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)
NB. The 23 W/m^2 is the net IR absorbed in the atmosphere [the first ~30 m], 40 W/m^2 escapes to space [Trenberth et. al. 2009]. The 356 figure is the 23 plus 333 'back radiation', which is imaginary.
“we do not freeze to death each night. That's because the sky also emits heat” (Denning)
To paraphrase the tabloids/Eastenders: I can’t believe I’m reading this!
He doesn’t think retained ground heat has anything to do with it, then?
Denning's comment re: all skeptics and ideology has nothing to do with hearsay. He is just guilty of a couple of logical fallacies with it.
But there is another fallacy that is more interesting -- his dismissal of skeptics because they have so many different problems with the IPCC view. I've never heard that used as an argument before -- "because so many people find so many different problems with our theory that proves we are right."
I think he's arguing that small problems with lots of it does not affect the argument as a whole - and using that as proof that we can't find anything wrong with the theory in total. They don't seem to get that as an 'ensemble' theory, it's only as strong as its weakest part.
If the raw data is wrong, the thing falls down. If the statistical method is wrong, the thing falls down. If the modelling technique is wrong, the thing falls down. If assumptions are wrong, and those assumptions have a high sensitivity in the output, then the thing falls down.
The other problem with this is they are arguing over the mostly undisputed territory - basic GH warming. It's poor pickings there. Ask about tipping points and feedbacks, that's where all the cataclysm comes from.
Hi BigYin: my first post describes how 150 years of assumption about 'basic GH warming' may just have been shown to be an experimental artefact [indirect thermalisation]!
Will Happer warned in 1993 that climate science had got its IR physics wrong. The problem is that as with much of the rest of the science, these people do not seem to have been taught the basics. Thus with GH heating, you must understand that Gibbs' Principle of Indistinguishability means a GHG molecule with an absorbed photon vanishes into a sea of similar molecules and one of those ejecting the same energy photon in a random direction [pseudo-scattering] restores Local Thermodynamic equilibrium so there is very little if any direct thermalisation.
These people really have messed things up in their eagerness to prove their point.
Maybe you're right, dog, I still haven't had time to examine your claim, though I'm naturally skeptical that a major blunder has been made as you claim. But I'm open-minded.
What irks me most about these exchanges is the paternalistic attitude of manistream science. I don't mind if I'm wrong, if dog is wrong, if Keenan is wrong. But don't insult us with simplistic explanations that attempt to obscure the real approximations happening. It's almost as if we're allowed to ask questions, but we must accept the answer - no matter how incomplete the explanation - just because they do.
I know this is o/t Your Grace, but maybe a post on Lindzens reply to the critique of his HoC lecture would be appropriate...it seems even learned gentlemen like Deening do not actually understand what is being discussed.
Lindzens reply is also eye watering to read....and explains Lindzens more simplistic approach to the HoC presentation, for which certain quarters questioned him for (being simplistic). So read Lindzen in full 'put down' mode. Then read Deening again. Then decide who is doing the hand waving.
No offence meant BY but I have 40 years' post PhD experience in many fields including process engineering, measuring and predicting combined conduction and radiation. We built from scratch IR pyrometers for very difficult low emissivity systems so I know how they work..
Climate science has installed 1000s of 'pyrgeometers' which by shielding radiation from the ground and reconstructing a black body signal at the local air temperature, actually measure 'Prevost Exchange ' from the atmosphere, normally annulled by part of the opposite radiative flux. Until you shield the upward radiation, it does not exist in terms of being able to do thermodynamic work.
Denning apparently believes in this radiative tooth fairy and wants to tax us back to the stone age on the basis of the stupidest experimental failure I have ever seen. But it's peer reviewed..........
None taken. Someone called me a bad word farther up the thread, so you have a long way to go before offending me :)
If you are right, and I'm sure you believe you are, then perhaps you need to start popularising it through a paper, or a website? With layman's (well, undergraduate level) explanations and references etc. I for one would love to read it and will quite happily be convinced. In fact, I would help with a website.
In an ideal world, a postgrad looking to make a name for themselves should take up the gauntlet, but the climate (ho-ho) won't support that at the moment, so you may need to go the 'McIntyre' road, and self-publish.
TBY
“I don't mind if I'm wrong”
Me neither, but then I haven’t staked my career on being right! Scientists shouldn’t have to, of course, and that is the key to the problem, IMO - science is meant to be pure-minded, apolitical and agenda free, and barking up the wrong tree (pun intended) should be part of the process.
Hi BY: I have written one paper which shows why the 'cloud albedo effect' cooling is a fallacy because Sagan got the physics wrong. I am now working in the IR and radiation part so it's on my mind all the time.
The trouble is, climate science people are arrogant because they are in large numbers and well funded, and it takes time to pull the rug especially when you attack the very basis of the income stream.
mdgnn
You need to be working on these people!
Link
Although you probably already are...
For what it is worth, mydog, I think that you are right. But then what do I know? I only have 30 years postgraduate experience as a physicist, and my highest qualification is M.Sc (although I was a C.Eng. for several years, until I stopped paying the fees).
But I do know a bit about computer models. I know - with absolute certainty - that unverified and unvalidated models can not provide evidence for anything at all.
I found this comment of Denning's revealing:-
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.
So the years of machinations by Phil & the CRU Boyz , their buddies at the Met and Big Jim "The Hat" Hansen - refining and nuturing their fragile little trendlings to convince us we were getting a wee bit warmer were all about what exactly?
In fact, since the basic thermodynamics were worked out more than a century ago - he would appear to be saying that the whole recent "climatology" bit was a forty odd year multi-billion dollar waste of time since they'd all decided on the answer before they started.
I suppose it fits the theory of Donna's book when you think about it. A bunch of activists decided to build a political movement around a simple bit of physics - lent on the world government mob to set up the IPCC - and all the "science" since has been smoke & mirrors to baffle the plebs.
Nice of him to finally come clean really.
Douglas J. Keenan: are you seriously suggesting that if I put a foot in hot water my body does not warm up? Both feet? Still no? Both legs? Up to my neck? I guess you mean that, of course it warms up but that the warming results in changes in the skin and that the heat is radiated/evaporated (sweat) away; eventually my body returns to its previous equilibrium after all the heat has radiated/evaporated away. But that is not what you said (could we claim that as dishonesty? ;-). I don't suppose any scientist would object to a claim that, if the earth's surface temperature is warmed as a result of CO2 then, all other things being equal, it might return to somewhere near its previous equilibrium in several million years (ie after the CO2 has been absorbed and the earth has had a chance to radiate and sweat off the heat). It is what happens in the first few hundred years whilst it is warming that scares the pants off people.
Mike Haseler: "I've yet to meet a sceptic who does not believe the science of CO2 warming." Really? Have you read what people write here? How many contributors here agree with that?
TheBigYinJames: thanks for your 1,2,3 ranking. Very helpful - and kind of contradicts what Mike Haseler says. Your comments make a lot of sense to me. But I would be in 0 camp I guess. The 0 camp is the population that are not scientists and know they are not competent to judge the science (even if they are numerate and scientifically literate). They may also know enough to judge that the basic science is sound, can see changes occurring around them and understand that the consequences of significant warming could be disastrous. They conclude that the sensible approach is to do whatever is necessary to avoid a bad outcome. They may also be aware that there are vast economic possibilities from changing to a low-carbon society, but that vested interests (who do very well from the current model) will do all they can to prevent that change.
I love the way leftie climate activists come on here and demand deference to themselves.
Thank you Jamesp: notice the Philipona et. al. equation? The emf U is the difference emf across the thermopile. It measures Flux in - black body Flux from the local temperature, calibrated against an external black body, and you add to this the corrected internal BB flux from theory.
And amazingly, I have just worked out another crassly stupid part of this farrago. Stick it under a cloud with ~0.8 emissivity, a near grey body, and what you get is Flux from cloud plus about 20% of the theoretical internal BB Flux plus a temperature gradient term. Stick it out in a desert with 0.1 emissivity from the sky and the signal is mostly the internal BB plus a temperature gradient term. So they've even bu&&ered that!
And because Sagan's aerosol optical physics is wrong. all the satellite optical depth data are suspect. This will be a real humdinger of a story if the press get hold of it.......
William Morris
Your type 0 seems to be a bit woolly and all encompassing. If 0 has some "that are not scientists and know they are not competent to judge the science" and also possibly has some who "may also know enough to judge that the basic science is sound" and some who "understand that the consequences of significant warming could be disastrous" maybe you should create a grid with some letters across the top?
I like this variant (maybe 0d?)
Just get these 0's to monetize their "awareness" and you'll have no problem pursuading me ;)
"They may also know enough to judge that the basic science is sound"
But what if you know (just) enough to suspect that it isn't?
I'm happy to accept that there is a general warming trend (following a rather long cold snap in the 18th/19th centuries) but how much of that is down to natural variation and how much to our CO2 production remains moot, as does the likely damage from continued warming.
It's all a question of degree, but the alarmists aren't willing to consider any scenario that doesn't scare us all witless (and write them large cheques to make it go away).
William Morris; climate science has only got one thing right, the PR. Everything else is a Big Fail.......
They conclude that the sensible approach is to do whatever is necessary to avoid a bad outcome
This seductive allusion to the precautionary principle, like most such suggestions, makes the assumption that "its better to be safe than sorry" must exclude the possibility that "being safe can also make you sorry". In the case of CAGW the cost of insuring against the potential risk is so enormous both in sociological, political and financial terms that a greater degree of certainty is necessary before embarking on sich a course of action.
That's sadly typical. A scientist makes some pretty uncontroversial statements and some journalist accuses him of "dishonesty". Keening's claims are worth looking at:
(i) Keening's analogy. This is a silly one since it presupposes a homeostatic mechanism (the human body and thermoregulation) that is of little relevance to the climate system. We know that the climate system doesn't have tight "thermoregulation" since we have very good evidence that the planet has undergone large swings of temperature in the past (snowball earth, Carboniferous glaciation; ice age cycles; Paleo-Eocene thermal maximum, and so on).
(ii) Radiative forcing and its consequences. Denning is quite right. The evidence indictes that doubling of atmospheric CO2 is equivalent to a radiative forcing at the top of the atmosphere of the order of 4 Wm-2 globally averaged. A load of empirical evidence supports an earth surface response at equilibrium in the range of 2 - 4.5 oC from this forcing.
(iii) Keening's appeal to authority on behalf of Prof. Lindzen and his iris hypothesis. Two problems with this. Firstly, Lindzen's hypotheses may be provocative but they are often incorrect. His assertion that the upper troposphere would dry out as a result of enhanced greehouse-induced warming [ see R.S. Lindzen (1990) Bull. Met. Soc. Am. 71, 288-289/ (1991) Nature 349, 467] is comprehensively incorrect as shown by a large amount of empirical measurements of the tropospheric water vapour response to contemporary greenhouse forcing. One can't base a scientific argument on the assertions of a single scientist; we really needs to consider the scientific evidence.
Is there empirical evidence for the "iris hypothesis"? Not really. The rather limited direct empirical tests (see work by Dessler and Clement) is simply inconsistent with the "iris hypothesis". And where was the "iris" during the snowball earth or Carboniferous glaciations or PETM, not to mention the rather large warming of the 20th century.
(iv) Part of Keenings accustion of dishonesty seems to be that Dr. Deening might not have considered a couple of papers that "have been in the news recently" [Lindzen and Choi (2011) and Davies and Molloy (2012)]. But Lindzen and Choi's method has been rather comprehensively shown to be incorrect in the scientific literature [see Chung, E.-S., B. J. Soden, and B.-J. Sohn (2010), Revisiting the determination of climate sensitivity from relationships between surface temperature and radiative fluxes, Geophys. Res. Lett., 37, L10703; Murphy, D. M. (2010), Constraining climate sensitivity with linear fits to outgoing radiation, Geophys. Res. Lett., 37, L09704; Trenberth, K. E., J. T. Fasullo, C. O'Dell, and T. Wong (2010), Relationships between tropical sea surface temperature and top-of-atmosphere radiation, Geophys. Res. Lett., 37, L03702], and Davies and Molloy's data doesn't have very much to say about any real cloud feedback since their data covers only a 10 year period and the trend (in effective mean cloud height) is dominated by the effect of the large La Nina in 2007/8.
It simply isn't scientific to assert fundamental interpretations by selecting the work of a single scientist or citing a couple of papers that might appear to support the chosen interpretation. To my mind Keening's responses rather support Dr. Denning's statement about the non-scientific nature of quite a lot of so-called "skeptical" argument...
mdgnn
"the Philipona et al. equation"
Who could argue with that, eh? I suspect it's Phlogiston theory though, really...
Hmmmmmmm....
My extensive survey of "warmists" shows that - without exception - they are all hell bent on de-industrializing the advanced economies and want to drag our standard of living back to the stone age. Each and every one of them wants to confiscate trillions of our dollars to be given to corrupt African dictators by faceless unaccountable bureaucrats from the U.N. in charge of a new world order that renders our existing national governments totally powerless.
Details upon request.
chris
"the planet has undergone large swings of temperature in the past"
A few degrees out of nearly 300K? We notice it because some of it involves the freezing point of water, but it's astonishingly well regulated really.
@Doug Keenan
The truth or otherwise of what you say in no way alters whether it's an insult or not. "You are either ignorant or dishonest" is an insult. If I say you're wife is dog ugly I doubt you will shrug and say, "well, she is". Arguably the insult is greater if it's true.
So Denning was somewhat patronising. I'm sure you can live with that.
(I have no acquaintance with your wife or even know if you're married).
Scott Denning wrote:
"We can confidently predict a warmer climate under elevated CO2..."
1) If you are confident about this, then I don't think you should be, given that the feedbacks aren't understood.
2) "A warmer climate." Warmer than what? Warmer than it would be without the extra CO2 - but we don't know how warm it would be without the extra CO2. Would global temps be going down? Going up?
3) How MUCH warming will the extra CO2 create?
4) Why would the problems of some extra warming outweigh the benefits?
I cannot take seriously anyone who uses one of the most gross of words, "gotten".
depends what you mean by "well regulated" jamesp! That's the fundamental question (as is the physical basis of "regulation"). Swings of temperature of say 20 oC (if we include snowball earth) might seem numerically small in the context of 300K, but of course that's a semantic game. There doesn't seem a huge point in considering temperatures below the blackbody temperature of an atmosphere-free earth (~ 255K nowadays), for example, and I doubt you'd be impressed if someone put you in a -10 oC freezer in your pyjamas overnight with the admonishment that you'll be over 260 Kelvins above absolute zero!.
In what sense is the climate system "well-regulated"? It's largely because the primary forcings "tend" to stay reasonably constant over shortish timescales (i.e. of human interest). It's not because there is much in the way of internal "regulation". After all small shifts in the earth's orbital properties can cause truly astonishing shifts from one climate state (glacial) to another (interglacial) - where were those supposed "homeostatic" mechanisms then?? Pretty massive drawdown (snowball earth) or release (PETM) of greenhouse gases can cause very large temperature rises and falls. You may not consider that 5 oC (or 15 oC!) globally averaged temperature changes to be very large numerically-speaking, but I suspect you wouldn't be too thrilled to experience these worlds.
Other than that there are very, very slow "restoring" feedbacks involving weathering that tend to readjust temperatures through greenhouse gas sequestration...however these are active only on 10's of 1000's of year timescales and not very relevant to us here and now. If the climate is pretty stable it's because the solar output, greenhouse gas concentrations, continental configuration and Earth orbital state is pretty constant over timescales we consider relevant. However a large and rapid change in any of these causes a pretty large response in the earth system; that's simply what evidence of the past indicates...
After reading the complete e-mail exchange, I conclude that Keenan lost.
He lost because he did not expose the wrong physics, especially the back radiation arguement.
"Without this extra heat emitted by CO2 and H2O molecules in the sky,".
Co2 cannot emit extra heat. A cooler atmosphere cannot heat a warmer Earth surface.
I have no qualifications above A level when it meant something. But I would not approach a heat probelm involving fourth power responses, convection, radiation and evaporation by averaging out all the heat transfers across the whole of a wet tilted spheroid with multiple surface textures rotating and heated from one side as a first step towards producing a notional temperature effect also expressed as an average. But that's just me.
Oh, did I mention the spheroid was in an atmosphere? It is.
James Evans, surely Dr. Denning is entirely correct in stating that "We can confidently predict a warmer climate under elevated CO2...". After all I don't think there is anyone with at least a basic understanding that supposes that the greenhouse effect doesn't actually exist. More radiative forcing = higher temperatures. of course the sun might do something weird or we or our descendents might get struck by a devestating impact from out space. But the response to enhanced greenhouse forcing is quite a strong prediction.
And yes, there is some uncertainty about the feedbacks, but certainly not about all of the feedbacks. The empirical evidence indicates rather clearly (despite the assertions of a certain Dr. Lindzen 20 years ago!) that the tropospheric water vapour concentration tends to rise much as predicted by theory and models, as the atmosphere warms under enhanced greenhouse forcing; the water vapour feedback that consititues a large part of the total feedback seems to be occurring much as expected.
The land and sea ice albedo feedback seems rather rock solid too wouldn't you say? In a warming world the land and sea ice tends to retreat. We can see that with our own eyes.
That leaves the cloud feedback as a relative unknown. The very few direct measures of cloud response to changes in surface temperature actually suggest that the cloud feedback is positive (see quite recent work by Dessler [A Determination of the Cloud Feedback from Climate Variations over the Past Decade; Science 330, 1523-1527 (2010)] and by Clement et al. [e.g. Observational and Model Evidence for Positive Low-Level Cloud Feedback; Science 325 460-464 (2009), but it certainly isn't yet pinned down. However a rather large amount of evidence from paleodata suports the interpretation that the earth warms with something in the range 2-4.5 oC per doubling of [CO2], and so that tends to support the conclusion that any cloud feedback doesn't put much of a brake on greenhouse warming.
It's rather unlikely that the "benefits" of sgnificant warming (say >2 oC above current temperatures) would come anywhere near the "problems" in terms of impacts. History tells us that that amount of warming is enough to (eventually) pretty much eliminate polar ice equivalent to the entire Greenland volume with 20 feet of raised sea level, the amount of CO2 required to achieve that warming would induce dangerous acidification of the oceans, and the already expanding regions of the earth experiencing enhanced drought through the last 50 years, would shift further to lower and higher latitudes. That's what the evidence of the past indicates.
It takes a while for these consequences to accrue and they may not impact too badly on us...it's our near descendents who will have to cope with these nasties...
Gosh - we seem to have a rather sudden influx of "concerned citizens".
This is one that's trotted out regularly and really baffles me. Even if everything put out by the "climatologists" were 100% true - it amounts to a temperature increase of less than one degree so far.
I've been around for quite a few decades and all I've ever seen is "weather".
Long before I ever heard of AGW, I worked in an electronics factory, in the Welsh tropics in the early 70's, when we had a heatwave so intense we had lots of transistors fail in thermal runaway - never seen anything like it since.
When I was a kid in Durham, I remember weeks when the school bus didn't make it through the snow and my late dad told me in 1947 the village he lived in was cut off without food for a week.
Christmas evening two years I saw -13C on my car temp gauge in the Welsh hills.
It's a source of wonder to me that AGW true believers can look around them. sniff the air and proclaim "yes the average has definitely increased 0.01C since the last time I passed this way".
Bit like those people who see Jesus in their coffee grounds if you ask me.
That chris is a true believer, isn't he? If all the feedbacks amount to positive, why hasn't the temp run away to some top limit centuries ago, when it was warmer than now?
Roger Clague, Dr. Denning's statement about "extra heat emitted by CO2 and H2O..." is fine so long a one doesn't stand on pedantry. Dr. Denning is making a simple explanation that is understandable in simple terms..yes?
Of course he could say that asymmetric bond vibrations in certain non-homodiatomic molecules absorb long wave infra-red and either reemit photons or cause localised warming by transferring excited vibrational state energy to surrounding atoms by molecular collisions. He might say that the intercepting by greenhouse gases of long wave IR emitted from the earth's surface suppresses the escape of thermal energy to space, and thus tends to cause an increase in the height in the atmosphere at which IR escapes so as to maintain radiative equilibrium. Since the earth must re-equilibrate radiatively-speaking this requires that the atmosphere warms up a tad at all levels right down to the surface to bring those parts of the atmosphere up to the temperature required to achieve radiative equilibrium.
There are lots of ways to explain the greenhouse effect with greater or lesser precision. The fact that a scientist uses a simple "shorthand" doesn't mean that the greenhouse effect ceases to exist as a result!
...and I'm sure if the two communicators were to be limited to absolutely precise "science-speak" Dr. Dennigng would "win" hands down - after all we've seen that it doesn't take Mr. Keenan very long to resort to insults ("a.k.a. accusations of dishonesty)!
RR
>the most gross of words, "gotten"
It's an old English word, I'm afraid - perfectly correct, just not used much here since the Pilgrim Fathers took it with them. I only know because Bill Bryson mentions it in his excellent book 'Mother Tongue'.
It's disconcerting to read Dr Denning complaining in one paragraph about the narrow perspective of skeptics and then in the next one focusing on C02 as the obvious or only cause of observed warming. It's really quite rare to find knowledgeable skeptics who dispute the warming properties of CO2. It's also perfectly reasonable to insist on the importance of variability in explaining the observed warming. Mainstream climate science has no generally accepted physical explanation for decadal and longer variability; even the best models do not replicate it. On the other hand, Doug and others point towards research that demonstrates how to reproduce the general properties of the time series using a handful of random processes. Nice though this is, it is still only a mathematical model of the data. It hints at the kind of physical processes that must be involved, but the description of those processes is still missing. Without better understanding of the variability, my feeling is that everyone will continue to find it an uphill struggle to win an argument about the magnitude of the CO2 warming.
Keenan> "One of the big problems in global-warming research is that so few people want to call out dishonesty. That effectively supports dishonest researchers acting with impunity"
Completely correct! I've not been able to understand how climatology could attempt to brush their ongoing revelations under the carpet. This does not happen in science (as opposed to climatology) - see e.g. Schoen (etc.)
Rhoda, yes the science is rather believable. It's how we know stuff. sadly there are always people that attempt to misrepresent imporatant stuff for what are usually pretty dreary agendas!
I'm not sure that all of the feedbacks are positive. As I said (and several have pointed out) the cloud feedback remains uncertain, 'though historical evidence and direct measurement indicates it's unlikely to be a large ngative feedback.
Why hasn't the temperature "runaway" in the past when it was warmer than now? It's because the temperatures are always limited by the forcings which were never strong enought to produce "runaway" effects. And remember that net positive feedback doesn't mean a tendency to runaway. If for example raised CO2 causes the atmosphere to warm 1 oC which induces a water-vapour feedback of a further 0.5 oC which in turn induces a further water vapour feedback, the total temperature change is 1 + 0.5 + 0.5^2 + 0.5^3 ....
which is 1/(1-0.5) which is 2 oC. So the effect of the feedback is effectively self-limiting (it converges) so long as the feedback isn't large in relation to he primary warming (which it isn't happily!).
chris
"I don't think there is anyone with at least a basic understanding that supposes that the greenhouse effect doesn't actually exist"
You haven't met mydogsgotnonose, then? :-)
Philip, I would say that science has a good handle on natural variability on a range of timescales. Of course one can't precisely model (as forecast) the aspects of the variability involving stochastic processes (volcanic activity, ENSO, non-cyclical solar variability). But models do quite a good job of modelling variability (O.K. I'm just responding to your negative assertion with a positive one of my own, and if I have time later I'll cite some relevant papers!).
One of the things that natural variability can't do is to conjure up the huge amount of thermal energy that is pouring into the oceans under enhanced greenhouse warming, and which measurable direcly or indirectly through the thermal component of sea level rise.
Apr 12, 2012 at 2:37 PM Douglas J. Keenan
Just one problem with the groupthink that is climate science is that they earnestly believe they are "doing good science" (Phil Jones) and that dishonesty is exclusively what is done by the people who question them. (Hence Mann refering to "Climatefraudit" - Steve McIntyre's website on which he meticulously documented his interactions with Mann and co.).
Climate Scientists -even Gleick - absolutely do not see themselves as dishonest.
Chris, that is what I mean by runnig away to a stop. If all the feedbacks are positive, the temperature has to top out somewhere. The feedbacks do not care what the forcing was, There have been enough instances in history both positive and negative to assume as a working hypothesis that the range between the two stops is not large. As for your two degree disaster, this is like a month in time, or five minutes in the sun, or two hundred miles south of here, or in the village down the hill from here. It is not at all scary. You have to make up more and more effects such as ice-melting and ocean expansion too make it scary, and it doesn't work. And ocean acidification. That old chestnut. Not scary at all.
chris
"Mr. Keenan"
I think you'll find he's better qualified than that. He is also admirably persistent..
Link
chris:
"James Evans, surely Dr. Denning is entirely correct in stating that "We can confidently predict a warmer climate under elevated CO2...". After all I don't think there is anyone with at least a basic understanding that supposes that the greenhouse effect doesn't actually exist. More radiative forcing = higher temperatures. of course the sun might do something weird or we or our descendents might get struck by a devestating impact from out space. But the response to enhanced greenhouse forcing is quite a strong prediction."
I disagree. The response to the forcing seems like a very weak prediction to me. If you'd like a little bet on how well the climate models will perform over the next 10 or 20 years I'd be happy to arrange something.
The physical properties of CO2 are well known. But the feedbacks in the climate system aren't well understood. Nor are the other forcings, in my opinion.
"And yes, there is some uncertainty about the feedbacks, but certainly not about all of the feedbacks."
It only takes one poorly understood feedback to mess up the sums.
"That leaves the cloud feedback as a relative unknown."
That'll do it.
"It's rather unlikely that the "benefits" of sgnificant warming (say >2 oC above current temperatures) would come anywhere near the "problems" in terms of impacts."
Do tell.
"History tells us that that amount of warming is enough to (eventually) pretty much eliminate polar ice equivalent to the entire Greenland volume with 20 feet of raised sea level,"
When is this 20 feet of raised sea level going to happen? If it's within my lifetime, fancy another bet? BTW, that's quite a bit of land that's going to be freed up by all this melting ice. Perhaps the people of the pacific islands could move to Greenland, which apparently will be ice-free and toasty warm. Sounds rather nice.
"the amount of CO2 required to achieve that warming would induce dangerous acidification of the oceans,"
Dangerous acidification. Sounds awful. Will it reach pH7?
"and the already expanding regions of the earth experiencing enhanced drought through the last 50 years, would shift further to lower and higher latitudes."
I feel another bet coming on.
"That's what the evidence of the past indicates."
Blimey, you must live in a gloomy world.
"It takes a while for these consequences to accrue and they may not impact too badly on us...it's our near descendents who will have to cope with these nasties..."
Oh OK. Let's have our grandchildren make these bets then.
foxgoose
I can certainly confirm my village being cut off in the '47 winter — in Northumberland rather than Durham but let's not quibble. I also remember a Christmas walk in Midlothian about 15 years ago when the temperature in mid-afternoon was -8C.
And we mustn't forget the summers of 75 and 76.
And so on.
All weather events.
"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."
Deary me. It's amazing how this simplistic picture refuses to die. The greenhouse effect is a bit more complicated than that.
"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."
Well over a hundred years ago, Fourier, Arrhenius, Tyndall, and others came up with a theory involving very simple physics, but other scientists like Angstrom and Woods showed that it was incorrect, and the theory was dismissed by atmospheric scientists for the next 50 years. Some time around the 1960s Manabe and other researchers came up with a new theory, that did indeed give greenhouse gases a role in keeping the surface of the planet warm, but it wasn't quite as simple as the old (wrong) theory. Nevertheless, the old theory keeps on getting used in explanations to the public, and often even to students. They use the new theory to calculate with, but describe it as a minor adjustment to the old one. It isn't - the dynamics is completely different. But with all the confusion thrown up by the skydragon people, it's nearly impossible to get them to listen.
"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."
A material that was totally transparent would not. Although oxygen and nitrogen are not totally transparent at visible and infrared wavelengths, it's a fairly good approximation.
"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)"
If you cover the ground with a layer of water, as in a shallow pond, the ground will receive more backradiation from the water than it would from the open sky. But it does not warm up as a result.
Sunlight passes through a shallow pond to be absorbed at the bottom, but water being opaque to IR the heat radiation emitted by the bottom cannot escape. The water radiates it all back. And yet the pond does not boil. In fact, you get no temperature rise at the bottom of a pond at all. When you understand why not, you can have a go at explaining why the same thing doesn't happen in air.
The greenhouse effect is real, but backradiation is not how it works in a convective atmosphere.
"But it seems disingenuous to assert that heat doesn't change temperature. Everyday experience with teapots, hands, and feet refute such a claim."
I have a pot of water boiling on the stove. I stick a thermometer in, and find the temperature is 100 C. I turn the gas up from 2 to 4. By how much does the temperature of the water rise?
"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."
8 Watts is 8 Joules per second. In every year, there are 31,536,000 seconds, and so each square metre gains 8*31536000 = 252 MJ. That will warm a cubic metre of water about 60 C, or 100 cubic metres 0.6 C. Every year.
So after a century we can expect 60 C of warming to have accumulated, and shortly thereafter the top 100 metres of the oceans in the tropics will start to boil.
Clearly, that's utter tosh. The number being quoted is a quantity called the 'radiative forcing', which is the imbalance that would result at the top of the atmosphere if the GHGs increased but the temperature of the atmosphere did not change. Since it does change, the 8 W/m^2 is an entirely imaginary construct, it is not the amount of extra heat accumulating in the system.
Denning is wrong, Keenan's explanation is correct so far as it goes but doesn't explain the details.
If you've never seen it, go read my explanation at 'Best of the Greenhouse' on Judith Curry's blog.
The Leopard In The Basement: I guess I was describing myself, and though your comment is amusing (made me smile :-) the description hangs together: I am no more able to judge the whole of climate science than most posters here. I don't have the evidence at hand or the time to analyse it or the skills necessary. I have to choose whether to believe what I hear. But I can judge the *basic* science and non-science trotted out (eg put your foot in a bucket of water and your body doesn't warm!) because I have enough scientific knowledge to know when I hear BS.
On '0d', do you doubt that changing our whole economy to low-carbon can generate growth? Maybe you would challenge what growth is. Digging more carbon out of the ground and burning it would certainly fit in your model, I guess. Extracting carbon from flue gasses and burying it would presumably not. Or am I wrong? Turning silicon into solar panels, installing them on roofs and generating electricity would seem like a generator of growth - or are all those who are in this business in non-jobs creating no prosperity for themselves and others? Building nuclear power stations, creating and installing insulation products, laying HVDC cables, retrofitting buildings etc. Am I missing something?
One seeing changes, sure its partly just 'weather'. But when spring comes progressively earlier, ice caps melt, new sea routes open up, land becomes cultivable when it previously wasn't (or vice-versa) - these are real events that certainly give the perception of a change in climate.
One other thing is this idea (attributed to BYJ type 1 people) that warming to < 1 degree is accepted. So you can accept that 0.999 degrees is possible but not that 1.001 degrees? And if 1.001 is ok, why not 1.002? etc. It is a nonsensical constraint. Where does this magical 1 degree limit come from?
BTW, I'm not a leftie.
Chris @ 6:54 PM,
Thanks for your reply -- If you know of research that you think proves your point, please do be sure to mention it here. I'm not myself aware of anything particularly telling, but perhaps you can find something! It would be most convincing I think if you could find discussion of GCM runs of 100 or more years that use the understanding of variability you mention to reproduce the general characteristics of the observed time series.