Shorter Superman: Some of my thoughts make sense, so I’m not totally crazy, just higher and better than all of youse. My handle says it all. My exalted elevation releases me from most obligations to cite.
+1 for Hank Roberts, #445
Supe, at this point, less is more. You’re about at the point where I see your handle and skip the comment.
Dan H.says
Susan,
RC is not immune to this posting. Sevreal posters here have acknowledged that they are not cliamte scientists, and some are not even scientists. At least CD has attempted to distinguish the climate experts from the novices. Many other sites do not. Unfortunately, many sites are sensationalizing certain weather events in an attempt to garner much-needed support. This will only backfire in the long run. Only openly honest discussions will prevail.
SecularAnimistsays
Dan H. wrote: “Only openly honest discussions will prevail.”
I assume the moderators’ taste for low-brow slapstick comedy is the reason that Dan H’s comments are not going to the bore hole.
454. Perhaps Superman can be persuaded to turn his baleful attentions to Dan H. Now *that’s* entertainment.
bobbsays
@402 (and 391). Thanks for your great suggestions. Patrick (@402), is it reasonable to expect that there is somewhere a series of time varying spectograms showing the increase in absorption of IR light by the increase in greenhouse gasses in the Earth, say taken by satellites over the last 20 years. I’m thinking this might be a good “smoking gun” for the class. To show that energy that once was emitted is not absorbed and re-radiated. Then I can show where it is going (mostly into the oceans as you note). Also, something I’ve wondered is why the plot of Earth’s total heat content here http://www.skepticalscience.com/graphics.php?g=46 is not monotonically increasing. Would this be due to volcanos or man-made aerosol emissions? Or is this simple uncertainty?
> I’ve wondered is why the plot of Earth’s total heat content here
> is not monotonically increasing.
since that’s one of the really stock denial talking points, I’m glad you’re reading this stuff at Skepticalscience.
Tamino covers it, and may be quoted on it at SS.
If you’re not up on the top 100 frequently rebunked claims to where you can just point to them at SS, you’re not prepared to go up against any kid who hears those talking points frequently.
Patrick 027says
Re 456 bobb –
satellite measurements – great idea; since it is TOA (top-of-atmosphere) radiative disequilibrium that is responsible (see caveats in my prior comment), over time, for accumulation or depletion of the heat content of the climate system. Satellite measurements are tricky, though; satellites can have orbital changes over time, issues with calibration – I would expect in particular if there are no time (and space?) periods where one satellite’s record overlaps with another. Also, satellite data may infer different things, so watch out. At any given wavelength and any given atmospheric composition, you can see farther down into the atmosphere and/or more of the surface (thus less of the atmosphere) if you look straight down than at some other angle. While increasing CO2 reduces OLR specifically in a pair of spectral bands on either side of ~ 15 microns wavelength, the accumulation of heat resulting from that will tend to increase OLR – and so there will be a net increase in OLR outside where the climate forcing occured (depending on feedbacks; less OLR increase where H2O vapor acts on the spectrum, and also spatially where cloud positive LW feedback occurs); satellites measuring at some wavelengths may show an increase in OLR even when the total global OLR hasn’t returned to equillibrium. Also, if there are SW (solar heating such as via changes in albedo) forcings or feedbacks, the equilibrium OLR must also change.
IR light – I advise using the terms shortwave (SW) and longwave (LW) radiation (OLR = outgoing longwave radiation), because (in the definitions used in the study of atmospheric radiation and climate) the greenhouse effect deals with LW, while solar heating is mostly SW – the cutoff is somewhere around 4 microns, so SW radiation includes some IR as well as visible and UV (and shorter wavelengths, though those don’t contribute much energy, but do have significant effects on a small fraction of the mass of the atmosphere at it’s ‘top’). Some (well, at least one) have claimed a reduced role for CO2 based on looking at it’s SW IR effects and confusing that with it’s greenhouse effect. (Look up the Planck function to understand why such a distinction can be drawn about 4 microns; if the Earth (surface and atmosphere) and Sun (photosphere) were at more similar temperatures than the distinction between SW and LW radiation wouldn’t be so convenient.)
“that energy that once was emitted is not absorbed and re-radiated.”
Actually, that is how the greenhouse effect works. … except that re-radiated may imply a photon of the same energy, which isn’t generally the case – see below.
It would be possible to base a greenhouse effect on scattering, which may be thought of like the reflection of photons over some particular probabilistic distribution of directions. A greenhouse effect might even be made by having LW-phosphorescence – might have to be engineered, though? (maybe on a planet hot enough for _______ clouds…??? I have no idea).
For Earthly conditions, though, the greenhouse effect is mostly due to the absorption and emission of photons – at approximately LTE (local thermodynamic equilibrium)- meaning that molecular collisions are sufficiently frequent to redistribute the energy among the available states and among all the molecules in a given small volume so that the distribution of energy is maintained at an equilibrium for a particular temperature – and that the same temperature approximately applies to the different kinds of molecules present (if not, one could still work with LTE given different temperatures for different substances that happen to occupy the same volume, but that’s not generally necessary for most of the atmosphere). Thus, at any given frequency (photon energy), and if necessary, direction and polarization (not necessary for randomly-oriented molecules or particles or spherically-symmetric particles) CO2 and other greenhouse gas molecules, and cloud particles, absorb radiation from a direction based on their optical properties and how much radiation is incident on them, while they emit into that direction according to the Planck function AND THE SAME OPTICAL PROPERTIES. This can be summarized as Kirchoff’s Law (of thermal radiation): http://en.wikipedia.org/wiki/Kirchhoff%27s_law_of_thermal_radiation : emissivity = absorptivity.
Kirchoff’s Law (of thermal radiation) satisfies the second law of thermodynamics – because it implies that however radiation may be scattered, refracted (noting blackbody radiation intensity is actually a function of the index of refraction, but this is typically not brought up in climatology because air’s index of refraction is near that of a vaccuum), partly or totally reflected, (but setting aside partial emission or absorption, where a photon scatters with some change in energy, such as in Raman or Compton scattering – it gets more complicated when this happens) if there are some pathways between two seperately LTE volumes V1 and V2 of temperatures T1 and T2; if T2 is greater than T1 (V1 warmer than V1) the flux of radiant energy from emission in V2 to absorption in V1 will be greater than the flux from emission in V1 to absorption in V2; it is this way for any single frequency, direction, and polarization, and thus must be for the total radiant energy. If T1 = T2, the two fluxes are equal. The difference is the net flux, and it is the radiant heat that flows from higher to lower temperature as one would expect (PS the second law of thermodynamics generally deals with net processes that are the averages of things which go on in opposite directions at the same time on the microscopic level. Because radiation can in some conditions travel macroscopic distances between interactions, these opposing radiant fluxes happen to occur at a macroscopic level).
(If there are photon scatterings that don’t preserve photon energy, I would expect there should still be a general tendency for radiant energy to flow from higher to lower temperature, and this includes the flow of energy into the population of photons; blackbody radiation describes the population of photons that would be in thermodynamic equilibrium with some other matter at a given temperature.
Even if that matter only weakly interacts with photons, such equilibrium would be achieved given sufficient time in isolation; hence ‘cavity radiation’.)
For LTE, any given molecule or unit of substance will emit some number of photons per unit time, on average, in some part of the spectrum. A perfect blackbody that would do the same has some size, and this size is the emission cross section of that unit of substance. For LTE, the emission cross section into a direction is equal to the absorption cross section facing that direction.
For randomly oriented or spherically-symmetric particles or molecules, etc, they act (in a time-averaged or population-averaged sense) like spherical blackbodies which present the same cross sectional area in every direction. Random overlap leads to an exponential decay in unaffected photons over distance (in a crystal, overlap is not random, but (**I think**/**it’s my understanding based on inferences from other stuff I know**) the cross section of each unit may be smeared out over some larger area – it wouldn’t look like a single opaque circle but rather a partially transparent absorber; hence it absorbs some fraction of photons along any particular path as would randomly distributed cross sections); the cross section per unit volume is a cross section density, and is the amount of area per unit area facing some direction, per unit distance along that direction. Distance can be measured in terms of cross sectional area’s fractional areal coverage; this is called optical thickness or optical depth: http://en.wikipedia.org/wiki/Optical_depth.
An incident beam of photons decays exponentially over optical depth; however, if the temperature is nonzero (absolute scale), then emission will also occur in proportion to the portion of optical depth that comes from absorption (as opposed to scattering); emitted radiation will also be absorbed (or scattered), so, in the absence of scattering, it approaches a blackbody value asymptotically. In the presence of scattering, it would still tend toward that value because radiation can be scattered into a beam and this radiation has to be emitted somewhere. So if optical thickness over some isothermal distance is large enough, including over all directions that radiation is being scattered into and from, the radiant intensity inside approaches the blackbody value – and this is true for all directions, so the net flux through space approaches zero.
But if optical thickness is not too large, then temperature gradients become visible. Think about what you can see when in a fog; vary the thickness of the fog. Now imagine the fog is not scattering light but rather glowing incandescently according to it’s temperature (as are any objects within it). That’s what the greenhouse effect looks like. When or where or at whatever frequencies the atmosphere is transparent, for LW radiation (approximately excluding the sun) the Earth’s surface sees mostly only the cold dark of space, and space sees only the Earth’s surface (although actually, the Earth’s surface has some small nonzero albedo for LW radiation, so some of what space sees is actually it’s own reflection). Adding scattering to the atmosphere would make space and the surface see more of their own reflections. Adding absorbing opacity (along with emitting opacity, as required for LTE), The surface and space see less of the other and more of the air in between. Because temperature declines through the troposphere (see prior comment about convection), except where the stratosphere’s opacity becomes sufficient, adding opacity either to the troposphere or in some evenly-distributed way (by mass), adding more absorbing opacity to the atmosphere (increasing optical depth) results in space seeing less of the surface, and then less of the warmer lower atmosphere, etc., so even when the surface has dissappeared from view, adding more opacity continues to have an effect. Likewise, the surface will see less of not only space but the cooler upper atmosphere as well. The OLR above clouds depends on cloud temperature and thus cloud height. Water vapor is concentrated in the lower atmosphere and thus doesn’t have as strong an effect on OLR as it does on radiation at the surface, relative to a (approximately) well-mixed gas like CO2…
Well I’m out of time but you get the idea.
Just one more point. Optical depth is proprotionate to amount of substance, other things being equal. It generally varies over wavelength. For CO2, there are a bunch of wiggles in the spectrum, but the general tendency is a roughly…
(I think it’s roughly, not exactly, though I’m not sure offhand; anyway it depends on whether you’re viewing the spectrum in terms of wavelength or frequency; whichever you choose, it’s fine, just as long as the Planck function (the spectrum of blackbody radiation) is put in the same terms))
… exponential decay away from a peak near 15 microns (for CO2’s most important absorption band for Earthly conditions; other part(s?) of the absorption spectrum play a significant role on Venus).
Thus doubling CO2 effectively widens it’s absorption band by some amount over the spectrum. The central part of the band is now saturated – or nearly saturated ? – at the tropopause level (upward radiation nearly the same as downward emission from the stratosphere) – although farther changes in OLR are achievable (I think adding to stratospheric cooling, and indirectly to a downward adjustment to tropopause level forcing after stratospheric adjustment) – but there is room to decrease the net upward LW flux at the tropopause on the sides of the CO2 band.
Patrick 027says
… oh, and some of the variation including wiggles is from forcing (volcanoes, anthropogenic stuff, etc.), but even without that there could be some wiggles – some if from internal variability (weather, ENSO – more later if I get to it) and maybe some from forced cycles (day, year) – though I’m not sure of the significance. Generally, an equilibrium climate encompasses shorter term variability as well as horizontal fluxes of energy, so there can and will be radiative disequilibrium at any one place and time.
And buy a cheap (like $14) infrared thermometer and let the kids take it home one after another — meter things around the house, meter the nighttime sky, meter the daytime sky at the horizon, at the zenith, at true north (note whether it’s clear or cloudy, day and night) report back, add to a list, read up on why: http://mynasadata.larc.nasa.gov/804-2/1035-2/
Discuss how you can make ice in the desert in shallow trays on clear nights. They can look that up.
(Note anything shiny won’t give a proper IR Thermometer reading, and explain why — and why the instructions are to put a piece of dull masking tape over it — which quickly attains the same surface temperature and meters correctly).
Kiehl, J. T., Kevin E. Trenberth, 1997: Earth’s Annual Global Mean Energy Budget. Bull. Amer. Meteor. Soc., 78, 197–208.
doi: http://dx.doi.org/10.1175/1520-0477(1997)0782.0.CO;2
(some of that doi won’t appear here because it has html coding brackets; here’s the doi without those brackets: http://dx.doi.org/10.1175/1520-0477(1997)078 0197:EAGMEB 2.0.CO;2
link: http://journals.ametsoc.org/doi/abs/10.1175/1520-0477(1997)078%3C0197%3AEAGMEB%3E2.0.CO%3B2 (the link from the wordpress site above doesn’t work anymore; use this one)
full text available – click on the pdf
See fig. 1 for the spectrum of OLR – it is a calculated OLR but should resemble the actual global average OLR. The smooth curve is the Planck function for Earth’s average surface temperature; take away the whole greenhouse effect (including H2O and clouds) and the OLR increases by the differences between the curves; then, the Earth would cool until OLR returned to the same value – except for changes in solar heating (in reality, if you took all clouds away, there would be a heating effect from reduced albedo. But it’s hard to do that except as a modelling excercise; you can more easily (in principle) take out CO2. Then cloud and H2O changes would be feedbacks, as would snow and ice. Etc.
The surface Planck function is, I think (from memory or assumption) 288 K; you can graphically reproduce a Planck function over wavelength for any other temperature by horizontally compressing it by the ratio of temperatures and vertically stretching it by the fifth power of that, keeping (0,0) at the same point.
The OLR was calculated for a 1-dimensional model, with some approximations. Some caveats/approximating errors are discussed here:
Some actual measured spectra can be found here http://www.geo.mtu.edu/~scarn/teaching/GE4250/AtmoEmission_lecture.pdf
PS as an example of infering based on spectra, consider the Barrow Alaska curve on p. 5/9. ‘Backradiation’ gets larger going into the CO2 band, but there’s a dip in the radiation around the band’s peak (centered near 15 microns or ~ 667 cm-1, roughly (667 cm-1 is the inverse of 15 microns. I don’t have the exact peak of the band memorized so I’m giving nominal values)). I would infer that there was a temperature inversion near the surface; at smaller opacities, that layer would be optically thin enough that the general increase in temperature going down in the troposphere would dominate the trend, but at wavelengths where the atmosphere is sufficiently optically thick, the inversion, being nearest the ground, dominates the trend.
… (with some approximation – from memory, I think there may be an issue regarding surface emissivity)
for example, there is a small net downward flux for midlatitude summer with rain and nimbostratus. This should not be, because the temperature still decreases with height from the surface up through the cloud base (that’s really the only altitude range that matters in this case, I think). I could calculate blackbody radiation for the surface temperature to be sure, but at this point I’m infering that some nonzero LW surface albedo is included in the calculation for the upward flux – however, what is lost from that albedo should be replaced by reflected backradiation – this will satisfy the second law of thermodynamics, etc. This isn’t done in this model. But I don’t think this makes much impact on the difference between 300 ppm and 600 ppm of CO2 at TOA or tropopause level – or even at the surface – etc.
Patrick 027says
… for the record, measurement(s?) from satellite(s?) have shown a reduction in OLR (specifically in the part(s) of the spectrum that it should be found, I think), but I’m not sure if there’s a continuous time series or not.
Patrick 027says
however, what is lost from that albedo should be replaced by reflected backradiation
– in proportion to LW albedo, at least at any given direction and frequency, etc. The resulting upward flux (all direcions, any frequency or whole LW spectrum) from the surface including reflection will still be smaller than if the LW albedo were zero (assuming temperature decreasing with height through sufficient optical path), but it will be larger or at least equal to the downward flux (given the same assumption about temperature distribution).
Thanks, Hank – Interesting Wikipedia read about the 1861-2 flood referenced in the SciAm article, guess that weather event wasn’t as history-worthy as a Civil War.
By the way the ‘atmospheric rivers’ phenomenon may be another prediction borne out — can the modelers confirm what the SciAM article says?
As a commenter put it: “the same meteorological event now observed, was predicted before in derivatives of the computer models that model global warming.”
Susan Andersonsays
SciAm world report (cited ~468)
I make that Celsius not Fahrenheit, less 0.4. Now I’m looking for the place where I seem to remember the world report said this is by 2060, not 2100, but not finding it, so perhaps I should (sic) calm down … or not (metaphor in second par below, your witness):
Of all the findings in the 2012 edition of the World Energy Outlook, the one that merits the greatest international attention is the one that received the least. Even if governments take vigorous steps to curb greenhouse gas emissions, the report concluded, the continuing increase in fossil fuel consumption will result in “a long-term average global temperature increase of 3.6 degrees C”.
….
In a report that leads with the “good news” of impending US oil supremacy, to calmly suggest that the world is headed for that 3.6 degree C mark is like placing a thermonuclear bomb in a gaudily-wrapped Christmas present.
fwiw, my “reading” of the spectacular triple vortex in the water vapor rather fizzled but it has been interesting to revisit the atmnospheric rivers item in context. No doubt the AGU has been and will be rather soggy.
Superman1says
Walter Pearce #455,
” Perhaps Superman can be persuaded to turn his baleful attentions to Dan H. Now *that’s* entertainment.”
You have made my case, inadvertently; thank you. Dan H. should be the ‘poster boy’ of this site. He cites the published literature ad nauseam, as my critics seem to require. The fact that the documents he cites are selected to bolster his AGW denier viewpoint is another issue.
Let me make my position crystal clear. I do not come to this blog for published references. If I want published references, I will access a database like the Science Citation Index (or Medline, if on a medical topic), enter a crafted query, and retrieve exactly what I want. I come to a blog like this for ideas on how to extricate ourselves from this climate change morass that we have created. I am interested in ideas and concepts, based on other people having spent time looking through references, attending meetings, and reading related articles. I want their distillation of their experiences and intuition in readable narrative form. The most useful postings I have seen are from people like Aaron Lewis and Lewis Cleverdon, where their focus is on the major problems we face, the requirements to solve these problems, and sometimes potential solutions. The least useful are posters who throw up one reference after another without summarizing the significance based on their intuition and experience.
I could care less about background or credentials or lifestyle or degree of activism of who is posting; concepts and logic reign supreme, as far as I am concerned. If a concept does not pass the ‘smell test’, I won’t buy it, irrespective of the credentials of the poster, or the numbers of references presented. Also, if a concept might be useful, such as installation of solar or wind facilities, but its implementation and deployment requirements will end up not producing a bend in the right direction of the CO2 emissions and temperature curves in the appropriate time frame, I won’t buy it either. Secular Animist, take note.
Frankly, I have seen nothing suggested on this site that comes anywhere near what is required to make a significant dent in the total climate change problem. One reason has been the decoupling of the proposals made from the overall end-point requirements that a credible Roadmap would include. In my last long post, I tried to lay out what I believe is necessary to address the problem we face. I realize better than anyone how futile it appears today to bridge the gap between 1) the all-out race that now exists to find and extract and consume as many fossil fuel resources as possible and 2) the need to effectively eliminate all use of fossil fuel ASAP to bend the CO2 emission curves and temperature curves in the desired direction. And, I realize that people with political and activist agendas don’t like these types of extreme recommendations even mentioned, since they have the potential to ‘turn off’ future recruits to the cause. But, as should be obvious from my postings, I am neither a politician nor a diplomat, and I have presented the truth of what is required from my perspective. Let the chips fall where they may!
Susan Andersonsays
Supe, while I agree with this statement,
I realize better than anyone how futile it appears today to bridge the gap between 1) the all-out race that now exists to find and extract and consume as many fossil fuel resources as possible and 2) the need to effectively eliminate all use of fossil fuel ASAP to bend the CO2 emission curves and temperature curves in the desired direction.
I also agree with others who ask that you support your self-proclaimed credentials at some checkable level and feel are free to dispute your “solution” when they don’t agree. As noted before, the masthead without my added typo says:
Climate science from climate scientists
and I’d say they are doing their best, as many of us aren’t, simply using our guest status to bloviate one way or another (myself especially). While the Gores, DeChristophers and Balogs of this world go a bit further, and the extremely well funded campaign to discredit them proceeds apace, not all of us have the gumption to go that far.
As for Dan H, please ignore him. His status as agent provocateur may be amateur rather than paid, but it makes no difference. He wastes a lot of other people’s time here. When he realizes he was wrong, and in this discussion being that wrong is immoral, it will be too late.
Superman 473: “I could care less about background or credentials”
If that’s true, it didn’t make much sense to brag about your “well over two hundred papers in the peer-reviewed journal literature”. You’ve been asked repeatedly to support that claim, with no results. After you asserted your moral superiority (@431, “Codes of Honor”) I asked a few simple questions to verify your exalted status, but again, no reply. I don’t see what purpose your continued pontification could possibly serve, other than disrupting this forum.
SecularAnimistsays
Superman1 wrote: “I have seen nothing suggested on this site that comes anywhere near what is required to make a significant dent in the total climate change problem.”
That’s because you choose to ignore, or simply dismiss, other commenters’ well-documented posts “suggesting” how to do exactly that.
Your futility-colored glasses are keeping you from “seeing” many things.
for Superman1
Geosci. Model Dev., 5, 599-609, 2012
http://www.geosci-model-dev.net/5/599/2012/
doi:10.5194/gmd-5-599-2012
Shorter Superman: Some of my thoughts make sense, so I’m not totally crazy, just higher and better than all of youse. My handle says it all. My exalted elevation releases me from most obligations to cite.
+1 for Hank Roberts, #445
Supe, at this point, less is more. You’re about at the point where I see your handle and skip the comment.
Susan,
RC is not immune to this posting. Sevreal posters here have acknowledged that they are not cliamte scientists, and some are not even scientists. At least CD has attempted to distinguish the climate experts from the novices. Many other sites do not. Unfortunately, many sites are sensationalizing certain weather events in an attempt to garner much-needed support. This will only backfire in the long run. Only openly honest discussions will prevail.
Dan H. wrote: “Only openly honest discussions will prevail.”
I assume the moderators’ taste for low-brow slapstick comedy is the reason that Dan H’s comments are not going to the bore hole.
454. Perhaps Superman can be persuaded to turn his baleful attentions to Dan H. Now *that’s* entertainment.
@402 (and 391). Thanks for your great suggestions. Patrick (@402), is it reasonable to expect that there is somewhere a series of time varying spectograms showing the increase in absorption of IR light by the increase in greenhouse gasses in the Earth, say taken by satellites over the last 20 years. I’m thinking this might be a good “smoking gun” for the class. To show that energy that once was emitted is not absorbed and re-radiated. Then I can show where it is going (mostly into the oceans as you note). Also, something I’ve wondered is why the plot of Earth’s total heat content here http://www.skepticalscience.com/graphics.php?g=46 is not monotonically increasing. Would this be due to volcanos or man-made aerosol emissions? Or is this simple uncertainty?
> I’ve wondered is why the plot of Earth’s total heat content here
> is not monotonically increasing.
since that’s one of the really stock denial talking points, I’m glad you’re reading this stuff at Skepticalscience.
Tamino covers it, and may be quoted on it at SS.
If you’re not up on the top 100 frequently rebunked claims to where you can just point to them at SS, you’re not prepared to go up against any kid who hears those talking points frequently.
Re 456 bobb –
satellite measurements – great idea; since it is TOA (top-of-atmosphere) radiative disequilibrium that is responsible (see caveats in my prior comment), over time, for accumulation or depletion of the heat content of the climate system. Satellite measurements are tricky, though; satellites can have orbital changes over time, issues with calibration – I would expect in particular if there are no time (and space?) periods where one satellite’s record overlaps with another. Also, satellite data may infer different things, so watch out. At any given wavelength and any given atmospheric composition, you can see farther down into the atmosphere and/or more of the surface (thus less of the atmosphere) if you look straight down than at some other angle. While increasing CO2 reduces OLR specifically in a pair of spectral bands on either side of ~ 15 microns wavelength, the accumulation of heat resulting from that will tend to increase OLR – and so there will be a net increase in OLR outside where the climate forcing occured (depending on feedbacks; less OLR increase where H2O vapor acts on the spectrum, and also spatially where cloud positive LW feedback occurs); satellites measuring at some wavelengths may show an increase in OLR even when the total global OLR hasn’t returned to equillibrium. Also, if there are SW (solar heating such as via changes in albedo) forcings or feedbacks, the equilibrium OLR must also change.
IR light – I advise using the terms shortwave (SW) and longwave (LW) radiation (OLR = outgoing longwave radiation), because (in the definitions used in the study of atmospheric radiation and climate) the greenhouse effect deals with LW, while solar heating is mostly SW – the cutoff is somewhere around 4 microns, so SW radiation includes some IR as well as visible and UV (and shorter wavelengths, though those don’t contribute much energy, but do have significant effects on a small fraction of the mass of the atmosphere at it’s ‘top’). Some (well, at least one) have claimed a reduced role for CO2 based on looking at it’s SW IR effects and confusing that with it’s greenhouse effect. (Look up the Planck function to understand why such a distinction can be drawn about 4 microns; if the Earth (surface and atmosphere) and Sun (photosphere) were at more similar temperatures than the distinction between SW and LW radiation wouldn’t be so convenient.)
“that energy that once was emitted is not absorbed and re-radiated.”
Actually, that is how the greenhouse effect works. … except that re-radiated may imply a photon of the same energy, which isn’t generally the case – see below.
It would be possible to base a greenhouse effect on scattering, which may be thought of like the reflection of photons over some particular probabilistic distribution of directions. A greenhouse effect might even be made by having LW-phosphorescence – might have to be engineered, though? (maybe on a planet hot enough for _______ clouds…??? I have no idea).
For Earthly conditions, though, the greenhouse effect is mostly due to the absorption and emission of photons – at approximately LTE (local thermodynamic equilibrium)- meaning that molecular collisions are sufficiently frequent to redistribute the energy among the available states and among all the molecules in a given small volume so that the distribution of energy is maintained at an equilibrium for a particular temperature – and that the same temperature approximately applies to the different kinds of molecules present (if not, one could still work with LTE given different temperatures for different substances that happen to occupy the same volume, but that’s not generally necessary for most of the atmosphere). Thus, at any given frequency (photon energy), and if necessary, direction and polarization (not necessary for randomly-oriented molecules or particles or spherically-symmetric particles) CO2 and other greenhouse gas molecules, and cloud particles, absorb radiation from a direction based on their optical properties and how much radiation is incident on them, while they emit into that direction according to the Planck function AND THE SAME OPTICAL PROPERTIES. This can be summarized as Kirchoff’s Law (of thermal radiation): http://en.wikipedia.org/wiki/Kirchhoff%27s_law_of_thermal_radiation : emissivity = absorptivity.
Kirchoff’s Law (of thermal radiation) satisfies the second law of thermodynamics – because it implies that however radiation may be scattered, refracted (noting blackbody radiation intensity is actually a function of the index of refraction, but this is typically not brought up in climatology because air’s index of refraction is near that of a vaccuum), partly or totally reflected, (but setting aside partial emission or absorption, where a photon scatters with some change in energy, such as in Raman or Compton scattering – it gets more complicated when this happens) if there are some pathways between two seperately LTE volumes V1 and V2 of temperatures T1 and T2; if T2 is greater than T1 (V1 warmer than V1) the flux of radiant energy from emission in V2 to absorption in V1 will be greater than the flux from emission in V1 to absorption in V2; it is this way for any single frequency, direction, and polarization, and thus must be for the total radiant energy. If T1 = T2, the two fluxes are equal. The difference is the net flux, and it is the radiant heat that flows from higher to lower temperature as one would expect (PS the second law of thermodynamics generally deals with net processes that are the averages of things which go on in opposite directions at the same time on the microscopic level. Because radiation can in some conditions travel macroscopic distances between interactions, these opposing radiant fluxes happen to occur at a macroscopic level).
(If there are photon scatterings that don’t preserve photon energy, I would expect there should still be a general tendency for radiant energy to flow from higher to lower temperature, and this includes the flow of energy into the population of photons; blackbody radiation describes the population of photons that would be in thermodynamic equilibrium with some other matter at a given temperature.
Even if that matter only weakly interacts with photons, such equilibrium would be achieved given sufficient time in isolation; hence ‘cavity radiation’.)
For LTE, any given molecule or unit of substance will emit some number of photons per unit time, on average, in some part of the spectrum. A perfect blackbody that would do the same has some size, and this size is the emission cross section of that unit of substance. For LTE, the emission cross section into a direction is equal to the absorption cross section facing that direction.
For randomly oriented or spherically-symmetric particles or molecules, etc, they act (in a time-averaged or population-averaged sense) like spherical blackbodies which present the same cross sectional area in every direction. Random overlap leads to an exponential decay in unaffected photons over distance (in a crystal, overlap is not random, but (**I think**/**it’s my understanding based on inferences from other stuff I know**) the cross section of each unit may be smeared out over some larger area – it wouldn’t look like a single opaque circle but rather a partially transparent absorber; hence it absorbs some fraction of photons along any particular path as would randomly distributed cross sections); the cross section per unit volume is a cross section density, and is the amount of area per unit area facing some direction, per unit distance along that direction. Distance can be measured in terms of cross sectional area’s fractional areal coverage; this is called optical thickness or optical depth: http://en.wikipedia.org/wiki/Optical_depth.
An incident beam of photons decays exponentially over optical depth; however, if the temperature is nonzero (absolute scale), then emission will also occur in proportion to the portion of optical depth that comes from absorption (as opposed to scattering); emitted radiation will also be absorbed (or scattered), so, in the absence of scattering, it approaches a blackbody value asymptotically. In the presence of scattering, it would still tend toward that value because radiation can be scattered into a beam and this radiation has to be emitted somewhere. So if optical thickness over some isothermal distance is large enough, including over all directions that radiation is being scattered into and from, the radiant intensity inside approaches the blackbody value – and this is true for all directions, so the net flux through space approaches zero.
But if optical thickness is not too large, then temperature gradients become visible. Think about what you can see when in a fog; vary the thickness of the fog. Now imagine the fog is not scattering light but rather glowing incandescently according to it’s temperature (as are any objects within it). That’s what the greenhouse effect looks like. When or where or at whatever frequencies the atmosphere is transparent, for LW radiation (approximately excluding the sun) the Earth’s surface sees mostly only the cold dark of space, and space sees only the Earth’s surface (although actually, the Earth’s surface has some small nonzero albedo for LW radiation, so some of what space sees is actually it’s own reflection). Adding scattering to the atmosphere would make space and the surface see more of their own reflections. Adding absorbing opacity (along with emitting opacity, as required for LTE), The surface and space see less of the other and more of the air in between. Because temperature declines through the troposphere (see prior comment about convection), except where the stratosphere’s opacity becomes sufficient, adding opacity either to the troposphere or in some evenly-distributed way (by mass), adding more absorbing opacity to the atmosphere (increasing optical depth) results in space seeing less of the surface, and then less of the warmer lower atmosphere, etc., so even when the surface has dissappeared from view, adding more opacity continues to have an effect. Likewise, the surface will see less of not only space but the cooler upper atmosphere as well. The OLR above clouds depends on cloud temperature and thus cloud height. Water vapor is concentrated in the lower atmosphere and thus doesn’t have as strong an effect on OLR as it does on radiation at the surface, relative to a (approximately) well-mixed gas like CO2…
Well I’m out of time but you get the idea.
Just one more point. Optical depth is proprotionate to amount of substance, other things being equal. It generally varies over wavelength. For CO2, there are a bunch of wiggles in the spectrum, but the general tendency is a roughly…
(I think it’s roughly, not exactly, though I’m not sure offhand; anyway it depends on whether you’re viewing the spectrum in terms of wavelength or frequency; whichever you choose, it’s fine, just as long as the Planck function (the spectrum of blackbody radiation) is put in the same terms))
… exponential decay away from a peak near 15 microns (for CO2’s most important absorption band for Earthly conditions; other part(s?) of the absorption spectrum play a significant role on Venus).
Thus doubling CO2 effectively widens it’s absorption band by some amount over the spectrum. The central part of the band is now saturated – or nearly saturated ? – at the tropopause level (upward radiation nearly the same as downward emission from the stratosphere) – although farther changes in OLR are achievable (I think adding to stratospheric cooling, and indirectly to a downward adjustment to tropopause level forcing after stratospheric adjustment) – but there is room to decrease the net upward LW flux at the tropopause on the sides of the CO2 band.
… oh, and some of the variation including wiggles is from forcing (volcanoes, anthropogenic stuff, etc.), but even without that there could be some wiggles – some if from internal variability (weather, ENSO – more later if I get to it) and maybe some from forced cycles (day, year) – though I’m not sure of the significance. Generally, an equilibrium climate encompasses shorter term variability as well as horizontal fluxes of energy, so there can and will be radiative disequilibrium at any one place and time.
And buy a cheap (like $14) infrared thermometer and let the kids take it home one after another — meter things around the house, meter the nighttime sky, meter the daytime sky at the horizon, at the zenith, at true north (note whether it’s clear or cloudy, day and night) report back, add to a list, read up on why:
http://mynasadata.larc.nasa.gov/804-2/1035-2/
Discuss how you can make ice in the desert in shallow trays on clear nights. They can look that up.
(Note anything shiny won’t give a proper IR Thermometer reading, and explain why — and why the instructions are to put a piece of dull masking tape over it — which quickly attains the same surface temperature and meters correctly).
see also
http://chriscolose.wordpress.com/2008/12/10/an-update-to-kiehl-and-trenberth-1997/
which references:
Kiehl, J. T., Kevin E. Trenberth, 1997: Earth’s Annual Global Mean Energy Budget. Bull. Amer. Meteor. Soc., 78, 197–208.
doi: http://dx.doi.org/10.1175/1520-0477(1997)0782.0.CO;2
(some of that doi won’t appear here because it has html coding brackets; here’s the doi without those brackets:
http://dx.doi.org/10.1175/1520-0477(1997)078 0197:EAGMEB 2.0.CO;2
link:
http://journals.ametsoc.org/doi/abs/10.1175/1520-0477(1997)078%3C0197%3AEAGMEB%3E2.0.CO%3B2 (the link from the wordpress site above doesn’t work anymore; use this one)
full text available – click on the pdf
See fig. 1 for the spectrum of OLR – it is a calculated OLR but should resemble the actual global average OLR. The smooth curve is the Planck function for Earth’s average surface temperature; take away the whole greenhouse effect (including H2O and clouds) and the OLR increases by the differences between the curves; then, the Earth would cool until OLR returned to the same value – except for changes in solar heating (in reality, if you took all clouds away, there would be a heating effect from reduced albedo. But it’s hard to do that except as a modelling excercise; you can more easily (in principle) take out CO2. Then cloud and H2O changes would be feedbacks, as would snow and ice. Etc.
The surface Planck function is, I think (from memory or assumption) 288 K; you can graphically reproduce a Planck function over wavelength for any other temperature by horizontally compressing it by the ratio of temperatures and vertically stretching it by the fifth power of that, keeping (0,0) at the same point.
The OLR was calculated for a 1-dimensional model, with some approximations. Some caveats/approximating errors are discussed here:
Trenberth, Kevin E., John T. Fasullo, Jeffrey Kiehl, 2009: Earth’s Global Energy Budget. Bull. Amer. Meteor. Soc., 90, 311–323.
doi: http://dx.doi.org/10.1175/2008BAMS2634.1
http://journals.ametsoc.org/doi/abs/10.1175/2008BAMS2634.1
http://www.cgd.ucar.edu/cas/Trenberth/trenberth.papers/TFK_bams09.pdf
Some actual measured spectra can be found here
http://www.geo.mtu.edu/~scarn/teaching/GE4250/AtmoEmission_lecture.pdf
PS as an example of infering based on spectra, consider the Barrow Alaska curve on p. 5/9. ‘Backradiation’ gets larger going into the CO2 band, but there’s a dip in the radiation around the band’s peak (centered near 15 microns or ~ 667 cm-1, roughly (667 cm-1 is the inverse of 15 microns. I don’t have the exact peak of the band memorized so I’m giving nominal values)). I would infer that there was a temperature inversion near the surface; at smaller opacities, that layer would be optically thin enough that the general increase in temperature going down in the troposphere would dominate the trend, but at wavelengths where the atmosphere is sufficiently optically thick, the inversion, being nearest the ground, dominates the trend.
See also
http://forecast.uchicago.edu/Projects/modtran.html
for calculated spectra (with some approximation – from memory, I think there may be an issue regarding surface emissivity).
… (with some approximation – from memory, I think there may be an issue regarding surface emissivity)
for example, there is a small net downward flux for midlatitude summer with rain and nimbostratus. This should not be, because the temperature still decreases with height from the surface up through the cloud base (that’s really the only altitude range that matters in this case, I think). I could calculate blackbody radiation for the surface temperature to be sure, but at this point I’m infering that some nonzero LW surface albedo is included in the calculation for the upward flux – however, what is lost from that albedo should be replaced by reflected backradiation – this will satisfy the second law of thermodynamics, etc. This isn’t done in this model. But I don’t think this makes much impact on the difference between 300 ppm and 600 ppm of CO2 at TOA or tropopause level – or even at the surface – etc.
… for the record, measurement(s?) from satellite(s?) have shown a reduction in OLR (specifically in the part(s) of the spectrum that it should be found, I think), but I’m not sure if there’s a continuous time series or not.
however, what is lost from that albedo should be replaced by reflected backradiation
– in proportion to LW albedo, at least at any given direction and frequency, etc. The resulting upward flux (all direcions, any frequency or whole LW spectrum) from the surface including reflection will still be smaller than if the LW albedo were zero (assuming temperature decreasing with height through sufficient optical path), but it will be larger or at least equal to the downward flux (given the same assumption about temperature distribution).
> atmospheric river
Hey, I guessed that one wrong:
“From weather satellites that measure atmospheric moisture, we can see the narrow plume of water vapor…an atmospheric river..that has been feeding the California rainfall.”
Thursday, November 29, 2012, Cliff Maas weather blog:
Heavy Rain and Massive Snow
http://1.bp.blogspot.com/-bAzsjPlVJ-w/ULjcxLwMPTI/AAAAAAAAMG4/B-pfVmBHqLU/s1600/mosaic20121130T110000.gif
and more:
Mysterious Atmospheric River Soaks California, Where Megaflood May Be Overdue
and also in SciAm, being released early online from the January 2013 issue because it’s, er, timely: A recent review … seven different climate models from around the world has indicated that atmospheric rivers will likely continue to arrive in California throughout the 21st century. In the projections, air temperatures get warmer by about four degrees Fahrenheit on average because of increasing greenhouse gas concentrations. Because a warmer atmosphere holds more water vapor, atmospheric rivers could carry more moisture.
Thanks, Hank – Interesting Wikipedia read about the 1861-2 flood referenced in the SciAm article, guess that weather event wasn’t as history-worthy as a Civil War.
huh, CAPTCHA: Phowsf Bay
#460, tangentially–
How it was done 200 years ago:
http://doc-snow.hubpages.com/hub/Global-Warming-Science-In-The-Age-Of-Washington-And-Jefferson-William-Charles-Wells
By the way the ‘atmospheric rivers’ phenomenon may be another prediction borne out — can the modelers confirm what the SciAM article says?
As a commenter put it: “the same meteorological event now observed, was predicted before in derivatives of the computer models that model global warming.”
SciAm world report (cited ~468)
I make that Celsius not Fahrenheit, less 0.4. Now I’m looking for the place where I seem to remember the world report said this is by 2060, not 2100, but not finding it, so perhaps I should (sic) calm down … or not (metaphor in second par below, your witness):
http://www.aljazeera.com/indepth/opinion/2012/11/20121129115317765753.html
fwiw, my “reading” of the spectacular triple vortex in the water vapor rather fizzled but it has been interesting to revisit the atmnospheric rivers item in context. No doubt the AGU has been and will be rather soggy.
Walter Pearce #455,
” Perhaps Superman can be persuaded to turn his baleful attentions to Dan H. Now *that’s* entertainment.”
You have made my case, inadvertently; thank you. Dan H. should be the ‘poster boy’ of this site. He cites the published literature ad nauseam, as my critics seem to require. The fact that the documents he cites are selected to bolster his AGW denier viewpoint is another issue.
Let me make my position crystal clear. I do not come to this blog for published references. If I want published references, I will access a database like the Science Citation Index (or Medline, if on a medical topic), enter a crafted query, and retrieve exactly what I want. I come to a blog like this for ideas on how to extricate ourselves from this climate change morass that we have created. I am interested in ideas and concepts, based on other people having spent time looking through references, attending meetings, and reading related articles. I want their distillation of their experiences and intuition in readable narrative form. The most useful postings I have seen are from people like Aaron Lewis and Lewis Cleverdon, where their focus is on the major problems we face, the requirements to solve these problems, and sometimes potential solutions. The least useful are posters who throw up one reference after another without summarizing the significance based on their intuition and experience.
I could care less about background or credentials or lifestyle or degree of activism of who is posting; concepts and logic reign supreme, as far as I am concerned. If a concept does not pass the ‘smell test’, I won’t buy it, irrespective of the credentials of the poster, or the numbers of references presented. Also, if a concept might be useful, such as installation of solar or wind facilities, but its implementation and deployment requirements will end up not producing a bend in the right direction of the CO2 emissions and temperature curves in the appropriate time frame, I won’t buy it either. Secular Animist, take note.
Frankly, I have seen nothing suggested on this site that comes anywhere near what is required to make a significant dent in the total climate change problem. One reason has been the decoupling of the proposals made from the overall end-point requirements that a credible Roadmap would include. In my last long post, I tried to lay out what I believe is necessary to address the problem we face. I realize better than anyone how futile it appears today to bridge the gap between 1) the all-out race that now exists to find and extract and consume as many fossil fuel resources as possible and 2) the need to effectively eliminate all use of fossil fuel ASAP to bend the CO2 emission curves and temperature curves in the desired direction. And, I realize that people with political and activist agendas don’t like these types of extreme recommendations even mentioned, since they have the potential to ‘turn off’ future recruits to the cause. But, as should be obvious from my postings, I am neither a politician nor a diplomat, and I have presented the truth of what is required from my perspective. Let the chips fall where they may!
Supe, while I agree with this statement,
I also agree with others who ask that you support your self-proclaimed credentials at some checkable level and feel are free to dispute your “solution” when they don’t agree. As noted before, the masthead without my added typo says:
Climate science from climate scientists
and I’d say they are doing their best, as many of us aren’t, simply using our guest status to bloviate one way or another (myself especially). While the Gores, DeChristophers and Balogs of this world go a bit further, and the extremely well funded campaign to discredit them proceeds apace, not all of us have the gumption to go that far.
As for Dan H, please ignore him. His status as agent provocateur may be amateur rather than paid, but it makes no difference. He wastes a lot of other people’s time here. When he realizes he was wrong, and in this discussion being that wrong is immoral, it will be too late.
Superman 473: “I could care less about background or credentials”
If that’s true, it didn’t make much sense to brag about your “well over two hundred papers in the peer-reviewed journal literature”. You’ve been asked repeatedly to support that claim, with no results. After you asserted your moral superiority (@431, “Codes of Honor”) I asked a few simple questions to verify your exalted status, but again, no reply. I don’t see what purpose your continued pontification could possibly serve, other than disrupting this forum.
Superman1 wrote: “I have seen nothing suggested on this site that comes anywhere near what is required to make a significant dent in the total climate change problem.”
That’s because you choose to ignore, or simply dismiss, other commenters’ well-documented posts “suggesting” how to do exactly that.
Your futility-colored glasses are keeping you from “seeing” many things.