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)
Consideration of heat transfer within the system of Earth-atmosphere ignores the bigger picture of equilibrium of incoming - outgoing radiation. Any atmospheric *greenhouse* component has to reduce albedo if it is to raise temperature. If we consider the meme de jour of *greenhouse CO2* then we can see that this trace gas partly reflects incoming IR directly to space. This reduces energy entering the system and in equilibrium condition, that leaving. It has increased albedo. An incremental increase in CO2 will do likewise. CO2 in an equilibrium condition (and I suspect all states in between) is a refrigerant. All attempts to understand it as contributor to heating will therefore fail, however long the argument.
"Any atmospheric *greenhouse* component has to reduce albedo if it is to raise temperature."
I think what you're talking about there is the temperature at the average altitude of emission to space, not the temperature of the surface. The two are not the same. IR radiates to space from a level about 5-6 km up, on average, the temperature here is fixed by the overall equilibrium.
If the two get further apart, as the emission altitude rises, then the convection/pressure related temperature gradient will increase the temperature difference between them. The upper temperature is fixed, so the lower temperature rises.
The water vapour argument is probably spurious because [agreed] [H2O] is proportional to expT but you can also transfer that extra latent heat to the air by precipitating the water, thus increasing convection.
I think this is called being hoist by your own petard!
I accept the rise in the tropopause. However, the calibration of the GHE is wrong. The claim of 33 K present GHG warming is way over the top and I have seen plausible claims of ~9 K being the balance between GHG warming and extra cooling by clouds.
The cloud physics is at the amateur stage because at least 40% of low level clouds, with bimodal droplet size distributions, behave differently because that introduces a second optical effect.
In time climate science will accept that it has got things very wrong and will start again with better physics. I give it it 7/10 for effort, 4/10 for scientific credibility.
NiV
"The upper temperature is fixed, so the lower temperature rises."
Again, that is just energy distribution within the system. As albedo is increased by additional CO2, how do we get to Catastrophic, Global and Warming by those additions, Anthropogenic or otherwise?
The water vapour feedback is probably wrong, observations contradict the models. That's where attention should be concentrated. Clouds, too.
Latent heat transfer is another way of transporting heat that works in parallel with convection. It actually reduces convection by making it more efficient. (Same heat transfer, by means of less movement.) In practice, the two effects are usually combined by modifying the adiabatic lapse rate for moist air. You get about 6 C/km in moist air instead of 10 C/km in dry air.
The atmosphere emits from throughout the troposphere, the average is in the middle at about 5-6 km up. The greenhouse effect magnitude is 6 C/km times 5.5 km = 33 C. The tropopause is *not* the average altitude of emission. The tropopause is a lot higher, at about 10-15 km up.
"As albedo is increased by additional CO2, how do we get to Catastrophic, Global and Warming by those additions, Anthropogenic or otherwise?"
Albedo isn't affected directly by CO2. And I'm not a believer in CAGW.
Doubling CO2 ought to raise the emission altitude about 150-200 m, corresponding to a temperature rise of around 0.2 km times 6 C/km = 1.2 C. A variety of feedbacks, poorly understood or unknown, modify that up or down. The issue is over the feedbacks, not the basic mechanism.
If the feedbacks turn out close to zero, then 1.2 C per doubling would give about 0.6 C for half a doubling (a 40% rise), which is pretty much what we've seen over the 20th century. The temperature rise over the 20th century was about 0.6 C.
That doesn't necessarily mean anything; there are lots of ways it could have happened even if sensitivity was higher. But the default position for sceptics should be that the basic emission-height-lapse-rate mechanism is correct, but the magnitude is far lower than the alarmists claim because they have exaggerated the feedbacks and downplayed the uncertainties and the multitude of other factors. The climate is very poorly understood, as yet.
NiV
"Albedo isn't affected directly by CO2."
Ah but it is, and in the IR, by partial reflection of the incoming flux. All other *greenhouse* atmospheric components do likewise (excepting water vapour in clouds which acts additionally on SW radiation).
"If the feedbacks turn out close to zero..."
I.e. non-existent. Then adding a trace to a trace gas will have a very small effect indeed without that multiplier. Such as that changed by the change in albedo for example. Oh, and there is Svensmark's hypothesis to be considered as well.
"The climate is very poorly understood, as yet."
And will continue to be while numbers chase an anthropogenic bogey-man.
At last, a payoff. It's wonderful fun watching the cranks and misrepresenters arguing over DLW.
Now what was it that Science of Doom actually said to you on the Curry thread in the end NiV?
Care to jog my memory, or shall I look it up?
No need to look it up. That was the one you imagined was the devastating refutation of everything I had said, yes? Let's deal with it now.
(judithcurry.com/2010/11/30/physics-of-the-atmospheric-greenhouse-effect/#comment-17521)
He said:
"In atmospheric physics text books and papers on the subject, when climate scientists “try to explain it” the explanation is correct."
Not quite true. Sometimes it is and sometimes it isn't. But this was really a criticism of my having said "when they try to explain it" without qualifying that to "to the general public". Arguably implied at the time, but I'm always happy to learn and usually put the caveat in now. On the main point, he says:
"Many websites set up to explain to the general public in media-friendly sound-bites probably do explain it badly. Or non-technically. Or completely wrongly."
which I think is an admission of a kind.
He then goes on to try to make the distinction to say it's perfectly OK for NASA or the Met Office to get it wrong when they explain it to the public, if it's right in textbooks and papers that the public are unlikely to ever see. It's precisely this attitude that causes the problem.
Then we move on to the physics.
"The “real mechanism” as Nullius and Leonard Weinstein describe is correct – as more “greenhouse” gases are present, the effective height of radiative cooling to space increases. And because temperature decreases with height due to adiabatic expansion, a higher altitude for this radiation = less radiation = less ability to move heat out of the climate system and therefore = “a heating”.
This explanation is the one you find in the atmospheric physics textbooks, and the papers."
Thus, we have agreement from an atmospheric physicist that the physics I set out is correct. It is, as I said, the version they use themselves, but which is rarely shared with the public.
However, being a loyal member of the orthodoxy, he tries to offer a weak defence of the "back-radiation" version that usually gets trotted out.
"However, the idea that “back radiation” is irrelevant is not really correct. It is essentially a complementary effect."
This is meaningless. Complementary in what sense?
"How is it possible for surface temperatures to increase under this model? Surface fluxes must balance. Yet solar radiation is still the same. A higher surface temperature will cause a higher convective flux and a higher radiative upwards flux. (Increase in energy from the surface)."
True statements. And implied in my model. So not contradicting anything I said.
"How is this possible? There must be a balancing surface item. The balancing item is the back radiation. More “greenhouse” gases will cause more downward radiation (lowering effective altitude of downward radiation)."
This is again true, and is again implied by what I said, but is besides the point. If I put another inch of water in the pond, the upward radiation from the original surface must be balanced by something, which turns out to be the downward radiation from the top inch. It's a true statement, but it's got nothing to do with explaining the temperature profile of the pond - why the pond is at a constant temperature and the atmosphere at a constant gradient. It's a necessary condition to make this possible, but it's not an explanation.
"It isn’t one vs the other. One is a consequence of the other. The “controlling mechanism” is the radiative cooling to space which is determined by the effective height of the radiation. Downward surface radiation from the atmosphere increases as a result. All are linked."
And this again repeats exactly what I had said. Back radiation exists, and is very large compared to other heat fluxes, but it does not control the temperature. And that's what this is all about.
The emission-altitude-lapse-rate explanation controls the temperature, and increased back radiation is a consequence of it. (So is increased upward radiation, of course, but we don't see that being offered as an explanation.)
I found it amusing that you hadn't even followed the logic of what he was saying to realise that it hadn't contradicted me in the slightest. He had complained that I hadn't mentioned that their super-secret explanation was correct, although I had, and he complained that although I was correct about what controlled the magnitude of the effect I shouldn't have dismissed back radiation entirely since it was a part of the physics and it changed as a consequence, which of course I hadn't.
I found it disappointing that you was so determined to prove me wrong that you couldn't even read what your own evidence actually said. It's all surface impression with you. 'It sounds like it's disagreeing, and it's written by an expert, so I'll copy it out and hope people are impressed.' That's the way to fail the Turing test.
NiV
Interesting. An inversion of the way everyone else sees it. The altitude of the tropopause increases as the troposphere is heated by increased radiative forcing by GHGs. This reduces the amount of radiative loss at the tropopause and the entire troposphere heats up. And of course, so does the surface.
The determining factor is radiative forcing, not convective heat transport. Convection offsets the effect of radiative forcing but is ultimately constrained by the effects of radiative forcing. It can never be equal or dominant.
Look at the real world. There's no evidence that convection can balance or negate the effects of radiative forcing. That would be to argue for a very insensitive climate system.
Doing so directly contradicts the entire paleoclimate record.
BBD: how do you explain this: http://bobtisdale.files.wordpress.com/2011/12/figure-101.png
GHG warming?
Tell it to the Marines.
Yes, BBD, like I said, that's the wrong (but usual) explanation. It gets it backwards - they look at the radiation, assuming convection is a minor correction, but actually it is the convection that dominates in the sense of controlling the temperature profile within the troposphere. The surface is so much warmer than the average emission altitude because of the adiabatic lapse rate.
And as we've already discussed, the water pond is evidence from the "real world" that convection can negate the effects of radiative forcing. Otherwise, the bottoms of ponds would be very hot.
Personally, I don't think it says anything at all about sensitivity, or the paleo record. It doesn't confirm or refute consensus views on either. But even if it did, not liking a conclusion is no reason to dismiss an argument. That would be an "appeal to consequences" fallacy. I'll assume that wasn't what you intended.
NiV
Oh dear. I know I'm supposed to be the stupid one, but sometimes...
Thanks, NiV, for a great post yesterday at 10:31. Unfortunately, as well demonstrated by this thread, blogs make for great conversations but are less great for technical discussions, due to the difficulty in using equations and diagrams, and the willingness to assume that the others are ideologically blinkered idiots who know nothing - even if they are saying essentially the same thing.
Anyway, as I understand it, the physics you describe are in broad terms those that are present in GCMs - so are by definition those of the consensus. My own view is that this broad picture is unlikely to be fundamentally wrong - the subtler question of how much the effective emission rises or drops in response to perturbations is where the key question is.
NiV
Re-reading my post at 3:27PM it sounds as though I am being combative. I am not and apologise if you found it to be. I do have a question though;
As the average altitude of emission to space rises, would that not also increase the surface area of emission and, as I believe it must, change albedo once equilibrium equilibrium is reached? If the answer is yes, then for incoming to equal outgoing flux albedo must reduce. As CO2 is opaque to IR, additional CO2 would have the contradictory effect of increasing albedo: no?
SSAT, the area is of order R^2; the change in area is of the order R times dR - dR is tiny compared to R so the change is tiny.
Jeremy,
Thanks. It's helpful if people say if they agree; it makes it easier to judge if I've got the explanation right.
Diagrams would sometimes help, one of these days I'll get round to doing some. I tend to try to avoid equations - they're great for the precision they enable for those that can read them, but a lot of people get put off by heavy maths. And it can sometimes obscure lack of understanding. You can plug numbers into formulae without knowing what they really mean.
Actually, the biggest problem I have with these debates is when too many people are talking at once, all trying to explain their own pet theory, and the discussion loses focus. You get diverted down dozens of rabbit-holes, and get spread too thin. I think that's good, though. I'd rather see people thinking about it for themselves and coming up with their own theories than regurgitating stuff out of books without understanding, and a broad range of arguments and points of view is more likely to pick up errors and unstated assumptions, provide new insights, suggest new ways of explaining. People do not change their opinions over night, but if you keep chipping away, the 'fittest' arguments are the ones that survive.
As Milton said: "I cannot praise a fugitive and cloistered virtue, unexercised and unbreathed, that never sallies out and sees her adversary but slinks out of the race, where that immortal garland is to be run for, not without dust and heat."
There's lots of dust and heat in the climate debate, but "who ever knew Truth put to the worse, in a free and open encounter?"
SSAT,
Don't worry, I didn't find it combative. In fact I decided earlier that it was close enough to correct not to be worth arguing with.
You are correct that CO2 will affect the IR-albedo of the Earth slightly. It's a point that's usually ignored, since the vast majority of the incoming radiation is in the shortwave, and the albedo of atmospheric CO2 is not all that different to the sea/land.
The change in surface area with a higher emitting surface changes both the area that incoming IR can hit as well as the area it is scattered from. The total outgoing increases, but so does the total incoming. The ratio of the two stays the same. A material with an albedo of 50% will still have an albedo of 50% whether it is in the form of a ball 1 km across or a ball 6000 km across.
I'm not sure if you're thinking of 'albedo' as the ratio of all incoming radiation to all outgoing, and supposing that because the smaller solid surface is absorbing and the larger atmospheric surface radiating, the heat radiated per unit area reduces as the CO2 increases.
This isn't what 'albedo' means, but it would, technically, be true. The surface area of a sphere is 4 Pi r^2, the derivative with respect to r is 8 Pi r, so the increase in area for a change of dr is 8 Pi r dr. As a fraction of the total area, this change is (8 Pi r dr)/(4 Pi r^2) = 2 dr/r, so the radiation needed per square metre drops by about 200/6,371,000 = 0.000031. You can work out the corresponding drop in temperature if you like, but it's not going to be much.
Hope that helps.
Sorry, that should be
400/6,371,000 = 0.000062.
Isn't it odd how you always spot the errors about a minute after hitting 'send'?
NiV
The number may be small but we also may be arguing about nano-effects when it comes to the Big Picture. To Jeremy, you stated "Diagrams would sometimes help, one of these days I'll get round to doing some."
If you have not seen them, you may be interested in a current series of diagrams at Tallbloke's which coincide rather well with my visualisation of the processes of Earth system heat transfer in equilibrium condition.
Okay, let's not talk about why NiV's 'pet theory' is incorrect.
The altitude of the tropopause increases as the troposphere is heated by radiative forcing from GHGs. This reduces the amount of radiative loss at the tropopause and the entire troposphere heats up. And of course, so does the surface.
The determining factor is radiative forcing, not convective heat transport. Convection offsets the effect of radiative forcing but is ultimately constrained by the effects of radiative forcing
And of course arguing for some kind of climate homeostasis mechanism is to argue for an insensitive climate system. Which does contradict the entire paleoclimate record.
That's how we know that what NiV argues is incorrect.
BBD: you explains the earth coming out of ice ages by a mechanism that doesn't involve any GHG concentration change in the amplification mechanism.
There may be some CO2-GW, but it's at the most ~15% of the median IPCC claim which is based on provably incorrect physics.
Excellent BBD!
And since we've already got agreement that this is the actual mechanism implemented by all the climate models, and according to SoD the one used by all the textbooks and papers too, then you've just falsified all of climate science!
Well done! Welcome to the club of climate naysayers!
Or is it possible you haven't understood a word I've said...? Climate homeostasis mechanism?
NiV
You are now waffling.
MDGNN
You haven't 'proved' a single thing on this or any other thread at BH except that you are a serial misrepresenter with some very cranky notions.
BBD; the evidence is plain to see.
Just look at any cloud preparing to rain and contrary to the accepted physics, albedo becomes very high as mean droplet size increases. This goes exactly the opposite way to the two-stream approximation physics.
There's a second optical effect; van der Hulst and Sagan got it wrong; the climate models are broken; GHG-GW is much less than claimed..Just accept it and go and fight another battle - you can't buck experimental observation and many besides me are working on it.
MDGNN
What experimental observation would that be? Dark rainclouds. Come on.
I can just as easily say that the high albedo of developing convective cumulus is driven by a high rate of nucleation (rapid condensation as air rises) and small droplet size.
You prove nothing but claim a hell of a lot. It does not engender confidence.
Nullius - you are right, a huge virtue of blogs is that few concepts are allowed to remain unexcercised and unbreathed! The contrast with science education, where there's very little arguing and reexpressing in other words, os space made for incorrect but interesting ideas, is reallly refreshing. You didn't comment on my other point, about the level of distrust, and the widespread opinion that people perceived to be on the other side are automatically assumed to be malevolent as well as wrong. That makes discussion quite tiresome at times. Anyway - thanks for the link to the Judith Curry thread. One of the most educational I can remember reading.
BBD: the basis of the climate models is a curve fit of albedo vs optical depth, a monotonic function, albedo increasing as optical depth increases. Theoretically, optical depth is proportional to 1/droplet mean diameter.
However, look at a rain cloud with increasing mean droplet diameter and these relationships break down.The upshot is that 40+% low level clouds behave very differently and if you restrict droplet coarsening, the 2md AIE, it's a substantial GW mechanism, easily outstripping CO2-(A)GW.
Climate science has been badly misled by GISS/NASA still claiming net AIE is becoming increasingly negative to try and keep the high feedback CO2-AGW idea alive.
MDGNN
Fine. Publish and convince me and everybody else that cloud optical physics is currently in error.
BBD: on its way.
MDGNN
I'll believe it when I see it. Given the nonsense and serial misrepresentation we've had from you here at BH, I'd be staggered if you've got anything that could pass review.