oceans smaller, but now I think we’re just getting academic rather than the plausibility of “burning all the coal.” Kasting (1988) describe the runaway greenhouse in good detail.
Another very important constraint in the types of climates of this sort is that at very high greenhouse content, Rayleigh scattering in a high CO2 atmosphere is sufficient to cause a very high albedo and act as a constraint to even further higher temperatures. For example, without the sulfur clouds, the albedo from CO2 in the Venusian atmosphere would be about 40%, which isn’t quite the ~70% it is now but it’s still high. In fact, in some domains it is even plausible to decrease the surface temperature by adding CO2; in regimes where CO2 is a rather ineffective greenhouse gas you can increase the surface pressure more rapidly than you increase the saturation vapor pressure, drying regions of the upper atmosphere of water vapor. Note that while I said the inner edge of the astrophysical “habitable zone” is set by the runaway greenhouse effect, the outer edge is constrained by the fact that eventually you can’t really increase the greenhouse effect anymore since your gas will just condense at super high pressure (and you’ll have a pretty good albedo cooling effect).
It looks like Dr. Pierrehumbert’s inline response beat my comment…hopefully it is still useful
I really do want to make the point though, only for the sake of how easy it is to be misrepresented in “disagreeing with Hansen” or “CO2 isn’t important!” that this is a bit esoteric in the sense that we’re well outside the domain of modern Earth-like conditions, to which dhogza’s simple point that “several degrees celsius warming is quite likely in the next several decades is more than enough reason to take action” is right on target.
It’s still fun to talk about, and it is important to people working on other planets, the evolution of climates, and presumably as astronomers continue to find new planets on a rapid basis (particularly in the habitable zone, as one or two planets may be in the Gliese system), conversations of this sort of “exotic cases” can be very relevant.
What Ray wrote above, we could already gather from his articles and the excellent draft of his book. It’s nice to have it confirmed in so many words though.
The question of whether there is any evidence for Hansen’s claims is different. There is good reason to believe a runaway can’t happen (see Ray’s comment plus the evidence for a hotter climate in the relatively recent geological record). But we don’t know (well, I don’t) what evidence if any Hansen is basing his opinion on. What hypothetical mechanism would bring about a runaway to begin with? If there is any evidence (and I mean ANY), we need to know about it. If there isn’t any evidence for a possible runaway the balance of evidence would weigh so heavily in the other direction that we can safely dismiss the threat I think.
How would you do risk assessment, Hank, if not based on evidence? The personal opinion of experts is only sufficient when the experts are unbiased and there is a broad consensus among them. Of course it would be rational for humanity not to burn all the fossil fuels based on current expert opinion and known evidence. But there is no world government. The issue at hand is: absent a global consensus on the issue, would it be rational for states who have the means to do so or even non-state actors to take the matter into their own hands. The existential threat a possible runaway greenhouse constitutes is relevant to that determination I think.
Comment by Anonymous Coward — 7 Nov 2010 @ 5:24 AM
Y’all posting as ‘anonymous coward’ — why don’t you get a name or a consistent pseudonym? Otherwise we can’t tell if you’re just ignoring the FAQs and the suggestions on what to read, or if it’s some new AC each time asking the same FAQs. You can look this stuff up. Don’t bother people with the simple questions you can find for yourself.
Don’t be so paranoid, Hank. This isn’t the first time you’ve imagined things…
“Anonymous Coward” is just as good as “Hank Roberts”. And there’s only one of us.
Comment by Anonymous Coward — 7 Nov 2010 @ 12:38 PM
Since this post is about feedbacks, here is some grist to chew on – a draft of a paper submitted to JGR by Lindzen and Choi in order to update their 2009 GRL paper. They claim that this new, corrected version yields the same result – a low value for climate sensitivity. The link is Lindzen-Choi-2010
The paper hasn’t been published (perhaps not even accepted yet), so we may not hear much in the way of official responsess from others, but it’s worth reviewing as a way of refining our own perspectives. In my view, the draft improves on the 2009 version, but still has problems. I don’t believe that extrapolation from the tropics to the global climate is yet adequately addressed. I also have questions about judging long-wave feedbacks only after a one-month lag following temperature changes originating in the ocean (probably mainly ENSO events). That interval was chosen simply because of a high correlation coefficient – is that the best way to judge when a feedback is strongest? Does it make sense to assess LW feedbacks at one month and SW at 3 months, or is this a form of cherry-picking? Is one month nearly adequate to ascertain the full effect of feedbacks that may begin to operate on longer timescales? Does the choice of a no-feedback sensitivity parameter Go based on global data justify its use for tropical data when the relationship of forcing to temperature change in the tropics differs from the global average? Is it reasonable to assume a parallel between the feedback responses observed from ocean warming imposed on an unwarmed atmosphere and those expected from the effects of a warmed atmosphere imposed on a previously unwarmed ocean (e.g., effects due to GHG forcing)? Certainly, the immediate changes in relative humidity, clouds, and lapse rates might differ. These are some of the questions that might be considered.
Re 95 -
“The existential threat a possible runaway greenhouse constitutes is relevant to that determination I think.”
I don’t think you need to go that far to find an existential threat.
It is possible to construct a scenario with many little runaways – a scenario where the equilibrium climate lurches to warmer and warmer states, with finite sensitivity in between steps. In particular if we are not talking about Charney sensitivity but instead sensitivity to anthropogenic emissions, where biogeochemical feedback is included – suppose you get to a certain point and then one place releases all it’s CH4, and then stops, and then you get warmer and get to another point where some other place releases a bunch of CH4, and then stops, etc. Not that this is what will happen, it’s just a physically interesting scenario, not necessarily much worse (depending on the number and size of steps) than a steadier release of CH4 … of course, if the steps are more than a few years apart than the effect of each CH4 release decays and can’t add so much to the next, though if it is a net removal of C from soil/etc, then you’ve still got a CO2 feedback…
Runaway also happens in reverse. If the Earth ever was in a runaway state it would have been at the beginning – well, around that time, for example, after the Moon-forming impact. At some point in the cooling process, the escape of geothermal heat + solar heating would not be able to sustain the amount of H2O vapor in the atmosphere, but once condensation starts, it’s still runaway – but it’s runaway cooling because the OLR stays constant and is less than the solar+geothermal heating, so cooling must continue until the temperature exits runaway territory.
If it ever got so cold that a large amount of CO2 would form dry ice clouds, then the albedo effect of those clouds could (depending on insolation) make it difficult for geological outgassing of CO2 to ever end a snowball state; *HOWEVER*, those dry ice clouds have a greenhouse effect as well (in this case, via scattering, which in general can be very potent, as it can actually bring OLR down to near zero (at least for whatever part of the spectrum is involved; I don’t know the details) if the clouds are thick enough (depends on single scatter albedo and how thick could dry ice clouds get relative to the gaseous optical thickness; I’d guess probably hard to actually get OLR down near zero near 15 microns (unless the T is low enough anyway)? since a certain amount of gaseous CO2 must remain especially at low pressures in the upper atmosphere; the dry ice cloud scattering would probably have a different spectrum than CO2 gas absorption, though… etc.))
Lindzen really, really has to tap-dance a lot to push his faith in a low climate sensitivity. Similarly, the stuff by Spencer with “internal radiative forcing” is just not convincing to anyone. The new thing now is that the IRIS hypothesis caused tremendous amounts of high clouds in the early Earth, to offset the faint young sun. Seems like magic rather than physics.
Reading this document reads very much like a talk Lindzen gives in front of lay people– like “This amount of warming is not considered catastrophic, and, more importantly…” or “the fact that these feedbacks are strongly positive in most models is considered to be a significant indication that the result has to be basically correct. Methodologically, this is an unsatisfactory approach to such an important issue.” In general I think it’s starting to get tedious to continue to respond to this stuff time after time, and many of the issues pointed out by Trenberth I don’t consider to be just “mistakes” rather than a clear indication of why people just don’t believe his stuff.
Maybe others will comment on this new paper, and I might get a bit more interested if it gets published, but I just don’t see this type of stuff as robust. I personally think the the sensitivity estimates inferred from satellite is a dicey approach, and there’s still a lot of room for specific data point dependence and judgment calls (like introducing a factor of “2″ in one of the equations to share the tropical feedbacks over the whole globe). I’m sorry but I find the many lines of evidence from observational and paleoclimate studies (see Knutti and Hegerl, 2008) much more convincing, and if people want to show evidence for a low sensitivity they really need to convince me how Earth’s climate has been prone to the type of change it has experienced.
And to be blunt, this person is going to need to be someone else than Lindzen. I can’t reproduce everything he has done on my own, but I really don’t believe stuff he says anymore. You may find this unreasonable, but that’s my take…
To Chris (102). I thoroughly agree with you that multiple sources of evidence converge to indicate that climate sensitivity (to atmospheric perturbations from CO2 at least) significantly exceeds the no-feedback response because of positive feedbacks. To me, that is not the issue with Lindzen-Choi 2010 (LC10). Rather, I believe it would enhance my understanding of climate dynamics and the reliability and implications of observational data if I could clearly define why I can justifiably judge LC10 to be invalid. In that sense, I see LC10 as a learning opportunity. Secondarily, I see it as a challenge in the sense that its widespread circulation in draft form has presumably been designed to reinforce contrarian arguments, and so refuting it (if it deserves to be refuted) will be a step toward maintaining an accurate perspective on climate change within the blogosphere.
I’ve suggested above some reasons for questioning the validity of LC10 as a basis for concluding that long-term sensitivity to perturbations arising in the atmosphere exhibit low climate sensitivity when applied globally. I remain interested in whether my perceptions are accurate, and/or whether other considerations are more important. I also understand that the accuracy of observational data is an issue, but I would feel uncomfortable if inaccurate data are the only items standing between LC10 and reality. Since this is an area where you are very knowledgeable, maybe you can devote some additional attention to the paper when you get a chance.
Addendum to my comment 105 – To Chris and others. I was intrigued enough to look up some literature, which indicates that a strongly elevated OLR has commonly been associated with El Ninos, and has been attributed to the anomalously strong deep convection observed regionally with this phenomenon. The failure of models to simulate this pattern has also been reported on more than one occasion, and so LC10 are reporting nothing new in this regard. I interpret all this to confirm the conclusion that short term feedbacks originating regionally from perturbations within the ocean will bear no necessary similarity to long term feedbacks operating globally as a result of atmospheric forcings such as increases in CO2.
[Response: In defense of Hansen and the runaway greenhouse issue, I should say that many people seem to use "runaway" in a loose sense to refer to a broader range of positive feedbacks that bring the Earth to a very warm state, even if not into a Venus-type runaway (which may not even have really happened on Venus). For example, the PETM warming could be considered a "carbon cycle runaway" involving oxidation of a lot of near-surface organic carbon. That's not something we can rule out for our own future. In Hansen's AGU plenary talk a few years back, it did seem that he was referring to a Venus type runaway, but in other writings this is less clear. I myself think that the term "runaway" should be reserved for situations where the KI limit is exceeded, since that is precise and accepted usage.]
Chris and Fred,
regarding the LC10 paper, does assessing LW at one month and SW at three months influnce the results? I cannot tell from the paper. I do not see any “inaccurate” data in this paper, just the way that it is analyzed.
I cannot say that I agree that short-term oceanic feedbacks will bear no similarity to long-term global feedbacks. I would expect to see a strong influence, even if it remains as perturbations on the long-term.
One positive out of the paper is the attempt to correlate theory with data. Too many papers fail to correlate climate theory or models with climate data.
Oceans are very deep. The heat travels from the upper warmer body to the deeper cooler body and that just keeps on going. Now, when heat capacity is met heat does transfer to the atmosphere (convection) but various types of clouds form and not just those that lead to a positive net warming either.In this process too heat leaves the planet as well. It is very unconvincing that so much warming can happen when in fact in accordance with physics it is global heating and not warming.
You cannot have a runaway with all of the buffering on this planet; sorry.
[Response: Most of us do not want there to be any chance of a runaway, so I'm not sure what you're sorry about. No doubt Pielke Jr., and maybe Judy Curry, would think I'm making a value judgement outside my purview as a scientist when I say I think it would be a bad thing for the Earth to turn into Venus, but I'm willing to go out on a limb and say that anyway. But anyway, you should keep the science straight. The "buffering" has nothing to do with the runaway issue. It's the lack of sufficient solar radiation to sustain a runaway. --raypierre]
Dan H (110) and Rocco (111) – first, the links to the paper don’t always work, but at present, the link I used in comment #100 seems to work.
Dan H – The choice of one month and three month lag intervals completely determines the conclusions as can be seen from figure 7. Other choices could have converted negative feedbacks into positive ones. The choice was justified on the strength of the correlation coefficient R, but this is inadequate justification, and so the conclusions must remain tentative, even for climate sensitivity over these short intervals. They have almost no relevance for long term effects. As to whether one can reliably translate climate sensitivity derived from ENSO events (regional warming or cooling starting in the ocean and affecting an atmosphere that had not undergone a temperature alteration) into climate sensitivity involving CO2-mediated global temperature changes starting in the atmosphere and imposed on a previously unwarmed ocean, the answer is simple – you can’t. Each will predictably differ in terms of relative humidity, convection, cloud formation, precipitation, and global effects, and so similarities would be coincidental.
Rocco – LC10 did address the AMIP/CMIP issue, defending the comparisons with AMIP because according to the authors, that allows SST changes to be isolated for study. Whether that’s true of not, it is already known that the models simulate ENSO events poorly. It is also known that strong El Ninos are likely to generate strong increases in OLR, consistent with a negative feedback, and LC10 simply confirms this (compare Figs 2 and 3 in regard to the 1998 El Nino). In essence, the paper says very little that is new about ENSO events, and while it may therefore be justified, despite its flaws, in attributing a low climate sensitivity to ENSO changes, the attempt to draw conclusions about climate sensitivity to CO2 is unsustainable. If the paper is eventually accepted for publication, I expect that the journal will compel the authors to delete dogmatic claims about CO2 and focus mainly on the short term responses of the climate system to perturbations arising in the ocean.
I know this is a bit off topic by If I may insert a rare comment into the proceedings…
As usual the discussion here is fascinating and informative. And the participation in it is way too small. I’m hoping, as the new House of Representatives opens hearings on climate change in an effort to discredit climate science and its scientists the tables will be turned on the benighted ones as you use the opportunity to educate the public about the true nature of the threat.
You guys are smarter than they are. You should never waste an opportunity to be heard. These hearing could be a good thing if you play your cards right. It may well turn out that as the denialists are revealed as wasting taxpayer money on moot points we’ll wish you had _more_ time to explain the nature of what shortsighted thinking will do to everyone’s children.
Comment by David B. Benson — 10 Nov 2010 @ 8:32 PM
Underwater Suspension Tunnels solve all of the above problems!
If placed in the gulfstream there are two phases of operation. Cooling and Non- Cooling phase. In cooling phase it upwells cooler water to the surface to regulate Sea Surface temps anywhere between 70 and 90 degrees to the nearest 1/10 of a degree while generating enormous amounts of hydro electrical power from the Kinetic Energy in the gulfstream current. In non-cooling phase just the warm water flows through it but it still generates the electrical power. They actually regulate climate.
Tim Jones: this may be more appropriate to the “narrative” thread, but…. no matter how effective the experts testimony to congress is, Fox and Friends will not report it in that light. The divide will remain.
Here in the UK the tabloids are completely without conscience, and I expect them to swing from one extreme to another quite a few more times before we actually end up in a climate catastrophe.
If I understand this correctly – man made emissions of CO2 (doubling sometime during the course of the next century) will result in a forcing which equates to around a 1.2C increase in temperature and this will cause a positive feedback to increase the temperature further.
But hasn’t the temperature of the earth been 1C higher than normal many times in the pass? Why did we not see the affects a this positive feedback then?
Surely if the dominant climate feedback is positive that the earth’s climate would vary widely which is inconsistent with the historical record? Given the relative stability we have actually seen this would indicate the opposite affect?
[Response: Past climate has varied wildly - you go from a Neo-proterozic snowball earth to a hothouse Cretaceous with no ice at all. Not sure I understand your point. - gavin]
Huge, sudden swings in temperature from initial forcings an order of magnitude smaller than that from GHGs. Eyeballing the graphs, it looks like 14F changes in a couple of thousand years. I really want to stress the “sudden” in that description. Geologically speaking, the change happens in the blink of an eye. In some of those graphs, the change from the lowest trough of glaciation to the peak temp is almost vertical to the axis. When the climate changes, it doesn’t dilly-dally.
To Neil (123) – The nature of your question wasn’t completely clear to me, but I think I know what you were getting at. You were asking why earlier changes in forcing didn’t trigger positive feedbacks that would have caused the climate to become completely unstable, when it fact, it wasn’t.
Part of the answer, as already provided by others, is that the climate has in fact experienced wide swings in the past, but not a “runaway” in the sense sometimes hypothesized for Venus. In that sense, we can say that stabilizing influences did ultimately prevail. However, it’s important to realize that “positive feedback” in the lexicon of climatology refers to a magnification by feedbacks of the effects of an initial temperature perturbation. Without “feedback” in that sense of the word, the climate would stabilize at a higher temperature for CO2 doubling estimated as a 1.2 C increment. When positive feedbacks exceed negative feedbacks, the increment is larger. However, at whatever level the temperature rises to, stabilization is reached through the so-called Planck response, which merely states that a body that has absorbed more heat also radiates more heat (and other electromagnetic radiation), so that extra heat absorbed is eventually balanced by heat emitted. The confusion arises from the fact that the Planck response is not always referred to as a feedback, although technically it is the negative feedback that always suffices to restore a balance between incoming and outgoing energy. If the Planck response is included within the term “feedbacks”, net climate feedbacks are always negative. A “runaway” climate would be an exception, but conditions for runaway don’t currently exist on planet Earth.
I took the time to read Hansen’s Chapter 10 in ‘Storms of my Grandchildren’ which was published last year. It is titled ‘The Venus Syndrome’, and he is indeed talking about a runaway sufficient to autoclave the surface of the Earth. He runs through several lines of evidence. You might be interested in reading it. It is presently not checked out of your library. http://www.lib.uchicago.edu/e/index.html
Thanks you Gavin, Jeffrey and Fred for your responses to my post.
To clarify the question I was asking a little more . . .
We know that we get a forcing of 1.2C which will cause global temperatures to raise all thing being equally. But the main concern is not with this rise but whether positive feedbacks will produce and even bigger rise.
My main point is that the feedbacks are not related to CO2 (I have not seen anyone suggesting that increased CO2 will cause more CO2 etc.) but to absolute temperature itself. Hence if there are positive feedback in play that would cause the 1.2C increase to jump to 6.0C, then this would occur everytime the temperature reached the current Temperature plus 1.2C.
I realise that analysis of past temperature records are difficult but I believe that current scientific concensus (what ever that might be) is that the temperature will have been at the current temperature plus 1.2C many times in the past and I believe there was only one event where there was a subsequent additional jump?
We have seen period of significant rapid change in earth temperature and these are high suggestive of some sort of positive feedback process being responsible. But I believe all but one of these where when we went from Ice Age to current interglacial warm period?
Geniuely interested in understanding this more.
Many thanks in advance for any insight anyone can give.
Hi Neil (127) – Before addressing your main question, I’ll note that increasing anthropogenic CO2 is capable of mediating additional CO2 increases – a “carbon/carbon” feedback. This occurs because CO2-mediated ocean warming (or any cause of ocean warming for that matter) reduces the solubility of CO2 in the water, so that an increased quantity remains in the air, increasing the atmospheric concentration. This feedback is rather slow, and is typically neglected in discussions of short term feedbacks.
On to your other questions. Your mental image of positive feedbacks differs from how they are treated in the climate literature. The 1.2 C rise postulated from doubled CO2 (the “no-feedback response”) can’t actually be observed, because feedbacks begin to operate the instant the temperature responds to the original forcing. For example, if CO2 were to be instantaneously doubled, and sufficient time then elapsed, we would see a combination of forcing and feedbacks estimated at equilibrium to yield about a 3C increase (as you may know, the exact magnitude is uncertain, but the range appears to be about 2 to 4.5 C). In other words, the forcing response doesn’t occur first, followed after an interval by a “jump” representing the feedback responses; rather they proceed concurrently, and all we can measure is the combined responses. Much data from current times extending back hundreds of millions of years indicate that the combined response exceeds the calculated (but unobservable) no-feedback response. This has occurred in the past and is presumably occurring today, and in some ancient time has resulted in extraordinary temperature excursions, plus or minus 20 C for example.
As I mentioned earlier, stabilization is ultimately achieved, albeit after a magnified temperature change when positive feedbacks dominate. That stabilization involves the Planck response (and sometimes other negative feedbacks). As stated earlier, when the Planck response is factored in, net feedbacks always end up as negative. Note that since the Planck response is the heat-shedding response of a heat-absorbing body to a temperature rise, it happens in response both to forcings and to feedbacks such as the water vapor or ice/albedo feedback.
Neil @127 — When close to equilibrium (currently the climate is not), more CO2 leads to evven more CO2 due to ocean degassing at increased temperature. CO2 concentrations in the atmosphere went up from ~180 ppm to ~280 ppm during the transition from lGM to Holocene.
Comment by David B. Benson — 15 Nov 2010 @ 10:32 PM
Fred provided a well-articulate and accurate response. I’ll try to mention a few more things (or similar things maybe in a different way) since I want everyone to be thinking about feedbacks correctly (at least qualitatively) after they read these entries!! I agree with Fred that your mental image of how to think about the issue may be off a bit.
To begin with, I wouldn’t spend too much attention on the “1.2 C increase” value– it’s just an example of a no-feedback temperature rise that you get from an arbitrarily selected forcing (in this case, a doubling of CO2). If you chose a 1% increase in sunlight instead, it would be something closer to half a degree. And just to drive home the point, it’s the CO2 rise (or the solar increase) that we call the “forcing,” not the temperature rise itself (that’s the response to the forcing). Of course we can’t actually observe that theoretical temperature increase because we don’t live in a laboratory Earth where we can hold everything else fixed.
As an aside, Fred and David’s responses, while accurate, may be a bit confusing in the context that I discussed feedbacks in this post. You are correct that the feedbacks, at least the ones I discussed in my two-part series, respond primarily to temperature and not the specific forcing agent itself (i.e., more CO2 causing more CO2). Even Fred’s example in his first paragraph, is intrinsically a temperature response and not a direct CO2 increase response. There are examples of responses which are unique to CO2 increase, both radiatively (such as a cooling stratosphere) and in the carbon cycle (such as increasing the partial pressure of CO2 in the air equilibrating with the ocean layer) but they were not the emphasis of my posts.
In Part 1, I made the distinction between the radiative responses and the carbon based responses. In the first version we prescribe the forcing (e.g., a doubling of CO2) and then ask how the temperature changes. Diving the temperature change by the forcing (or in some versions, the other way around) gives you the sensitivity estimate of the climate system, with dimensions of a temperature increase per forcing.
With carbon cycle feedbacks, it’s a bit different. Stuff like melting permafrost releasing CO2, changes in ocean solubility releasing/uptaking CO2, etc are still “feedbacks” in the sense that they only happened because of the initial temperature rise, but in the way I phrased the issue, these changes in CO2 are still acting to modify the “forcing” part of the equation (since you can’t fix your CO2 rise at a doubling anymore). Put another way, the sensitivity parameter “lambda” in my first set of equations is independent of these effects. This is why defining sensitivity relative to a CO2-concentration target (like a doubling of CO2) is a more convenient way to separate the climate part of the response from the socio-political decisions that affect how much emissions we release, and just how much the CO2 rise (like the temperature rise “by 2100″). Any carbon-cycle feedbacks therefore only affect how fast you get to the concentration target, not the sensitivity once you are there (hopefully I’m not causing more confusion than good here).
More related to your question (finally!) is what Fred answered. Once you release a slug of CO2 into the air, the temperature begins to rise. The initial response (for a fixed T) is to decrease the outgoing longwave radiation to space. This radiative flux will end up increasing again in response to the rise in temperature that is physically mandated to occur (re-establishing a new equilibrium at a higher temperature), although the outgoing radiation is also modified by the water vapor feedback and lapse rate issues (other feedbacks like albedo alter the incoming energy side of the energy balance equation). In general if you add up a series of feedback gains, you can still converge to get a finite value. This is the way Gavin described it in this earlier post for example (which is worth the read as an extension of this post and the comments).
#131–”…hopefully I’m not causing more confusion than good here.”
Well, it isn’t an easy paragraph (nor, to be fair, topic.) I think the sentence I’m struggling with the most is this one:
This is why defining sensitivity relative to a CO2-concentration target (like a doubling of CO2) is a more convenient way to separate the climate part of the response from the socio-political decisions that affect how much emissions we release, and just how much the CO2 rise (like the temperature rise “by 2100″).
I suspect that the “more” here may be misleading and redundant, and the intended meaning may be just “a convenient way to separate. . .” If I’m wrong, then “More convenient than what?,” ’cause I don’t know!
More substantively, I also think “response” here may be suggesting to me something different than was intended: syntactically “the climate part of the response” is separated from the “socio-political decisions”–but I’d think that the latter aren’t part of the former anyway, being a precondition leading to a specific forcing to which the climate then responds.
Put that way, the response is ALL “climate”; there isn’t “another part” to that response, as the sentence structure seems to suggest. Socio-economic decisions drive emissions, which in turn determine concentration trajectories in concert with climate response and associated carbon feedbacks; sensitivity determines the final equilibrium temperature. Do I have this remotely correct?
It also looks as if there’s a slight typo to confuse things a tad more: was “just how much the CO2 rises” intended?
Lastly, I had to think a bit on “Any carbon-cycle feedbacks therefore only affect how fast you get to the concentration target, not the sensitivity once you are there” because in my mind, it seemed rather bizarre that the sensitivity would only apply “once you are there.” But that’s not the point (or really what’s being said); what’s being emphasized is that the carbon-cycle feedbacks do have an effect on concentrations prior to (say) the doubling point.
Now I’m hoping that I didn’t create more confusion. . .
Once agains many thanks for taking the time to respond to my comments which is greatly appreciated.
The information on CO2 feedbacks was new to me and interesting. Also I understand that in the real world any actually response will be a result of the forcings and all the feedback combined.
The bit I am having some difficulties with (and this may just be my lack of understanding) is historical responses to increases of temperature (from whatever source) when the earth’s temperature was around the same as it is today?
Perhaps another way of looking at this would be as follows:-
- Historical records suggest (I do not profess to be any sort of expert on this) that many times in the past the earth would have been at current temperature – http://en.wikipedia.org/wiki/File:Vostok_Petit_data.svg)
- On many of those occasions there would have been some external forcing that caused the temperature to increase.
- If positive feedbacks dominate (over negative ones) then I would expect to see the temperature continue to rise due to the feedback process.
- Looking at the Vostok data at least (I understand one set of data is not proof – just using this as an example) then we do see a rise of 3C max (if I can read the graphs correctly?).
- Now that in itself may be be evidence that positive feedbacks do “dominate”, but we must also consider two other aspects of the data:-
1) We know the Vostok temp rises where accompanied by CO2 rises and would expect this to explain some of this 3C rise.
2) It would appear from the Vostok data at least that this temperature rise had been in process for sometime (form -8C to +3C) and therefore some other mechanisms (albeo changes due to ice reduction) are also “in play”
“1) We know the Vostok temp rises where accompanied by CO2 rises and would expect this to explain some of this 3C rise.”
Yes, you are correct. The math says that the orbital changes initiating warming or cooling were far too small to account for observed temperature swings. Feedbacks must account for the balance–the main one being CO2 concentration changes.
Neil @133 — Ok, look at the Vostok data for interglacial 2, the Eemian interglacial just prior to the Holocene interglacial. Shortly (geologically speaking) before the maximum of the Eemian the temperature was the same as it is today. Orbital forcing and the positive feedback of CO2 (followed instantly by the water vapor component discussed in this thread) continued to cause temperatures to increase to about 2 K warmer than today. However, before that occurred the orbital forcing began to decline and with some considerable phase lag eventually the temperatures followed the orbital forcing down. All that the positive feedback due to CO2 and whatnot did was to increase the maximum temperature above the open loop (no feedback) amount and to extend the lag time (phase lag) of the response.
Comment by David B. Benson — 16 Nov 2010 @ 5:14 PM
Many thanks for your responses. If I am honest not sure I follow this 100% but that is probably down to me and I need to do some more background reading and research.
D. Price @142 — The climate was rather different during the Pliocene for a variety of reasons. The estimate of but 2–3 K warmer than now is rather a crude one.
Comment by David B. Benson — 18 Nov 2010 @ 7:24 PM
Doubling CO2 from current atmospheric concentration and sustaining it at that level would likely result in temperatures a good bit higher than 2-3C over today. There are at least three reasons why, aside from any differences between now and the Pliocene:
+3C/doubling does not include some albedo feedbacks which aren’t taken into account in the usual definition of sensitivity. You’d expect a significantly higher temperature increase if that CO2 level was maintained for 1000 years or so.
The current temperature average is depressed because temperatures have not reached equilibrium with the current CO2 atmospheric concentration yet, even without taking slow feedbacks into account.
Aerosols are also depressing current temperatures. That could change fast.
Comment by Anonymous Coward — 18 Nov 2010 @ 7:46 PM
Didactylos, thanks for the response. But I look at this data quite a bit, but I haven’t seen this big of a jump before. If you have specific examples of other such spikes in Arctic data, please do point them out.
It _is_ early, preliminary data, and it perhaps will be revised downward later. But if it’s not, could it be evidence of some kind of event–underwater land slide or something that caused a sudden, large release?
But I just tried going to http://www.esrl.noaa.gov/gmd/ccgg/iadv/ and choosing Svalbard (farthest North dot on the map) and CH4 and generating a chart — which gives a less scary picture. The most recent data points are high but not way out of line with the previous rate of increase (shown gray as preliminary). Maybe someone knows where that peakoil image came from?
Comment by Anonymous Coward — 19 Nov 2010 @ 3:23 AM
IIRC, the Svalbard methane spike was noticed a little while back on Neven’s sea ice blog. It looks like the value is not coming down just yet, which suggests it’s a little less “fluky” than it first appeared. I’ll see if I can confirm my recollection.
“Preliminary data include GMD’s most up-to-date data and have not yet been subjected to rigorous quality assurance procedures. (…) In all graphs, preliminary data are clearly identified. Users are strongly encouraged to contact the appropriate program chief before attempting to interpret preliminary data.”
Thanks, Hank and CM. Hank, the site you are linking is, I believe, in the process of being retired in favor of the newer site I linked to. It appears that it has not been updated as recently as the new site, so is missing the newest ‘outlier” data points. Perhaps something in this change over has caused the anomalous data points. I’ll give the appropriate program chief a call Monday to see what he has to say.