Bishop Hill The IPCC versus Stevens
Mar 20, 2015 Climate: sensitivity I've updated Nic Lewis's graph of his new climate sensitivity estimates by adding the IPCC's likely range of 1.5°C–4.5°C as a grey box. Something of a contrast here I would say.
;)
The situation for TCR is only marginally better.
;)
Bishop Hill
In the comments at CA, Shub and Nic Lewis point to another important implication of the Stevens paper:
SHUB: Do low estimates for aerosol cooling imply the 1940-1978 drop in global temperatures were not due to coal plant emissions from post-war industrialization?
LEWIS: Yes, they strongly suggest that the main reason for global temperature going down rather than up from 1940 to the mid-1970s despite quite strong greenhouse gas forcing (+0.7 W/m2 for long-lived GHG, +0.85 W/m2 including ozone) lay elsewhere. Internal variability (here the AMO) seems the obvious cause. On Steven’s best estimates, aerosol forcing became a bit under -0.3 W/m2 more negative during this period. Sulphate emissions from coal plants etc. grew rapidly and reached their peak level in the mid/late 1970s.
Reader Comments (134)
More than happy to be proven wrong, but I suspect that this more highlights a problem with Nic Lewis's method than suggesting that equilibrium climate sensitivity is probably less than 1.5K. Given all the other evidence, I think it is highly implausible that it can be this low. I realise that most will probably shriek "but observations", but that doesn't make it right. Also - don't get me wrong - it would be wonderful if it was. However, assuming that it probably is, is - IMO - the wrong type of optimism.
ATTP "Given all the other evidence, I think it is highly implausible that it can be this low."
List a few examples of evdence.
List a few examples of evidence.
Biased model 1
Biased model 2
Etc etc
aTTP
You should really focus on Stevens and his findings of a lower limit for total aerosol forcing, not on Lewis and his graphs. Steven's findings seem to imply lower climate sensitivity
All Lewis has done in this post is illustrate the impact of Stevens. Whether Lewis' methods are optimal is not really the issue
Tiny,
An illustration of why I shouldn't bother...
...but, of course, I will. Some examples:
Paleoclimate - how did we move into and out of glacial periods if ECS is this low?
Greenhouse effect - how can it be 33K if ECS is this low?
Feedbacks - why is the net feedback so low? Clouds, but they're thought to be overall small. Lapse rate, where's the hot spot if lapse rate feedback is so strong?
The simple issue, though, is that if your method is starting to diverge significantly from others, then you really should consider that there's something about your method that is wrong or that it's missing something. That doesn't make it true, but not being willing to seriously consider this is not optimal.
Ken,
What you or anyone else 'thinks' is not the point.
If science is based on opinion we know it is broken.
I'm assuming your monicker refers to the physics of the Tyndall experiment. Well guess what, the physics of that work in isolation in the lab. It does not scale to planetary levels where other factors kick in. This is the central fallacy of the global warming scare.
Re: aTTP
> Paleoclimate - how did we move into and out of glacial periods if ECS is this low?
No idea. The fact that we do not know, have only proxy records of varying degrees of accuracy, does not trump the observational data.
> Greenhouse effect - how can it be 33K if ECS is this low?
If it can't be 33k then some assumptions and/or measurements and/or calculations made to arrive at this figure are incorrect.
> Feedbacks - why is the net feedback so low? Clouds, but they're thought to be overall small. Lapse rate, where's the hot spot if lapse rate feedback is so strong?
No idea. In reality feedbacks are what 97%™ of the discussions are about
ATTP
I really am delighted (no, seriously) that you would be happy if Stevens' findings proved to be accurate. If you are being honest you will agree with my suggestion in the neighbouring thread that there are those who will either move heaven and earth to prove him wrong rather than take the findings on board and consider them seriously or will simply stick their fingers in their ears and look the other way.
Hardly actions which will advance the cause of science or the good of humanity, I submit.
As to your own criticism, I'm intrigued to know why the views of an astrophysicist should be accorded more weight than the Managing Director of the Max Planck Institute for Meteorology, who,amongst other activities has been Head of the Institute's Research School for Earth System Modeling, a visiting scientist carrying out research related to the representation and effect of geophysical boundary layers in climate models, and is also a professor and principal investigator and steering committee member of the Cluster of Excellence ”Integrated Climate System Analysis and Prediction” at the University of Hamburg.
Perhaps he knows something about clouds, hotspots, and the greenhouse effect that you don't?
Of course, he could be plumb wrong, just as you could be spot on with your crit of his paper. Have you read it, by the way?
AndyL,
I wasn't really focusing on anything. Stevens results may be right, maybe not, time will tell. I was simply suggesting that if a consequence of this is to imply that one method produces likely ECS values below 1.5K, then one really should consider if that method is robust enough to make such estimates. It may be, but not considering this would be sub-optimal.
Mike Jackson...Not an appeal to authority shirly...
Mike,
I wasn't suggesting that it should be. I wasn't even arguing against his result. I'll repeat my point: if this result implies - using a particular method - that ECS is probably less than 1.5K, then it would be worth considering that there is some issue with that method as this result is very different to what other methods suggest.
I have read it. The paper isn't suggesting a low ECS; it's suggesting that the range for the aerosol forcing is probably between -0.3 and -1.0W/m^2.
In fact, there something that people should bear in mind about the argument being made in the paper. One argument is that climate models underestimate the warming between 1920 and 1950 (I think) and he uses this to suggest that this is because they were over-estimating the aerosol forcing. However, these climate models almost certainly have ECS values in excess of 1.5K. Therefore, how consistent is it to use models with ECS values above 1.5K to argue for an ECS value below 1.5K.
ATTP:
Millikan.
RP Feynman
ATTP: There is no "greenhouse effect" (except in a greenhouse or similar). The earth's temperature (not that there is such a thing) is determined by standard heat transfer mechanisms, with radiatively active gases (plus direction radiation from the surface) cooling the earth and ensuring that the energy received from the sun is balanced by the energy radiated to space.
Philip,
Either you're describing the greenhouse effect, but refusing to actually call it the greenhouse effect (I've had such discussions before) or you're talking complete and utter nonsense. There isn't a third option.
I agree with ATTP. As I always say whenever 'skeptics' argue for ECS....how do you explain the paleoclimate record if it was? I also love it when 'skeptics' say (on the one hand) that there was a global and warmer MWP than now, and in the next sentence say that ECS is low!
That's why they're not really skeptics...
First, I'll say that it's quite right for you to be sceptical, and something to be encouraged. It's a brand new paper, so it's not been properly challenged yet. And it will take time for us to understand how it works and for that knowledge to be propagated - blind faith in contrarian scientists is no better than blind faith in mainstream ones.
And since the scientific credibility of a theory is built on the strength of the attacks and criticisms it survives, we *need* you to attack it in order to build up its credibility. So go for it!
"Paleoclimate - how did we move into and out of glacial periods if ECS is this low?"
Because ECS isn't a constant. We're estimating the gradient of a curve at the current temperature, but at lower temperatures the curve slopes differently.
Glacial mass balance physics is non-linear, and can include 'runaway feedbacks' - this is the basis of the 'ice sheet collapse' scare predictions. You get the mass increasing from precipitation in the middle, which is roughly proportional to area, and mass loss from calving at the boundaries, which is roughly proportional to the length of the boundary. Increasing the radius of the ice sheet increases the precipitation area and boundary length at different rates, depending on the geography. But you can get a situation where boundary length is linear and area is quadratic, and the two lines cross at an unstable equilibrium. Smaller than the critical value, and the ice sheet shrinks. Larger than the critical value, and the ice sheet grows without limit. There's hysteresis, and path dependence, and it's heavily influenced by mountains and stuff getting in the way.
There's also some suggestions that ocean currents have a big, and similarly non-linear effect. What happens if you stop the thermohaline circulation, or redirect it? What happens if Antarctic ice reaches South America and there's no longer a circle of open ocean all the way round?
Plus, of course, we've got very limited information about what was going on back then. For example, how do you tell what the humidity was from ice cores?
"Greenhouse effect - how can it be 33K if ECS is this low?"
33 K is talking about the current *value* of the forcing-temperature curve, ECS is talking about its *gradient*. The two are independent variables.
"Feedbacks - why is the net feedback so low? Clouds, but they're thought to be overall small. Lapse rate, where's the hot spot if lapse rate feedback is so strong?"
"... thought to be..."?! :-)
The lack of lapse rate feedback is evidence of a lack of water vapour feedback, since the lapse rate change is associated with the predicted increase in humidity associated with higher temperatures. If there's no water vapour feedback, that would answer your question.
Nullius,
Careful, the ECS calculations from glacial cycles treats the ice-albedo feedback as an external forcing to compensate for this. Therefore, even these ECS calculations are fast feedbacks only and the non-linearity you're describing may not apply.
It's clearly possible that the ECS is temperature dependent, but remember that the 33K is based on a fixed albedo so if there is a strong temperature dependence, it has to be related to the fast feedbacks and this is much harder to justify.
Sure, but enhanced water vapour is one thing about which there is reasonable confidence. We have to be very wrong about this.
To be clear, though, I'm not arguing for a higher ECS, I'm simply pointing out that rushing to suggest that this probably means it's below 1.5K is really jumping the gun.
Clovis
Tyndall didn't show that Co2 "traps" heat - he actually showed first hand that at atmospheric pressures Co2 is very good at absorbing IR radiation and transferring that to neighbouring molecules by collisions. Those collisions ultimately result in impacts to a solid surface where energy is then "thermalised". So he was correct in thinking that under constraint, whether by physical structure or by field, Co2 could lead to a heating effect. The problem is that the atmosphere represents a different type of restraint. Fixed on one side by a surface but subject to a "softer" constraint: gravity. And then there's clouds. So emission from surfaces is a lot more complicated and interlinked.
With regards to Co2, later on, atomic physics showed (and John Nicol has a nice paper reminding people of this) that the rate of absorbtion and thermalisation of Co2 around atmospheric pressures is much much faster than re-emission by radiation. Some (such as Angstrom and Heinz Hug) also stated that this means the primary IR radiation from the surface gets absorbed in the first 10 to 20 metres of the atmosphere.
Nicol argues that if you look at relaxation rates alone, adding more Co2 won't affect this initial absorbtion . It will only effect the secondary bulk emission of IR radiation from the Co2 column to space. So hence no 300+ W/m2 back-radiation, or at least no significant back radiation. On that note the only way to properly measure radiation using a pyrgeometer is to make sure you also take the dark field signal away from the bright sky signal. Since it's a thermopile and may produce spurious signals just by being hot. Or you cool it or a spectrometer and characterise the spectrum change. It's similar to measuring the capacitance of nano-capacitors but having a large parasitic resistance just by having an electrode. You map the change in electrode size which should scale, leaving the residual nano-capacitance.
The thing is, everything I've said about IR absorption can be tested in a lab. So I'm not coming here and saying I am right or wrong, or making any assertions. As a first experiment, you simply need to produce a coherent beam of IR radiation at power levels equal to what 300K would produce (for example) - so 10s of W/m2 and shine it through 10 to 20 m of dry air with 400 pm Co2 and measure the attenuation. You can also measure the off axis re-emission, which I believe MODTRAN/HITRAN models already produce ( I saw this on Science of Doom's site). Using that set-up you could work out the saturation threshold for Co2 and prove/disprove Angstrom.
And, you could also back this up with measuring spectra outside - use a crane lift. It may be coarser due to collimation issues but it should be in the ballpark. The whole thing shouldn't cost millions and millions. It's such a simple characterisation test I'm surprised Exeter Uni isn't doing it.
Another theoretical conundrum is that for certain pressures Co2 and water vapour may couple, such that the absorbtion of IR radiation by Co2 which then transfers to water vapour by collisions, may effectively widen the water vapour absorption window. And vice versa. But water vapour is the only one that undergoes significant phase changes through the atmosphere. Just a thought, but cross coupling happens quite a lot in plasmas and leads to interesting behaviour.
Like I said though, do the characterisation so some of the more basic ideas about the greenhouse effect come into focus, or at least refocus.
Feynman would approve of that no doubt.
PS Apologies for posting this here - it may be better on Dung's "Where's the evidence?" thread.
@ATTP
Why do you want to pontificate about the work done by others, completely distorting their message according to your rather biased views? There is not a single reaction which is left without your scathing comments. Your message is not inconvenient, it is pure distraction of in your view unwelcome developments. Let's discuss the implications and merits of the Stevens publication and the effects on the previously published estimations of ECS and TCS. If the Stevens work stands out the test of critics, it will have the effect on all model studies to lower the estimations of climate sensitivity to increase of CO2. And thus it will reduce the need for panic-driven draconian measures. Which would be good.
Another point made by Nic and Shub at CA is that the often-made claim that the cooling from around 1940-1970 was caused by aerosol cooling also takes a hit as a result of this new lower estimate of total aerosol forcing. It's more evidence that the climate science community overestimates the importance of responses to forcing, and underestimates natural fluctuations.
The author Bjorn Stevens seems to be well regarded by the IPCC - he was a lead author of the relevant chapter (7) of IPCC AR5, which cites several of his papers.
Unfortunately I can't get access to the paper. Has anyone found a free version? It's interesting that he doesn't go on to explore the obvious consequences. Maybe that wouldn't have been allowed ;)
"Careful, the ECS calculations from glacial cycles treats the ice-albedo feedback as an external forcing to compensate for this."
But does that work?
I'll give you another example from a different bit of physics - the Mpemba effect.
There is a persistent claim that hot water when put in a freezer freezes faster than cold. "Nonsense", said the the scientists. "Obviously, the hot water has to cool to the temperature of the cold water first, after which they would both cool to 0 C and freeze in the same time. So hot water cannot possibly freeze faster than cold."
But experimental evidence shows this to be wrong. The problem is that the scientists are modelling the water as a single dimensional variable: 'the' temperature. But a tub of water is not all at a single temperature; heat flow in water is dominated by convection, which is driven by temperature differences.
If you plot the curve of cooling rate versus temperature you find the hot water and cold water moving on different curves. Hysteresis is when the curve as you move to the left is different to the curve as you move to the right. How in heck can you represent this sort of behaviour by just adding a few terms to your existing one-dimensional linear model?!
All the stuff about "the" forcing and "the" temperature is a similar sort of simplification. Sometimes such simplifications work, sometimes they don't.
"but remember that the 33K is based on a fixed albedo"
33 K is based on the *currently observed* albedo. Nothing says it's fixed.
"Sure, but enhanced water vapour is one thing about which there is reasonable confidence. We have to be very wrong about this."
There's lots of confidence, but is there lots of evidence?
http://wattsupwiththat.com/2013/03/06/nasa-satellite-data-shows-a-decline-in-water-vapor/
"To be clear, though, I'm not arguing for a higher ECS, I'm simply pointing out that rushing to suggest that this probably means it's below 1.5K is really jumping the gun."
Agreed. But I also think that based on the even weaker evidence underlying the models, rushing to suggest that ECS is very high is likewise jumping the gun. We don't know yet.
MH Corbett
I continue to be baffled by the trapping phenomena of CO2 and the 'greenhouse effect'. All molecules contribute to the additional warming of the earth's surface because they are all behave as atoms or molecules thermally agitated and follow the gas laws. Even if they have no quantum traps, they will raise the earth's surface temperature above that if there was no atmosphere. But CO2 (and water) do have (shallow) quantum traps. When trapped, the thermal energy absorbed goes entirely into the bond structure and apparently 'disappears'; when released, this thermal energy (photon) reappears and the re-enters the thermal agitation/trapping pool. So what possible impact does the trapping phenomena have?
I can understand water to CO2 quantum trapping linkage, but not the other way round.
All that is required to understand that it is impossible to accurately model the climate is to read the wide discrepancy of opinions on this one, tiny thread. Yet here we have climate sensitivity measured to an accuracy of one tenth of a degree.
Nullius,
I don't know, but that isn't really relevant to my point.
The 33K is based on an albedo of about 0.3. I wasn't claiming that it is fixed, I was simply pointing out that that is what is assumed when calculating the greenhouse effect. Of course, in reality, if we were to start with no atmosphere, then we'd be a ball of ice with a very high albedo and be much more than 33K colder than we are now.
Claiming that it is very high would indeed be incorrect. There is, however, a massive difference between claiming it is high, and it possibly being high.
The so-called "greenhouse effect" is a fake analogy designed to fool people who aren't expert in the fields of fluid flow and heat transfer. You only have to look at the Trenberth 'Earth Energy Budget' to see how it is done. You have to be very gullible to believe that the sun only provides 1/3 of the energy absorbed at the earth's surface, the rest coming from this mythical "greenhouse effect".
" I wasn't claiming that it is fixed, I was simply pointing out that that is what is assumed when calculating the greenhouse effect."
Hmm. We may be using different definitions of "fixed" here. I assumed you meant 'constant over time', which the calculation doesn't assume since it's not considering changes - only the equilibrium at an instant. Was you thinking of something else?
" There is, however, a massive difference between claiming it is high, and it possibly being high."
Agreed! The science isn't settled! :-)
@ATTP
In general, Nic's work has nothing at all to do with the fact that GCMs in fact do use aerosol feedback factor significantly higher than what's realistic according to the paper. I don't understand in which way is that supposed to prove Nic wrong.
You also appear to be just pointing at uncertainities rather than providing any support to your claim.
ECS discussed here is sensitivity to CO2 changes. There's no proof that CO2 plays any important role in glacial cycles, instead there is evidence it doesn't (delay of CO2 behind temperature). Uncertainity is that the process is still not very understood.
ECS discussed here is sensitivity to CO2 changes. Major part of greenhouse effect is due to water vapor. Uncertainity is H2O vapor reaction to changes in CO2/temperature.
I'm not exactly sure what you're discussing in this point but it appears to me to be two more uncertainities.
You sure are supposed to double check, but if you did so, a divergence is not a proof you're wrong.
As far as I understand Nic's work, it goes around uncertainities and uses statistical analysis of observation history in place of detailed understanding of underlying physical processes. It is irrelevant that we don't know how things work in detail if they behave consistently on large scale. AFAIK that's exactly the method used by GCMs as well, just on a different scale. Given your uncertainities, Nic's work, GCMs, or both can be wrong. Not just Nic.
Note to moderator: the Preview Post feature doesn't work for me (Chrome reports lost connection), sorry for any broken formatting.
I need to understand something here: If, as some claim - or imply, ECS is constant, how the devil did the world move into and out of a couple of ice-ages?
Nullius,
I just mean the following. You can calculate the equilibrium temperature of the Earth based on the energy received from the Sun using
pi R_E^2 sigma T_Sun^4/(pi a^2) = (1 - A) 4 pi R_E^2 sigma T_E^4
where A is the albedo. Assuming I've typed that out correctly, A is normally taken to be 0.3 and the result is about 255K. The average surface temperature is, however, 288K. Therefore the greenhouse effect is resulting in the surface temperature being 33K higher than it would be if there was no atmosphere and the albedo were still 0.3. Of course, if the surface temperature were 255K, the albedo would not be 0.3, hence the calculation assumes a fixed albedo.
Yes, but if we keep doing nothing, then we really are going to have to hope that it isn't high.
Philip,
You don't understand the greenhouse effect or Trenberth's diagram.
Harry,
Seriously? Okay, during the glacial cycles, the variation in CO2 and the variation in albedo (through changes in ice cover) produces a total change in forcing of around 6W/m^2. If the ECS is around 3K, then that implies that a change of 3.7W/m^2 would produce a change in temperature of 3K. Therefore a change of 6W/m^2 will produce a change in temperature of 5-6K, more than enough to move us from a glacial to an inter-glacial, or vice-versa. It's the equilibrium response that is thought to be broadly constant, not the temperature itself.
This is one reason why a value as low as 1.45K is somewhat problematic, since the glacial cycles are associated with global temperature changes of 5-6K which is difficult to understand if the ECS is as low as 1.45K.
"The simple issue, though, is that if your method is starting to diverge significantly from others, then you really should consider that there's something about your method that is wrong or that it's missing something."
The original sensitivity was calculated by Charney from two computer models in 1979, one of which estimated it as 2C and the other estimated it as 4C. Charley got his sensitivity range by adding 0.5C to the top figure and subtracting 0.5C from the bottom figure. Hence the range 1.5 - 4.5C with a most likely sensitivity of 3C.
This stab in the dark has withstood billions of dollars of research and 2^18 improvement in computer power and to this day remains the range chosen by the IPCC.
In the meantime the CMIP 5 models using this range have consistently overestimated future temperatures, which leads the Brain of Britain to suggest that if someone comes up with the idea that the range might be lower than the failing models it is the method that shows the lower sensitivity that should be taken with a pinch of salt rather than the models using the age old 1.5 - 4.5C derived from models on computers that pre-date the Sinclair Z80.
I blame it on the introduction of comprehensives.
ATTP: You don't understand the so-called "greenhouse effect" or Trenberth's diagram.
ATTP:
I once thought you to be a patronising g*t...now I know for sure. Do you teach? I bet your students really love your supercilious and superior attitude. Thanks.In any case, your explanation does not explain how the processes (going into/out of an ice age) actually got started, only how it was was sustained.
"The average surface temperature is, however, 288K. Therefore the greenhouse effect is resulting in the surface temperature being 33K higher than it would be if there was no atmosphere and the albedo were still 0.3."
Ah! I was thinking of a different calculation!
The surface temperature is the effective radiative temperature plus the lapse rate times the average height of emission to space. The effective radiative temperature depends on the albedo, and with the current values is about 255 K as you say. The lapse rate is about 6.5 K/km and the average altitude of emission to space (which you can work out with MODTRAN and friends) is about 5 km. 6.5*5 = 32.5 K, which is the difference.
If you make all the terms functions of time, nothing changes about the reasoning. You just plug the values of albedo and so on for the current time to get the current surface temperature. If the albedo is changing over time, the surface temperature will change to match. Nothing needs to be constant for the calculation to work.
"Yes, but if we keep doing nothing, then we really are going to have to hope that it isn't high."
And if we do something, (like cutting fossil fuel use in the developing world,) we're really going to have to hope it's not low. There are costs and risks on both sides of the decision.
esmiff
I agree. My stance is that if we can start to reacquaint ourselves through experiment with the easy stuff, the things that are supposed to be "basic science", it can help with the more difficult stuff. But until that happens we are going to see many an opinion here and there.
I also don't think I'm unique in that opinion.
Harry,
Jeepers, I kind of knew I shouldn't have bothered, but now I know. FWIW, none of my students - that I'm aware of - have ever called me a patronising git. I'm actually trying to work out how else I should respond to your comments. Consider the following: if you weren't so fundamentally unpleasant, maybe I wouldn't respond in a way that leads you to call me a patronising git. Just a thought, mind you.
Nullius,
Yes, agreed.
Yes, agreed, but if you include the change in albedo with time (or with temperature) the difference won't be 33K, which is all I was pointing out. The 33K comes from assuming a fixed albedo of 0.3. Hence, the 33K is essentially a fast-feedback greenhouse effect.
Agreed, but that doesn't really change my point.
Stevens is consistent with the 18 years haitus, agw theory and the models are not
So where should we concentrate our doubts ?
"but if you include the change in albedo with time (or with temperature) the difference won't be 33K, which is all I was pointing out."
Mmm. Only if you include the change in albedo with time but *exclude* the corresponding change in surface temperature with time.
Nullius,
I don't really understand what you mean. In our current state, the equilibrium non-greenhouse temperature is 255K and the actual surface temperature is 288K. The greenhouse effect has, therefore, produced a warming of 33K, compared to what would be the case were there no greenhouse effect and the albedo was still 0.3.
In reality, however, we would expect that in the absence of a greenhouse effect, the albedo would be significantly higher than 0.3 (there would be more ice) and hence the equilibrium non-greenhouse temperature would be below 255K. Therefore, in reality, the greenhouse effect has taken us from a ball of ice with a high albedo and an equilibrium non-greenhouse temperature below 255K, to what we are today, a surface temperature of 288K with an albedo of around 0.3. Therefore, if you were to model this properly, you should find significantly more warming than 33K, partly due to the radiative influence of the atmospheric gases + lapse rate (as you point out above) and partly due to the decrease in albedo as we warm. So, the 33K refers only to the former influence (i.e., the radiatively active gases plus the lapse rate) and doesn't include the influence of a changing albedo.
I'm slightly confused as to why we're debating this, as it seems fairly obvious.
To be able to determine ECS sensitivity in the ice-ages, one needs to know how much the Earth's Albedo changed in the ice-ages.
It is not hard to imagine that Albedo increased enough, all by itself, to produce the temperature changes, even with Zero ECS.
All that extra glacier, sea ice, desert, sea level decline, reduction in vegetation, reduction in low cloud cover changed the Earth's Albedo by a profound amount. Any value for ECS is, indeed, plausible.
"I'm slightly confused as to why we're debating this, as it seems fairly obvious."
We were discussing what you meant when you said the calculation assumed the albedo was "fixed". I don't think there's any such assumption - the albedo can change, and the other variables will change with it. If you agree, then we can stop arguing about it.
As the so called greenhouse effect is mostly concerned with the water vapour in the atmosphere and that is not only constantly fluctuating but we have no idea what is was during or after ice ages it seems that genuflecting towards the God Gas CO2 is a pretty pointless exercise. Evidence has it that the earth system has never had run away warming but has had frequent runaway cooling. In fact cool seems to be it's natural state. Most of the CO2 that started in the atmosphere is now contained in the coal seams, marine sediments and Dover cliffs etc, So we are at a very low atmospheric level currently. The magma puffs a few pulses of CO2 plus a few smellier things into the atmosphere on occasion yet there never has been runaway warming. It is a real stretch to say that an ECS of 1.5 or even 4.5 is going to make any difference to the earth. The water vapour will vary as it must have done in the past and the feedback will be negative. I would be more concerned by the reflectivity of the sea ice in Antarctica which now stretches beyond the Antarctic circle and if it continues to increase will exert a cooling effect on the climate. Nothing is certain except that mankind is a pimple on a planet and probably has less effect on the whole than termites.
It seems a bit pointless to say it but if those who foresee some kind of doomsday from increasing CO2 were genuinely concerned they would have advocated a switch to gas electricity generation in the short term and a massive building of nuclear power plants to replace them in the long term. France already has that system yet is building wind turbines and letting the nukes go out of business. The certainty that this is faux doomsday is that the doomsayers themselves do not take it seriously.
Nullius,
Okay, we agree. I'll stop there :-)
Micky H Corbett
Yes. Thanks.
Ivor Ward
Here in the glens of Alex Salmond's Brigadoon, we are often updated on record breaking passenger numbers at the local airport and that Banny Scattland wants to be the greenest country on earth. But, most of all.
IT'S OOR OIL.
How anyone who claims to be a physicist can talk about the earth's temperature being 255K or 288K, when temperature is an intensive property, is beyond my comprehension.
Philip,
Okay, the Earth emits as much energy per square metre per second as a 255K blackbody. The surface emits as much energy per square metre per second as a 288K blackbody. Okay? Happy now?
ATTP:
There speaks a man with very little self-awareness - and, considering many of the comments addressed to him on this blog, one with very little comprehension.Harry,
There speaks a man with whom any form of discussion is clearly entirely pointless. Carry on being remarkably rude and unpleasant if that's how you wish to behave. I'll ignore you, as any person with any sense would obviously do. I had thought that maybe my last response might make you realise that I would happily respond in kind if you were to choose to not be such a prat. Clearly you have no wish to do so.
A high ECS is a bad explanation of the glaciations as a high positive feedback would tend to drive the earth into an extreme (hothouse/icehouse) from which it would be difficult to exit from. Fractal dynamics in the hydrological cycle is a far, far better explanation that fits paleo obs perfectly and doesn't require a high ECS.
The 33K greenhouse effect is dominated by water vapour not CO2, which is a far more powerful GHG and does not require anything like the same sensitivity.
Our models of the hydro cycle are a joke and nothing like reality. Sufficiently so to call into queztion not just CMIP5 but the work by Stevens and Lewis too.
The black body temperature of the moon is ~270K according to NASA because it has a lower Bond albedo than earth, despite being essentially at the same distance from the sun. The moon is essentially devoid of atmosphere. Yet the average measured temperature at the equator is just 206K (and lower for latitudes away from the equator) according to measurements made by NASA's LRO Diviner project. If the simple black body model fails in circumstances without an atmosphere, what hope is there when an atmosphere is included?