Wednesday
Jan182012
by 
Bishop Hill
Bishop Hill Richard B at Nature
Jan 18, 2012 Climate: Sceptics Climate: other Richard Betts, writing at Nature's blog, says upholders of the climate consensus should talk to dissenters.
I think the only solution is to talk about the science as science, in the context of all its implications and also for its own academic interest – and talk about it to everyone irrespective of their position in the policy debate. This includes talking with sceptics, and not in defensive mode but as scientists willing to talk around the issue. It used to be the received wisdom that climate scientists should not engage with “sceptics” beause, it was said, it only wasted time and gave credibility to arguments that had already been countered many times before. In my view this is no longer a helpful strategy, if it ever was.
Reader Comments (231)
BBD
If we make the atmosphere less transparent to IR, OLR from the surface will heat it. - Agreed.
The atmosphere will now radiate more energy back towards the surface (as well as upwards). - Agreed.
This is added to the solar DSW flux. Agreed.
But the surface is already cooler by the amount of LW radiated to the atmosphere, only about half of which is radiated back to the surface.
I'm not sure either about your claim that the earth is being heated by the sun at a constant rate. This might be theoretically true but doesn't hold good for any given point on the surface where the solar energy peaks at noon and falls to zero after dark.
At which point there is no solar DSW to augment.
MJ
The rotational period is constant so averaging the diurnal cycle is assumed. Let's just stick to the basic problem.
You seem to be losing energy somewhere.
It is vital to remember that the Earth is being heated by the sun at a constant rate. (See 'solar constant').
If we make the atmosphere less transparent to IR, OLR from the surface will heat it. The atmosphere will now radiate more energy back towards the surface (as well as upwards). This is added to the solar DSW flux. So the NET energy at the surface increases and the surface heats.
"Where are the errors in what I said at Jan 19, 2012 at 9:39 PM?"
Well along with this:
"Yes, if the cooler object is made increasingly IR-opaque and the warmer object subject to constant heating."
and this:
"Philip Bratby
Roy Spencer is talking nonsense. A cooler object cannot make a warmer object get even warmer
Confusion between thermal conduction and radiative transfer appears to be at the root of your rejection of otherwise uncontroversial atmospheric physics."
Pretty much all of it as far as I can see. I think you are very confused and you need to get the issues properly sorted out in your own mind before you start making silly comments about other people's understanding. I suggest you reread and try to take on board the actual content of Phillip's original comment:
*******
1) BBD
Roy Spencer is talking nonsense. A cooler object cannot make a warmer object get even warmer; in the absence of a source of energy, all the cooler object can do is slow down the rate of cooling of the warmer object. If there is a source of energy, the warmer object may get hotter because it is receiving more energy than it is losing; and it is losing energy to the cooler object at a lower rate than it would in the absence of the cooler object, because the cooler object is blocking radiation from the warmer object going out to, say, space. It is the extra energy from the source that warms the warmer object, not energy from the cooler object.
Jan 18, 2012 at 9:32 PM | Unregistered CommenterPhillip Bratby
***********
I also think you should do a few simple experiments to get a feel for the things you are attempting to discuss.
BBD
OK. I'll take the solar energy as constant.
But you seem to have ignored the point that radiation from the surface is cooling the surface and that only about 50% of that radiation is reflected downwards.
I haven't lost energy; it looks as if you have found some that does more work than it's capable of.
Non dimensional relationship inverse relationship of CO2 and temperature.
A planet with atmosphere, when in a state of equilibrium, will emit the same quantity of energy as it receives from an external source. Consider a photon leaving the sun in the IR absorption band of CO2. As it enters an atmosphere with CO2, it has a chance of interception and a further chance, ~50%, of being reflected to space rather than passed along to the surface. Over time ~50% of that intercepted will be reflected and therefore, the presence of CO2 in an atmosphere reduces incoming energy at this stage. For equilibrium, outgoing energy must also be less. If all else remains equal, it would seem intuitive that the temperature attained by the system to cause outgoing to balance incoming flux will be lower than would have been the case if CO2 had been absent.
Daytime (net inflow);
Consider photons arriving then leaving the surface in the IR absorption bands of CO2. In these bands there will be no net incoming flux as a photon has the same chance of continuing its journey outwards after interception by CO2 as one intercepted while incoming. However, as these interactions are within the system, energy resides in the atmosphere in the form of the raised energy state of CO2 molecules. It should be seen that with no net inward flux at the absorption bands, surface temperatures themselves do not rise. The surface warming that does occur and which maintains equilibrium must therefore be (at least primarily) from radiation outside the frequencies of the CO2 absorption bands.
Night-time (net outflow);
Consider photons leaving the surface in the IR absorption band of CO2. The chance of reflection of a photon back to the surface by any CO2 has not changed but net flux is outward from both surface and atmosphere. Because of rotation of the system, the daytime raised energy state of the CO2 molecules is lost to space within that flux.
Day / night cycle (equilibrium);
Accepting that IR at the CO2 absorption frequencies does no work within the system if intercepted in the atmosphere but does have an impedance effect on outgoing IR at those frequencies then it only indirectly warms the surface by reducing outgoing flux. IR that is not intercepted in the atmosphere and all other frequencies reach the surface and that which is not directly reflected is absorbed there by conduction and spread to the atmosphere by convection. It is that process that does direct work on the system and is the primary driver of temperatures.
Additional CO2;
The non-dimensional question is: does the impedance of additional atmospheric CO2 to outgoing radiation overcome its partial blocking of incoming and lead to higher temperatures?
A small increase in CO2 concentration would lower day-time temperatures by the initial partial reflection to space. Lower initial night-time temperatures would follow. Taking the increase in concentration alone, it can be seen that the equilibrium average temperature must also be lowered. Therefore, changes in GAT (global average temperature) correlate inversely with increasing CO2 concentrations.
For that to be false, the amount of energy in the system to cause an increase in GAT would require an increase in emissivity to allow equilibrium. As the only change is a reduction in emissivity due to the impeding presence of increased CO2, then the conclusion is true.
:)
nby
"Yes, if the cooler object is made increasingly IR-opaque and the warmer object subject to constant heating."
You say this is incorrect but do not explain why.
MJ
And if that 50% became 51%? What would be the effect on net energy at the surface? Would there be less, the same, or more?
I've left it as an exercise for the student. Do some tests and see what results you get.
SSAT
In other words, you are talking only about IR. Which does rather ignore solar SW... to which CO2 is effectively transparent.
nby
So you cannot explain why this is incorrect:
"Yes, if the cooler object is made increasingly IR-opaque and the warmer object subject to constant heating."
Then just say so.
BBD
Not at all: see last sentence of *Day time* paragraph.
"Then just say so."
Have you run any cases yet? When you done something and got some numbers come back and we'll discuss them. Night night BBD.
SSAT
I suspect you are pulling my leg. But anyway:
Hansen & Sato (2011) Paleoclimate implications for Human-Made Climate Change:
http://arxiv.org/ftp/arxiv/papers/1105/1105.0968.pdf
65Ma of cooling in broad correlation with falling CO2 ppmv. And with an energetically sufficient explanation for that correlation too. Makes you wonder.
This thread has done a Schettino. Perhaps take it to a 'back radiation' thread on Discussion?
BBD: you asked 'why doesn't the temperature fall below zero at night?'
I presume you're talking about Spencer's solar oven. There is also heat transport to the walls of the box by convection. This is why the Bedouin dig a pit to get the water to freeze.
Awake again. Mornin', all.
BBD
Why should I assume that the ~50% becomes 51%? I could equally assume it was only 49%. Either way, unless it is 100% then the reflected radiation is less than original transmitted radiation.
The flaw in your argument seems to be the question of constant irradiation which is why I've also decided I'm not keen on your idea of constant solar irradiation. While the theory might be sound, the practice isn't. Just because the emission from the sun is constant this does not mean that what reaches the earth's surface is constant. In fact it isn't. It varies according to latitude and time of day.
Which also makes me question your question about what stops the earth freezing.
I'll answer your question with a question (sorry about all this 'question' business!). Absent any other influence what time if day is Tmin and why?
BBD: your faith in CO2 as the explanation of the Cenozoic is touching.
It's because you can explain the +2.88 W/m*2 [attributed in AR4 to GHGs] from the LGM to the pre-industrial age by 3.5% fall in average cloud albedo, easily achievable when you look at the real aerosol optical physics, not the flawed variety in the climate models.
BBD
"I suspect you are pulling my leg."
Forget all numbers other than the 50% that is used to define the characteristics of CO2GHG molecule and think of a narrative that describes photons in the GHG spectrum leaving the sun, arriving at then leaving the earth that causes a net surface warming rather than a cooling. I have tried and my post at 10:44 PM yesterday is a result of that. Numbers are ultimately necessary but first the concept has to be right. And yes, I do accept that a mass with a temperature greater than zero Kelvin radiates against a temperature gradient.
Re Tamsin
Guest post please! :)
I read this comment and thought "which hypothesis?" given there seem to be arguments for both a positive and negative feedback role. Plus behind those hypotheses are some rather photogenic little critters which have may have some role in climate change, ocean acidification, albedo, DMS effects etc.. and proxies.
Or just be really neat having evolved shiny body armour and their own air conditioning. Lots of fascinating science wrapped around a tiny organism.
Atomic
It was interesting to see that the takedown was by one of Charlson's PhD students. A nice example of self-correcting climate science :) It generated lots of interest, funding and therefore better understanding of the relevant processes. But time to put it away. We talked a bit about some of the reasons it might have taken 25 years and whether this was a typical timescale.
My new blog will be up and running in the nearish future for longer posts...
Mike Jackson
I've explained how it works in the simplest terms I possibly could. That's all I can do. Apart from point out that you are apparently determined not to see that the explanation provided is both coherent and sufficient. That would be your problem, not mine.
I can see why other commenters (eg steveta-uk gave up on this thread).
>>SSAT
Yes, and the standard version is correct and your CO2-cooling stuff is wrong. Please explain the geological-scale correlation between Cenozoic cooling (ca 50Ma - present; typo in original comment) and CO2 in the light of your hypothesis.
Tamsin Edwards
Please do summarise the demise of the CLAW hypothesis once you get the blog going. One commenter in particular here has been making very strong statements about cloud-phytoplankton interactions and I'm sure he will be as interested as I am in the gory details.
Failing that, you could risk a couple of paragraphs on this thread, but refuse to comment further ;-)
Thanks for the request! And the back-up plan :) I will hopefully have a blog by the start of next week and perhaps some content...
BBD
I am currently preoccupied with how GHG theory might be wrong: a harmless and oddly fascinating endeavour. You appear to be occupied with how it might be right. I am not alone however as this has just popped-up at Tallbloke's today. You might want to take a look.
SSAT
Galileo delusion.
Tamsin Edwards
I'll keep my eye out for it. Very much look forward to the debut of a new scientific climate blog.
Thanks, BBD. People give up on this thread and all of a sudden it's my fault. Sheesh!
And you have not "explained" anything. All I have so far are your usual delphic utterances which conceal rather than reveal.
I'll try again.
1. Why doesn't the temperature fall below zero at night? In the first place it does frequently and over wide areas. Secondly there is nothing magic about the figure of zero. It may mean something to us because we are obsessed with patterns in numbers but in the world of heat transference by whatever means there is nothing special about 273K. If I'm wrong about that you can explain why.
So your question is meaningless.
2. I asked at what time of day Tmin normally occurred, absent any specific considerations. The answer — as I'm sure you know — is at or about dawn. Which also renders your question meaningless.
So I am suggesting in all seriousness and humility that you are wrong to talk about solar radiation being constant and using that to argue that it is possible for a cooler object to heat a warmer object if the warmer object is being subjected to a constant heat because the surface is not being subjected to a constant heat.
If you take hourly temperature readings during a summer day in southern England you will find that temperature continues to increase beyond local noon and peaks at around three or four in the afternoon which I am assuming (since this is a blog and not a physics class we're in I'm not going to waste an evening by chasing up text books) is at least partly due to the greenhouse effect which you are describing so to that extent only I will agree with you.
As solar radiation declines so also does the level of radiation emitted by the surface and the surface and air temperatures fall to a minimum at about dawn after which, with an appropriate time lag, the process starts again.
So now I've done the explaining of my understanding. If you don't agree then you can explain why — as can anyone else who is interested.
ssat
I followed the link to Tallbloke's. That is an interesting way to explain things and ideal for people like me who prefer the visual approach. Whether he's right of course ...
MJ
Jan 19, 2012 at 10:29 PM
"The rotational period is constant so averaging the diurnal cycle is assumed. Let's just stick to the basic problem."
MJ
Sigh. I ASKED:
"What is it about the atmosphere that stops (hemispherical) temperatures falling to below zero at night? How does that work?"
Jan 19, 2012 at 8:39 PM
Rubbish. HEMISPHERICAL and BELOW ZERO. There is *nothing* 'delphic' about this. I am asking you to recognise the physical reality of atmospheric DLW. You know - the thing that stops all the OLR vanishing off into space and freezing the surface at night.
This is why I gave up. You just do not bother to read my comments properly. Or think. ALL you do is skim enough to come up with some half-baked 'objection' or other. And then you blame your failings on me.
I have tried to help you. And now I have given up.
Good luck.
BBD
That's all very well and I started off agreeing with that but your argument, as you state it, is that a cooler body can heat a warmer if the warmer body is being constantly heated.
I an positing that overall the effect is neutral because the surface is not being constantly heated. You are in essence taking an average of solar radiation (across the whole surface as well as time I presume) which is fair enough but then you must take an average of the effect of the back radiation also.
Which is net positive by day and net negative by night and therefore broadly neutral.
Simply repeating an earlier posting does not answer the question.
BBD
Posts crossed.
I was quoting from your 4.03pm reply to mdgnn though I don't see that the addition of the word "hemispherical" actually adds anything to your argument.
But you're probably right just to give up.
Mike J;
"Whether he's right of course ..."
I have, unfortunately, come to the same conclusion as in my post yesterday. I say unfortunately as I have now to find where I may be wrong! I'm hoping the Tallbloke thread helps in that.
BBD;
I take your comment to be a straw man argument and not one which was deliberately offensive.
Re Tamsin
I'm intrigued, especially after a quick search threw up this from Charlson very recently:
Sounds like science to me, and if uncertainty has been reduced from when the original hypothesis was floated, it's surely a good thing. From my own quick literature search though, I still can't decide whether the new consensus should be positive, negative or it's just not significant. But that's all part of the fun. My search also showed up continued controversy around other claws and whether they were grooming or gripping, which is a debate that's been going on longer than 25 years. So climate science may have moved quite quickly to a new consensus by comparison :)
BBD to MJ - "I have tried to help you. And now I have given up."
Translation - "I have tied to baffle you and bludgeon you with nonsense, yet you have the gall to resist! Be gone!"
So BBD - getting back onto your education programme and these positive night time temperatures - can you give us the data source in support of your assertions?
nby
WRT the mysteries of radiative transfer and NET energy:
"Yes, if the cooler object is made increasingly IR-opaque and the warmer object subject to constant heating."
You say this is incorrect but do not explain why. All you need to do is point to the errors.
BBD - do you have any numbers to support all your armwaving? If so, show us and prove yourself right.
nby
If the cooler object is made more IR-opaque and the warmer object is subject to constant heating, the net energy at the surface of the warmer object will rise.
True/false?
Not a number in sight!
Night night BBD
nby
If the cooler object is made more IR-opaque and the warmer object is subject to constant heating, the net energy at the surface of the warmer object will rise.
True/false?
It's easy! Yes, or no?
damn...I just checked the temperature. It is night. The thermometer registered -2C. According to BBD, that is impossible.
"If the cooler object is made more IR-opaque and the warmer object is subject to constant heating, the net energy at the surface of the warmer object will rise."
BBD, we already went through this one at KK's.
Shallow pond of water, sunlight shines through water and warms bottom, radiates IR upwards. Cooler water is opaque to IR, absorbs and re-radiates up/down. Every minimally-opaque layer of water above it does the same, each of which is 20 microns thick, so there are thousands of mini-greenhouses stacked on top of one another in a deep pond. Result: back-radiation greenhouse effect mechanism predicts intense heating at the bottom of all ponds.
If you make the water more IR-opaque - e.g. reducing the optical depth to 10 microns, say - does the constantly-heated bottom of the pond get hotter? Yes or no?
The back-radiation mechanism is wrong because it ignores convection, which prevents any heat differential due to radiative effects building up. The atmosphere is convective too.
When Spencer made the claim in his blog post, he used a vaccuum chamber to ensure that heat could only be transferred by radiation. The statement made is not true when there are other, more efficient means to transfer energy.
The thermodynamics of radiation between hot and cold objects is a completely different subject to the mechanism of the greenhouse effect in a convective atmosphere. Back-radiation exists, and in certain specialised circumstances radiation from cooler objects can cause heated objects to get warmer, but has absolutely no effect on the temperature of a rapidly convecting fluid. It is irrelevant to the greenhouse effect in our actual atmosphere. The back-radiation explanation is wrong.
But the back-radiation argument is not wrong because breaks any of the laws of thermodynamics to have cool objects radiating towards warm ones and affecting their temperature. It's only wrong because it ignores the effect of convection in a real atmosphere.
Nullus in Verba: sorry, but you're wrong and here's why [repeat of previous comment]:
Assume that you have a clear sky, emissivity and absorptivity 0.2 and are on the beach in summer, air temperature 25°C, sand temperature 30°C and it’s windy. You put up a wind break and to keep convected plus radiated heat transfer from the sand constant the sand temperature rises to 45°C. These are realistic figures.
Assuming an emissivity for the sand of 0.85 and 20% of the extra IR is intercepted by GHGs and half that comes back, you’ve just increased DLR by 8.7 W/m^2 or 5.4 times AR4’s estimate of total net AGW.
The temperature rise is the UHI writ small. Not even the IPCC claims the UHI causes global warming……..that would be to admit CO2 was far less important. This type of argument is called reductio ad absurdum.
[You can adapt the argument for water by having lower obstacles to convective heat transport, scaling via the dimensionless numbers I used to know by heart and which were the result of deep thinking by brilliant experimental physicists: their knowledge of experimental design has been lost, to be replaced by the computer models and GIGO! Hint. look at the ripple spacing at the bottom of the pond!]
PS
This is not to deny that the extra impedance to IR does not cause warming. However, you must not use the S-B equation for the 'bottom of the water emitter' to devise an energy term that heats the bottom of the pond. That energy is virtual because it is totally annihilated by the Prevost Exchange Principle.
To think otherwise is a breach of the 2nd Law of Thermodynamics because you would get positive feedback, the fundamental mistake in the climate models hence the predicted warming is not happening - experimental proof the models are wrong.
Sorry: This is not to deny that the extra impedance to IR causes warming.
mdgnn,
I don't understand why you think your argument explains why mine is wrong. You're talking about whether DLR causing heating of the Earth's surface. I've just said that it doesn't cause heating of the Earth's surface. You've just said a windbreak to reduce convection locally raises the temperature. I've just said convection is the main issue in a real atmosphere.
Either you didn't read what I wrote, or I'm missing your point.
Would you like to try again?
The reason for the reductio ad absurdum is to point out that because there is convection, a point both of us agree on, if back 'radiation' heating existed, you could vary it by controlling that convection..
Thus, in the limit, the way to minimise global warming would be to flatten every structure and mountain, cut down all trees and genetically engineer every plant and animal to have very short stalks and legs.
Indeed, the aim would be to make the surface of the planet mimic Terry Pratchett's Discworld.
It is absurd: back radiation whilst measurable with a radiometer is only measurable because the radiometer shields the detector from radiation coming the other way, most of which is annihilated except in the unique case of a temperature inversion, or peculiar quantum effects.
Indeed, I'll go further and with respect state that anyone who claims different in the macroscopic world should be subjected to remedial heat transfer training and forbidden to use a radiometer unless for every upwards' reading they reverse it and measure the energy from the opposite direction so they establish the difference!
An alternative is only to supply these devices in pairs, welded back to back with the difference signal as output. Then we would never again have this confusion of energy with heat!
PS just re-read what you wrote: it appears you accept that DLR cannot cause the surface to heat so you think as i do that in most circumstances, it is a virtual energy source.
Mmmm.
You control back radiation by controlling the temperature or the emmisivity of the atmosphere - convection only has an effect on back-radiation to the extent that it does so.
Flattening structures wouldn't have any significant effect on convection. Globally, it's caused by the equator-pole difference in sunlight, and clouds.
Discworld had mountains on it.
Back-radiation would still get measured even without shielding. You'd just get a mixture of both. It's not anihilated, the radiation still exists, but its heat-transfer effect is partially cancelled because it is going in both directions.
Yes, I'm saying increased DLR is not what causes the sunlit surface to heat when the atmosphere becomes more IR-opaque, *but for a different reason*.
It *would* cause the surface to warm up, only convection prevents it.
We're getting nearer.
The key is that the imaginary positive feedback in the climate models is because they add the back radiation to the IR energy coming from the Earth and iterate.
That is why they predict 3-5 times real warming [assuming most of it has been from CO2-AGW, not natural], then have to back it off by the imaginary cooling by polluted clouds and about 10% more baseline albedo for low level clouds than reality [double the optical depth]..
The reality is that the polluted cloud argument is fundamentally wrong, easily proved, and the data for real cloud optical depths are available. No longer can they claim the positive feedback is hidden. It doesn't exist.
This is not science, it's alchemy.
"The key is that the imaginary positive feedback in the climate models is because they add the back radiation to the IR energy coming from the Earth and iterate."
No it isn't. The positive feedback is primarily because a small warming will evaporate more water vapour, which will raise the average altitude of emission to space, which in turn will cause more adiabatic warming at the surface. Back radiation has absolutely nothing to do with it.
The greenhouse effect is the product of the average altitude of emission to space (where energy radiated out has to balance the sunlight coming in) and the adiabatic lapse rate (which sets up a fixed vertical temperature gradient due to convection-driven expansion and compression of air). The adiabatic lapse rate is unaffected by radiation, changes in convection will cancel the effect of any changes in internal-to-the-atmosphere radiation.
Added CO2 does *not* cause warming because it increases DLR, it causes warming because it increases the average altitude of emission to space.
Climate scientists know all this, and implement it that way in their models, but they don't explain it that way to the public. They instead use this idiot back-radiation explanation, which is wrong. If you want to be cynical, you might even suspect they do it that way as a decoy. You'll waste hours and hours arguing over DLR, and they'll just sit there and laugh.