Thursday
Apr122012
by 
Bishop Hill
Bishop Hill Heat exchange
Apr 12, 2012 Climate: Sceptics Climate: other Yale Climate Forum reports on a heated exchange between Doug Keenan and Scott Denning, a climatologist who has made outreach efforts to sceptics, notably attending the Heartland Conference last year.
I find the whole thing rather exasperating to tell the truth. Keenan's point - that we cannot detect any global warming signal in the temperature records - and Denning's point - that CO2 is a greenhouse gas - both seem to me to be substantive, but not decisive. The conversation would be more meaningul if both parties recognised this, and discussed what would be decisive.
Update on Apr 12, 2012 by
Bishop Hill
Bishop Hill
Doug Keenan suggests that I publish the whole of his correspondence with Prof Denning. Given that much of this has appeared on Yale Climate Forum already, I guess this is OK.
Dr. Denning,
The Yale Climate Forum quotes you as saying “Almost everyone that dismisses climate change as a problem does it for ideological or political reasons, not for scientific reasons”. You appear to have done what Richard Betts warns against in the Forum article: gotten your “impression of the other group second-hand”. As Betts notes, that “leads to further misunderstandings and increased bitterness”.
I ask you to read the reasons that skeptics have given. Last year, I published an op-ed piece in the Wall Street Journal, which was subheaded thus: “What is arguably the most important reason to doubt global warming can be explained in plain English”. If you have a rebuttal to that piece, I would be much interested is seeing it.
Dear Dr. Keenan,
Thank you for your note.
Actually I have personally spoken with literally thousands of people who don't "believe" in climate change. I meet regularly with such groups: at the Heartland Institute's annual conference; at Colorado Christian University; and the Western Cattlemen's Association; and at public presentations across the US. Nearly all of them have been opposed almost entirely on ideological rather than scientific grounds. This is not hearsay -- it's simply been my personal experience.
I respect ideology and belief. I understand that people are opposed to big government and inefficient political intrusion in the free market. I am very sympathetic to these beliefs, and have found that mutual respect can help people to find common ground on climate and other issues.
I do recognize that there are people, yourself included, that have specific scientific objections to scientific results on climate. However, I find each person's objection to be rather idiosyncratic. You complain about autoregression in timeseries, for example. Others have similarly narrow objections based on temperature trends of Saturn's moons, Milankovitch cycles, numerical approximations, cloud parameterizations, urban heat islands, etc. The list seems endless. But there is no unified "contrarian" critique of mainstream science; merely a thousand tiny details without a theme other than anger.
The criticism you level in your WSJ opinion piece is a great example of my point. You pick a tiny issue (autoregression in timeseries analysis), and analyze it in detail, giving the false impression that this is somehow an important objection to mainstream science. The false premise is that concerns about future warming are based on extrapolation of recent trends. This is certainly not the case, as the mainstream science is based on laboratory spectroscopy of CO2 gas that is backed up by 150 years of experimental data!
Climate scientists are concerned about future warming not because it's been getting warmer lately, but because we know that (a) burning fossil fuel emits CO2; (b) CO2 molecules emit heat; and (c) heat warms things up. We can confidently predict a warmer climate under elevated CO2 for precisely the same reason we can predict that Miami will be warmer than Minneapolis this year.
I urge you to spend some time really listening to scientists, as I've spent countless hours listening to contrarians. It's been a wonderful experience for me, and I'm sure you could broaden your horizons as well!
Sincerely,
Scott Denning, Ph.D.
Dr. Denning,
My op-ed piece explains that a whole chapter of the most-recent IPCC report is unfounded: the chapter, moreover, which claims global temperatures have been significantly increasing. Your message asserts that this is a "tiny issue". Clearly, the assertion is untrue and you know it to be untrue.
Your message additionally asserts that because "CO2 molecules emit heat" global warming must be substantial. By such reasoning, a person who put their feet in a bucket of hot water would have their hand temperature increase. Earth's climate system has mechanisms for dealing with heat, and CO2 concentrations have been higher in the past. You know all this.
Etc.
I previously wondered if you were dishonest or just confused. I no longer wonder about that: your reply is substantively dishonest.
Douglas J. Keenan
Dear Mr. Keenan,
Thanks for your reply. If you wish to be taken seriously, please keep your correspondence respectful. I don't claim to be infallible, but I assure you I am not dishonest. You specifically asked me to rebut your opinion piece in the WSJ, and I have taken your request at face value. I am more than willing to listen and discuss, but I am not interested in trading insults.
Scientific concern about climate change arising from CO2 emitted by burning fossil fuel predates the IPCC by well over 100 years. The concern is based on very simple physics, not on rising temperatures or timeseries analysis.
Everything in the universe emits heat (yes, even ice water!). At a given temperature, CO2 molecules emit much more than the oxygen and nitrogen molecules that make up 99% of the atmosphere. This effect has been known quantitatively since 1863. The emissions have been independently measured wavelength-by-wavelength thousands of times in hundreds of spectroscopy laboratories around the world, with increasing precision and cannot reasonably be disputed.
The Earth's surface is warmed by the Sun during the day. But at night there is no sunshine, yet thankfully we do not freeze to death each night. That's because the sky also emits heat that is absorbed by the Earth's surface. We can easily measure the heat received from each source (the sun vs the rest of the sky). The measurements show that every square meter of the Earth's surface receives about twice as much heat from the warm sky (333 Watts) as from the Sun (161 Watts). Again, these are simple measurements that have been repeated all over the world. Without this extra heat emitted by CO2 and H2O molecules in the sky, the oceans would long ago have frozen solid, to the bottom.
It is perfectly reasonable to ask how sensitive (in degrees Celsius) the Earth's climate is to changes in heating (in Watts). But it seems disingenuous to assert that heat doesn't change temperature. Everyday experience with teapots, hands, and feet refute such a claim.
Doubling the number of heat-emitting CO2 molecules adds 4 Watts per square meter to the Earth's surface. Assuming that China and India emerge as industrial economies in the 21st Century, and continue to drive these enormous economies with coal, the number of CO2 molecules in the warm sky will not merely double, but quadruple relative to 20th Century values. In that case there will be 8 extra Watts of heat provided to each square meter of the Earth's surface, 24 hours per day, 365 days a year, for many centuries.
By comparison, 18,000 years ago, when ice sheets straddled Europe and North America the Earth's surface received about 7 fewer Watts of heat per square meter. Evidently a few Watts per square meter, applied over time, make a big difference to surface temperatures! The 7 Watts per square meter of post-glacial heating was applied gradually over 100 centuries of melting ice. Yet Plan A is to apply a similar heating in the 21st Century to accommodate the welcome economic transition of the developing world.
Personally, I believe in capitalism, freedom, and the power of market incentives to drive innovation. I'd be interested in your thoughts about how these principles might best be used to provide a decent standard of living for billions of people without dramatic changes to the energy balance of the Earth's surface.
Sincerely,
Scott Denning, Ph.D.
Dr. Denning,Your message claims that "Doubling the number of heat-emitting CO2 molecules adds 4 Watts per square meter to the Earth's surface". Here is an admittedly rough analogy. If one end of a beam is put in a bucket of hot water, the other end will warm: that is simple physics. A person who puts their feet in a bucket of hot water, however, will not have their hand temperature increase. The reason is that person is a complex system that has mechanisms for dealing with heat ("feedbacks"). Similarly, Earth's climate system has mechanisms to deal with heat. Because of such mechanisms, the simple physics that you describe is misleading.As an example, it has been proposed that as Earth heats, clouds shift to allow more heat to escape into space; temperatures on Earth's surface are thereby reduced. This is sometimes called the "iris hypothesis", in analogy with how the eye's iris works. The hypothesis exemplifies how it is essential to understand feedback mechanisms dealing with heat.The iris hypothesis was proposed by Richard Lindzen, in 2001. Note that Lindzen is usually considered to be the world's leading expert on clouds.Substantial discussion of feedback mechanisms dealing with heat is given in the most-recent (2007) Assessment Report from the IPCC: section 8.6. That section is part of chapter 8, with deals with climate models. The reason that this issue is usually discussed with climate models is that the various mechanisms are numerous, nonlinear, interacting, etc.: climate models are often considered the best to deal with such complexity. The IPCC section concludes that "it is not yet possible to assess which of the model estimates of cloud feedback is the most reliable", which alone counters your claim.Discussions pertaining to feedback mechanisms have of course continued since the publication of the IPCC report. I have not followed them though. One paper that I recall is by Lindzen & Choi [2011]. Recently, Davies & Molloy [2012] has been in the news.We now have two options.1. You are truly ignorant of all of the above.2. You are aware of at least some of the above and your message is dishonest.Your web page says that you (a) have a Ph.D. in atmospheric science, (b) have been working in this area of climatology for many years, and (c) have been an editor of the world's top journal for climatological research, Journal of Climate; hence option 1 is not credible. I conclude that you are dishonest. This is in addition to the evidence presented in my previous message.I would not usually reply to such dishonesty, but the e-mail from Bud Ward indicated that an elaboration of my previous message might be appropriate.
Reader Comments (154)
"or are all those who are in this business in non-jobs creating no prosperity for themselves and others?"
This sounds like a variation on the 'broken window' fallacy.
Creating jobs is easy. Just employ half the people to dig holes, and employ the other half to fill them in. This difficult bit, and what people usually mean by "creating jobs", is creating the value to pay the wages for those jobs.
People are selling energy, and if it takes 100 people to produce $1000-worth of energy in a day, they each get $10/day. Now suppose you switch to a different method in which it takes 1000 people to produce $1000-worth of energy in a day. Have you thereby created 900 jobs?
I am a bit perturbed by Keenan's claim that Earth's climate system has 'mechanisms' for dealing with heat, supported by his example of a person standing in hot water. This seems perilously close to Lovelock's twaddle about 'Gaia' - the earth as some kind of self-regulating organism. Real biological organisms have often evolved mechanisms that (within limits) regulate such variables as temperature, blood sugar levels, etc. But we have no reason (without appealing to divine wisdom or such-like) to suppose that planets have 'mechanisms' in this sense. Climate systems do contain various positive and negative feedbacks, but I see no reason for optimism that the negative feedbacks are such as to maintain equilibrium, and the geo-historical record of ice ages and other major changes suggests otherwise.
No, it doesn't; natural variability explicitly fails to capture natural behaviour across timescales, e.g. the following paper:
Anagnostopoulos, G. G., D. Koutsoyiannis, A. Christofides, A. Efstratiadis, and N. Mamassis, A comparison of local and aggregated climate model outputs with observed data, Hydrological Sciences Journal, 55 (7), 1094–1110, 2010.
Nature has and done just this as evidence from the last hundreds of thousands of years of sea level variation shows; indeed the exit and entry to glaciations can result in sea level change more than twice the present rate.
Hmmm.....
I see we've subtly changed the script from "seeing changes occurring all around us" to relating third party memes about arctic sea routes, melting ice caps etc. (assuming you're not an arctic explorer by profession).
Why is it always like this with true believers? Confident assertion until challenged - then a rapid shuffling of the goalposts & muddying of the waters.
So, basically you can't relate a single thing you've personally witnessed which might indicate global warming - but you believe in it anyway.
It's a religion isn't it?
"I am a bit perturbed by Keenan's claim that Earth's climate system has 'mechanisms' for dealing with heat, supported by his example of a person standing in hot water."
The bloke-in-a-bucket analogy is not a very good one, but the general idea is correct. Part of it is that convection can carry away any excess that would otherwise build up near the surface whenever the gradient exceeds a certain threshold. Part of it is those feedbacks that happen to be negative. He mentions a few.
But see my earlier comment.
"Doubling the number of heat-emitting CO2 molecules adds 4 Watts per square meter to the Earth's surface".
I think I have just solved the world's energy problem. Could someone answer me this: If I were to fill my greenhouse with pure CO2 (ie 1,000,000 parts per million), how much energy could I generate?
Rhoda enquired about measurements.
This is not an answer but it does highlight what I consider to be a serious shortcoming in modern climate science. Hardly anyone seems to make any measurements. All the "important" findings you get to hear about were done by people sitting in front of a computer and processing someone else's data.
The provenance of the data does not seem to be important, neither does keeping the data or showing it to anyone else. In fact, the base data can be spuriously adjusted, spacially averaged anomalies of the reciprocal of the partial rate of change of entropy with respect to internal energy recorded at sundry points on the planet's surface and the results used to indicate that taxes should be increased.
It reminds me of that classic program on BBC radio: The Navy Lark.
"With cabbages at 3 and 6 a pound and all the rest have thirty one and all distances measured from Charing Cross except on Thursdays, I would say: Left hand down a bit chief.
"Left and down a bit it is, Sir."
William Morris
I'm more impressed by people just doing it and not impying there is something holding them back. "Digging more carbon out of the ground " to aid growth fits historical actuality and is a good bet for fair while in the future too - not up to my opinion or my model - it just is a fact ;) It will be done otherwise in the far future I feel sure - just a feeling - if it can be done otherwise sooner then good luck - the less help from rent seeking the better the growth I say. As for "Extracting carbon from flue gasses and burying it " mmm, exciting, sound like that would need some help ;)
This is the same for the others in your list of examples - they seem like the cliched list that gets trotted out when someone tries to whip up green growth as an argument - no one is a millionaire in those yet unless they are Chinese who have turn sand into solar panels faster than the Europeans can or Camerons mates who stick up windmills on their land faster than they can rust. I like your end item of that list. "am I missing something". Not just you, we are all are missing something the innovations that frighten the alarmist because they don't feel confident humans can create them. I am more optimistic.
The "it's simple physics" meme fails abjectly because warmists jettison simple physics whenever they feel like explaining away those persistently contrarian observations; like the phony deep water heating that somehow doesn't heat the surface first, or a warming ocean somehow being a net sink of CO2 rather than a source. We are bound to conclude that if it isn't always so simple then it needn't ever be so simple. There's a lot of ideology in the warmist arguments but what you see depends on where you stand.
Yes skeptics of the right are more inclined to be skeptical of anything that advocates extra tax because of their ideology and hence they look at skeptical arguments versus alarmist arguments and note that there is plenty to be skeptical about. But in such an important subject it's a crying shame that there are not more skeptics from the left. It's even more shameful how warmists totally dismiss the idea that they might be causing more harm than good with their alarmism. It is just taken for granted that new technology will prevent that happening. In that sense they are greater believers in the market than anyone else.
Did I just read Scott Denning dismiss all of Michael Mann and the Team's work? Maybe he doesn't get away from the lab much, but I dont think they will be much pleased with his summary of Climate Science.
Scott may well not think he is being dishonest, so understandably must be hurt by the accusation, but he also does not answer Douglas Keenan's argument, which seems a bit foolish given that Doug is no lightweight.
Watched a fascinating lecture today by Murry Salby all about CO2 levels not being quite what you thought they were... a must see if you havent already. Maybe we should ask Scott if he has seen it.
tinyurl.com/bme7c3l
Nullius in Verba: I hadn't heard of the name for that (broken window fallacy)
but it is an interesting concept. But it doesn't fit here. People have been
insulating houses and building power stations fitting solar panels even before
any thought of GW. It is real activity with real value. I guess you could
apply the fallacy theory to the military - all of our military spending is
making things in order to destroy things which are of no real threat to us.
And yet we happily spend billions on them. Welfare spending likewise - paying
people to do nothing is surely a similar concept, yet society spends hugely on
this project. We have to build new facilities so why not make them as
efficient as possible and as non-dependent on foreign oil producers as
possible. It just makes sense. Covering the place with solar panels or
windmills is however of debatable value (see MacKay, Sustainable Energy
Without the Hot Air).
Foxgoose: note that I said "see changes occurring around them", and not
"seeing changes occurring all around us" as you quoted. But details aside,
your complaint is unfair. The comment on climate change was a small part of a
large paragraph. It was challenged by someone and I expanded upon it; now you
don't like that the expansion does not say exactly the same thing. To say the
same thing I only needed to repeat the sentence, which would be pointless.
Did I really shuffle any goalposts or muddy any waters? You may doubt that
arctic sea ice is reducing or that the Russians and shipping lines are now
considering the use of newly thawed arctic routes or that there are now
disputes between Canada and USA on the ownership of coastal areas that have
now become accessible. Maybe such talk is all lies but I find that unlikely.
Here in Ecuador I have seen areas that for many years were uncultivable that
are now in use. The advancement of spring might pass you by, but biologists
have certainly noticed. If you live in a family of biologists, you will hear
of species that are changing their ranges. If you listen to scientific news
you will hear of devastation to Canadian forests due to beetles expanding
their range. However if you just listen to Jeremy Clarkson you will probably
hear exactly what you want to hear.
The Leopard In The Basement: you are right. It wasn't a good example :-) On
my list, I made it up, so no cliche. I don't have any background in these
arguments beyond the last week or so, so I'm learning :-)
Apr 12, 2012 at 2:37 PM Douglas J. Keenan
First, Douglas J. Keenan, let me say I admire your work.
Having thought about it, I think it is insulting to call somebody dishonest in the middle of a discussion with them. At conscious level, I am pretty sure that Denning does not consider himself in the slightest bit dishonest. From his perspective at least, it would therefore have been insulting to be told he was being dishonest.
After many months, and in the middle of a hangover, I have miraculously understood what mydogsgotnonose is on about with shielded pyrgeometers, Prevost Energy Exchange and the impossibility of back-radiation doing thermal work.
A truly Damascene moment. Who'da thunk it would arrive in reading the comments on the exchange between Mssrs Keenan and Denning?
Seems Denning suffers from the all-too-usual hubris of climate scientists. But I think Doug's comments on dishonesty might better have remained unsaid in their exchange.
William Morris - you may not have noticed, but us sceptics have never said that climates don't change; what we are saying is that any changes in climate are very obviously not driven by increases in CO2.
And, as someone with some knowledge of the history of the arts, I find your appropriation of 'William Morris' as a pseudonym to be quite odd, but if that is your acual name, I apologise.
Your reference to Jeremy Clarkson is rather odd - I find him and 'Top Gear' very entertaining and very honest about reality as he and his crew see it, but that has absolutely nothing to do with this thread.
And, like Gixxer Boy, I admire Keenan enormously but feel that him accusing Deeming of being a liar was ill-advisedly intemperate, but frustration with Deeming's shallow arguments probably drove Keenan to make the accusation.
Chris,
I am a school science teacher. I believe that Dr. Denning has done well to explain his understanding of the greenhouse effect ( GHE) in clear simple words. He says CO2 creates extra heat.
You say CO2 "surpresses the escape of thermal energy" and " tends to cause an increase in height.. at which IR escapes".
Please explain this or give a reference that explains it.
How does it create extra heat? All the heat comes from the sun. There is no extra heat. Why does he say there is? Cause we're too stupid to understand? There is no extra heat being created. CO2 does not emit heat in any meaningful way. Why do they need to cheat and devieve?
Deceive not deveive. Roger, are you being tongue in cheek? Is this sarcasm? If not I fear for science in your school.
William Morris (nice name) Apr 13, 2012 at 12:13 AM. I have had the same experience about hearing of the signs of a globally warmed world. But those same biologists also say it was as warm or warmer in medieval times.
And that is the whole point. It is not that the climate changes, it does. It is not that CO2 is a greenhouse gas, it is. It is that somehow those two things mean we are heading to some mystical tipping point because we have sinned by burning the earth and must repent by building monstrous temples to the wind gods and generally try to live in poverty. Super, but why?
Rhona,
I liked Denning's explanation because he does not hide his thinking.
I don't agree with it, or with the longer explanation by Chris. That is why I ask for a reference.
Roger Clague
Dr Denning may well have explained HIS "understanding of of the greenhouse effect ( GHE) in clear simple words." But I sincerely hope that you see the flaw in his notion that "CO2 creates extra heat." Otherwise I must second Rhoda's comment at Apr 13, 2012 at 12:01 PM.
Arthur Dent said:
I agree. You cannot spend the same pound twice. If AGW *is* a catastrophe waiting to happen we will not prevent it with wind turbines, expensive lightbulbs, five year plans and carbon rations but we will also not have any money left to be able to afford adapting to it.
"I am a school science teacher. I believe that Dr. Denning has done well to explain his understanding of the greenhouse effect ( GHE) in clear simple words."
The problem is there are two separate mechanisms by which a 'greenhouse effect' can occur: one applies to non-convective atmospheres, and the other applies to convective ones. The non-convective one was invented first, but it was realised around the start of the 20th century that it didn't work for the Earth's atmosphere. Around 1950 the second mechanism was discovered, which does work, and is the basis of the calculations. However, for reasons I don't entirely understand, a large subset of climate scientists insist on using the initial non-convective explanation, treating the developments since 1900 as a minor correction barely worth mentioning.
I gave a link earlier to a previous explanation of mine, but people evidently don't follow links, so I'll try explaining again.
The pure radiative greenhouse effect occurs only when convection and conduction can be neglected. The argument goes as follows.
We have a material that is transparent to visible light but opaque to thermal IR. We imagine horizontal slices through it to split it into minimally opaque layers. Sunlight shines through all the layers to be absorbed at the bottom, warming it, but the radiation from the bottom cannot escape directly. It is absorbed in the first opaque layer, which warms and re-radiates it equally up and down. The radiation going up likewise cannot escape directly, but is absorbed by the next layer up, and so on. The topmost layer radiates directly to outer space. If the sunlight contributes X units of power, then you get balance when the topmost layer radiates X units upwards. The whole atmosphere warms or cools until it does. Since it radiates X units downwards as well, the topmost layer is losing 2X units of power, which it must get from somewhere, and the only place it can get it is the layer below. That layer radiates 2X up, 2X down, and needs 3X from the layer below it to balance. And so on. Every opaque layer radiates an extra X units of power compared to the layer above, and has to be a little bit hotter to do so.
The atmosphere doesn't have many layers, but if you calculate how much this mechanism would warm the surface, the average surface temperature would be about 60 C. [Manabe and Strickler 1964, Thermal Equilibrium of the Atmosphere with a Convective Adjustment, figure 4]
Since the average surface temperature is about 15 C, that hypothesis is falsified by observation.
And a similar calculation in a pond of water, which is likewise transparent to visible and opaque to IR, but with a minimally-opaque layer thickness of about 20 microns, the temperature rises hundreds of degrees within the top metre. The backradiation emitted downward by each layer grows massively. The oceans would boil. Likewise, this is also falsified by observation.
The reason it doesn't work is convection. Hot air is less dense and rises, cold air is denser and sinks. As soon as heat starts to build up near the surface, convection cycles start up and transport the heat away far faster than it can accumulate. The more heat there is, the faster convection works. The radiative resistance to heat transport is totally short-circuited.
However, in the atmosphere things are not quite so straightforward, because air is compressible, and when you compress air it gets hot and when you let it expand it cools. This is the mechanism by which a refrigerator works. So with convection driving vertical motion of the air, rising air expands as the pressure drops, and that cools it. As the circulating air falls again it gets compressed by the weight of the air above it and warms up. The effect of this is to stabilise the air against convection. You can get cold air resting on top of warm air so long as the difference in temperature is less than the cooling that would occur if it was to rise and expand. This threshold is called the adiabatic lapse rate.
If the slope is less than or equal to the adiabatic lapse rate, the air is still. But the moment you go over, convection eliminates the excess and flattens it out.
In a convective atmosphere, the temperatures at every level are tied together by this fixed slope: the difference in temperature between two layers is just the adiabatic lapse rate times the difference in their heights.
So how does the greenhouse effect work? Well, you still have the top layer radiating X units to outer space, and settling at the right temperature to be able to do so. But if the atmosphere is opaque, the radiation is emitted from high up in the atmosphere, and it is this layer that settles at the -20 C needed to balance the incoming sunlight. The layers below it, and the solid ground, are warmer than that because of the adiabatic lapse rate. The equation for this is
T_surf = T_eff + ALR * AEH
Surface temperature equals the effective radiative temperature (for heat balance) plus the adiabatic lapse rate times the average emission height. (See http://adsabs.harvard.edu/full/1967ApJ...149..731S for an example of its use, (with a famous author).)
For the Earth, T_eff = -20 C, ALR = 6.5 C/km, AEH = 5 km, greenhouse warming = 33 C
For Venus, T_eff = -41 C, ALR = 10 C/km and AEH = 70 km, greenhouse warming = 700 C
For Mars, T_eff = -56 C, ALR = 4.5 C/km and AEH = 1 km, greenhouse warming = 4 C
For a pond of water, ALR = 0.1 C/km, AEH = 0.001 km, greenhouse warming = 0 C
There's lots of backradiation in a pond (even with convection), but no greenhouse warming. The greenhouse effect is due to the average altitude of emission to space, and the adiabatic lapse rate. Adding greenhouse gases works by increasing the average altitude of emission to space.
Backradiation has nothing to do with it. Denning shouldn't be using it as his argument, but there's no point in other people disputing its existence, since it doesn't affect any of the post 1960s theory.
Nullius, I don't accept estimation of what planets ought to have as average surface temperatures without a consideration of length of day. I think that makes a massive difference. I have never believed the figure of 33C as what the temperature ought to be. I think the real life problem is more complex than that sort of simplistic analysis. There is no comparing a wet rotating planet with variable albedo against a dry one with a different day and an invariable surface.
Rhoda,
Of course it is a simplification. You've got days and nights and summers and winters and clouds and sunny days and snow and the dark polar winters. You've got horizontal mixing and Hadley cells and nocturnal boundary layers and humidity. It's an incredibly complicated system, most of which we don't understand.
But I can't explain everything in a single blog comment. This is, to first order, roughly how it works.
You can't properly argue against a hypothesis until you understand it. Climate scientists who keep on giving the backradiation argument certainly ought to know better. But there is no point in us wasting time trying to debunk an incorrect explanation of their own theory. It's a bad place to start from in trying to understand things.
Once you've understood the basic mechanism, you can start adding on things like the day/night cycle. But until everybody understands that backradiation is a complete red herring, we'll get nowhere.
Well, if you think it helps..I'd rather say some things can be simplified and it helps understanding, others not so much. When protagonists base arguments on the spurious 33C and proceed to use eight doublings of CO2 in order to produce an estimate of sensitivity, as if it was anything but a thought exercise, I despair. And they do, you know. I'd rather not encourage it.
William Morris: "I don't have any background in these arguments beyond the last week or so, so I'm learning."
Learn first, comment later.
Josh: some CO2 with your skepticism sir? Greenhouse or non-greenhouse?
Warmed to less than one degree or a just little more sir? Skepticism is such
a flexible feast ;-)
But both sides have their wayward acolytes. You will no doubt find there are
those (the hair shirt brigade) who want to return us to the stone age, but you
of course exaggerate (such is the stock in trade of both sides) by suggesting
that all 'warmists' want such an outcome.
Nullis: thanks for your explanation (1:33pm).
Jane Coles: "Learn first, comment later." where's the fun in that?
Denning is surely one of of the most wanton ignoramuses, since almost everyone that embraces climate change as a problem, does it for ideological or political reasons, not for scientific reasons. This includes the scientists, almost all of whom are politically paid for.
I looked back at NulliusInVerba's earlier comments, as he suggested, to see if he had explained more fully the point that perplexed me. I cannot see that he did. Of course I accept that convection currents in an atmosphere (gaseous or liquid) will help remove heat from a planetary surface (assuming this to be hotter than the atmosphere above it), but my point was that there is no compelling reason to think that the surface temperature will tend towards any definite equilibrium, as some of Keenan's comments seemed to imply. NulliusInVerba's example of a pot of water at 100 degrees C is hardly helpful to his case. The pot remains at 100 degrees, despite any increase in the input of heat, so long as there is any water left in the pot, but this is not a sustainable equilibrium state. The temperature in the pot only remains constant because water is boiling away and taking with it the 'latent heat of evaporation'. As soon as the water has all boiled off, the temperature of the pot will increase dramatically.
Why is Doug Keenan so rude in this exchange? In what way do accusations of dishonesty help anyone? Baffling.
Well, maybe Doug has got fed up with being lied to, cheated and generally mistreated while he was still being polite. Denning was at the very least disingenuous, his verbal conduct was unacceptable and Keenan called him out on it. Then Denning mounted the elevated equine. We do ourselves no favours when we stand for misbehaviour. Having said that, I have no problem with the polite ones on the sceptic side such as the Bish or McIntyre or their enforcement of polite behaviour on their blogs. But how long are you expected to put up with someone lying to your face?
"I looked back at NulliusInVerba's earlier comments, as he suggested, to see if he had explained more fully the point that perplexed me. [...] but my point was that there is no compelling reason to think that the surface temperature will tend towards any definite equilibrium"
I'm not entirely sure what you mean by "any definite equilibrium".
The point of the convective mechanism is that it only carries away heat if the gradient exceeds a certain limit. The point of the radiation to space is that if the temperature of the top layer is below T_eff it radiates less than the Earth receives, warming everything up, and if the temperature is above T_eff then it radiates more than the Earth receives and it cools things down. The top layer approaches a definite equilibrium by radiation, and the surface reaches a definite equilibrium relative to it by the interaction of convection and compressibility. The position of the equilibrium can change, depending of the amount of solar radiation absorbed, the changes in the adiabatic lapse rate with humidity, and of course the average height of emission to space, but for given values of those variables there is an equilibrium.
I had thought it was obvious that there would be a tendency towards an equilibrium, so you presumably meant something else, but I'm not sure what, or even if you do. Do you mean that with conditions constantly changing the system is always moving towards equilibrium but never reaching it? Or did you assume Keenan meant the system would always move towards the same equilibrium no matter how the conditions changed?
Keenan is only speaking of extra heat, not of climatic conditions generally. Denning is trying to sell a simple story - there's an extra 8 W/m^2 of heat, and heat inevitably results in a temperature rise. This is not true. Extra heat can sometimes lead to faster heat flow (as with convection) or reduced heat input (if heat causes more clouds) or more efficient transport (if heat increases evaporative cooling) or lots of other potential mechanisms. There is not necessarily any straightforward relationship with temperature.
Do we know that the net contribution of all these feedbacks definitely *will* cancel the effect of the extra forcing? No. The feedbacks are poorly understood and not yet resolved. But we do know that Denning's simple story of extra back radiation causing heating directly cannot happen, because of convection, and that the story is much more complicated and controversial than he pretends. And that as a climate scientist who has been deeply involved with the scientific debate in this area for years, he must know this.
Denning is doing the equivalent of saying that the asteroid will inevitably hit the Earth because heavy objects fall downwards, and has calculated the enormous and unsupported weight of the asteroid as proof. Keenan is saying it is more complicated than that, and that as a scientist Denning must know it. That doesn't at all mean the asteroid isn't getting closer.
As for your bit about the pot boiling dry, I can only assume you're deliberately seeking to avoid having to admit the point. I'm not playing.
NulliusInVerba:
I agree that if the input of heat remains constant, the system will reach some equilibrium. If the input of heat is increased, the equilibrium will be at a higher average temperature. I thought your 'pot at 100 degrees C' example was denying this, because in this special out-of-equilibrium case the pot remains at the same temperature if the input of heat is increased, until all the water has boiled away.
Did I "assume Keenan meant the system would always move towards the same equilibrium no matter how the conditions changed"?
I didn't 'assume' this, but I wondered if his comments about a planetary 'mechanism' were hinting at some such proposition. This is precisely the kind of thing that Gaia-nuts believe: they think the Earth has mysterious mechanisms that enable it to maintain conditions suitable for life. This implies some kind of upper limit for surface temperatures, e.g. average temp no higher than 100 degrees C. I know of no reason to think that the Earth has such mechanisms. Maybe I was wrong in raising such suspicions in Keenan's case, but if the issue is whether climate change would endanger human life (or civilisation, etc), then it is important to be clear about the point. The general proposition that 'the system will reach an equilibrium' would give false comfort if in fact that equilibrium is at an uncomfortably high temperature.
The 'greenhouse effect' - whatever that is, may well exist.
What we've been fed, simplified, is absolute nonsense. I was just looking at Popular Science historical archives (http://www.popsci.com/archive-viewer?id=vgAAAAAAMBAJ)
"This implies some kind of upper limit for surface temperatures, e.g. average temp no higher than 100 degrees C. I know of no reason to think that the Earth has such mechanisms."
You may find this interesting, then.
NulliusInVerba:
Not really. I admire Willis Eschenbach, but my eyes rotate upwards whenever I see him trotting out his ideas about homeostasis. Extraordinary claims, etc.
BTW, looking back through Keenan's comments again, I think it was this one that aroused my suspicions:
"If one end of a beam is put in a bucket of hot water, the other end will warm: that is simple physics. A person who puts their feet in a bucket of hot water, however, will not have their hand temperature increase. The reason is that person is a complex system that has mechanisms for dealing with heat ("feedbacks"). Similarly, Earth's climate system has mechanisms to deal with heat."
Comparing the Earth's climate system to a person (or any other mammal) is profoundly misleading. Mammals have evolved various mechanisms (sweating, shivering, panting, flapping their ears, etc) which keep their body temperature within fairly narrow limits. (Unless of course their tolerance is exceeded, in which case they die, and quickly reach ambient temperature.) Disregarding Intelligent Design (and is that really lurking somewhere in the background of these discussions?), we assume that these mechanisms have evolved as adaptations through natural selection. In the case of planetary climate systems, there is nothing corresponding to natural selection, as Richard Dawkins pointed out when he skewered Lovelock's Gaia in 'The Extended Phenotype'. If, in fact, the Earth's climate system does have negative feedbacks which keep the surface temperature within narrow limits (which is doubtful in view of 'Snowball Earth'), this is just a lucky accident - so far.
The purpose of my last e-mail to Scott Denning was to explain to the people at Yale Climate Forum (who were Cc’d) that what Denning was claiming was plainly false. The last e-mail tried two main approaches, in addition to citing the IPCC for support.
The first approach was by analogy, with the human body. The second approach was by example, with the Iris Hypothesis. Each approach can be reasonably criticized. A reasonable criticism of the first approach is that Earth’s climate system is not a biological process; the analogy was described as “admittedly rough” for that reason. A reasonable criticism of the second approach is that the Iris Hypothesis is just a hypothesis; i.e. it might not be true.
I was aware of the problems, but those approaches were the best that I could think of at the time. Note that my e-mails were originally intended to be just e-mails, and so were not as carefully written as a blog post would tend to be.
Does anyone have constructive recommendations for approaches that would be better, considering the intended audience (i.e. people for whom the concept of negative feedback might be new)?
"Not really. I admire Willis Eschenbach, but my eyes rotate upwards whenever I see him trotting out his ideas about homeostasis. Extraordinary claims, etc."
I find it an extraordinary claim that Argo data plots can be refuted simply by noting that it was Willis Eschenbach plotting it. It's a neat trick.
I guess the logic is that anything that goes against your prior beliefs is too extraordinary a claim for any conceivable evidence to support. So it doesn't matter how much evidence Willis plots, his conclusion can't be true, therefore there must be something wrong with the evidence.
The question is, though, what's your evidence for the extraordinary claim that homeostasis can only occur in biology, as a result of natural selection? Even after I've explained how it works, offered everyday examples like boiling water, and shown you Willis's graphs that explicitly show the limit? Is your belief system falsifiable?
Incidentally, the point of the Gaia hypothesis was that life processes can affect the local climate, (e.g. Pseudomonas Syringae) and therefore there is something like natural selection. Not that I take the concept too seriously myself.
[rolls eyes] "Just a lucky accident..."
"Does anyone have constructive recommendations for approaches that would be better, considering the intended audience"
Most people have come across thermostats and boiling water. I don't think it's the concept of negative feedback that is the problem, so much as awareness of how it might apply to the atmosphere. I think you would do better to concentrate more on the examples. If you look at my link to Willis's Argo data above, there's a link to Roger Pielke giving more information. Collect a few more examples of actual negative feedbacks.
And once you've shown that someone isn't telling the truth, you don't need to say it, and it works better if you don't. Saying it just gets people's backs up, and it let's them attack the messenger instead of the evidence. Ask questions to get people thinking along the right lines. If you make the conclusion inescapable, they will come to it themselves, and then they'll think it's their idea...
But with some audiences, nothing is going to work. Don't sweat it.
Oh, yes, and Lindzen was quite keen on the faint sun paradox. He mentioned it in his House of Commons talk.
There are 2 statements
a CO2 is a greenhouse gas
b we cannot detect global warming in temperature records
you seem to expect that only one of these statements can be true
in fact both are true, there is just some missing information
CO2 is present in minute quantitites in the atmosphere around 390 parts/million
Far to low an amount to cause signifcant observable warming
Water vapour, clouds, is by far the most prevalent GHG in atmosphere
it is assummed that CO2 acts in some unspecified why to influence
the behaviour of water vapour. There is (as far as I know) no explanation
of how this mechanism works (something with photons and energy levels of molecules
would be required). But this assumed affect has been built into all climate models.
I made this point in a comment to this post
http://bishophill.squarespace.com/blog/2012/4/7/continental-hindcasts.htm
on 8 April (10:41)
do you read the comments?
do you disagree with my point?
If you have not watched Nir Shaviv's presentation I urge you to watch it
http://www.youtube.com/watch?v=L1n2oq-XIxI
Nir explains that climate models have a very bad record
of matching extreme events (e.g. volcanoes) when run backwards.
However if you minimised the difference between the output of
climate change models and past observations you obtain the best
fit when climate sensitivity is reduced so that CO2 has no effect
on temperature (surprise surprise).
Surely if there is no observable rise in temperature due to global warming
that's a knock out blow and it's game over
Add to that the false assumptions and illogical basis of the models
for example as pointed out by many commentators to these posts
http://bishophill.squarespace.com/blog/2012/4/7/continental-hindcasts.html
http://bishophill.squarespace.com/blog/2012/3/19/climate-models-for-politicians.htm
what is there to discuss?
Is there a reason why you wish the same points to be discussed for ever?
At the risk of cross posting
you asked for simple explantion for polticians
You've noticed that the weather forecast is rarely right for today, let alone tomorrow
what chance have they got of prediciting weather 100 years from now?
NulliusInVerba:
I don't dispute the Argos data plots. I do dispute that they show any fixed 'maximum ocean temperature', whatever the input of heat from theSun, let alone 'homeostasis', which requires a lower as well as an upper limit! (which incidentally also means that boiling water is not a case of homeostasis).
What the data show is that ocean temperatures seldom (not never) exceed 30 degrees C. Is this surprising? Does it need any explanation at all, beyond the banal fact that the input of heat from the Sun, averaged over a year, does not vary greatly?
The idea that there is some 'thermostat' limiting temperature to 30 degrees is just so bizarre that I would want much, much stronger evidence before I would take it seriously. Apply the Principle of Sufficient Reason. (OK, it's not an absolute law, but it's a useful rule of thumb.) Why should the limit be 30 degrees? Why not 25 or 35? There is no physical principle that points to 30 degrees. (It would be different if the limit were 100, or whatever is the boiling point for sea water.) Extraordinary claims require extraordinary evidence, and this is an extraordinary claim indeed.
In the tropics it is not so extraordinary a claim. Anyone can see the energy in the afternoon thunderstorms. If one speculated that variations in incoming heat might have a main effect of heating the sea to the point where the thunderstorms transfer kicked off, and that was the hottest the surface was going to get, then the incoming heat will only change the time of the thunderstorm, not the temperature of the surface. That is a conjecture. When the measurement of the surface tend to support it then you have a reasonable assertion. I don't think it is presented as more than that by anybody. If you don't like the assertion you might try to show that the temp can rise over 30 (or whatever temp is asserted). Many of us in the sceptica lcamp think that convective and evaporative effects are underestimated by warmists. That is why I keep going on about observations and measurements of what is happening at the surface. We shouldn't be arguing about it, we should know by now.
David,
Why do you say "averaged over a year"?
Willis already offered an explanation for "why 30?".
NulliusInVerba:
I say 'averaged over a year' because the oceans have such a large heat capacity. The maximum temperature of the upper layers of the ocean must be affected by the heat received over a long preceding period.
I do not see where Willis has explained what is special about 30 degrees. He simply asserts that this is where his hypothetical 'curves cross'. Well, he would, wouldn't he!
Looking at it from another angle, would we expect surface temperatures anywhere in the ocean to exceed the summer temperatures in the Sahara Desert, where there is little cooling effect from evaporation or clouds? As far as I can make out from various online sources, average daily temperature (night+day) for the summer months in the Sahara seldom exceeds or even reaches 30C.
I don't see the timescale. I don't see why the ocean surface can't shed the heat of a day by the next day. A base temp, no accumulation in temp, extra energy going into ocean circulation. And all the effect of back radiation and extra CO2 accounted for by the afternoon thunder coming a few minutes earlier. But I could be wrong. That's why we need to measure it.
...I should probably clarify that by 'input of heat from the Sun' I was thinking of the heat received by the Earth at some given latitude, which varies with the seasons. The heat received by the planet as a whole presumably hardly varies during the year, except for some refinements to do with its elliptical orbit.
Rhoda: "We shouldn't be arguing about it, we should know by now."
So who's going to measure it and where? There's a lot of ocean. How many sensors do you want? One every mile? Or every 100 miles? Or every 1000 miles? And presumably not just round the coasts. That is going to be a lot of sensors. How much would it cost? Are you suggesting we waste even more of our taxes to pay even more scientists to do this; if not who pays/who does the job? And what's the frigging point when we already know there is no AGW?
Ocean sensors
Certainly they would help find out if there is any of Trenberth's heat hiding out down there or not.
And sure we can afford them - just divert funds from the modelers.
Punksta: you don't think buying or making, deploying, collecting and maintaining thousands of sensors might possibly be tad more expensive than sitting in a lab running models? Sensor and sea time don't come cheap.