the Air Vent

Because the world needs another opinion

Greenhouse Thought Experiment

Posted by Jeff Id on January 1, 2011

This post is now replicated at the center of the internet.

Derek has been in a war with ScienceofDoom over the what appears to be Planck radiation.  I’m actually not sure of his position because it doesn’t make sense yet to me but he left a thought experiment on the thread which could make for some interesting discussion.  Some will find it pretty easy, while I bet others will get all tied in knots over it.  As a suggestion, taking a thought experiment to an extreme is often a good way to identify a preferred design path or to understand differences in similar situations.  I will give the answers in the coming days, they are already written so I can’t back out but as you consider them I’ll warn that this post is not about the subtleties but rather about the bulk differences.

I’m going to paraphrase Derek’s experiment below and then add another of my own.  If it’s not the exact same as his it doesn’t matter the idea is still interesting.

For our experiment assume we have a bolometric camera for measuring emitted thermal radiation as an image.  IOW a cool toy which in this case happens to detect all EM wavelengths with perfect sensitivity.  To be clear, the camera integrates to measure the radiative emission temperature of the object.

We have two plants, one is contained in a transparent box (greenhouse) the other in open air, both thermally stable (temperature isn’t changing).  We take an image of the two plants in the early afternoon on our fancy camera, what do you find in the image?

Derek asserts that the greenhouse plant will be warmer and therefore brighter, but lets continue this experiment further.

For our second experiment we have two thermally stabilized earths, one which has today’s CO2 and one which has 2X today’s level.  All other conditions are identical and for some quirk of Id-ian physics, they orbit one right behind the other around the sun such that we can observe them simultaneously on our fancy camera.  Now the CO2 of the higher concentration planet will block some of the emitted radiation creating the AGW greenhouse effect so the planet has a 1C warmer surface temperature.  (For this thought experiment basic physics are required, planets are stabilized and I’m going with a 1C estimate chosen at random).  Since it’s my universe, I’m staying on the warm Earth with a functional economy (right side) and sending all the vegetable eating enviros over to the cold economically devastated one on the left.  haha- too fun, I probably should stick to the science for this though.

Now from a distant point we observe our otherwise identical worlds using our amazingly fancy camera.  What would our camera reveal?

I’ll give the answers to these with supporting explanations tomorrow or the next day depending on how much fun people are having.


56 Responses to “Greenhouse Thought Experiment”

  1. Jeff Id said

    Don’t be afraid to give your explanations, nobody is right every time and being wrong is part of blogging in my experience😉. The purpose of this post is to help build understanding in the community.

  2. Gary Palmgren said

    Greenhouses do not warm because the glass stops IR. They work because the glass stops convection. This was shown back around 1910. The “greenhouse effect” is not how greenhouses work!

    The planet is complex because the radiation can come from many different layers. In the transparent windows in the atmosphere the radiation from the ground can be seen. In the bands that CO2 and water absorb, the only radiation that is seen is from the uppermost layer of the CO2 and water vapor. Nothing will be seen below the depth by which the optical density reaches ~1 starting from above the atmosphere. The water vapor is highly variable so simple static arguments are not valid.

    The camera that responds to all wavelengths is interesting. If it is a gray scale image so all wavelength information is lost one has a very tricky problem. Consider just a absorption CO2 band. Adding CO2 as a step will initially increase the absorption and the temperature of the CO2 at a given level, but the camera will see less deep into the atmosphere and the higher level CO2 will be cooler in the troposphere. What will happen in the stratosphere where temperatures increase with height? What is the optical density of that CO2 band down to the tropopause?

  3. Jeff Id said

    Gary, I updated the camera description to include this:

    To be clear, the camera integrates to measure the radiative emission temperature of the object.

  4. Carrick said

    Both “greenhouse effects” work by impeding the rate of transmission of heat energy.

    In the case of the plant in the box, it absorbs visible light, so we have a heat energy source at the center of the box. Reduce the rate at which heat energy can escape (since we’ve increased the thermal resistance) and from Fourier’s law of heat conduction, the temperature of the center has to increase.

    An analog to this would be replacing a “leaky” blanket (that allows air exchange with the center) with a “heavier” blanket that prevents the exchange of air. Even Derek, who demands “real world” observations, should admit that you’ll stay warmer with the heavier blanket.

    In the case of the atmospheric greenhouse effect, visible light is not impeded by CO2 as it impinges on the Earth’s surface, however, because CO2 preferentially absorbs certain wavelengths (that are not otherwise absorbed). All of the other physics is not modified, and the primary mechanism by which the heat energy gets transmitted from the ground to the “top of the atmosphere” is via convection.

    See this figure from one of SoD’s posts.

    Since the rate at which convection can transport heat energy is fixed (the tropospheric lapse rate is not affected to first order by the change in CO2), the atmosphere responds by increasing the height of the convective layer (the “radiative top of the atmosphere” has to move upwards to compensate). Since the temperature at the top of the atmosphere is nearly the same in both cases (there are unimportant geometric corrections for example), this implies the surface has to warm in response to the additional CO2 (all other things being equal).

  5. Carrick said

    I should mention that the explanation given for the “real greenhouse gas” effect is incomplete.

    It is true that the interior of the greenhouse can warm more in the daytime, but paradoxically it can cool more rapidly at nighttime.

    The reason is that typically at nighttime a temperature inversion is set up, and in the “unprotected environment” as you get advection of air (“wind”) across the ground you get air exchange between the surface and higher altitudes (the wind moves faster higher up than it does near the surface due to surface friction)—paradoxically when you get a wind gust at night, you see a jump in ground temperature as a result of this.

    The greenhouse, because it is blocking advective air motion, cools to the temperature that would be present if there were no mechanical exchange of air between higher and lower altitudes…. only on a perfectly windless night would you expect the two cases (ground exterior and ground interior to the greenhouse) to converge. [This is a prediction, I’ve not seen data for that case.]

    The effect of the interior of a greenhouse getting cooler at night is shown in this document.

    It also shows that if you add IR blocking material, the temperature is higher than it would have been without the IR blocking material.

  6. Jeff Id said

    I’ve made a couple of updates in the above description to make the examples more clear. Including adding the time of measurement for the greenhouse — thanks to Carrick who obviously spent a good deal of his youth making trouble. 😀

  7. Carrick said

    By the way, one of the big protections that greenhouses provide at nighttime is that it keeps the wind off of the plants root masses (which have moisture and hence cool more rapidly due to evaporative heat loss). Much of the same benefits of a greenhouse for nighttime protection are afforded by a simple row covering. (Row covers also protect from frost… I’ll let somebody else explain how that works.)

  8. Carrick said

    I forgot to bring up that we’re talking about growers here.. you have plants in pots sitting on the ground, so the root masses (while enclosed in a pot) are exposed to air both on the top of the root mass and from the weep holes on the sides and bottom of the pot.

    Jeff ID:

    thanks to Carrick who obviously spent a good deal of his youth making trouble.

    LOL. That’s me. I spent a fair amount of time annoying school teachers with my questions, I’ll admit to that!

  9. Jeff Id said

    Carrick,

    Nice, I originally wrote that Carrick who obviously spent a lot of time in the back of class teasing the professor. Then I realized just how stupid it would be to unwittingly imply myself as the professor in this crowd. haha.

    See guys, I do have a filter!

  10. Steve Fitzpatrick said

    Were the glass perfectly non-reflective, the emissions woulds be pretty much the same. But since real glass reflects about 8% of the light that falls on it’s surface, the thermal emission from the green-houses will be a bit lower; the total emission (thermal plus optical) would be always the same.

  11. Derek said

    Woah, err, thanks, I think Jeff..

    Jeff wrote,
    ” I’ll give the answers to these with supporting explanations tomorrow or the next day depending on how much fun people are having. ”

    I will reserve my comment / response untill after that is posted.

  12. mondo said

    I am probably approaching this problem from a naive amateurish perspective – that of a gardener. I know that if we had this situation here in Oz, the plant within the transparent box would be wilting and heat stressed due to the fact that heat removal by convection couldn’t happen (unless the box is huge!). The one in the open air would be functioning as it should with transpiration managing its heat balance with emissions into the convective atmosphere.

    The test a gardener uses to determine whether a plant is being stressed is to hold a leaf in your hand. If it feels hot, it is stressed. If it is cool, it is functioning as it would normally.

    For these reasons, I figure that the plant in the box will be at a higher temperature, and if the camera could record an image of the plant (rather than the box), then that would show.

    I suspect that there is quite a lot going on here….. We have a complex system!

  13. Brian H said

    The convection losses from the outside plant would be unimpeded, but would be limited inside the box, and taper off to zero when the box was in “equilibrium” (losing as much heat as possible from contact with the outside air, and from radiation). That would be at a higher temp than the outside air.

    As for the 2 Earths, the high CO2 one would have vastly higher agricultural productivity. That would have far more impact than the 1°C temp difference.
    But the plants are doing work to “fix” the CO2 as hydrocarbons, and that can’t be free, and that work is coming from use of the Sun’s energy. So I think we have a problem with postulating that higher temperature. The energy equations don’t seem to balance …

  14. Nic L said

    Jeff

    A query on the first experiment. For the avoidance of doubt, can you confirm whether or not the fancy camera, when taking an image of the plant located inside the transparent box, is also located inside that box?

  15. Jeff Id said

    The camera is outside of the box.

  16. Jeff Cagle said

    OK, my naive answer: The greenhouse will be warmer than the open air; since the greenhouse is not a perfect black box, the outside walls will still be warmer than the open air. Radiation is proportional to T^4, so the greenhouse radiates more.

    Someone tell me where I’m wrong.🙂

  17. […] Guest post by Jeff Condon (reposted by request from The Air vent) […]

  18. suricat said

    Mine host, Jeff.

    You do realise that your scenario is the antithesis of Derek’s?

    Derek postulates less than depth to extinction distances in which ‘the camera’ is able to differentiate plant temperatures. However, you postulate greater than depth to extinction distances in which ‘the camera’ is unable to differentiate surface temperatures (‘the camera’ can only observe ‘OLR’ [outgoing long-wave radiation], thus, the Planck level of the emitting atmosphere that provides equilibrium for this planet and another planet receiving identical insolation).

    Was this unintentional, or was it intended to lead on to a planet’s biological diversity (photo-chemistry etc.) in a later post, where insolation energy is attracted to chemical, rather than thermal, conversions and the planets with identical insolation can still show a divergent Planck energy for their radiant temperatures?

    There should be more than just ‘thermal equilibrium’ considered to prove stability.

    Best regards, Ray Dart.

  19. M. Simon said

    When you said “plants” I got confused. I was thinking of something Ziegler-Nichols would apply to.

  20. alcuin said

    The effective height from which thermal radiation leaves the higher concentration planet will a bit greater than that of the lower concentration planet, so its radiating surface will be somewhat greater in area. Therefore, in order to radiate equally, its brightness (radiating temperature) must be slightly less. Extrapolating downward to the earth’s surface from the effective height of radiation, at the adiabatic lapse rate, the surface temperature of the higher concentration planet will be somewhat higher because of the greater height through which adiabatic convection must extend. Presumably both planets will absorb or reflect sunlight equally at wavelengths that do not interact with the greenhouse gases, and energy deposited at the surface will largely come from the absorption of sunlight.

  21. Geoff Sherrington said

    If you put a plant in a sealed box in the sun it will probably die. Is the box sealed or unsealed?

    What equation is used by the instrument to integrate the whole spectrum to a single equivalent temperature?

    In California, is the plant legal or “hot”?

    Always answer a question with another. Why?

  22. Geoff Sherrington said

    If you put a plant in a sealed box in the sun it will probably die. Is the box sealed or unsealed?

    Is the atmosphere inside the box dry or saturated with water vapour” Is there condensation on the glass interior?

    Is the plant in a growing phase or has it passed maturity and is declining?

    Does the plant have a sun-following mechanism or is it stiff and one shape?

    What equation is used by the instrument to integrate the whole spectrum to a single equivalent temperature? Is it dependent on powers of light intensity at different wavelengths?

    In California, is the plant legal or “hot”?

    Always answer a question with another. Why?

    For Carrick the accused larrikin in class: We saw yesterday a doco about Barry Humphries and his alter egos like Dame Edna Everage. In “Who’s Who” he says “Self-educated. Attended Melbourne Grammar School”. A former teacher recounts that the child Barry would attend football games for sports, but would seat himself with back to the game (not against the written rule) and conduct other activities, such as knitting (also not forbidden). Resonances?

  23. Ron House said

    Very interesting concept, except for the snide remark about vegetarians. I am a vegetarian and I support all the same policies, and advocate the same truths about physics and oppose the fallacies of AGW as you do, so I am a bit mystified why you would want to alienate me from enjoying your thoughts.

    Well in fact you can’t alienate me because I think rationally. But most people don’t. They respond to emotions, and your emotions are telling them “He is opposed to the nice people.” Forget that you too are a nice person, forget that the environmentalists are pursuing policies that would (if they succeeded) destroy a good portion of the life on Earth, forget too that acting upon your understanding would result in the world being a much happier and flourishing place than it will be when governments act upon their highly damaging misunderstanding of the role of CO2. The fact that you poke fun at ‘nice’ people is the only thing that will stick in their consciousness.

    We need all the allies we can possibly get to demolish the AGW anti-life, anti-wealth, anti-happiness insanity. Please, please, do not alienate entire categories of potential allies. We all have prejudices, but we should be wise enough to put a lid on them.

  24. Brian H said

    Need the vegetarians? Doesn’t seem possible, or worth the effort. Especially if they don’t bother using “Beano”. Off to Planet 2 with the lot of ’em!
    🙂

  25. kim said

    East and West so jest
    Of Pythagorean beans.
    Same old same old same.
    ===========

  26. wayne said

    Ron House, long time sice I have replied to you.

    Veggies, I like them too but in proportion. Your, right, this should not get into personal preferences, how childish with such huge questions screaming to be correctly answered. To me anyone is included if they bring their best effort at the truth. (I can’t believe someone brought up what you eat! Brother!)

  27. DeWitt Payne said

    I’m assuming that you mean the covering of the greenhouse with the plant is perfectly transparent at all wavelengths. The plant inside the greenhouse during a clear day will be warmer than a plant outside a greenhouse. The radiative only lapse rate is much higher than the convective adiabatic lapse rate. That means the irradiated surface that has convection blocked will be hotter, probably a lot hotter, depending on the latitude and season. The camera shouldn’t care whether it is looking through the wall of the greenhouse or not so the plant in the greenhouse will have a higher temperature measured by any means you care to use.

    The two planets as observed from deep space, however, will have the same temperature within the likely error of measurement of the camera. Energy in equals energy out. The geometric effect isn’t going to be very large at all.

  28. Jeff Id said

    Sorry Ron, I know it’s not your personal style but I’ve had too many veggies and greenies push their “superior” lifestyles at me. Everyone is welcome to eat whatever the heck they want on the right world, everyone who would dictate what to eat can go to the left one.😉

  29. Jeff Id said

    This is obviously more difficult than I thought it would be so I’ll give a clue on how to get the answers.

    Write the energy balance equations with the inputs and outputs to each system.

  30. ktwop said

    I presume the 1 degree temperature difference is at the surface of the planets and the higher carbon dioxide concentration in the surrounding atmosphere is just sufficient to attenuate the higher surface radiation from this higher temperature such that the total radiation balance is maintained.
    That itself provides the answer I think. An observer outside the planet /atmosphere systems will only see two bodies in radiation equilibrium with the sun where the surface temperature or the CO2 concentration or any other internal system parameters would be invisible.Taking brightness to be an unambiguous measure of the outgoing radiation would require that both planet systems exhibit the same total brightness.
    Incidentally I find the “loose” talk of a single number as the earth’s temperature in climatology rather misleading since temperature is not an intrinsic property but merely a parameter describing the statistical mean of the energy state of some defined system. For the two planet systems here the system temperatures must be identical.

  31. Carrick said

    Jeff ID:

    This is obviously more difficult than I thought it would be so I’ll give a clue on how to get the answers.

    I’ve been assuming realistic physics on the two planets. That said, the atmosphere is not totally opaque at all IR frequencies… there are windows that can be used to “view” the oceans. So if the temperature of e.f. the ocean changes, that changes the pattern of radiative energy observed from space (as a result, with the real Earth as viewed by satellites, the blackbody temperature of the surface of the ocean can be measured through the supposedly “opaque” atmosphere).

    Since there isn’t just one black-body temperature spectrum as viewed from space, it’s confusing as to exactly how it integrates to measure the “radiative emission temperature of the object”. We’d need details of the algorithm used to answer the question in this case.😉 I was supposing you really meant “integrate the irradiance of the planet across all wavelengths and over the surface of the planet as viewed from a fixed point,” aka the planet’s “luminosity”. That stipulation simplifies matters somewhat.

    If you meant luminosity and were thinking the TOA (e.g., ignore IR windows), then for the planet with more CO2, the TOA is slightly higher up, and you end up with a slightly larger surface area radiating the same radiative power per unit area, and hence will have a slightly greater net luminosity. (The planet with more CO2 ends up looking “brighter” because in the sense of the TOA it is “bigger”… you get maybe an additional 0.06% or so greater luminosity.)

    Write the energy balance equations with the inputs and outputs to each system.

    Well that’s part of the trouble here….it’s a semantics issue. It’s not an “energy balance” but a balance in the rate of radiative energy inputs and outputs…and of course this only occurs once radiative equilibrium is reached.

    I bring this up because a lot of the confused comments I see from people who reject or doubt the greenhouse gas effect originate from this confusion in terminology. They have it grilled in their head that energy can neither be created nor destroyed. What we’re talking about is rate of energy exchange (measured in watts not joules), and that can certainly fluctuate over time without creating or destroying energy (rather it just releases or stores heat energy). Things like the storage of radiative energy into plants in response to changes in radiative forcing (and fertilization effect) affect how long it will take to reach equilibrium. But the only statement that is true at equilibrium is, viewed from “outside” of the planets atmosphere, the net radiative energy loss by the atmosphere et is equal to the net radiative energy impinging upon that atmosphere.

  32. Jeff Id said

    Carrick, I can’t play until I give my answers in the morning but agree with your comments about energy. It’s not actually an energy balance but a power balance. I could probably write a post on that as well because when people mess it up, it drives me crazy.

  33. Terry said

    DeWitt # 27

    The planet with 2xCO2 will register a slightly higher temperature due to the new equilibrium established between increased absorption and slightly higher radiative emission. Overall the increased absorption is balanced by increased radiative emission due to incr temp.

  34. Ron House said

    Brian, Wayne, Jeff,

    The reason I was motivated to write (about veggies) was that I know a young lady who (along with all her friends) voted Green in the recent fed. election. She knew about my arguments showing AGW to be fraudulent, but she said “At least they are trying to help the environment”. That’s illogical. If they are actually damaging the environment why vote for them? But the perception out there is that our side is a bunch of heartless cynics (right or wrong) and their side is loving, caring, tiptoeing through the tulips enviro people (right or wrong). And most people want to be with the ‘nice’ people (right or wrong). Logic, evidence and truth will never win against emotion. Like it or not, at least half of the world is like that.

    Of course you and I know that logical people have emotions too, and nice emotions at that, but it is filtered through rationality and doesn’t always show on the surface. The rationally challenged who vote green don’t see it in us, but they are needed on our side because this scam gets its power from emotional control of masses, just as Nazism and communism did. Fine emotions can lead to terrible evils.

    But we can win the emotional argument (as well as the rational one) because it really is nice and planet-loving to put plant food into the air and provide more food for people and animals. Emotion is on our side because we are morally and factually right. So why ‘blow’ it just because the fritter-headedness of some people gets at us once in a while?

  35. DeWitt Payne said

    Re: Carrick (Jan 2 04:19),

    The IR windows don’t matter for the integrated spectrum. If you get more through the window, you get less from the rest of the atmosphere. At steady state and averaged for some number of full orbits, luminosity, the total emitted EM radiation (W, not W/m2) viewed from a distance must be the same for both planets. Teff will be very slightly lower for 2xCO2 because the emitting area is slightly higher. But it’s unlikely that the instrument precision would be good enough to resolve this difference given the normal fluctuations in emission in time and space. A window would give you a measure of the surface temperature if you just look at emission in the window. But the experiment specifies a bolometric camera. A bolometer measures luminosity over a wide band. Since the bandwidth isn’t specified, the logical (to me anyway) assumption is that it’s measuring over the entire thermal IR range.

    If you meant luminosity and were thinking the TOA (e.g., ignore IR windows), then for the planet with more CO2, the TOA is slightly higher up, and you end up with a slightly larger surface area radiating the same radiative power per unit area, and hence will have a slightly greater net luminosity. (The planet with more CO2 ends up looking “brighter” because in the sense of the TOA it is “bigger”… you get maybe an additional 0.06% or so greater luminosity.)

    Nope. The luminosity is the same. For 2x CO2 the total power will be spread out over a slightly larger surface area so it will be slightly dimmer, not brighter. And an increase in effective altitude of 150 m (Tsurf + 1 C at a lapse rate of ~6.5 K/km) changes the surface area by 0.005%. If planet 1 radiates 240 W/m2 then planet 2 radiates 239.9889235 W/m2 and Teff is lower by 0.003 K. Good luck measuring that.

  36. Alan McIntire said

    Apparently the original question was intended to elicit the response that the two planets with 1X and 2X CO2 will radiate the
    same wattage to space as they receive, though in slightly different frequency distributions. The total average energy received at the surface is about 492 watts, partt radiated in sensible heat, part carried higher in the atmosphere by convection and conduction . With doubled CO2 absorbing an additional 3.8 watts, that would increase average surface radiation to somewhere between 493.85 and 495.8 watts. It occurs to me that the surface albedo and temperature of the earth is not constant. There’s a significant difference between temperatures and reflectivity of land and ocean at different latitudes and longitudes, the surface area is not distributed evenly,
    the difference between 492 and 495.8 is not that great. There will be changes in measured radiation over the course of a day that will be much larger than the average difference between the two planets. It will take precise measurements over a significant period of time to detect any difference in the average outgoing sprctra of the 1X CO2 ans 2X CO2 planets.

  37. thermally stabilized earths, one which has today’s CO2 and one which has 2X today’s level.

    note how most responses have been off topic.

    one of two.
    you will “see” less radiation from the 2x CO2 (id bet not much) because the co2 radiates it “back” to the surface. OR
    The two are in equilibrium, SO, it has the same as the radiation IN equals the radiation OUT.

    Tim L

  38. Carrick said

    DeWitt:

    If you get more through the window, you get less from the rest of the atmosphere

    It does matter if your measurement process is trying to fit to a single Planck radiation curve of course, since it will screw with your answer.

  39. Jeff Id said

    I’ve put my answer up on the new thread.

  40. Carrick said

    DeWitt:

    Nope. The luminosity is the same. For 2x CO2 the total power will be spread out over a slightly larger surface area so it will be slightly dimmer, not brighter. And an increase in effective altitude of 150 m (Tsurf + 1 C at a lapse rate of ~6.5 K/km) changes the surface area by 0.005%. If planet 1 radiates 240 W/m2 then planet 2 radiates 239.9889235 W/m2 and Teff is lower by 0.003 K. Good luck measuring that.

    You’re correct, if you assume that the of the energy makes it to the surface of the planet. It’s interesting to think about a more “real world” version where the UV gets absorbed by an expanded cross-sectional area in the stratosphere, the albedo of the planet increases slightly, but I’m not going to try that without at least writing out modeling equations for that. Sounds like a problem for Lucia.😉

    I like your way to estimate the change in the TOA… I just used a WAG and said “1km”, which is obviously too high.

  41. Jeff Id said

    Carrick, DeWitt,

    Will at WUWT made a point that the emission altitude will go up with more incoming energy. He has a low tech blog denying AGW so it didn’t surprise me that he thinks I’m an idiot – a lot of people do. I replied that increased energy input wouldn’t change the average emission altitude. While basically it’s true IMO, this though doesn’t include potential saturation effects. I wonder if either of you has an opinion on that.

  42. Carrick said

    I think the average emission altitude (radiative top of atmosphere aka TOA) does go up, and in fact such an effect is claimed to have been observed (e.g., Santer et al 2003). However, at first order—as DeWittt points out—this has no effect on luminosity. The reasoning is that most of the solar radiation impinges on the surface and/or the lower part of the troposphere (cloud layer).

  43. Jeff Id said

    Carrick, In the example above I agree the emission altitude goes up with more CO2. What I don’t believe is that if the sun were brighter that we would see the emission altitude change.

  44. Carrick said

    Jeff ID:

    What I don’t believe is that if the sun were brighter that we would see the emission altitude change.

    I think we would.

    What Will was claiming (as far as I can decipher his mixed up jargon) was that the only way the TOA changes is if the solar luminosity increases. Not true, because he makes the same mistake of most people in terms of using energy rather than power as the units for solar radiation. As I explained there, temperature is a measure of stored heat energy, if you store more of the solar radiation coming in, the temperature goes up without requiring that the amount of radiation increases. (In equilibrium, you stop storing additional heat energy.)

    This is a mistake that even people who are normally very precise like ScienceOfDoom have made (and as far as I see continue to make). I think it comes from the historical (aka retarded) way that thermodynamic quantities are often written.. because they are trying to hide the fact that quantities are changing over time. E.g.

    dU = dQ – dW

    Really it should be written dU/dt = dQ/dt – dW/dt. Is there anyplace where writing it as differentials actually helps? Certainly not for this problem.

  45. Jeff Id said

    From my way of thinking, if we have two identical in every way planets, one with slightly higher incident solar intensity, each watt of power would still take the same time to travel from the surface to the average emission altitude in the upper atmosphere.

    Perhaps if I write that the mean path length of each photon won’t change just because the sun is brighter so the emission altitude doesn’t change but the emission brightness would. Adding CO2 shortens the mean path length and increases the mean emission altitude.

  46. DeWitt Payne said

    Re: Jeff Id (Jan 2 16:25),

    The altitude of emission is a function of optical density. If you increase the optical density by adding CO2 (ignore the details), the emission altitude goes up. With a constant lapse rate, the surface temperature goes up as well.

    A change in incident solar power, OTOH, does not change the optical density to a first approximation. The effective altitude of emission remains the same but the intensity increases because the temperature is higher. A second order effect is that the atmosphere expands a little because it’s warmer. That would increase the effective altitude of emission and act as an amplifier or feedback.

    Another second order effect is that adding CO2 cools the stratosphere, which should shrink it somewhat. That would lower the effective diameter of the planet and reduce the total amount of solar energy absorbed. Sunlight would warm the stratosphere as well as the troposphere and increase the effective diameter.

    Since all these effects are much smaller than the main effect, we’re talking millidegrees, I don’t think you can say with confidence that the 2X CO2 planet absorbs more solar radiation than the 1X CO2 planet without doing very detailed calculations. Even then you’ll probably leave something out.

  47. hr said

    Brian H (#13) writes: ‘As for the 2 Earths, the high CO2 one would have vastly higher agricultural productivity. That would have far more impact than the 1°C temp difference.
    But the plants are doing work to “fix” the CO2 as hydrocarbons, and that can’t be free, and that work is coming from use of the Sun’s energy. So I think we have a problem with postulating that higher temperature. The energy equations don’t seem to balance …’
    Interesting point, Brian. Although it’s perhaps slightly o/t w.r.t Jeff’s question, I’d like to ask a question.

    I might have written ‘vegetational’ for ‘agricultural’, as presumably plants of all types might respond at least initially to the increased fertilisation by growing bigger or faster. So until the system reaches a new equilibrium at a higher atmospheric CO2 level slightly more of the incoming solar energy would be used to drive the plant’s processes, and at any given moment some more energy would be stored in the form of the plant’s biomass rather than re-emitted to space.
    But how much more? And would this be reflected significantly in surface temperatures?

  48. DeWitt Payne said

    Re: hr (Jan 3 11:09),

    The total amount of solar energy used in photosynthesis of biomass is a tiny fraction of the incident radiation, about 1% according to this Wikipedia post. But what’s important is not the total used but the amount that biomass increases year to year because biomass also decays back to CO2 releasing the stored energy. That total is even smaller. In other words, it’s insignificant. Plants absorb a lot more solar energy than that, but if it doesn’t end up as biomass, it doesn’t count because it isn’t stored. Wind and water circulation uses more energy, but it isn’t stored either. It all ends up as heat which must be radiated away.

  49. Derek said

    As Jeff has stated he is paraphrasing me, I thought I’d look the words meaning up.

    http://en.wikipedia.org/wiki/Paraphrase

    Paraphrase may attempt to preserve the essential meaning of the material being paraphrased. Thus, the (intentional or otherwise) reinterpretation of a source to infer a meaning that is not explicitly evident in the source itself qualifies as “original research,” and not as paraphrase.

    Unlike a metaphrase, which represents a “formal equivalent” of the source, a paraphrase represents a “dynamic equivalent” thereof. While a metaphrase attempts to translate a text literally, a paraphrase conveys the essential thought expressed in a source text — if necessary, at the expense of literality. For details, see “Dynamic and formal equivalence.”
    End of quote.

    If you have paraphrased me Jeff, it is beyond my comprehension how.
    Also please stop declaring who I am, or maybe according to you “at war” with,
    without first making it plainly obvious that it is in your opinion..

    As for the “experiment” it is so far removed from my description of what a thermal image of a greenhouse AND it’s surroundings ACTUALLY shows,
    that I am not inclined to comment upon it, as it sees to be trying to assert some sort of “radiative balance / equilibrium” that as far as I am aware has never been shown at a global scale in the first place.
    Infact there are numerous good reasons to suggest there can not be a planetary “radiative balance”, so
    I would not of bothered if I was you…Too late.

  50. Jeff Id said

    Gee Derek, sorry if you are offended. It’s a plant in a transparent box, essentially similar to a greenhouse wouldn’t you say? You know the greenhouse which would be warmer… And for that portion of the experiment we agree, I thought.

    After you go back and forth with ScienceofDoom a dozen times, you get the ‘at war’ label by default but I couldn’t understand your disagreement well – sorry.

  51. Derek said

    Jeff, I simply do not “get” either the “Planck” or “Maxwellian” versions of climate science “maths”.
    Although I do think I have a good grasp on conduction and convection, and how P works in “that” equation.

    I will have to do a post “at home” about the “maths” (which is also the physics come to think of it),
    when I get the simile written up I am trying to get to work at present.

    Thanks for letting me vent, and thanks for the ride.
    Maybe I am just a lot less trusting these days of (supposedly) “higher authorities” than most,
    “principally” because of “climate discussions”.

  52. Jeff Id said

    Derek,

    You may have seen this post:

    https://noconsensus.wordpress.com/2010/08/06/radiative-physics-simplified-ii/

    Global warming is really only about the shifting of the two planck curves shown in Figure 2. Even if Planck’s curves aren’t exact you can see the outgoing radiation shift into the little tiny peak that is absorbed by CO2. No more proof than graph 2 should be required to understand that the effect is real. Study the bond calculations that give the absorption curves, then study Planck. You’re done.

    You can say the effect is minuscule, immeasurable, nothing in comparison to nature, I won’t disagree. You can say it’s huge, I won’t disagree but am more doubtful every day. If you say it doesn’t exist, we disagree completely.

  53. Derek said

    I am having a “Brego” moment……

    As well as a obviously dominant within the climate system latent heat of water vapourisation moment.

    Jeff, the gas measurements are they from closed (flask) samples?
    Chemists and physicists disagree about the specific heat of CO2 in regards to closed and open systems.
    AND,
    No one ACTUALLY knows what happens to the molecules anyway.

    Then there is the usually ignored mean free path length of a photon.

    Any idea of “radiative balance” vanishes with, that used by life, or the number and varying time scales of oceanic phases, or that locked up in limestone, chalk etc, etc, etc..

    Is oil abiotic, is also relevant, because if it is abiotic (to my best understanding it is) then burning oil is releasing a good portion of geothermal input, not old solar input AND, if oil is formed from earth’s fissile waste products then the released CO2 is new, not recycled carbonates.

    I am more persuaded by the there is no greenhouse effect at all arguments, but I will admit I do not actually know either way.
    The AGW CO2 effect as presently proposed is certainly immeasurable, even the sign of such an effect, if it exists, is unknown at present.

  54. Jeff Id said

    Derek,

    The gas measurements of Fig 2 are calculations which have been verified to a fair degree and are not flask samples. The widths of the absorption lines can vary but the basic locations will not. The rest is subtleties. Look up MODTRAN, and study absorption by molecules. It shouldn’t take long and is a direct path to the answers. While you are doing it, note that the math would have to be very very very wrong to change the conclusions. Then find a paper confirming the curves in Fig 2 by measurements. It’s all out there in various forms.

    This has nothing to do with specific heat and everything to do with the mean free path of the photon.

    Radiative balance is not a requirement but a simplification often used for explanation. It is completely moot in considering the absorption of CO2. The new CO2 vs old also doesn’t matter. It just does or doesn’t capture some heat and the basics say it does. That’s what makes it difficult. They want to label us deniers or whatever so we can be discounted as weak minded. The believers love deniers, yet that is not where the argument lies — which was the end purpose of this post — get the basics right.

    A valid but weak angle might be whether we’re responsible for atmospheric increases of CO2. I think we are, have read some papers, but don’t know.

    A strong one is whether clouds cause positive vs negative feedbacks.

    Do solar particles influence cloud formation such that the minor variations in the sun are bigger than we thought.

    Why do models overshoot measurements on average.

    What about UHI.

    I can keep going but any of the above influences finish the dramatic conclusions that we’re destroying the planet with CO2 and all of them are undecided in climate science.

    So from their core argument they can claim consensus, but on the rest, there is none.

  55. Derek said

    ” The gas measurements of Fig 2 are calculations which have been verified to a fair degree and are not flask samples. ”

    This is news to me, I am not sure it is correct. As I understand Fig 2 is based upon flask samples / measurements.
    If I am wrong, then so be it.

    ” note that the math would have to be very very very wrong to change the conclusions. ”

    I believe the maths is that incorrect, and MODTRAN does do peculiar things in climate models.
    Today I intend writing up a simile to illustrate how wrong I think climate science “maths” is,
    or rather, why I do not “get” any of the present versions of the “maths”.

    ” Radiative balance is not a requirement ”

    Again this is news to me, as I understand at present it is a requirement for AGW, as it is our supposed upsetting of this “requirement” that is the cause of “man made” supposed “global warming”,
    when the earth is apparently actually cooling at least over the last decade or so, and certainly over the Holocene period.

    There is so much “back tracking” going on at present it is difficult to discern the actual position of almost all AGW proponents,
    and “mainstream skeptics”.
    In particular I would note how no one has actually challenged my interpretation of what a thermal image of a greenhouse AND it’s surroundings actually shows. ie, conduction and convection are far, far more powerful than radiative losses, and therefore the basic “greenhouse” simile as commonly used is plain wrong, if not a deliberate misdirection / misconception.

  56. Jeff Id said

    Derek,

    “I believe the maths is that incorrect, and MODTRAN does do peculiar things in climate models.”

    As I’ve written above, the calculations are backed up by observation.

    Radiative balance is never truly achieved. It is just pushed in a warmer direction – however slight or strong it may be by Fig 2.

    “There is so much “back tracking” going on at present ” – I don’t see it.

    “In particular I would note how no one has actually challenged my interpretation of what a thermal image of a greenhouse AND it’s surroundings actually shows. ”

    I think that every technically adept person agreed with you, although they may have misunderstood my description. Greenhouse is a misnomer.

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