I should start by saying that this post was partly motivated by an intersting comment from Pekke Pirila on another thread. Also, Eli already has a post that mostly cover this, so this is more from completeness, than anything else.
In a number of my recent posts, I’ve been referring to an effective emission height in the atmosphere that is set by the greenhouse gas concentration. Given that the tropospheric temperature gradient (lapse rate) is largely set by convection, if you know the temperature at some height in the atmosphere, then one can work back down the lapse to the surface in order to determine the surface warming due to greenhouse effect. I haven’t, however, really defined this effective emission height. In equilibrium, the Earth radiates as much energy back into space per unit time as it receives from the Sun. If you determine the average amount of energy radiated per square metre per second (about 240 Wm-2) you can use the Stefan-Boltzmann law (F = σT4) to determine the temperature a blackbody would need to have so as to radiate this amount of energy per square metre per second. For the Earth (with an albedo of 0.3) it is about 255 K. The effective emission height is the height in the atmosphere at which the temperature matches this temperature. In the Earth’s atmosphere it is at about 5km.
In reality, however, the actual emission is much more complicated. To illustrate this, I’ve used the MODTRAN radiation transfer code. If you use the 1976 U.S.Standard Atmosphere, set the CO2 concentration to 400 ppm, and lookdown from 70km, you get the following.
The left-hand panel is the spectrum, and the right-panel is the temperature profile. The outgoing flux is 258.58 Wm-2 which, if you use the Stefan-Boltzmann law, corresponds to a blackbody temperature of 259.9K. Looking at the temperature profile, this would correspond to an effective emission height of between 4 and 5km. However, the spectrum itself is clearly not a 259.9K blackbody spectrum. For wavelengths beyond 17 microns, the emission is coming from temperatures between 260K and 240K (so heights around 5km in the troposphere). Between about 13 and 17 microns, the emission’s coming from a region with temperatures close to 220K – so, near the troposphere/stratosphere boundary. Between 7 and 13 microns, the emission is coming from a region with temperatures in excess of 280K which, in this example, is actually the surface. So, there isn’t a single emission region, but the emission is still equivalent to a blackbody with a temperature of 259.9K.
Now, if you change the CO2 concentration from 400ppm to 800ppm, the outgoing flux drops to 255.75 Wm-2, equivalent to a blackbody with a temperature of 259.1 K. If the system was in equilibrium at a CO2 concentration of 400ppm, it would now be emitting less energy per square metre per second than it receives. To retain equilibrium, it must warm. Again using MODTRAN, this requires increasing the surface temperature by 0.9K (here I’m considering only the influence of changing CO2 concentrations, and am not considering feedbacks). Since the temperature gradient in the troposphere is – to a large extent – set by convection, this means that if the surface warms by 0.9K, the temperature at all altitudes in the troposphere must increase by 0.9K (in this example I’ve, again, ignored water vapour feedback). Hence, once the system returns to equilibrium, the effective temperature will again be 259.9K, but this will now be at a higher altitude than when the CO2 concentration was 400ppm. Therefore, a significant fraction of the outgoing emission will come from higher in the atmosphere when the CO2 concentration is 800ppm, than when it is 400ppm.
So, I hope that’s reasonable clear and basically correct. It’s clear that there isn’t a single emission height in the atmosphere, but it is clear that one can define such a height, and it’s clear that increasing the greenhouse gas concentration increases the temperature at all altitudes in the troposphere and increases the height at which a significant fraction of the emission is coming from. That both illustrates the greenhouse effect and the consequences of increasing greenhouse gas concentrations. As usual corrections or comments welcome.
...and Then There's Physics 
Calculations that I made for the comment referred to in the post are based on a model that’s almost exactly equivalent to MODTRAN. There are some differences but not at a level that would make any difference for this case. When I looked at my comment I noticed that I forgot to tell precisely what I meant by CO2 tail in this figure. It refers to the wavelength range 13.0-13.9 µm. The lower limit is in the steeply falling part of the intensity curve and the upper limit near the lowest point of the curve to the left of the small peak at 15 µm.
I have calculated the corresponding curves also for a narrow band at the the 15 µm peak. Those curves lie totally outside (above) my figure, because the absorption is so strong in the stratosphere that essentially all outgoing radiation originates above 25 km, and a significant part in the upper and warmer stratosphere. Those wave lengths do not contribute to the warming from additional CO2. For that very narrow band the absorption is so strongly saturated that no further warming is caused.
The band 13-14 µm and a similar band close to 17 µm are the most important contributors to the further warming by CO2. The logarithmic dependence of the forcing on the CO2 concentration is due to the properties of the tails of the absorption peak. (The peak is not a single smooth peak but consists actually of hundreds of very narrow peaks. This is also important for the quantitative results.)
Hi Anders and Pekka. A couple of quick questions:
If there is a water vapour feedback to additional co2 that our instrumentation has somehow missed (it’s not been observed), then that would make the atmosphere more opaque to incoming solar radiation. More shortwave would be absorbed in the atmosphere and less would reach the ground. Half of that additionally absorbed energy would be radiated back to space. So while the atmosphere might get a bit warmer, it’s not clear to me how the surface temperature would be increased, since convection is ever upwards.
Second Q: If there’s no prospect of ever being able to measure the increased height of emission empirically, what value does it have as a theoretical construct? Nasa tells us that the thermosphere collapsed by 30% of its volume during the 2007-09 solar minimum. It seems at first flush that there would be a knock on effect lower down. Since the theoretical change in emission height due to additional co2 is only tens of metres, isn’t it likely to be swamped by natural variation?
TB,
What do you mean? You can’t explain the current data without feedbacks. If there were no feedbacks operating, we’d be in energy excess. We’re not. Let’s not start a debate about OHC data now, though.
I don’t believe that the absorption of incoming radiation is all that relevant. It’s the effect on the outgoing radiation that’s relevant.
It’s my understanding that there has been a measured change in the height of the troposphere over the last 30 years or so. There’s an SkS post with links to papers if you’re interested.
I’m sure there would be lots of natural variation but if the mean has changed then, on average, we’d expect a change in the average surface temperature.
Anders, re: tropopause height, which SkS post is that?
I have managed to find Santer et al (2003) which finds a clear trend in tropopause height, attributed approximately equally to GHG and Ozone changes, with smaller effects due to solar. Against that, however, there is Seidel and Randal (2006) which finds the trend in tropopause height is correlated to increased tropospheric temperatures, but more strongly correlated to cooler stratospheric temperatures. Given that at least half of the cooling of the stratosphere has been due reduced ozone levels, that would appear to make tropopause height join a substantial list of factors where the observed phenomenon is doing what we would expect from global warming qualitatively, but were a confounding factor exists so it is not possible to point to it as definitive proof of global warming. It remains, or course, evidence consistent with AGW, and improbable under other explanations of recent warming.
Tom,
The SkS post is this one which mentions the Santer et al. (2003) paper. It doesn’t mention the Seidel & Randall (2006) paper which I hadn’t seen before and which would seem to complicate the matter. I agree, one can’t point to it as definitive proof, but is still evidence that is consistent wuthg AGW.
The calculations presented in this thread are done for the U.S Standard atmosphere. That means that both the temperature profile and the absolute humidity profile are fixed. The results tell only about IR intensities. It’s also possible to determine the radiative forcing from the comparison of results for 400 pp and 800 ppm. No feedbacks have been included, not even the Planck feedback.
It would be possible to extend the calculations by modifying the profiles for 800 ppm in some way where the temperature profile or both profiles are made dependent on the surface temperature in a self-consistent way.
One possible choice corresponds to the no-feedback sensitivity of this single atmospheric profile class. In that the lapse rate and absolute humidity are kept constant at all altitudes up to the original tropopause. Some freedom of choice is in the handling of the tropopause and the stratosphere. The simplest choice is perhaps an unchanged temperature between the new tropopause and about 25 km altitude. In that choice the tropopause would rise a little to remove the discontinuity in temperature profile. Above 25 km self-consistency requires some stratospheric cooling. Even without an explicit calculation, I’m pretty sure that the radiative balance would be restored by a surface and troposphere warming of about 1 K, probably slightly more than 1.0 K.
It would also be possible to add some feedbacks, most easily a water vapor feedback based on the assumption of constant relative humidity. The humidity of the U.S. Standard atmosphere is so low that introducing a lapse rate feedback would be more artificial. Fixing its strength by some principle would also be difficult. Adding only water vapor feedback would lead to stronger warming, but that result is not of particular interest as the case is not realistic enough for making calculating feedbacks really meaningful.
I make some further remarks in a separate comment.
Pekka,
I don’t think is strictly correct as the MODTRAN version I was using allows you to set a ground offset temperature that then changes the atmospheric temperature. You can also change the water vapour scale, but I don’t think that includes any negative lapse rate feedbacks, though.
tallbloke,
Adding water vapor does not affect much absorption of solar radiation as long as no condensation takes place, and we have either aerosols or clouds, when condensation occurs.
Furthermore adding absorption of solar radiation in troposphere has almost the same warming effect as absorption on the surface, because heating by SW reduces the convection by that same amount leaving more heat at the surface. The level, where the energy balance works is close to the tropopause, and the troposphere is on the same side of that as the surface. The effect is surely not identical, but close to the same.
All satellite measurements of the spectrum of OLR are also measurements of the change of radiative heights. The are not only possible but a reality. Knowledge of temperature profiles are needed in interpreting these results, but does not make the measurement any less empirical.
Thermosphere has little obvious influence on the energy balance of the troposphere and surface. There are certainly some indirect effects, but I don’t see any mechanism that would make such effects significant. The energy balance of the upper stratosphere and everything above that is liked very weakly to lower parts of the atmosphere. The absorption of solar UV and other SW has a significant effect, but other influences are weak.
The relevant effective radiative height is a property of the lower part of the atmosphere up to 20-25 km, what happens higher up is not so significant, not even major changes in the thermosphere.
There has been some discussion of the height of troposphere. That’s not linked strongly to the effective radiative height. These two altitude parameters are controlled by different properties of the atmosphere and have only a weak causal connection. The radiative height is determined directly by the GHG concentrations and effects of clouds, tropopause height is not sensitive to GHG concentrations and depends more on thermodynamics of air and convection.
Pekka,
I will admit that I’m now getting outside my comfort zone, but I had wondered that myself. The effective radiative height is quite a bit lower than the height of the troposphere so it’s clear that other factors set the height of the troposphere, although one might imagine some dependence on the concentrations of GHGs. Tom’s earlier comment would seem to suggest that other factors can indeed influence this height.
ATTP,
It’s certainly possible to change manually the temperature offset, and I did actually discuss such modifications in my comments. Searching for a offset that restores the balance at 15 km or 20 km to the original level gives an estimate of the no-feedback sensitivity for the specific atmosphere.
One should not consider balance at higher altitudes, because the stratospheric profile is wrong at higher CO2 concentrations (it’s somewhat wrong already at 400 ppm). Consistency requires stratospheric cooling as the stratosphere builds its own energy balance very rapidly, and as forcing is defined taking that into account.
Pekka,
Okay, interesting, I didn’t realise that. It also explains why the ground temperature offset in your calculation was higher than I got.
ATTP,
As has been discussed so many times the effective radiative height is just a number calculated from values of more direct significance. That altitude has no distinctive features, and the number is affected equally by changes at all tropospheric altitudes. As it’s kind of weighted average, it’s not surprising that it’s somewhere halfway to the tropopause, but only very roughly.
On the other hand tropopause has a very clear meaning: the altitude where regular convection stops, and stratification begins. From this property it follows that the energy balance at or slightly above the tropopause is the most important energy balance of the Earth system. (All balances at higher altitudes are essentially equivalent, but more difficult to use as more corrections must be added to the most easily measured quantities.)
No ethical spectroscopist uses microns. Makes much more sense in wavenumbers.
Tallbloke, “If there is a water vapour feedback to additional co2 that our instrumentation has somehow missed (it’s not been observed), then that would make the atmosphere more opaque to incoming solar radiation. More shortwave would be absorbed in the atmosphere and less would reach the ground. Half of that additionally absorbed energy would be radiated back to space. ”
Has things backwards. All of the UV at wavelengths below 300 nm is absorbed in the stratosphere or higher by O2 and O3. Water vapor absorbs NO UV and vis, but there are overtones and combination bands in the NIR which absorb. However absorption in these bands is pretty well constrained, and there will be no emission (somewhat long story, the direct emission rate would be too slow. It would not be possible to excite such higher lying vibrational levels by collision at atmospheric temperatures, and if you did they would emit by losing one quantum to emit in the 3 micron and longer bands. Also where is the water vapor. Stuff like that is measured.
Pekka, the tropopause is a lot fuzzier than you think. Local up and downdrafts move it about like crazy.
Eli,
Giving myself away there 🙂 I find it much easier to think of in microns than in wavenumbers.
Eli,
I know perfectly well that the real Earth tropopause is fuzzy, but I didn’t want do discuss that more than adding the word “regular” in my sentence, where I told the nature of it. I cannot see any alternative for using simplifications an abstractions in net discussion on properties of the atmosphere. I have tried to be careful to avoid such simplifications that would distort the general picture.
This thread is built to a significant degree on looking at the U.S. Standard atmosphere, where the tropopause is not fuzzy at all. Choosing that case may be bit misleading as even the other standard atmosphere would indicate that the reality is a bit more complex. The reality is still a very different thing, where also stratosphere participates in the circulation on a less regular basis.
ATTP,
There’s a real reason to prefer wavenumber distributions in discussion of radiative heat transfer. Wavenumber distribution has the shape of energy distribution, while wavelength distributions does not.
Pekka,
I know there are reasons, I just find it easier to think in wavelength space than in wavenumber space 🙂
Pekka:
Is that just an obscure way of saying that energy varies linearly with frequency (wave number) and inversely with wavelength? If not, it makes no sense to me at all.
Tom,
That’s essentially the same, but stated from a different angle.
We also had a look at this topic in Visualizing Atmospheric Radiation – Part Three – Average Height of Emission.
I used a line by line model and graphed it in different ways to make it easier to see where the contributions were coming from:
– contribution to TOA flux vs height
– a 3d version with contibution to TOA vs height vs wavelength.
Of course, the results are for one particular atmosphere.
tallbloke asked on March 6, 2014 at 7:43 am:
It is simply a teaching idea to help people who don’t understand the “greenhouse” effect visualize what happens (without feedbacks) as more GHGs are added to the atmosphere. In conjunction with a declining temperature vs height (in the troposphere) it indicates that more GHGs cause a lower OLR which results in more planetary heat being retained.
The flaw of teaching ideas is that they are simplifications.
For anyone worried about the consequences of this teaching idea – it isn’t used in any GCMs or any other kind of practical climate models.
SoD,
Thanks, those are really useful.
And I should have added that the comments are the most useful part of that article – as a result, I then produced better graphs in the comments section.
Also, given the question about the value of the concept, here was my conclusion:
SoD
I find that’s true for many of my articles too 🙂
I add that the model of SoD is conceptually very close to Modtran. I believe that it’s as good or perhaps better than the implementation of Modtran available at the UChicago net page. One advantage of the SoD model is that it’s openly available and allows the user to make modifications and additions to it. As it’s so flexible, it’s certainly easy to force it to calculate totally false results.
I have experimented with a couple of extensions to the code, most importantly
– explicit handling of the azimuthal angle distribution of the radiation
– introducing the more accurate Voigt lineshape for the individual lines.
– cutoff of the tails of the individual lines
It turned out in all cases that the simplifications of the original SoD model are good. The essential results change very little for cases relevant for the Earth atmosphere at any conceivable CO2 concentration.
Handling the azimuthal angle explicitly increases significantly the share of photons emitted from the surface that penetrates trough the whole atmosphere, but that change is compensated by changes in the radiation from the atmosphere making the total OLR almost the same.
Voigt profile makes a major difference in the upper stratosphere, but that has very little influence on the troposphere, and also on the lowest part of stratosphere.
Cutoff of the tails becomes essential with very high GHG concentration, because both the Lorentz and the Voigt lineshape have a fat tail that’s unrealistically high far from the center of the peak. With high enough concentration that leads to too much absorption in the atmospheric window which is free of all significant absorption lines.
Modtran has all the same deficiencies at lest in the openly accessible form, and cannot be modified as SoD’s model can. Playing with such details is educating and interesting. On some points like the handling of the cutoff of the tails it’s possible to look at issues, where the progress of science is till going on (but more relevant to Venus than the Earth atmosphere).
The main weakness of the model is that it becomes computationally heavy when such modifications are introduced that I list above. One run may take hours or days when everything is included and a dense grid of wavenumbers used. The basic calculation takes, however, less than one minute.
The other problem is the need of Matlab. Octave (a free Matlab clone) might work, but I’m not sure of that. Computational efficiency is one point of worry.
I’ve a question which has been bugging me for years. The US Standard Atmosphere is defined based on some assumptions regarding boundary conditions, specifically, a surface temperature of 288.15k (15C) and no water vapor.
http://glossary.ametsoc.org/wiki/Standard_atmosphere
It would appear that those boundary conditions would tend to pertain mostly to mid-latitude locations. What are the effects of realistic surface temperature and humidity levels at other latitudes, such as the tropics with higher surface temperatures and the Arctic/Antarctic with much lower temperatures? In the tropics, the atmosphere is thicker, with the tropopause at a higher level, while in the polar regions, the tropopause can have a much lower pressure height. This question is important to many areas, such as the satellite temperature measurements, especially the UAH TLT, which apparently depend on the emission profiles as modeled by the US Standard Atmosphere. Then too, has AGW changed those boundary conditions since the US Standard Atmosphere was adopted?
These issues have led me to question the validity of both versions of the TLT product produced by UAH and RSS. Sad to say, I don’t have enough knowledge to perform a proper analysis myself.
Eric,
I don’t know enough to answer your question in any detail. You could have a look at MODTRAN because that certainly allows you to consider different atmosphere. I only used the U S Standard, because that’s what Pekka had used in his earlier illustration. So, I would guess that people do use more appropriate atmosphere models, but I don’t know that for certain.
Eric,
Six different standard atmospheres are in wide use. In addition to the U.S. Standard atmosphere the others are one tropical atmosphere, and two atmospheres (summer and winter) for midlatitudes and subarctic. All have a fixed temperature profile as well as a fixed moisture profile. The amount of water vapor is not zero in any of them but varies greatly from profile to profile.
The openly available UChicago implementation of Modtran allows fro selecting any one of these profiles. In addition it’s possible to modify them by adding some clouds as well as by changing the amount of water vapor and other GHGs of shifting the temperatures up or down. All such modifications make the profiles inconsistent in the sense that they have been constructed for exactly the original set of variables, but playing with the variations is educative in spite of this limitation.
The UChicago page http://climatemodels.uchicago.edu/modtran/ shows directly the temperature profile of the selected standard atmosphere. To find out the moisture profile it’s necessary to look at the raw model output.
I don’t think that much science is done using any of these profiles. They are used for educational purposes and some practical applications.
To understand what Spencer and Christy did, one needs to read their old reports. This one gives their first presentation of the TLT:
Spencer, R.W., J. R. Christy, Precision and radiosonde validation of satellite gridpoint temperature anomalies, Part II: A Tropospheric retrieval and trends during 1979-90., J. Climate 5, 858-866, 1992b
The MSU instruments scanned cross track with 11 scan positions, #6 being nadir. The TLT used the data from channel 2, combining some of the 11 positions with this equation:
TL2T = (T3 + T4 + T8 + T9) – 0.75(T1 + T2 + T10 + T11)
Defining:
Oranges = (T3 + T4 + T8 + T9 ) / 4
Apples = (T1 + T2 + T10 + T11) / 4,
We see this result:
T2LT = 4*Oranges – 3*Apples
Or, rearranging things a bit:
T2LT = Oranges + 3*(Oranges – Apples)
From this equation, it’s immediately apparent that the TLT uses the outer 2 scan positions on each side to “correct” the data from the middle 2 scan positions on each side and completely ignores the middle 3 scan positions.
My big question is the value of the weighting for this combination. Why is a value of 3 used, (as in 3.000000) instead of 2.6 or 3.3 (or whatever). How did they arrive at this value and does that value happen to depend on the use of the US Standard Atmosphere. To my knowledge, they have not provided a published explanation. Then, how well does their fitting process work in other real world situations where the lapse rate is different and there are clouds and moisture? Next, one wonders whether the scaling value should be different for different conditions, varying both with latitude and season. Since I can’t read their minds, I have no way to answer my questions. This might make for an interesting study, if one had the time and funding…
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Thanks gentlemen for an illuminating discussion. If as Pekka says, the ’emission height’ explanation of the greenhouse effect is just illustrative, then what is the actual explanation?
I ask because it appears that water vapour has been declining at higher altitudes where as Pekka points out, the radiative balance action occurs. Is this decline reflected in GCM output?
http://tallbloke.wordpress.com/2013/03/07/ken-gregory-water-vapor-decline-cools-the-earth-nasa-satellite-data/
Please could someone point me to up to date and definitive data for observed global OLR. I’ve seen a number of different plots on the net, none of which agree with each other.
Regarding stratospheric temperatures, there is disagreement there too, between the (undocumented) HADcru version and the NOAA version (which shows less cooling). Which dataset is used in parameterisation of GCM’s?
http://tallbloke.wordpress.com/2013/01/17/met-office-in-new-controversy-undocumented-stratosphere-dataset-2c-warmer-than-noaa-met/
Reblogged this on Tallbloke's Talkshop and commented:
Some useful discussion in comments below Anders post
The effective emission height depends on wavelength. I managed to calculate the “height” spectra for the main CO2 15 micron band from scratch using HITRAN. Instead of calculating radiative transfer from the surface up through the atmosphere to space, I did exactly the opposite. IR photons originating from space are tracked downwards to Earth in order to derive for each wavelength the height at which more than half of them get absorbed within a 100 meter path length. This identifies the height where the atmosphere becomes opaque at a given wavelength. This also coincides with the “effective emission height” for photons to escape from the atmosphere to space.
The result for CO2 levels 300ppm and for 600ppm are shown here
In fact this turns out to be a nice way to derive the greenhouse forcing for CO2. I was able to use this argument to derive the canonical formula S = 5.3 ln (C/C0) – except that that I got 6.6!
This is described in Radiative Forcing of CO2
Pekka,
You write “The radiative height is determined directly by the GHG concentrations and effects of clouds, tropopause height is not sensitive to GHG concentrations and depends more on thermodynamics of air and convection.”
I agree with the first point but not fully with the second point. The tropopause is the height at which radiative heat loss to space dominates and convection stops. So the height of the tropopause does depend on GHG. In some sense the tropopause is like the surface of a star radiating to space. Convection transports heat from the star’s core to the surface.
When we are looking at a complex system like the Earth system, all simple descriptions are “just illustrative” abstractions. They try to describe some aspect of the full truth. Such abstractions are always interpreted differently by different people, some can pick an interpretation that really improves understanding, while others may just get more confused.
That GHGs act to warm the Earth is not “just illustrative”, it’s based on well known physics in a way that does not leave anything essential open on the basic phenomenon. It’s indisputable that more GHGs in an atmosphere that’s otherwise unmodified reduces the share of radiation that escapes from lower atmosphere or surface to the space, and increases the share of emission from upper atmosphere. The shift upwards is uniform. Thus the height of point of emission of escaping radiation rises. The only question is, how to express the strength of this shift in altitude. One measure of this altitude is the effective height of emission. Because the lapse rate is relatively constant the change in the effective height of emission is directly linked to the warming of the surface.
The change in the effective height of emission is not the phenomenon, it’s a measure of a real change. It’s one number that can be calculated from a full analysis, but it’s not a number that is commonly used to calculate anything else. When that number is calculated, the surface temperature has typically already been calculated as well.
It’s, however, the case that calculating the change in the effective or average height of emission that results from added CO2 before warming has taken place is one way of estimating approximately the no-feedback climate sensitivity. Thus it can be used as an intermediary value in a rough estimation of the strength of GHE in absence of feedbacks. This can be demonstrated by the curves that I have already linked to in the comment mentioned on the first line of the opening post.
We can calculate an average emission height where the altitude 12.5 km is used for all emission from higher up to take into account the fact that tropopause is at 12.5 km. The result is 4.04 km for 400 ppm CO2 and 4.22 km for 800 ppm CO2. Thus the average altitude moves up by 180 m. (The change is so small, because emission from the surface does not move.) The effective radiative altitude is not the same thing, but should move by about the same amount. With an environmental lapse rate of 6.5 C/km 180 m corresponds to 1.15 C.
I have checked with a separate calculation that restoring the balance at 15 km (that’s a good height for the comparison) requires a surface temperature that’s warmer by a little more that 1 C in good agreement with that rough estimate. (I increased the temperature by 1 C and found out that a little more is needed to return the same balance with 800 ppm as the original temperature has with 400 ppm).
My calculation are for the U.S. Standard atmosphere. The real atmosphere is more complex, but the same mechanisms work there as well.
Clive,
GHG concentration does affect the tropopause height, but not necessarily very much. My main point is that the two changes in height (effective height of emission and tropopause) are not directly linked, but tropopause height depends on other factors as well. Another point is that it doesn’t really matter much for GHE, how changes in the tropopause height and tropopause temperature combine to be consistent with the temperature profile of the troposphere.
It’a helpful to realize that it’s not necessary to know all details of the tropopause to estimate fairly well the warming from extra CO2. Those details have a very small effect on the warming.
As Eli has written, the real tropopause is fuzzy, it’s so clear only in simplified abstractions like the U.S. Standard atmosphere.
The height of the tropopause is set by ozone in the stratosphere which creates a temperature inversion thereby putting a lid on further upward convection.
That height can be altered either by varying strength of uplift from below (primarily via periods of warm ocean cycles releasing more energy to the air) or from above (via solar induced changes in ozone amounts).
The effective radiating level (ERL) is a concept rather than a reality because it varies constantly as a negative system response to anything other than mass, gravity or insolation that seeks to disturb thermal equilibrium.
Furthermore, such constant variations in the ERL are in three dimensions and therefore infinitely adjustable.
Rather than just the ERL changing the entire global air circulation changes as necessary to retain radiative balance with space. In fact, the latitudinal and meridional circulation changes probably work to eliminate long term changes in the ERL.
That is why we see latitudinally shifting climate zones and changes in jet stream behaviour along with changes in the frequency and intensity of atmospheric ‘blocking’ events.
GHGs just lead to imperceptible circulation changes as compared to the large circulation changes from oceanic and solar variability.
If the system as a whole tries to get warmer than permitted by mass, gravity and insolation then more radiation is allowed out to space and the system cools back towards equilibrium.
If the system as a whole tries to cool to a level lower than that dictated by mass, gravity and insolation then less radiation is allowed out to space and the system warms back towards equilibrium.
The parameter that changes in order to return the system back towards equilibrium in each case is the relative proportions of kinetic energy and gravitational potential energy carried by the gas molecules of the atmosphere and for that purpose non GHGs participate fully in the process which reduces human emissions of GHGs to a trivial influence
Conduction and convection are the non-radiative processes that change scale, speed and location in three dimensions to effect the necessary negative system adjustments in the KE / PE balance.
” Since the temperature gradient in the troposphere is – to a large extent – set by convection”
I think that must be incorrect.
Convection is a result of a declining vertical temperature gradient overlying an unevenly heated surface.
Uneven heating allows different densities at the same height in the horizontal plane.
The decline of temperature and density with height then allows movement in the vertical plane which in turn allows lighter, less dense air parcels to rise above heavier more dense air parcels and the entire global adiabatic convective pattern develops from that.
Add rotation and one then sees latitudinally stretched climate zones around the globe’s circumference with jet streams threading between them.
What goes up must come down where the entire atmosphere is contained within a gravitational field so the kinetic energy (KE) converted to gravitational potential energy (PE) on uplift must (at equilibrium) be exactly equal to the gravitational potential energy being reconverted back to kinetic energy on the descent.
Thus far the whole scenario is created by the interaction of atmospheric mass, gravity and irradiation from outside the system.
If any other factor seeks to thermally destabilise the system then that factor will immediately unbalance the ratio of KE to PE and if unconstrained eventually lead to the loss of the atmosphere.
Atmospheres must therefore be retained as a result of internal circulation changes that rebalance the ratio between KE and PE within the atmosphere.
In the process of that rebalancing the ERL does of course need to move up and down or to and fro above the surface.
Stephen,
Maybe, but what I was getting at was that if the temperature gradient is larger than the lapse rate (more negative) then it becomes convectively unstable and convection will tend to act to drive the temperature gradient back towards the lapse rate. If the temperature gradient is smaller than the lapse rate, then it’s convectively stable, but as the surface warms it will tend to transfer energy into the atmosphere via raadiation, which will then increase the temperature gradient (make it more negative) but convection will then prevent this from pushing the temperature gradient much beyond the lapse rate.
So, yes, what you say may well be correct but I was simply pointing out that convection will tend to act to return the temperature gradient to the lapse rate. So, when I said “set by” I really just meant that convection will tend to act so the the temperature gradient remains (on average) close to the lapse rate. At least, I think that is roughly correct.
Hi, andthentheresphysics.
I agree with that.
It is implicit in my account that convection does have the negative effect that you describe.
I have previously suggested that convection is the process which irons out any system imbalances that arise as a result of the interplay between conduction and radiation.
So, the lapse rate gradient isn’t ‘set’ by convection. Convection works to bring the highly variable local lapse rates back towards the ‘ideal’ lapse rate set by mass and gravity.
A point I have made many times is that if an atmosphere is to be retained then all the multitude of local and regional actual lapse rates between surface and space must all eventually net out to the ideal lapse rate set by mass and gravity.
Looks like there is another ‘Wotts Up’ site still running:
http://wottsupwiththat.com/
Looks like we have another Slayer on this thread…
Stephen,
Yes, that’s why I specifically said “temperature gradient” rather than “lapse rate”. So far your comments have appeared quite sensible. Please tell me that you think the greenhouse effect exists. You’re, of course, welcome to believe that it doesn’t, but I’ve spent a bit too much of my life discussing the existence of the greenhouse effect with those who don’t believe it exists, to really commit any more of my time.
I don’t fully agree on the first sentence of Stephen Wilde:
Absorption of UV by ozone is a factor that affects the tropopause height. It’s also the reason for the temperature inversion of stratosphere. It’s, however, not the fundamental reason for the existence of the tropopause, and it’s a small factor only in the determination of the height of the tropopause, when that’s defined as Pierrehumbert does it most of his book on Planetary Climate. He first mentions the definition as the altitude of minimum temperature, but then he notes that such a definition is too restrictive. On page 173 he explains (my emphasis):
Later in the book he uses the terms troposphere and tropopause in the meaning explained above. That’s also the way I use them, when conditions are such that the definition based on temperature minimum leads to a different result. It’s common in the Earth atmosphere that the definitions agree, but in polar winter the minimum at tropopause may be missing totally and the temperature fall continuously far higher that the tropopause is under other circumstances. Therefore the definition based on the dynamic behavior leads always to a reasonable result, while the other definition may fail.
When the definition is based on the dynamic behavior, the tropopause would not be much higher up even without stratospheric absorption of UV. That’s the case, because the upper stratosphere cannot heat effectively the lower atmosphere as practically all downwards IR emitted there gets soon absorbed. Effects on stratospheric temperatures are large, but the related energy fluxes small in comparison of other fluxes around the tropopause and in the lowest stratosphere.
There is a greenhouse effect but it is mass induced. All the molecules in the atmosphere participate via conduction and convection rather than just the GHGs via radiation.
GHGs do have radiative characteristics but the effect is to alter global air circulation rather than surface temperature due to the operation of the Gas Laws.
That is why water vapour (as a GHG) affects the actual lapse rate in the troposphere (the moist rate instead of the dry rate) but the global air circulation then changes so that the effect is cancelled out by equal and opposite changes in lapse rates at higher levels.
I do not regard myself as a ‘Slayer’.
I don’t agree with Pekka:
“If the air were never heated by solar radiation its temperature would continue to fall as we climb. However, at a height of ~12 km a minimum of ~-55°C is reached, the tropopause***. Above that the temperature starts to increase again because the stratospheric air contains a sunlight absorber, ozone.”
http://www.atoptics.co.uk/highsky/htrop.htm
The temperature gradient in the lower atmosphere of all bodies in the solar system with significant atmospheres is negative. Specifically these bodies are Venus, Earth, Jupiter, Saturn, Titan, Uranus and Neptune.
The numerical value of the gradient approximates to the formula L = -g/Cp. The correspondence is precise for Jupiter but less close for Earth owing to the presence of water vapor which has the effect of lowering the lapse rate. Likewise for Titan where methane vapor lowers the lapse rate.
The scientific explanation is almost trivial given that the derivation of the DALR (Dry Adiabatic Lapse Rate) is taught in high schools. Notice that there is absolutely no reason to invoke MODTRAN or radiative transfer equations to arrive at the correct answer. All you need is Newtonian mechanics and thermodynamics.
Above the tropopause things are totally different. Frequently temperature gradients are positive and this can usually be explained by assuming that radiative transfer dominates.
When it comes to defining the effective radiative altitude it is simple enough in the case of Venus and other bodies with 100% cloud cover. The “Effective Radiative Altitude” is the cloud tops, roughly 58 km in the case of Venus.
In the case of Earth, cloud cover is not 100% so the concept of an effective radiative height that can vary is not necessarily crazy. Nor is the notion of CO2 “Modulating” the emissivity of planet Earth. What is lacking is a mathematical analysis capable of back casting Earth’s temperature with reasonable accuracy based on these ideas. Until someone can come up with a “Back Cast” that approximates to observations there is no reason to base public policy on what climate models predict.
Camel,
Sure, but you need MODTRAN (or something similar) if you want to have some idea of the outgoing spectrum and at what height in the atmosphere the different emission is coming from.
Without the heating by UV the temperature would, indeed, fall continuously with the altitude, but there would still be a tropopause. The nature of the resulting atmosphere is shown in this Figure 4.45, left panel from Pierrehumbert: Principles of Planetary Climate.
We see a point labeled as tropopause. That’s the level where convection stops and stratification starts. To me this is the only definition of tropopause that can be logically generalized from the real Earth conditions to other situations. That kind of definition is needed also under some conditions of the Earth atmosphere like the Polar winter in this Figure 2.1 from Washington and Parkinson: An Introduction to Three-Dimensional Climate Modeling
Pekka,
If there were no heating of higher layers by sunlight at all then the tropopause would effectively be the top of the atmosphere.
The tropopause would rise to a point determined by the mass of the atmosphere, the strength of the gravitational field and the level of insolation.
Kinetic energy can only lift matter against gravity to a height consistent with the weight of that matter.
That is implicit in the gas laws because the gas constant is defined as the amount of work (in Joules) required to lift 1 ‘mole’ of mass to a height where it is 1K cooler.
Obviously, the uplift must cease when all the kinetic energy that is freely available has been used up in work done.
The kinetic energy freely available is limited to that which is not radiated straight out to space as soon as it arrives.
That means that on Earth that extra 33K thermal enhancement (or whatever the true value is) represents the energy in the system that is available to maintain the height of the atmosphere by doing work lifting the molecules against the force of gravity.
That 33K constantly being used to maintain atmospheric height must be deducted from the radiative exchange with space.
It should not be included in consideration of the S-B equation.
Stephen,
I don’t think this is correct. Our atmosphere has accumulated energy so that it is able to support itself against gravitational collapse. However, it is now in a state in which – on average – the system radiates as much energy into space as it receives. Once you reach this equilibrium, the total amount of energy in the atmosphere doesn’t change (on average) because at all heights (on average) it gains as much energy as it loses.
Indeed, the total amount of energy in the atmosphere does become stable (though it can still act as a buffer).
However one still needs a rise in surface temperature to represent the energy stored in an atmosphere supported against gravitational collapse.
Ask yourself, should that portion of surface temperature still be included in the radiation budget as per S-B ?
I think not, because if you could use that portion of surface temperature for the radiation budget then it would be lost to space and gravitational collapse would occur.
Isn’t that the AGW error ?
Adding the surface energy needed to hold the atmosphere up against gravity to the surface energy needed to radiate to space.
You cannot have the same parcel of energy (worth 33K at the surface) for two separate processes at the same time.
Either it supports the atmosphere against gravitational collapse or it radiates to space. You can’t have it both ways.
The next question is as to where that extra energy at the surface for the 33K higher temperature comes from.
AGW theory supposes that it is Downward Infra-Red Radiation (DWIR) from radiative gases.
If that were right then the absence of radiative gases would cause gravitational collapse of the atmosphere.
Indeed the height / volume of the atmosphere would be related to the proportion and radiative power of radiative gases and nothing else.
That is clearly incorrect otherwise the Gas Laws could not work since they contain no term for radiative characteristics of constituent molecules.
What actually happens is that the surface temperature enhancement comes from adiabatic warming of subsiding air in the descent phase of convective overturning.
The adiabatic cycle is in balance but that cycle contains and fully accounts for the additional energy stored in the atmosphere to prevent gravitational collapse.
That is what gives the raised surface temperature and it is tied to mass and the amount of work needed to maintain atmospheric height.
It is nothing to do with radiative capabilities of constituent gases.
Stephen,
I know that on tallbloke’s you complained a bit about being described as a slayer here. Your most recent comment makes it hard to see why that description isn’t right. I really have discussed the GHE in great detail in the last few weeks with various people and I don’t really feel like continuing to do so.
A brief comment,
No, this is a huge oversimplification. As I was trying to get at in this post, some of the energy is radiated from within the atmosphere. Given that the atmosphere is cooler than the surface, for the total to match that of a 255K blackbody, the surface must warm until the system is in equilibrium.
Indeed they don’t, but this is really irrelevant. The gas laws simply relate pressure, temperature and density/volume. The gas laws themselves don’t really tell you if the gas is adiabatic, isentropic, radiative. That comes from the physical properties of the gas itself. If the gas was only weakly radiative, then most of the energy would be radiated from the surface and the surface would cool until it emitted as much energy per second per square metre as a 255 K blackbody. The atmosphere would cool (maybe slowly) until the temperature at the base of the atmosphere matched the temperature of the surface. Exactly what profile it then had would depend on its properties. It could still have a lapse rate if convection was important. If it gained some energy from radiation, it may become isothermal.
The first bits of what you say here may be roughly correct. The last bit is missing something fundamental. The radiative properties of the gases may not set the profile itself, but they do influence where the energy is radiated to space. The higher this is in the atmosphere, the greater the greenhouse enhancement. That’s really all the greenhouse effect is. The atmosphere itself cannot set a higher temperature on the surface unless the atmosphere is preventing some of the energy radiated from the surface from directly reaching space. That’s really all the greenhouse effect is.
Anyway, I don’t want to debate the greenhouse effect anymore. It’s well accepted. If you don’t want to believe it, that’s fine. I don’t, however, really want any more slayer-like comments here. There are plenty of other sites that encourage it.
Ok, I’ll leave it at that but note that you really do need to consider the role of mass in connection with the greenhouse effect.
As far as I can tell you think it is GHGs and nothing else that creates the 33K thermal enhancement at the surface.
Stephen,
If you mean convection, then it is included in the GHE.
Given that this isn’t really what I think, you’d probably be wrong. The atmosphere obeys all the laws of physics. What the GHGs do is determine the heights at which various wavelengths bands emit their energy to space. The atmospheric profile (which obeys all the laws of physics) then essentially sets the temperature of the surface that is required so that the total amount of energy radiated into space matches that absorbed. That’s really all that the GHGs do. Of course, there is a certain amount of energy that is transported through the atmosphere via radiation and in which the GHGs are involved, but some is transported via convection.
“The atmospheric profile (which obeys all the laws of physics) then essentially sets the temperature of the surface that is required so that the total amount of energy radiated into space matches that absorbed”
Not quite, but close.
The atmospheric profile (obeying all the laws of physics) changes in order to prevent the surface temperature changing so that the total amount of energy radiated to space continues to match that absorbed.
My objection to the Slayer label is that I accept the radiative features of GHGs as potentially warming the system if all else remains the same.
I simply aver that all else does not remain the same because the convective adiabatic cycle is capable of exerting an equal and opposite thermal response by virtue of the Gas Laws.
The two most basic processes of energy transfer are conduction and radiation. If they get out of balance so as to destabilise the system then convection regulates the energy flows in order to restore stability.
Hence latitudinally shifting climate zones and jets.
The only issue is the extent of such shifting from our emissions compared to natural solar and oceanic variations.
Note that I do accept a climate effect from GHGs. The Slayers do not as far as I know.
Stephen Wilde:
comments like:
“Isn’t that the AGW error ?”
and
“AGW theory supposes that it is Downward Infra-Red Radiation (DWIR) from radiative gases.”
Are telling, because of course atmospheric physics doesn’t care where the GHGs come from. This isn’t “AGW theory”. If the basic physics is in error, then everything atmospheric physicists think they know about how atmospheres work – not just on earth, not just in the presence of human emissions of CO2 and other GHGs, but everywhere – ends up in the toilet.
But your focus on “AGW theory” makes clear your motivation, and adds to the evidence that you are a “slayer”, IMO.
ATTP – the more quickly people are called out on points like this, the more quickly they can be ignored, IMHO, because the motivation makes clear the lack of interest in actually learning …
dhogaza,
My ‘motivation’ followed investigation of the science, is a consequence of my findings and therefore should not be taken as an indication of bias.
If I had found AGW theory to be scientifically sustainable I would have had no problem embracing it.
Apart from that,it is all too easy to avoid discussion of the facts by pointing to some alleged bias so that puts your motivation in question.
Stephen,
It’s not really possible to even start to discuss your theory as it lacks all justification. I have seldom seen a comment that makes nine short claims and gets every single one totally wrong. You succeeded in writing such a comment here.
Science is a progressive process where new knowledge is built on the earlier knowledge correcting in that also earlier errors. Jumping to something new that disagrees on every count on the existing knowledge of physics is an approach doomed to failure. Present physics just cannot be that wrong on every count.
Pekka,
If what you say is right then it should not be difficult to counter those nine points.
As far as I can tell those nine points are consistent with present physics in general but perhaps not consistent with relatively recent atmospheric radiative physics which apparently ignores non radiative processes.
I look forward to seeing Stephen’s nufysics paper published. May I suggest Pattern Recognition in Physics.
I do enjoy the lack of scepticism. “Ignore all those papers. Here are my assertions. It is up to you to disprove them.”
Stephen,
Having spent the last two or three weeks discussing the greenhouse effect (which is well accepted by almost all credible physical scientists) I can tell you that – in my experience – it’s far harder to counter these points than you apply. That’s not because it’s technically difficult to do so. It’s because those with whom you are having the discussion are almost certainly not going to acknowledge that you have.
What I would say to you is that I think that you don’t actually understand what the greenhouse effect is. You have certain ideas about what you think it is, but I think you’re wrong. If you did actually put some effort into understanding what it actually is (not what you think it is) you may discover that much of what you think disproves the greenhouse effect is actually entirely consistent with it.
Everything I have said is consistent with the surface temperature beneath an atmosphere being higher than predicted by the S-B equation. That is the greenhouse effect.
You say that it is a result of radiative gases.
I say it is a result of atmospheric mass.
I accept that GHGs potentially have a warming effect but aver:
i) That it is insignificant compared to the warming effect caused by mass and
ii) In any event it is negated by circulation changes.
And there we must leave it.
Stephen,
Can you explain what papers or text books you’re reading that are causing you concern? It’s pretty easy to get shoe boxed in a negative light if you show up ask a bunch of questions devoid of appropriate background information. (After 5 years of listening to ‘counter arguments’, that is the general approach from what we call trolls or deniers. I’m not saying you are one….) That’s why technical work is always full of references.
Citations can point to a specific fact or concern, and provide useful background information.
Personally, I tend to look askance at claims that the majority of PHDs got it all wrong. That’s just not in the cards at all.
Climate observations are showing that a small group of PHDs relying on the unproven theory of atmospheric (radiative only) physics have got it wrong.
I only need to wait.
Is anyone here really suggesting that atmospheric mass has an insignificant effect on the observed surface temperature enhancement otherwise known as the greenhouse effect ?
Stephen,
Ask yourself what would happen to the Earth’s surface temperature if the Earth were suddenly no longer orbiting a star (yes, hypothetical).
The mass of the atmosphere needs to be subjected to irradiation (if we ignore geothermal energy) in order to raise the atmosphere off the surface and as a by product create the mass induced greenhouse effect. Obviously the atmosphere would collapse to the surface and become a solid if the irradiation stopped.
As long as there is irradiation then the more atmospheric mass the higher the surface temperature relative to that level of irradiation.
The reason is that the more mass is present the more of the available irradiation it can store.
The mass acquires its energy primarily by the non radiative processes of conduction and convection.
The form of storage is as gravitational potential energy (PE) and the higher the atmosphere rises the more PE will be present.
Moving kinetic energy (KE) during uplift causes it to change to PE which does not register as heat.
Only when descending again does that energy become heat (KE) again.
It is all basic established thermodynamics but I realise that for those brought up on the radiative theories it will be unfamiliar.
The issue about GHGs then is whether or not they add to the mass induced greenhouse effect due to their radiative capabilities.
The ability of the global air circulation to reconfigure as necessary to maintain equilibrium would suggest not.
Stephen,
And the atmosphere needs radiatively active gases for all of what you describe to actually happen. The mass by itself cannot heat the surface. Anyway, it’s late and this is really heading into slayer territory, so I’d rather we called a halt and left it at that.
“The mass by itself cannot heat the surface. ”
It doesn’t need to.
All it needs to do is maintain the status quo, which it does.
It doesn’t need radiative gases, just conduction and convection.
Goodnight.
Stephen,
When your theories go so far from real physics that they have almost nothing in common with that, it’s not possible to say much more of them than that they make no sense to me.
If you wish to communicate constructively with people who know physics, you must first learn the real meaning of the words they are using and the concepts they are considering. As long as you have not done that, you are left alone. Nothing that you write is taken seriously even, if you would really get a useful idea, because you cannot make that idea understood.
The sentences you wrote in that post are all totally wrong when the words are used with their normal meaning. If you had something else in mind, I cannot see that.
No citations. [Mod: ad hom snipped]
I’ll just make a final comment and then stop bothering you all on this thread.
Radiative physics is not wrong, just incomplete.
It fails to deal with the thermal effect at the surface of the mechanical energy tied up in the adiabatic convective cycle within an atmosphere.
That mechanical energy which maintains atmospheric height against gravitational collapse requires a surface temperature enhancement but radiative atmospheric physics does not recognise that.
It needs a surface temperature enhancement because energy tied up in the mechanical process is no longer able to be radiated to space, you can’t have the same parcel of energy contributing to two separate processes simultaneously.
Not complicated or new.
Just basic thermodynamics and common sense. No specialist terminology required.
Observations prove that it must be so.
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To explain a little, what I have been writing about:
The above sentence cannot be understood. What is the mechanical energy tied up in the adiabatic convective cycle within an atmosphere? How should it be dealt with?
The reality is that all effects that can be thought to be part of what you write are included in the standard physics at the level needed for each application, and within the limits the required details have been observed or otherwise determined. You just claim that something has been missed, but fail to explain, what that is in a way anybody can understand.
There’s no mystery in the maintenance of the atmospheric height. Standard physics explains it fully and in agreement with observations. Your sentence does not make sense at all.
Again something that doesn’t make any sense.
The primary problem with your theories is that you discuss phenomena that are fully understood theoretically in full agreement with a huge amount of observations. You try to replace this well working system by a creation of your imagination. What you create in that way is not needed, is incomprehensible to others, and contains contradictions all around assuming that the interpretations others make of that have any relation to what you try to tell.
On the height of the tropopause.
With the atmosphere being heated from the surface, the temperature gets lower with increasing distance. (stratification in a gravity field) The reason the temperature stops getting colder and even increases with height above the tropopause is the warming by ozone (warmed by solar UV).
The tropopause isn’t a hard layer, according the definition it is just the height at which the temperature drop with height reduces below 2k/1000m.
(and don’t confuse an inversion due eg the polar front with the tropopause 😉
I do confess my meteorology study was in the mid 70’s.
Why the temperature on earth is over 90K higher than on the moon?
Because we have oceans, heated during their creation to the boiling point,
and kept warm (>270K) by geothermal ever since.
See http://tallbloke.wordpress.com/2014/03/03/ben-wouters-influence-of-geothermal-heat-on-past-and-present-climate/
Ben,
I’ll let your comment stand, but it’s sufficiently unscientific that I would encourage others to think long and hard before responding.
What specifically is unscientific?
The stratosphere : http://en.wikipedia.org/wiki/Stratosphere
The tropopause : http://en.wikipedia.org/wiki/Tropopause
This is the same knowledge I was taught some 40 years ago. Nothing changed afaik.
Geothermal? Earth consists of molten rock, with a core of molten metal.
This makes earth a planet with a temperature, not the 0K that is implicit when calculating a radiative balance temperature.
Pekka asked:
“What is the mechanical energy tied up in the adiabatic convective cycle within an atmosphere?”
Gravitational potential energy within every gas molecule that lifted off the surface. The higher, the more.
It does not register as heat but is created from KE during uplift and returned to KE on descent.
Basic thermodynamics and an entirely non-radiative process.
All your objections to my comments are based on your lack of understanding of that point.
Ben,
Check my quote of Pierrehumbert in comment
https://andthentheresphysics.wordpress.com/2014/03/05/effective-emission-height/#comment-16919
and my comment based on that. How to define tropopause most generally making the concept useful also in atmospheres different from the most typical Earth atmosphere is a somewhat complex issue.
The absorption of UV in the upper stratosphere warms those altitudes a lot, but affects the properties of the troposphere and even the region around the tropopause much less.
Check also the two figures I link in this comment
https://andthentheresphysics.wordpress.com/2014/03/05/effective-emission-height/#comment-16963
Stephen,
The physics of adiabatic expansion of rising movement is not exactly what you think. The gravity enters in a somewhat different way and that’s totally taken into account in the standard theory. Nothing is missed by atmospheric physicists. You just imagine that something would be missing from standard theory.
Ben,
The stratosphere aspect seemed fine. Currently our Geothermal energy is around 44.2 x 1013W. That’s roughly 1 Wm-2. Convert that to a temperature, it’s 64K. So, our geothermal flux only would make the Earth appear to be a 64K blackbody. So, negligible in an energy balance sense.
Pekka Pirilä says: March 13, 2014 at 10:52 am
“The absorption of UV in the upper stratosphere warms those altitudes a lot, but affects the properties of the troposphere and even the region around the tropopause much less.”
Fully agree, and without this warming we wouldn’t be discussing a tropopause. The atmosphere would just peter out with increasing distance from the surface (and at a much lower altitude).
The main problem I see in current climate science is the assumption that the atmosphere could warm the surface considerably.
Just looking at the moon (average surface temperature ~197K) the assumption seems to be that if it had an atmosphere like on earth the average surface temperature would rise to ~290K. (and we should increase the rotation rate and the gravity a bit 😉
I’m not buying, and I don’t need to, because I’m pretty confident there is a better explanation for our surface temperatures.
Once you realise that our deep oceans have a temperature of ~275K already, it is not difficult to see the sun warming a shallow surface layer to our pleasant ~290K.
Problem I’m having is that people seem to believe that the sun warming the upper ~200m of ocean is also the explanation for the temperature 4000m below the surface. It is not. Solar influence does not reach below the thermocline.
Warm water does not sink into cold, (much) denser water.
(and no the thermohaline circulation doesn’t cut it either)
We even have meromictic lakes were the sun does not warm the lower waters.
http://en.wikipedia.org/wiki/Meromictic_lake
Let alone an ocean 4000m deep
ATTP,
The value is one tenth of what you write or about 44 TW. That’s 0.08 W/m^2 or 0.035 % of the solar heating. That leads to an increase of 0.02 C in the Earth temperature. This effect has not changed much. Thus it does not contribute to any further trend in temperature.
andthentheresphysics says: March 13, 2014 at 10:58 am
“Ben,
The stratosphere aspect seemed fine. Currently our Geothermal energy is around 44.2 x 1013W. That’s roughly 1 Wm-2. Convert that to a temperature, it’s 64K.”
Actually the geothermal flux through the oceanic crust is only ~100 mW/m^2 (continents even less (~65 mW/m^2).
Point is that the 100 mW/m^2 warms the oceans from below (1K every 5000 years or so)
and that warmed water can not reach the surface, except at very high latitudes.
(unless you believe in back conduction)
Add to that large magma eruptions ( think 10.000.000 km^3 and much more) and we have a mechanism that explains to me the gradual cooling of our climate the last 84 million years, and why we are in a period of alternating iceages / interglacials right now.
Pekka,
Indeed, I read the number incorrectly. 4.4×1013W.
Ben,
The point is that geothermal energy is largely irrelevant both for the overall greenhouse effect and for the recent warming. I don’t have any interest in discussing this as it really should be obvious.
Pekka said:
“The gravity enters in a somewhat different way and that’s totally taken into account in the standard theory”
Then please explain. I really want to know. There are many others who would like to know as well.
By the way, I agree about the insignificance of geothermal energy on timescales relevant to the current issue.
Stephen,
The basic process has been explained in very many places, sometimes better, sometimes less clearly. One important question is, how much can be assumed to be known already. I add some comments here, for more you much search for additional sources.
Fundamental ingredients include:
– Something makes the air circulate. What drives strong circulation on the Earth is the combination of heating by sun of the surface and cooling of the upper troposphere by emission of IR out of the troposphere. The latter is totally dependent on GHGs. That makes them essential.
– When the air circulates some parts are moving up and other parts moving down. There’s also horizontal movement, which makes the real atmosphere more complex.
– When air goes up, it expands. Heat doesn’t move rapidly trough the boundaries of some big enough volume of rising air. Therefore the expansion is approximately adiabatic. Adiabatic expansion leads to cooling, but the loss of heat is not equal to the increase in gravitational potential energy as it depends on the specific heat of the gas. The amount of cooling has to be calculated based on the adiabatic expansion, not on the change in gravitational energy.
The temperature of the gas does not drop to compensate increase in the gravitational potential energy, as it drops equally much, when the gas is made to expand at a constant altitude by some device.
You may read more from very many places (one example is lecture notes of Caballero). Further details have been discussed also on this site in some earlier threads.
Stephen,
You could quite easily calculate the difference in gravitational potential of a gas parcel at 10km in the atmosphere and at the base of the atmosphere. I get it to the ratio between these potentials to be 1.00157, so rather negligible.
One way of thinking on what goes on is that a stone doesn’t cool from being lifted up. Neither does air, but air cools from expansion.
Does it matter whether air cools by expansion or lifting ?
Either way it cools but it loses no total energy since the KE is replaced by PE and the process is reversed on the descent.
If the energy value of the PE created is less than the energy value of the KE lost during uplift then we have a breach of the Laws of Conservation of Energy.
All one needs to produce the mass induced surface temperature enhancement is warming on the descent averaged around the entire globe.
The warming on the descent provides the necessary energy for the next ascent without needing to take anything from the solar energy passing through.
The surface having used the descent energy for the next ascent the surface is then free to receive and re-radiate the full amount of incoming solar energy without deduction so then we see long term radiative balance without needing DWIR but still wuth a surface temperature enhancement.
That all happens with or without GHGs because of the unevenness of surface heating and the creation of air parcels of different densities in the horizontal plane.
You can’t get away from the fact that the energy at the surface is needed for two separate processes and if surface energy ‘leaks’ from the non radiative adiabatic cycle to the radiation exchange for a long enough period of time then the atmosphere will collapse.
The non ideality of gases or the presence of radiative characteristcs are all dealt with by circulation changes swapping energy between the adiabatic exchange and the radiative exchange.
I understand that if you cannot accept the warming effect of the descent phase of the convective cycle then there will be no meeting of minds here so lets just agree that that is where the difference lies.
Stephen,
But the point is that the hydrostatic profile in an atmosphere on a terrestrial planet, isn’t really because of the change in gravitational PE as you go up in the atmosphere. It’s because of the pressure gradient needed so as to balance the downward force of gravity.
In a simple sense, what you need is
dP = – rho g dz
One could include that g actually depends on height and will depend on the mass of the atmosphere, but the mass of the atmosphere relative to the mass of the Earth is negligible and the height of the atmosphere relative to the radius of the Earth is also negligible. So, to a first approximation, the structure of the atmosphere depends on the gravitational influence of the solid Earth, and the thermodynamics of the gas.
Stephen,
The point is that no KE is replaced by potential energy. That’s not what takes place. It doesn’t take place in a stone when a stone is lifted, and it doesn’t take place when air is lifted by a convective movement of air.
Expanding air produces work. It uses the energy heat to push away air outside of the volume considered. It does in the same way produce work when it expands at fixed altitude to push a piston in some device. This transformation of heat to work is not directly connected to the upwards motion of the volume of air. There’s no increase of potential energy of that air linked to that.
These are things that you must understand and accept, if you wish that anyone with knowledge of physics will take you seriously at all. Fighting against a theory that has been so extremely successful and so thoroughly verified leads nowhere.
Stephen,
Pekka’s right. Consider an insulated box with a fixed density of gas at a fixed pressure on the surface of the Earth. Lifting it into the atmosphere won’t increase or decrease the temperature, or pressure, of the gas in the box. What will happen is that you will do work on the box, which will change the gravitational potential energy of the box (including the gas). If you then let go of the box, it will fall back towards the Earth and all that potential energy will then be converted into kinetic energy. If the volume of the box is fixed and if it is well insulated, then at no time during this process will the temperature or pressure of the gas in the box change.
Stephen,
Do you understand that ATTP, and Pekka are saying you are technically correct, but that the effect that you are concerned about is totally insignificant?
http://apollo.lsc.vsc.edu/classes/met130/notes/chapter2/potential2.html
http://apollo.lsc.vsc.edu/classes/met130/notes/chapter6/adiab_warm.html
Stephen,
I think you’re confusing two somewhat different things there. Yes (as I indicated in my response to you) if a parcel of gas falls within the atmosphere, it’s gravitational potential energy is converted into kinetic energy. If it rises again, then something must be work so as to get it to rise. This is standard physics.
However, the reason we have a pressure/temperature gradient in the atmosphere is because it will tend towards a state of hydrostatic equilibrium. This is a state in which – on average – the pressure gradient provides an upward force that acts against the downward force of gravity.
So, in some sense there’s a relationship between what you’ve presented and what I’ve just described.
Here’s the issue though. That alone doesn’t tell you what the actual temperature should be. In other words, the relationship between gravity and pressure doesn’t allow you, by itself, to determine the actual temperature structure in the atmosphere. Theoretically, an atmosphere of any temperature can settle into a state of hydrostatic equilibrium. For example, if it’s isothermal then the scale height is kT/mg. The scale height is the height over which the pressure drops by a factor of 1/e.
What determines the actual temperature are the thermodynamic and radiative properties of the atmosphere. The presence of GHGs traps some of the outgoing radiation. This means that the atmosphere and surface will warm until the amount of energy being radiated into space matches that being absorbed. This is the greenhouse effect.
If there were fewer GHGs, the temperature in the lower atmosphere would be lower than if there were more GHGs. In both these cases, however, the temperature gradient would be still be set by the balance between gravity and pressure.
“The presence of GHGs traps some of the outgoing radiation.”
It also allows a radiative window to space from a point above the surface which non GHGs do not.
A non GHG atmosphere has to return all its energy content back to the surface for radiation out to space but GHGs short circuit that process.
I suggest that after convective circulation adjustments the net thermal effect of more GHGs is zero.
“What determines the actual temperature are the thermodynamic and radiative properties of the atmosphere”
I don’t think you need radiative properties. For irradiated mass within a gravity field the baseline temperature is set by mass, gravity and insolation.
Introducing radiative properties only affects the circulation. If it were otherwise there could not be any long term equilibrium because the surface would be permanently too hot or too cold and the atmosphere would either boil off to space or congeal on the surface.
“This means that the atmosphere and surface will warm until the amount of energy being radiated into space matches that being absorbed. This is the greenhouse effect.”
Obviously correct but it is a matter of mass and not radiative properties though radiative properties do have a climate effect by altering the circulation pattern.
“the relationship between gravity and pressure doesn’t allow you, by itself, to determine the actual temperature structure in the atmosphere”
Correct but you only need to add insolation from outside the system to cause atmospheric lift off and any unevenness in surface heating sets up the convective cycle. GHGs not needed.
Energy in the convective cycle cannot be used for radiation out yet still requires a surface thermal enhancement.
The surface temperature enhancement is pure basic thermodynamics and is independent of the radiation budget.
I do not expect you all to agree but I am technically correct and any process that can warm descending air from 10C at 700 mb to 25C at the surface without addition of new energy is not insignificant.
I have never said that Stephen is technically correct. Up to now I haven’t seen anything significant that he has got right. It’s all mixed up and in contradiction with thermodynamics and fluid mechanics as these fields of physics are described in textbooks of physics.
Naturally there are individual sentences that are technically correct, but even then the next sentence tells usually that it has been interpreted incorrectly.
I don’t believe that anyone can understand physics without studying physics extensively enough. Thermodynamics appears superficially rather straightforward, but it’s actually quite a difficult field to understand. I have met many engineers who do routinely engineering calculations based on thermodynamics, but have major misunderstandings on some basic parts of thermodynamics.
When we are considering convection, we are not looking at parcels of air that ascend or descend by themselves. If that would be the case the ascending parcel would slow down by gravitational acceleration and the descending would speed up. In that the molecules of the gas would lose or gain kinetic energy. This is not what convection is about. In convection the parcel is made to move by the surrounding. It’s made to move in the same sense a rock can be moved up or down by a lift, not as the rock would move thrown up or left to fall.
For the above reason the cooling of the rising air or warming of the descending air is a totally different phenomenon. From the point of view of the kinetic theory of gases the cooling can be understood as consequence of the “walls” of the volume moving away. When a molecule hits such a wall it bounces back with a smaller velocity. In compression we have the opposite effect where the molecule gets extra energy from the wall. In atmosphere we don’t have any walls, but the expansion of gas has just the same effect from the point of view of the kinetic theory. That effect can be expressed as work done by the expanding gas or on the compressing gas on the surrounding as each colliding molecule pushes the “wall” outwards.
There’s no reason to think that a parcel of air must maintain a constant total energy in adiabatic ascent. It’s pushed up by the pressure differentials and that adds to it’s energy. That’s the source of the extra potential energy, not the heat of the parcel itself. That’s again exactly the same phenomena we have, when a rock is lifted up in a lift. It’s potential energy increases, and that extra energy is given by the lift.
Stephen Wilde, in industry if we have something useful to say, we present an argument (yours are confusing and verbose), we provide citations to back what we think (you refuse), and then we demonstrate calculations to show the significance of the issue (you have not demonstrated any knowledge in these regards).
I’m reasonably certain that Stephen Wilde represents a category of cute cuddly guy that spouts technical jargon, but doesn’t really understand it. The goal is to fill web pages with arguments, for which the cute cuddly guy absolutely refuses to back up. The arguments go on forever, and makes it look like there is something significant being said.
The hallmarks of this kind of activity are verbosity, lack of citations, and an inability to demonstrate the material.
And Then There’s Physics seems to be attracting this kind of activity.
Pekka said:
“It’s pushed up by the pressure differentials and that adds to it’s energy”
No it isn’t.
Warmer air rises because it becomes less dense than the parcels around it and therefore lighter.
When surface heating is uneven as it inevitably is on a rough surfaced rotating sphere there will always be parcels of different densities next to one another in the horizontal plane and lighter parcels will rise above the neighbouring parcels not because they are pushed up but because they are less dense and lighter.
There is therefore no addition of energy other than the initial uneven surface warming.
Once the parcel lifts off the ground it continues to rise with no more energy added because it constantly finds itself surrounded by more dense air as it rises.
Eventually it hits the tropopause which prevents further rising because the temperature inversion provides the rising parcel with equally dense surrounding air.
That is the long standing well established description of adiabatic uplift and Pekka seems unaware of it.
What goes up must come down elsewhere so the cycle is completed with or without GHGs.
Going down, the air warms at the dry adiabatic lapse rate which is how air of 10C at 700mb gets up to 25C at the surface with zero addition of energy.
Radiative properties have nothing to do with any of that.
I have provided relevant source material. Read and ponder.
Click to access op.pdf
“when the air is stirred (for instance, by convection), and a parcel of air rises, it expands,
because the pressure is lower at higher altitudes. As the air parcel expands, it pushes on the air around it, doing work; since the parcel does work and gains no heat, it loses internal energy, and so its temperature decreases.
(The reverse occurs for a sinking parcel of air.)”
For a descending parcel of air it gains internal energy so its temperature increases and it does so at the DALR with no additional energy added.
Stephen,
It’s pushed up by the surrounding air. It’s light enough to rise by that push, but it moves up only because it’s pushed.
A stone can be moved up in a lift, if the lift is powerful enough to create a sufficient push.
Neither the air not the stone moves up without a force that pushes them up.
Pekka.:
The denser air only slides in beneath the lighter air because the lighter air starts to rise and leaves lower pressure beneath it.
Low pressure systems in the atmosphere contain rising air but it is not being pushed up.
The warm less dense air starts to rise of its own volition and then denser air flows in from below.
If it acquires water vapour it will accelerate because water vapour is lighter than air.
You also tried to say that such movement imparted additional energy to the lighter parcel which is clearly neither the case nor necessary.
Your attempt to conflate the behaviour of solids and gases is very revealing.
I suggest you read some basic meteorology and have a look at the Gas Laws.
You might want to have a look at Pekka’s CV before condescendingly suggesting he have a look at the Gas Laws …
Argument from authority is worthless.
Stephen.
Take a “parcel” of air, i.e. a volume bounded by some surfaces. That parcel of air is the subject of some forces:
– the gravity pulls it down
– pressure from all sides pushes it to a direction perpendicular to the surface.
These forces add up to some net force. If that net force is up, the volume accelerates upwards, if it’s down it accelerates downwards. Gravity is always down. Thus the parcel would accelerate downwards, if it were not pushed up by the pressure. To get it started to move up some net force up is needed and to maintain that motion the pressure forces must continue to push it as strongly as gravity pulls it down.
All this is essential for this discussion, because that tells the source of the energy that makes it go up and gain potential energy. That source is the pressure from outside. The energy comes from other parts of the atmosphere, not from the heat of the parcel. The case is not that the extra potential energy is taken from the kinetic energy of the molecules in the parcel.
When one parcel goes up, some other goes down. This parcel is one of the sources that give energy that parcel that goes up.
Comparing with the lift again. If the lift and the counterweight are equally heavy, little energy is needed to move the lift up, when the counterweight comes down. Only enough to win the friction.
Argument from authority is worthless.
That’s like saying you can’t accept a scientific theory unless you go out and test it yourself.
Your comment to Pekka was condescending and I’m with OilMan here in that your comments lack credible citations. If you want your views to have credibility then my suggestion it to get them published in an academic journal.
Stephen,
I was tempted to try and explain where you’re going wrong again, but it’s late, I’m tired and I can’t face going through this again. Basically, I’m with Pekka.
The only ‘force’ required to initiate uplift is the injection of solar energy at the surface.
Pressure from the sides or the addition of other non solar energy is not necessary though geothermal might help.
With no sunlight an atmosphere lies frozen to the surface as a solid.
Add sufficient sunlight that it changes phase to a gas and it starts to rise off the surface of its own volition.
The more solar energy at the surface the higher the entire atmosphere eventually rises.
Or do you think some additional ‘force’ comes from the surface to push it up ?
Think of steam rising off water. It isn’t being forced up by pressure from the sides. It rises of its own volition because it is lighter. It is the same for a parcel of air warmed by the sun more than the parcel next to it. Maybe the other parcel is in shade or the angle of incidence for the sunlight is less.
Only after uplift has begun will denser air flow in to occupy the area of lower pressure created beneath it.
You cannot conflate the behaviour of solids and gases in a gravity field. You must know that the rules are completely different ?
You can have a scenario where fast descending air in one place (a strong high pressure cell) pushes up the air around it (to invigorate a nearby low pressure cell) but that is at the end of the convective cycle and caused by other factors such as the violent mixing that occurs as the climate zones caused by the Earth’s rotation interact with one another.
I don’t expect that I can present anything close to the full theory here or to get Stephen to agree on all what I claim, but perhaps we end up at an issue that’s basic and simple enough that I get my point trough on that. We have been moving towards such basics in the latest comments.
Thanks to Pekka and ATTP for a civilised exchange and reasonable moderation.
I know how emotional this stuff can get but we must get at the truth.
There are many out there who share my puzzlement at the radiative theories of atmospheric physics.
Stephen,
Solar energy at surface is not a force. It leads to changes in pressures and densities. Thus it leads to the circulation, but when we look at a parcel of gas, the forces that influence its motion are gravity, pressure forces and viscous forces related to the velocity gradients. For the basic consideration we can forget the viscous forces.
I have written somewhere up in this thread that the circulation is ultimately maintained by the pair of heating and cooling. Heating at higher temperature and cooling at lower temperature and higher altitude. This pair drives the general circulation, but that’s a consideration on the system level. When we look at the motion of a parcel of air, it’s gravity, pressure forces (and less importantly viscous forces).
Stephen,
Here’s the bit you’re missing though. If there are no radiatively active gases in the atmosphere, then the surface can radiate directly to space. If we assume a fixed albedo, then we know that it must radiate an average of 240Wm-2 (i.e., it would have an average surface temperature of 255 K). This means that the base of the atmosphere will be 255K.
Now consider that there are radiatively active gases in the atmosphere. This will prevent some of the energy from being radiated directly to space. Instead some of the energy will be radiated from within the atmosphere. Now, here’s the clincher. We still need the average amount of energy radiated to space to be 240 Wm-2. But, we know that – in the troposphere at least – the atmosphere must be cooler than the surface. Now, if we want the amount of energy radiated per square metre per second to be the same as a 255K blackbody – but to come from regions with different temperatures – then we know that some of those regions must be cooler than 255K and some must be warmer (the system will gain or lose energy until this is satisfied).
Given that the warmest will be on the surface, the surface will be warmer than 255K and – hey presto – we have the greenhouse effect. And that’s me done.
andthentheresphysics says: March 13, 2014 at 11:55 am
“Ben,
The point is that geothermal energy is largely irrelevant both for the overall greenhouse effect and for the recent warming.”
I can’t blame you for not immediately grasping the concept that we live on a planet that is extremely hot below our feet, and that all that heat has a profound influence on our past AND present climate. It took me a while.
But I surely hope that you are not saying that the eruption of some 140 million km^3 hot magma (~1300K) into our oceans (~1.400 million km^3 water) had no influence on the temperature of those oceans?
If so, then the only thing to understand is why it took those oceans 84 million years to cool down ~18K.
I’m assuming here that it is totally obvious that with deep ocean temperatures ~18K above present values earths climate was also much hotter, eg hardly any ice on Antarctica and forests growing up to 85 N and S.
And that the reason for our relatively cold climate at present (permanent icecaps on Antarctica and Greenland) is that the deep oceans have cooled down to ~273K at present.
And regrettably there is no sign that they have started to warm up again towards 5K (or more) above present values.
That would indicate the end of the severely damaging iceages earth experienced the last couple of million years.
Please indicate which of the above you feel is not correct.
Ben,
I’ve just done a quick calc. If you assume the oceans have an average temperature of 300K, then the total energy in the oceans is about 2.3 x 1027J. If the surface temperature was 300K, then it would lose this energy in about 500 years.
Sure, geothermal energy has played a role in our planet’s evolution (volcanic eruptions, tectonic activity,….) but overall, it is energetically irrelevant compared to the energy we receive from the Sun.
I appreciate that you may be well meaning, but I’ve spent the last 3 weeks talking with people who think that the mainstream ideas are wrong, and I’ve about had enough.
ATTP.
The bit you are missing is that even with no radiative gases the atmosphere would still absorb energy by conduction, retain it and have a convective circulation because of uneven surface heating.
However, that convective circulation would have to be faster in the absence of GHGs because more energy has to be returned to the surface to match radiation out with radiation in when there are no GHGs radiating from above the surface.
The energy absorbed and held by the atmosphere would still be kept out of the radiative exchange and would still require a surface temperature enhancement (greenhouse effect).
Now if you add radiative gases some of the radiation to space will come from the atmosphere and the convective circulation can then run slower.
The greenhouse effect is still present but caused by mass and the speed of the convective circulation adjusts for the presence of GHGs in order to keep the system stable.
Stephen,
I didn’t say this couldn’t happen, but in the absence of GHGs the surface still cannot warm above 255K and will still set the temperature at the base of the atmosphere.
255K is the surface temperature achieved if solar energy comes straight in and goes straight out.
If it does that there is nothing left over to maintain atmospheric height against gravitational collapse.
There is another block of energy being recycled constantly between surface and atmosphere in order to maintain atmospheric height.
That additional energy causes the surface temperature to rise above 255K.
That additional non radiative energy cannot be used within the radiative exchange without losing the atmosphere.
Stephen,
Under all conditions the surface energy balance is formed from the following components
+ heating by solar radiation
+ heating by DWIR from the atmosphere
– emission of IR
– heat loss by convection
– heat loss by evaporation
Only the two first are positive, the three others are always negative on the global level.
Including only the first and third we get the result that the temperature can be at most 255 K for the albedo of 0.3. The two last ones can only lower the temperature, because they are negative. The only way of getting the higher temperature we have now is to include the DWIR from atmosphere, i.e. from GHGs and due to the GHE.
What Pekka said!
In the recent discussion I have tried to imitate the practice of physics of expressing everything with formulas without the use of actual formulas. That should make it easier to pinpoint the sources of disagreement unless the other side gives completely up.
If Stephen disagrees on our claim, he must tell, where I have made the error. If he does that, we can dig deeper in the particular issue..
The previous similar point was the case of forces acting on a parcel of air.
Wilde and Wouters ought to look up the research on planetary atmospheres. Start with the term polytropic process and polytropic atmospheres and go from there.
To actually calculate the vertical distribution of Temperature/Pressure/Density requires the use of what are referred to as slab calculations to maintain conservation of mass and and energy.
For some atmospheres, the radiative properties emerge more strongly and for others the polytropic mechanisms are seen. These also change with altitude. The various regimes are identifiable as the lapse rate changes.
Pekka:
The error is that there is no net heat loss to space by pure convection because you must split the process of convection into its two components i.e. upward and downward.
Each is the mirror of the other so there is no net gain or net loss of energy from the system to space via pure convection.
The convective cycle is thermally neutral because (at equilibrium) it just switches surface KE into atmospheric PE and back again in equal amounts. None of the energy tied up in that process leaves the system for space except via radiation from GHGs or aerosols suspended in the air.
Water vapour complicates the situation because it can condense and the condensate radiates directly to space from a level above the surface but most if not all of the effect of that on the system is negated by the fact that the DALR on the descent is greater than the WALR on the ascent.
To the extent that any leakage to space does occur directly from the convective cycle you just get a small adjustment in the circulation and that leakage is then replaced by equal leakage from the surface radiative exchange back to the air by a small amount of conduction so exactly the same amount of energy stays in the convective exchange permanently unless one also changes mass, gravity or insolation.
It is the assumption of a net loss from convection which then requires a balancing radiative influence which the radiative theory deals with by adding DWIR as a net warming influence on the surface.
The trouble is that you then have an unbalanced scenario because you have both DWIR and adiabatic warming on descent both purporting to provide the same component of surface temperature i.e. the extent to which it rises above 255K.
The fact is you don’t need DWIR at all as a surface warming factor and it is the introduction of it that is the flaw in AGW theory.
Note too that adiabatic warming on descent doesn’t need to actively warm the surface, it only needs to preserve the status quo. It does that by slowing down radiative cooling in locations where solar input is weaker such as in shade or on the night side.
A good example of how well that works is the just past relatively mild West European winter when warm winds advecting across have given higher than average temperatures.
Thank you all for helping me to boil it down to this brief description which is implicit in my previous work but made more specific in this post.
i) + heating by solar radiation. Agreed.
ii) + heating by DWIR from the atmosphere. Not necessary as per my above post. Remove.
iii) – emission of IR. Agreed
iv) -heat loss by convection. Not necessary since cancelled by descent stage. Remove
v) heat loss by evaporation. Negated by the DALR being faster than the WALR. Remove.
So, having removed ii), iv) and v) we see perfect balance with heating by solar radiation equalling emission of IR exactly as observed.
The remaining surface temperature enhancement being due to atmospheric mass and the conduction / convection process which diverts a limited proportion of surface radiative energy permanently to the ongoing process of constantly moving molecules up and down within the atmosphere.
Stephen,
This really is tedious.
If the atmosphere does not absorb outgoing long-wavelength radiation, then surface can radiate directly to space and the amount of energy radiated by the surface (on average) cannot exceed that of a 255K blackbody (assuming a fixed albedo). None of the other processes that you mention can act to heat the surface. If they do, the surface will simply radiate this excess energy back into space and cool down until it is emitting as much energy per square metre per second as a 255K blackbody. The only way the surface temperature can exceed this is if there are radiatively active gases in the atmosphere that prevent the surface from radiating directly to space.
I’m not going to allow any more discussion of this as we really are disagreeing about very fundamental physics and if we can’t even agree on this, further discussion is largely pointless.
Stephen,
Having neglected all the other components you are left with only i) and iii). That means that the surface is 255 K. You cannot explain anything warmer, but the present temperature is higher.
Thus you must agree that you have failed.
How can the same unit of energy perform both conduction and radiation at the same time ?
It is an either / or scenario. not both.
An atmosphere containing energy that has been conducted to it requires a higher temperature at the surface to maintain it.
That higher temperature is not then available for radiation to space.
Stephen,
Wrong. If the surface temperature of the planet is T then it radiates σT4 J per square per second. That’s basic physics. You seem to be arguing that because some of the energy transport can be via conduction that the surface temperature will be higher. This is wrong. Conduction could cause it to be lower, but it cannot cause it to be higher, because if there are no radiatively active gases in the atmosphere, then the surface will radiate σT4 J per second per square metre. If this exceeds the amount of energy it receives per square metre per second, it will cool.
I think you also think that the atmosphere can get energy from the surface via conduction and then return it to the surface via conduction. Again, this may be possible, but if there are no radiatively active gases in the atmosphere, then the surface temperature cannot exceed (on average) 255K. Why? Because if the atmosphere gets this energy from the surface via conduction and then returns it to the surface via conduction, then it is self-cancelling.
Stephen,
Don’t try to confuse the issue by discussing something that does not affect the surface. You have no explanation for a warmer surface than 255 K. That’s where you fail totally, and everything that you have concluded is shown to be false.
I am reminded of the Monty Hall problem. When you first pick a door the probability that it has the goat behind it is one third (I am assuming that getting a goat counts as winning the prize as clearly having a goat is far preferable to having a car – I realise others may disagree) – whatever happens subsequent to this cannot retrospectively change this probability, therefore the sum of the probabilities of the other choices must be two thirds. No matter how convoluted the arguments get to teh contrary this basic fact cannot change.
Am I wrong to be so reminded?
andthentheresphysics says: March 13, 2014 at 9:12 pm
It’s obvious you haven’t looked at the oceans in any detail.
As long as you can’t explain why the DEEP oceans were ~18K warmer than today 84 million years ago, and can’t explain why they cooled down so slowly, you’re missing a major mechanism in our climate.
You might find this text a good starting point to expand your knowledge:
http://www.21stcenturysciencetech.com/articles/ocean.html
It’s written by an oceanographer.
It’s like a current account and a deposit account.
You decide to hold £255 in a current account. Income £240 and expenditure £240 and it stays at £255.
From time to time the income and expenditure vary a bit so balancing funds come from a deposit account containing £33 as necessary so that the current account stays at £255 but the balance in the deposit account fluctuates a bit.
In the Earth system the atmosphere with its stored energy content is the deposit account and the rate of convective energy transfer is the necessary variable.
If asked what your total assets are then it is 255 plus 33 which gives 288 but at any given moment you only have 255 in the current account.
The current account represents the portion of surface temperature attributable solely to the radiation budget at 255K with 240 in and 240 out.
The deposit account represents the energy stored in the atmosphere at 33K
The total asset value is the surface temperature at 288K
That is how it really works.
You guys have been backed into a corner in having to deny that atmospheric mass has any effect on surface temperature.
Good luck with that.
Stephen,
I repeat: Don’t confuse the issue by presenting empty talk that explains nothing about the surface temperature.
You have not introduced anything that can warm the surface to a higher temperature than 255 K.
The fact remains that GHE is the only explanation anyone has been able to present for that, all others have failed totally.
Stephen,
No, it’s not. You forgot that it’s a special type of account in which the interest rate is negative unless certain other conditions have been satisfied. Since your ideas don’t satisfy them, you lose the £33 and you’re left with an account with £240. Anyway, I really have had enough now, so can we stop going around in circles. You (and Ben) are free to believe whatever you like.
OPatrick,
Goats are great, and remind me of the advice to anyone considering starting a family.
Take a goat to the supermarket while you do your weekly shop. You can try this both with and without tethering the goat to your trolley. If you’re considering having more than one child, take more than one goat. See if you reconsider your choice afterwards.
This of course has nothing to do with radiative heat transfer, but then neither do Ben and Stephen’s comments, so I claim it as on topic regardless. Plus it’s Friday afternoon.
ATTP: He’s done what he set out to do in the first place. He’s pretended to be making some sort of technical argument, when he hasn’t. He’s used that to sully this blog. He’s trying to earn click throughs to his web site, which is full of bunk.
His babble is better than Bob Armstrong’s garbage, but in a very very similar vain.
He will never ever ever answer any technical questions on topic, because he doesn’t understand them… just like Bob Armstrong. In this case I’m reasonably certain Bob was using an auto jargon generator.
http://www.desmogblog.com/mann-handled-decade-ago-conservatives-attacked-scientist-and-created-leader
Conduction and convection are slower than radiation and so warm the system. Expressing it all in terms of fast radiative transfer misses out the reason why the surface can heat above 255K from more mass alone.
It also misses out that convection acts as a regulator between conduction and radiation.
Expressing it all in terms of almost immediate radiative transfers misses out the fact that the rate of convection can vary in order to achieve its regulatory function.
Stephen
Yes, but goats
Stephen Wilde: Still no science, math or formulas. Good luck with that.
verytallguy: That reminds me of a joke…
I was talking to a fisherman in a small village;
“See that boat over there? I built it. Do they call me the ‘boat builder’? No.”
“See that house over there? I built it. Do they call me the ‘house builder’? No.”
“But you f*ck one goat…” *shakes his head*
Now will there be bleating?
😉
Ben Wouters
Do you happen to have a reference for this?
Ben
The late Robert Stevenson’s 14-year old article is alarmingly confused. He doesn’t understand that the oceans are not directly heated by DLR, but rather cool less efficiently as tropospheric temperature rises. Nor does he seem to have heard of Ekman pumping, which is arguably the major mechanism by which warm surface water is mixed down into the intermediate layer. These two errors alone completely invalidate his argument.
Stephen,
Hoe does the surface get heated “from mass alone”. What’s the heat flux that comes to the surface from “mass alone”.
You have not told of any other heat flux to the surface than solar radiation. As long as there’s nothing that transfers heat from the atmosphere to the surface, the surface cannot get warmer than without an atmosphere.
You failed again.
Ben,
I’ll add one thing about geothermal energy. Clearly it enters the climate system and – to be in equilibrium – the system must lose as much energy as it gains, hence the system must radiate an amount of energy per square metre per second that matches the amount it gets from geothermal plus solar. The geothermal, however, is so small as to be largely negligible. It will, I imagine, play a role in heating the lower oceans. However, it’s always been there and will – on average – decrease with time (the source is mainly from our formation, differentiation, and from radioactive decay). So, yes, it plays a role in heating the climate system, but is negligible compared to the energy from the Sun and can’t have changed in the last century to in any way explain our recent warming.
@Stephen Wilde:
ii) + heating by DWIR from the atmosphere. Not necessary as per my above post. Remove.
======
The problem here is that you can not dismiss something as nonexistent when it has been observed/measured.
pbjamm
I didn’t dismiss DWIR as non existent it. I pointed out why it doesn’t need to have any net thermal effect at the surface because the same job is being done by adiabatic warming on descent. What probably happens is that extra DWIR causes the molecule doing the emitting to rise higher to a colder location which negates any thermal effect on the surface. That would be part of the negative circulation response that I referred to earlier.
Pekka, you know I was referring to irradiated mass held within a gravity field.
Anyway, the atmosphere here is getting hostile and the points I make are not being addressed so no point trying further.
However, I have acquired some new insights into the many ways that those who follow radiative physics fail to appreciate the implications of broader physical principles.
Stephen you have yet to make a point. No business would listen to, or act on your behavior, as it would be insensible to do so.
The correct way to make a claim is;
A) state your concern, be very specific, be very precise, (you waffle all over the place),
B) back it up with citations to the correct material (you refuse),
C) show the math and demonstrate the significance of the concern (you got nadda).
An engineer I really respect once said, “Show me the math, and let the data lead the way.” Doing anything else is a waste of time. And that is what you are doing.
But lets end this on a positive note. You have steadfastly refused to provide any substantiation for your concerns, and ATTP has numerically shown your concerns to be irrelevant.
Case closed.
Again, a measurable effect has no effect is what you are claiming.
“What probably happens…” – This is pure speculation. As AnOilMan pointed out hand waving is not sufficient. Give some numbers as others here have been polite enough to give you.
“Anyway, the atmosphere here is getting hostile and the points I make are not being addressed so no point trying further.” – The atmosphere here is far from hostile unless you count being allowed to have your say and being asked for supporting data as being hostile. Your ‘points’ have been addressed repeatedly and your only response has been to ignore ATTP and Pekka and state your unsupported opinion again.
Unless you provide some math, numbers, measurements, etc then the only thing you are right about is that there is no further point to this discussion.
Stephen,
You write “I was referring to irradiated mass held within a gravity field”.
So what. How does that warm the surface?
To warm the surface a heat flux must come to the surface. What’s that heat flux?
BBD,
bloody typical of you that is. Always butting in to other’s conversations…
vtg, is ‘goats’ a valid play in climateball? Perhaps it can be used to counter the otters. Willard would know.
VTG
I have the manners of a goat, I know…
😉
OPatrick,
rules are not required, nor necessary to play climateball
And beware of what’s under the bridge, trip trap trip trap…
BBD
Knock! Knock!
Who’s there?
Goat.
Goat who?
Goat to the door to see who’s knocking!
The key thing is that if initial conductive warming of air at the surface is being used up during convective ascent by doing work against gravity then you do need a higher surface temperature to create more convection as per AGW theory.
That is why the radiative theory needed to introduce a surface warming effect from DWIR in order to counter the apparent surface cooling caused by convection. Pekka confirmed that he sees convection as cooling the surface.
If one refers to the adiabatic process properly one can see that the initial conductive energy is not lost during uplift. It simply gets converted to PE and then ,crucially, it comes back to KE on the descent and so when the parcel gets back to the surface that initially conducted energy is still there.
That is why the surface is warmer than S-B predicts, that is why the surface then radiates to space the same as it receives.
The adiabatic energy exchange is net zero because cooling on the ascent is exactly the same as warming on the descent.
It has been said by Willis Eschenbach, ATTP and others that because the energy exchange between surface and air is net zero you can ignore it but you can’t because the energy within that exchange is still leaving energy at the surface which must be added to new energy arriving from the sun so the surface MUST be warmer than S-B.
The result is a surface temperature enhancement AND radiation out equalling radiation in.
Because of the peculiar, counterintuitive nature of the adiabatic process you don’t need DWIR to balance the energy budget.
As per one of Pekka’s comments radiative theory convection as a net cooling effect for the surface but that is wrong. Adiabatic convection is thermally neutral at the surface.
That is the error in AGW theory and it is rife even in the minds of sceptics because knowledge of the true nature of the adiabatic cycle seems to have been lost by nearly everyone since the education authorities substituted DWIR in place of the thermal effect of the adiabatic descent phase.
Stephen,
Here’s the bit you keep ignoring. I have one simple point for you to consider and I’d like your next response to address this and only this.
If there are no radiatively active gases in the atmosphere, then the surface can radiate directly to space. Agreed? If the surface temperature is T, it radiates σT4 J per square metre per second. Agreed? What you’re arguing is that it loses some energy to the atmosphere through conduction and some to space through radiation. Agreed? It then regains energy from the atmosphere through conduction. Agreed?
So, we can write the following
Surface loses energy via radiation directly to space – Foutrad
Surface gains energy via radiation from Sun – Finrad
Surface loses energy to atmosphere via conduction – Foutcond
Surface gains energy from atmosphere via conductin – Finrad
However, if Ts > 255K, the Foutrad > Finrad.
If the atmosphere contains no radiatively active gases then Finrad <= Foutrad.
Now you have a problem. The surface is losing more energy than its gaining and – unless my phyiscs training was very poor – it will cool and must cool to Ts <= 255K.
Having established that adiabatic convection is thermally neutral as regards the surface we can see that the heat acquired by the atmosphere via conduction from the surface never leaves the surface whilst new solar energy continues to arrive and depart.
That is how the mass of an atmosphere raises the surface temperature above S-B.
The next question is as to why even more energy arriving at the surface, such as by way of DWIR from radiative gases affects the convective circulation but not surface temperature.
The fact is that the amount of conductive energy that the air at the surface can hold on to is determined by the weight of the atmosphere above the surface.
Convection from a solid surface is just the same in principle as vaporisation from the surface of boiling water.
The maximum temperature achievable in both cases is pressure related (the weight of the atmosphere). 100C at surface pressure for boiling water and 33C above S-B at surface pressure for a solid surface.
So in both cases more energy coming from any source other than more mass, gravity or insolation results in faster processing of energy throughput and not a rise in surface temperature.
QED.
“The surface is losing more energy than its gaining and – unless my phyiscs training was very poor – it will cool and must cool to Ts <= 255K."
The energy engaged in the conductive / convective process whilst raising surface temperature above 255 (it must because it is in addition to solar incoming and departing) just sits there and holds the atmosphere off the ground against gravity by maintaining the adiabatic part of the convective overturning.
We can see from observations that radiative energy out equals radiative energy in so the system simply cannot be utilising that conduction induced surface thermal enhancement for radiation out.
I know you are all saying that a surface temperature of 288K MUST radiate out more to space than a surface at 255K but we can all see that it simply does not do so.
What is happening is that at the surface at the molecular level there is a haze of kinetic energy which at that point is neither radiative nor conductive energy.
Some of the surface kinetic energy goes to radiation to space but the rest is diverted to conductive energy which then just sits there and holds up the atmosphere.
It is the presence of mass interfering with the free flow of solar radiation through the Earth system that diverts a portion of the radiative throughput to conduction and convection.
Since conduction and convection is slower than radiation the system warms above the S-B level.
Stephen,
Okay, enough. Now you really are not making sense and I really have had enough. Given that this discussion has remained reasonably pleasant, let’s just leave it there.
Stephen,
Your fail so totally on conservation of energy that it’s really unbelievable that you don’t see that.
The surface is heated by the sun with an average power of about 160 W/m^2 only. Taking into account the surface emissivity, a surface with temperature as low as 235 K radiates as much energy. To have a higher temperature the surface must be heated by other energy fluxes. To reach the present temperature those energy fluxes must net to more than the solar heating. All energy losses from convection and evaporation must be added to that.
You have not accepted a single energy flux that can explain this huge difference between heating and cooling (cooling more than twice the heating with energy fluxes you admit to exist). You must know that the only mechanism that can remove the discrepancy is DWIR from GHGs with some help from DWIR from clouds.
Nothing in your gibberish can explain any part of that imbalance. Words do not warm the surface, an energy flux is needed for that.
You have failed again totally.
No breach of conservation of energy.
Radiation in from sun matched by radiation out to space.
Conductive energy raised up and brought down by convection exactly equal.
A slab of conducted energy sitting at the surface and raising surface temperature without going anywhere.
Bye.
Stephen
The surface alone must conserve energy. Your surface does not. You cannot hide that by discussing the atmosphere.
You failed again totally.
The surface does conserve energy, none has been gained or destroyed.
Its just like the backing up of water in a partially blocked drain.
Its all about energy flows after all.
Conduction and convection being slower than radiation the flow of energy backs up in that slab of conductive energy at the surface which then uses its ‘surplus’ energy to raise the gases of the atmosphere off the ground by working against gravity.
Perfect balance all around but a time delay in energy transmission.
QED
Stephen,
When the surface loses more energy than it reserves, it cools. With the present fluxes of solar energy and radiation from surface it cools to 235 K or less. Otherwise it does not conserve energy.
You don’t understand, what energy conservation means.
Correction: .. than it receives ..
@Stephen Wilde
Again, hand-waving and not a single calculation in all of that word salad.
How can you dismiss the known, measurable, observable phenomenon in your ‘theory’?
Pekka,
The surface is in radiative balance with space and conductive balance with the atmosphere.
In pure radiative terms you are right that it is out of balance so radiative theory must have DWIR to achieve radiative balance.
So what do you propose about the conductive balance between surface and atmosphere ?
You have left it out completely.
The higher temperature at the surface (above 255) comes from the conductive balance and the radiative fluxes within the atmosphere that you have referred to are a mere consequence of the temperature enhancement arising from the non radiative conductive balance.
The vertical thermal profile of the atmosphere has itself been created by the conductive balance.
There is no vertical thermal profile for energy radiating straight in and straight out. It is the conductive balance that gives us the observed thermal set-up in the atmosphere.
The radiative fluxes within the atmosphere do not cause any thermal enhancement in themselves. They must all net out to zero otherwise the balance between radiation and conduction is lost whereupon convection changes to restore balance.
Sorry, ATTP, may I continue if people keep making new points ?
Again, where are your calculations? You need to show your work. This is not good enough to pass High School Trig let alone to overturn 100 years of science.
Stephen,
Calculated over the whole surface the conduction from the atmosphere to the surface is always negligible. It may have some effect locally under exceptional conditions, otherwise it’s really, really small.
Furthermore that would require that the atmosphere is warmer than the surface. Thus the normal situation is that what conduction exists it adds to the cooling of the surface, not to the warming.
The atmosphere does not need to actively conduct heat to the surface. It only needs to restrain radiative cooling and thereby offset the energy that conducts from surface to air.
Consider this past warmish winter in western Europe when warm winds have prevailed and prevented radiative cooling of the land.
There is clearly a conductive balance between surface and air which keeps the air aloft and it is separate from the radiative balance.
The issue is whether the energy at the surface which keeps the atmosphere aloft is provided by DWIR or by adiabatic warming on descent.
Since radiative theory treats convection as a net cooling influence and thereby ignores adiabaic warming on descent which renders the adiabatic portion of convection thermally neutral I think there has been an error.
Better stop there.
“I think there has been an error” – I agree but I dont think we agree on where.
If you think there is an error then show where. With numbers rather than speculation because as of now you have provided nothing but guesswork and feelings.
Stephen,
Atmosphere cannot restrain radiative cooling in any other way than by radiating back, i.e. by back-radiation from GHGs. That’s the only way. Convection or conduction cannot contribute to that. They make the surface only still colder.
Even I understand this, so it cannot be very challenging or advanced.
Pekka said:
“Atmosphere cannot restrain radiative cooling in any other way than by radiating back, i.e. by back-radiation from GHGs. That’s the only way. Convection or conduction cannot contribute to that. They make the surface only still colder.”
The atmosphere prevents radiative cooling to space.
The hallmark of an atmosphere is conduction and convection. No atmosphere, no conduction and convection.
All atmospheres cause surface warming the scale of which is related to their mass.
Therefore conduction and convection always cause surface warming.
Write that out 100 times.
The reason is that any kinetic energy taken into the adiabatic convective exchange from the surface is returned to the surface on descent and has to be added to ongoing solar energy coming in.
The radiative fluxes that you then bleat on about arise as a result of and are not a cause of the extra surface warming and a result (not a cause) of the thermal gradient set up by conduction and convection under the influence of mass, gravity, insolation and the Gas Laws.
Radiative theory is just plain wrong due to incompleteness.
DWIR is sticking plaster to make it look plausible.
On your theory no GHGs, no DWIR and no atmosphere because nothing could then create the energy needed at the surface for conduction and convection to occur. There would be no initial atmospheric lift off without GHGs which is plain nonsense.
An atmosphere of zero radiative capability must rise off the surface anyway due to input of solar energy with consequent conduction and convection.
Radiative theory fails on basic logic.
Stephen,
Yes, that’s called the greenhouse effect.
Other than that, you’re wrong and you’re being condescending. Enough!
Some citations here:
http://hockeyschtick.blogspot.co.uk/2014/02/why-earths-climate-is-self-regulating.html?showComment=1393612872842#c6849087148825741864
Stephen,
I’ve spent about two weeks discussing this with Hockey Schtick on Twitter. He/she is also wrong.
Stephen,
For the umpteeth time. What happens in the atmosphere cannot warm the surface, if the heat cannot get to the surface.
You have accepted only one mechanism that can bring energy to the surface: the solar radiation.
You have accepted that the surface emits IR according to the Stefan-Boltzmann law.
From these two factors the surface gets cold (about 235 K based on the solar radiation that reaches the surface). You have not presented a single argument that would change that. The gibberish about what goes on in the atmosphere would not change that even, if it were a correct description of those processes (it’s not).
Everything that you have written about the atmosphere either maintains this temperature or cools the surface even more. Nothing makes it warmer as long as you don’t accept back-radiation.
Is this really not simple enough to you? It’s easy for most who learn physics at high school. Are you not that far?
“You have not presented a single argument that would change that.”
i) The adiabatic process is two way and so cannot cool the surface.
ii) Conduction and convection are slower than radiation and so heat must build up at the surface depending on the amount of conduction and convection.
Stephen,
If the atmosphere has no radiatively active gases then it simply radiates. That’s the point! But I really don’t want to keep going over this so can we please just stop this.
There could then be no atmosphere in the first place.
But I agree to stop because we are going round in circles.
Stephen,
You tell that some things don’t affect the surface (or if they affect they cool it even more). Thus they don’t change the conclusion that the temperature is at most 235 K without backradiation.
Stephen, when we refer to citations, we refer to scientific sources and peer reviewed sources at that. Not random bloggers on the internet. I want to see an article refereed to in Nature Climate Change magazine to back what you say.
Apart from refusing to back up anything you say with facts, figures and math, you’re really just walking around saying Hokus Pokus.
It takes more than an armchair to do technical work. I realize that you feel that you have it right, but you haven’t got anything at all.
No math, no measurements, no dice.
Extraordinary claims require extraordinary proof and you have yet to even gotten to the ordinary kind yet!
Furthermore I want to say that I believe your objective here is to intentionally waste everyone’s time and pretend to be offering scientific discussions. You are not doing that.
You are intentionally trying to make believe there is some sort of controversy with GHG emissions when there is none. More and more energy is being absorbed and stored in the atmosphere because of green house gasses. (Stephen, I built and sold working equipment that measures energy absorption by GHGs.)
You might try reading the first ‘source’ you originally linked to in its entirely before producing supercilious conjecture, and laser focused links. What you’ve provided stinks of selective and limited reasoning.
Since you never read that material before, I’ll provide your link back to you;
http://apollo.lsc.vsc.edu/classes/met130/notes/chapter2/index.html
Its never too late to read the section on GHGs for the first time. I recommend you do that before you show up and argue with the experts.
The hockeyshtick? On a science blog? Without irony? Quelle joie.
BBD says: March 14, 2014 at 4:40 pm
As long as you can’t explain why the DEEP oceans were ~18K warmer than today 84 million years ago
Do you happen to have a reference for this?
http://tallbloke.wordpress.com/2014/03/03/ben-wouters-influence-of-geothermal-heat-on-past-and-present-climate/
andthentheresphysics says: March 14, 2014 at 4:54 pm
“can’t have changed in the last century to in any way explain our recent warming.”
That’s what we call kicking in an open door in Holland.
I show warming and cooling rates of 1K every 2 – 5 million years.
You also could have noticed I’m not talking about the geothermal FLUX, but about geothermal HEAT.
Our oceans have a temperature deep down there. Warming them from above is not going to work.
From below, no problem.
Water heated at the bottom has to rise to the surface to cool towards the atmosphere and space.
You may have noticed the warm surface layer preventing this for almost the entire surface of our oceans. With surface ice no cooling either.
The 100 mW/m^2 can leave the deep oceans at perhaps only 1% of the entire surface.
So at that 1% area already 10 W/m^2 has to escape to space, otherwise the deep oceans warm.
Now lets discuss how much ocean bottom we have for every m^2 surface, how much hot vents, magma erupting in spreading zones etc. etc add to the deep oceans temperature.
Apparently enough to just about balance the cooling at high latitudes.
Add some large magma eruptions and they warm (considerably).
The 18K 84 million years ago is just the result of one of the seismic active periods in earths history.
I don’t think that a reference to a post you wrote on a blog whose owner believes relativity and the rest of modern physics is wrong, and that “the ether” is a reality, is exactly what BBD was looking for when he asked for a reference, Ben.
Ben Wouters
Worthington et al. (2006) is not sufficient.
Might I suggest that you look a little closer at OAE 3. It does *not* appear to have been a global event. So sweeping statements about deep ocean SST ~84Ma are risky.
Given that the other “reference” you provided was complete and utter nonsense, I suspect you have exceeded the limits of your reading.
Eh.
“deep ocean heat content” of course.
The proper reference would have been this paper:
http://onlinelibrary.wiley.com/doi/10.1029/2011JC007255/abstract
“Warming them from above is not going to work.” Oh, another physics denier. How tedious.
Even if the reconstructed OHC is correct, what about the profound cooling ~84Ma to ~70Ma and then the warming leading up to the Eocene Climatic Optimum ~50Ma?
A more useful way of looking at the slow, overall cooling characterising the Cenozoic would be to consider the various forcing changes.
Very roughly, across the Cenozoic, solar forcing has increased by 1W/m^2 as a consequence of stellar evolution, but atmospheric CO2 fell from ~1000ppm in the early Cenozoic to ~170ppm during Pleistocene glacials. This represents a decrease in forcing on the order of 10W/m^2.
There is a plausible physical mechanism that explains the generalised cooling trend across the Cenozoic.
AndThen has given me the keys to the lolly cupboard – he’s a brave soul – so anyone trying to deny physics and/or make comments without credible references has been put on moderation.
“With surface ice no cooling either.”
How will I cool my margarita’s for summer?
AnOilMan says: (March 15, 2014 at 11:22 pm)
“You are intentionally trying to make believe there is some sort of controversy with GHG emissions when there is none. More and more energy is being absorbed and stored in the atmosphere because of green house gasses.”
Just a couple of points relating to the above statement. It sounds as if you think energy is being stored in the atmosphere. I doubt if you meant that as it is clear that the heat capacity of the oceans is several hundred times greater than that of the atmosphere.
Every scientist I have ever met believes that celestial bodies with atmospheres have higher surface temperatures than they would have if the atmosphere was absent. The warming due to the atmosphere is often called the Greenhouse Effect. As you say, there is no controversy.
Controversy may arise when people attribute the GHE to trace gases (Arrhenius, 1896) while others attribute it to the main bulk of the atmosphere (Sagan, 1967).
Sagan correctly predicted the surface temperature of Venus even though the atmospheric composition of the planet was not known in 1967. As you will see from the attached correction to his papers, Sagan realized that Nitrogen and CO2 have similar specific heats at constant pressure so it makes little difference whether Venus has an atmosphere that is 100% Nitrogen or 100% CO2. The results of his calculations are shown here, if you click on the “Send PDF” button:
http://adsabs.harvard.edu/doi/10.1086/149625
Sagan quantified the GHE on Venus using Newtonian mechanics/gravity and thermodynamics. while ignoring radiative heat transfer. Sagan got the right answer while Hansen still can’t provide a mathematical analysis to back up his scary fairy tales.
gallopingcamel,
I don’t think you understand Sagan’s paper or the greenhouse effect.
gallopingcamel,
Maybe I should direct you to this sentence in my post
Hmmm, that seems to be roughly what Sagan was suggesting in his 1967 paper. Was he really ignoring radiative heat transfer? Not really. What he was doing was illustrating that given a temperature at some altitude in the atmosphere and a lapse rate, one could estimate the surface temperature.
We meet here again the confusion from misinterpreting the significance of the derivation of the adiabatic lapse rate.
When it’s known that the adiabatic lapse rate applies, it can trivially used to calculate the temperature difference between two altitudes like the Venus atmosphere at a high altitude and at surface. The value of the adiabatic lapse rate is, indeed, almost independent of GHG concentrations.
I emphasized the words when it’s known, because this is the most important question. We know that the troposphere has an lapse rate related to the adiabatic one (although not exactly that), while the stratosphere has nothing like that. The real physical question is, where does the adiabatic lapse rate determine the temperature gradient, and where not. When it’s concluded that Venus has such a lapse rate from surface to some specified altitude, that knowledge can be applied, but the conclusion must be justified.
The adiabatic lapse rate controls largely the real lapse rate, when atmosphere is effectively mixed in vertical direction by convective air flows. Maintaining such effective mixing requires a driving force, and it turns out that GHGs and GHE are essential for the existence of such a driving force.
gallopingcamel, it is clear you have absolutely no idea what Sagan did and what the greenhouse effect is. The greenhouse effect Venus is NOT the temperature difference between those of the clouds and the surface of Venus. This is the only thing that Sagan calculated (as can be read in the original paper).
You also appear not to know the papers Sagan wrote before and after his 1968 paper on, oh the horror!, the greenhouse effect on Venus, using that to explain (oh, more horror!) the high temperature of Venus. Take this paper:
Click to access jresv69Dn12p1583_A1b.pdf
(it’s short enough and a free pdf for you to read – which does not equal understand, I do realize that)
More elaborate papers:
http://www.sciencedirect.com/science/article/pii/001910356990030X
http://www.sciencedirect.com/science/article/pii/0019103562900155
And one early one:
here
But there are several more.
Gallopingcamel has a website, easily found by google. If you rest your cursor under the “education” tab, then click on the “education” link that pops up, you get …
“Not Found”.
[Mod: Last line snipped, disrespectful]
dhogaza,
I just checked that link and it worked for me:
http://www.gallopingcamel.info/education.html
I get a file not found error too, gallopingcamel. Not for the link you provided in the comment above, but when you select Education from the Education menu, it links to a different URL – http://www.gallopingcamel.info/Education.html (NB: Education is capitalised in this one)
[Mod: This comment has been removed by the moderator. If you want to continue with this argument, GallopingCamel, you will need to provide evidence in the form of links to other work. See the comments policy]
We are all the privileged recipients of more-or-less decent educations. It’s what we do with them that matters.
“anyone trying to deny physics and/or make comments without credible references has been put on moderation”
Policy change?
Policy change?
No, the moderation and commenting policy is still the same. I’m just not always consistent when implementing it – not on purpose though – and it’s easier when you’ve got time to think about a comment without worrying that lots of other commenters are going to respond to it especially if it’s likely to be moderated.
It was fun while it lasted! I was hoping that this blog would live up to its name given that I am a retired physicist, who still teaches quantum electro-optics on a part time basis.
Please accept the Mimophant award, first bestowed on Skeptical Science a few years ago:
http://www.gallopingcamel.info/docs/DeletedCamel.doc
gallopingcamel,
My first award. Wow!
And I’m a non-retired physicist who still teaches a number of different types of physics courses. I’m just not really interested in debating the existence of the greenhouse effect. It exists and is really the only viable way to explain how the average surface temperature is higher than one would expect based only on its albedo and its distance from the Sun.
I am puzzled that you somehow misunderstood my earlier comments (the ones that you have not snipped). The Greenhouse Effect is real and much larger than the 33 Kelvin claimed by respectable climate scientists such as Scott Denning.
The question I am trying to debate is whether the GHE is caused by trace gases (Arrhenius, 1896) or the main bulk of the atmosphere (Sagan, 1967).
gallopingcamel,
I really don’t want to start another lengthy debate about this. Sagan is not arguing that the GHE is a consequence of the main bulk of the atmosphere. What he is suggesting is entirely consistent with Arrhenius.
I’ll try to explain this one more time. I’ll try to do it methodically.
Point 1 : Given our albedo and our distance from the Sun, the Earth needs to radiate the same amount of energy per square metre per second as a 255K blackbody. This is basic physics and we shouldn’t really dispute this. Also, it has to be radiation as we can’t conduct or convect energy into space.
Point 2: To first order, all that the GHGs do is prevent the surface from radiating directly to space. If they did not do this, the surface would radiate the same amount of energy per second per square metre as a 255K blackbody and the average surface temperature would then be 255K.
Point 3: Because of the GHGs, some of the energy is radiated from within the atmosphere and not directly from the ground.
Point 4 : Because of the bulk properties of the atmosphere, the troposphere typically has a temperature gradient that is – to a first approximation – set by the lapse rate. This means that the temperature in the atmosphere (in the troposphere at least) decreases with altitude.
Point 5 : If the energy radiated to space comes from different regions (some from the surface and some from within the atmosphere) and these regions have different temperatures, then – in order for the total to match that of a 255 K blackbody – some of these regions must be cooler than 255 K and some must be warmer than 255 K.
Point 6 : Since the surface, due to the lapse rate, is typically warmer than the atmosphere, it’s temperature will – on average – have to exceed 255K so that the total radiated per square metre per second matches that of a 255K blackbody.
Summary : The greenhouse gases are simply acting to prevent the surface from radiating all its energy directly to space. Some of the energy that is radiated to space comes from within the atmosphere. Given that the properties of the atmosphere are such that – in the region of interest – it is cooler than the surface, the surface will warm to above its non-greenhouse temperature until the energy radiated to space matches that received.
That’s the greenhouse effect. All that Sagan was doing was recognising that if one could estimate the lapse rate and measure the temperature at some altitude in an atmosphere, one could then estimate the surface temperature. He wasn’t suggested that the enhanced surface temperature was a consequence of the bulk of the atmosphere and not because of GHGs.
As I said, I don’t want to continue debating this. There are other ways to explain this. I’ve written a number of recent posts. I’ve written many comments. Pekka has done the same, as have others. Feel free to read them and give it some thought. There are other sites that also explain the GHE. If you disagree and think that somehow the warming is a consequence only of the bulk properties of the atmosphere, then that’s your right. I, however, don’t want to spend any more of my time on this topic.
@gallopingcamel
If you are saying that the GHE is not caused by GHGs but instead by Nitrogen and Oxygen then you need to supply us with a physical mechanism to explain how that works. There is one for the GHGs that is simple and makes sense. If you disagree with that explanation then yes, you kind of are denying the Green House Effect.
[This comment has been removed by the moderator]
Gallopingcamel,
Being a physicist does clearly not guarantee understanding of physics of the atmosphere. It’s not part of the standard physics courses (or at least was not years ago), which may explain in part the lack of understanding. Maintaining the belief that GHGs are not the reason for the difference between the Earth surface temperature and the effective radiative temperature seems, however, every time as incredible as a view of a physicist. Either thermodynamics is a not part of the present knowledge of physics or an active attempt is needed to avoid learning the facts.
The (too) many comments to Stephen by myself and others presented a very direct and very simple proof of the absolute need of GHGs in explaining the present surface temperature. He good not propose any hole in those proofs, but tried time after time to divert the argument away from the clear logic. You are free to try to do better, but please, concentrate on factors that affect directly the surface temperature. The temperature is, after all, determined solely by such factors. As a physicist you should be able to see, what affects surface temperature and what not.
Concerning my comments you may start by this one:
https://andthentheresphysics.wordpress.com/2014/03/05/effective-emission-height/#comment-17100
Regardless of whether gallopingcamel has been taught the GHE or not, his supposed educational background should be sufficient to understand what Sagan wrote. Anyone with a proper sciences educational background would have no problem understanding that Sagan did not ascribe the GHE to “the bulk of the atmosphere”, as they would note that Sagan did not describe the GHE at all in the paper gallopingcamel (indirectly) referred to. They would also have no problem checking my links, and find that Sagan actually *did* assign the GHE to greenhouse gases like CO2; both before and after that 1967/1968 paper.
The question thus becomes, why is gallopingcamel unable to do what any properly educated person would be able to do? Is it incompetence? Is it unwillingness to learn what would contradict a potential core belief? Or is it just trolling?
Actually it’s not possible to discuss GHE on Venus without the bulk of atmosphere, because the Venus atmosphere is just CO2 with a few percent N2 and other gases (GHGs are the bulk). Therefore that point tells nothing on the role of GHGs in the Earth atmosphere.
The paper of Sagan does also contain explicit statements on the importance of verifying that the temperature profile is controlled by the atmospheric lapse rate. That’s not a trivial issue, but has to be justified by totally different arguments than the calculation of the value of the adiabatic lapse rate.
I would, however, prefer leaving the discussion of the lapse rate aside, when the issue is, whether the surface temperature can be explained without GHGs. It cannot, whatever the lapse rate is. Thus the simplest proofs of that fact don’t mention the lapse rate at all, and I have tried to push this simplest argument.
The lapse rate is needed, when the warming influence of GHGs is estimated quantitatively, but not for the qualitative observation that GHGs warm the surface, and that without GHGs the surface is cold.
Pekka,
Yes, I agree.
Our host makes several mentions of 255 Kelvin, the supposed temperature at the earth’s surface, “sans atmosphere”. Scott Denning, Monfort Professor of Climate Science, Colorado State University explains:
Denning’s calculation is exactly correct for a body at uniform temperature. That would imply that the earth is a thermal superconductor and we know that is not so. Is there anyone here who is big enough to admit that I am right on this important point?
Your reward for failing this simple litmus test is that I will leave you in peace.
gallopingcamel,
You’ll note that I fairly specifically said “the same energy per square metre per second as a 255 K blackbody”. That statement is correct and does not imply anything with regards to the temperature being uniform. I also said it specifically so as to avoid precisely what you are trying to imply.
Please do.
gallopingcamel,
Also Deming is incorrect. The temperature that the Earth would be observed to have (if computed based on its outgoing flux) is 255K, not 288K. The measured average surface temperature, however, is 288K.
As Stephan in many of his posts, Gallopingcamel presents here a point that makes the case even worse for his basic argument. An average fourth power of temperature equal to 255^4 means that the average temperature is less than 255, if it’s not constant.
Galloping [Mod: sorry OilMan, this bit can’t stay] all gone?
I should probably have phrased my comment above differently. I don’t know if what Deming was trying to present in his figure is wrong or not. Camel’s interpretation of it appears to be though.
Looking at the left figure, spectrum, if the blocked emission area falls towards the zero axis then doesn’t the emitting areas rise to compensate, so there is no change in the energy emitted?
Kelvin,
If I understand what you’re suggesting then that is essentially how the greenhouse effect works. If you block some energy in one part of the spectrum, in order for energy balance to be retained, it must increase somewhere else. In the case of the Earth this happens through a rise in surface temperatures. So, yes, overall the amount of energy we emit into space will – on average – match the amount of energy we receive. Given the presence of GHGs in the atmosphere, this requires that the surface temperature is higher than it would be in their absence.
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Ken, this is a very good explanation, and you’ve gotten right what many other folks (including SkS & RC) have gotten wrong. But I have a quibble with one small detail, namely this statement:
I think that range is too broad. Closely examining (digitizing!) your MODTRAN output, it appears that the range of wavelengths emitted from the tropopause (i.e., at close to 220K) is about 14.2 to 15.8 µm, not 13 to 17 µm:
I did the same exercise with a satellite-measured emission spectrum, and found about the same range.
Dave,
It may well be 14.2 to 15.8. The “about” was meant to indicate I was approximating.
Dave, I think they also include the wings of the absorption region. It’s true that not all of it has an effective temperature as low as 220K, but as you say that is a “quibble”. It is almost always possible to improve the wording of scientific statements, but (IMHO) there comes a point where the verbosity that is introduced gets in the way of communicating the science, especially when the diagram is pretty clear.
Dave, care to show where RealClimate (or SkS for that matter) gets it wrong? And I mean “decidedly wrong”, not some quibble about simplifying a concept, in your opinion, too much.
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Hi, I’m new to this line of thinking, so I have some questions:
In the starting post, you stated: “Now, if you change the CO2 concentration from 400ppm to 800ppm, the outgoing flux drops to 255.75 Wm-2”. I’m curious, did you calculate this from an equation or is the equation built into the MOTRAN? Do you know the equation used to determine the resulting flux with CO2 increase, and if so, please share it? Thanks!
Second set of questions: pbjamm states “If you are saying that the GHE is not caused by GHGs but instead by Nitrogen and Oxygen then you need to supply us with a physical mechanism to explain how that works.”
If “GHE” represents the radiation emitted by the atmosphere, I find NASA stating, “Electromagnetic radiation is produced whenever electric charges accelerate—that is, when they change either the speed or direction of their movement. In a hot object, the molecules are continuously vibrating (if a solid) or bumping into each other (if a liquid or gas), sending each other off in different directions and at different speeds. Each of these collisions produces electromagnetic radiation at frequencies all across the electromagnetic spectrum. However, the amount of radiation emitted at each frequency (or frequency band) depends on the temperature of the material producing the radiation.”
“Any matter that is heated above absolute zero generates electromagnetic energy. The intensity of the emission and the distribution of frequencies on the electromagnetic spectrum depend upon the temperature of the emitting matter. In theory, it is possible to detect electromagnetic energy from any object in the universe.”
(https://radiojove.gsfc.nasa.gov/education/educationalcd/RadioAstronomyTutorial/Workbook%20PDF%20Files/Chapter3.pdf)
If all matter, even oxygen and nitrogen, emits radiation when above absolute zero, wouldn’t the mechanism be that the GHG’s absorb radiation, warm up, share the heat with other air molecules by contact, then all of them emit radiation in a blackbody pattern reflecting their temperature? Wouldn’t the air molecules heat by contact with the ground, share the heat with other air molecules by contact, then all the molecules emit radiation? Wouldn’t that be the back radiation that helps warm the planet? Wouldn’t all the air molecules be radiating into space? Would the presence of GHG’s cause a deficit in absorbed wavelengths (those that are below the green 260K line on your graph) and then a corresponding surplus in the emissions not absorbed (shown in the wavelengths above 260K), if the heat is being shared and all gases are emitting radiation? Is NASA wrong on this point?
Ray,
I did this more than 6 years ago. I think I got the numbers from Modtran, but the basic calculation for how you relate a change in forcing to a change in atmospheric CO2 is
where
is the change in forcing, 
is the new atmospheric CO2 concentration, and 
is the initial atmospheric CO2 concentration.
Technically, a continous blackbody spectrum only comes from a body that is opaque, or dense. A single molecule doesn’t emit a blackbody spectrum. The atmosphere near the surface does indeed radiate back towards the ground. The reason that all the molecules don’t emit into space is because if they’re too low in the atmosphere, the energy is then re-absorbed. It depends on the altitude and on the wavelength/frequency of the emission. I don’t think NASA is wrong, but I’m also not quite sure what you’re getting at at the end of your comment.
Thanks for the equation! Yeah, me being 6 years behind the conversation is about right.
My questions at the end were about whether nitrogen and oxygen can emit radiation into space and also contribute to back radiation. The NASA quote seems to indicate that they do, whenever they collide with other molecules. I understand that one molecule emits radiation at a change of velocity at a specific wavelength based on the change of velocity and would only produce a blackbody pattern over time after multiple collisions (right?) and that a blackbody pattern generally is produced by multiple molecules having multiple collisions/emissions and that those assemble typically to form a blackbody curve based on temperature.
If n2 and o2 do indeed emit radiation into space, wouldn’t the spectrum shape at the top of the atmosphere be the result of a conversion of wavelengths caused by GHG’s absorbing some wavelengths, sharing the heat with n2 and o2 via collisions, and then all the types of atoms emitting radiation- producing a deficit of wavelengths absorbed and a surplus of wavelengths not absorbed?
Thanks for responding even though I was late to the discussion!
ATTP & Ray, that “5.35” coefficient is not known with such high precision.
The formula is usually given as:
ΔF = α·ln(C/C₀) W/m²
where α = 5.35 ±0.58
which is 3.7 ±0.4 W/m² per doubling.
It comes from Myhre 1998, who also reported an uncertainty “of order 10%,” which would be about ±0.54.
That represented about a 15% reduction from an earlier IPCC estimate of α = 6.3 (SAR §6.3.2, p.320).
Prof. Joshua Halpern gives α = 4.35, but I don’t know what his source is:
Prof. Will Happer reported calculating, based on corrected modeling of CO2 line-shapes, that the “5.35” coefficient is about 40% too high, which would make α ≈ 3.8
Feldman et al 2015 measured downwelling LW IR “back radiation” from CO2, at ground level, under clear sky conditions, for a decade, to determine the effect of increasing atmospheric CO2 concentration. They reported that a 22 ppmv increase (+5.953%, starting from 369.55 ppmv in 2000) in atmospheric CO2 level resulted in 0.2 ±0.06 W/m² increase in downwelling LW IR from CO2. 5.953% happens to be almost exactly 1/12 of a doubling, which makes their measured result +2.40 ±0.72 W/m² per doubling of CO2.
However, radiative forcing is normally defined at TOA, not at the surface. The effect of GHGs on radiation balance at the surface is similar, but not identical, to its effect at TOA. Here’s NASA’s 2014 (latest?) version of the famous Trenberth energy flow diagram:
The diagram shows:
1. Incoming solar radiation at TOA = 340.4 W/m². That’s 1/4 of the 1360 to 1365 W/m² which is typically estimated as the value of the “solar constant,” because the 136x W/m² figure is radiation at TOA where the Earth directly faces the Sun, and the 340.4 figure is averaged over the entire globe, including the back side. (The surface area of a sphere is exactly four times the area of a circle of same radius.)
2. Estimated outgoing radiation at TOA is 239.9 W/m² IR + 77.0 + 22.9 = 339.8 W/m², which is 0.6 W/m² less than the incoming solar radiation. (That figure is poorly constrained, and not directly measurable; I’ve also seen estimates of 0.7 or 0.8 W/m².) That is their estimate of the “radiation imbalance,” which represents warming “in the pipe,” but not yet realized.
3. Downwelling “back radiation” at the surface, from GHGs in the atmosphere, is estimated as averaging 340.3 W/m². That’s about the same as the solar irradiance at TOA, but ≈29% greater than the average amount of solar radiation which makes it to the surface.
4. About 22.6% (77 W/m²) of the incoming solar radiation is reflected back into space, before it ever gets to the surface.
Thus, an increase of 1 W/m² in LW IR at the surface from GHGs in the atmosphere has an effect on surface temperatures which is similar to a 1 / (0.774) = 1.29 W/m² increase in average solar irradiance at TOA (i.e., like a 5.16 W/m² increase in the “solar constant”).
Adjusting for having measured at the surface, rather than TOA, yields 1.29 × (2.40 ±0.72) = 3.10 ±0.93 W/m² per doubling at TOA, which makes the coefficient α = 4.47 ±1.34
That’s very close to Halpern’s “4.35”, and closer to Happer’s “3.8” than to Myhre’s “5.35,” but the uncertainty interval is wide enough to encompass all three estimates. It does preclude the SAR’s “6.3” figure.
Ray,
In a sense, all molecules/atoms emit and absorb at quite specific wavelengths/frequencies. However, if the relative motion of molecules will shift the wavelength/frequency (Doppler effect). Therefore, if you have a dense/opaque body (and this includes the atmosphere if you consider a deep enough column) then all this washes together to produce a blackbody spectrum, which ends up depending only on temperature. If you consider the figure in the post, you can consider to be a combination of blackbody spectrums coming from layers in the atmosphere. Some of the energy is being radiated directly from the surface, and some from different layers in the atmosphere. For the Earth to then be in energy balance, this then requires that the surface be warmer than it would be in the absence of an artmosphere.
My understanding of O2 and N2 is that they must emit and radiate in some bands, but that they are not important absorber in the infrared, hence do not play a big role in the greenhouse effect (at least in the sense of abording outgoing long wavelength radiation).
Dave,
Yes, this 5.35 isn’t exact, I was simply giving the generally accepted functional form of the expression.
To Dave Burton: Very informative, thank you. So the coefficient (5.35 or other) is determined from mathematically comparing measurements of CO2 levels with measurements of back radiation over a span of time? Also, something jumped out at me from the NASA chart. The TOA is 340.4 and the total reflected is 99.9 W/m2. Wouldn’t that make the albedo .293? If the albedo is .306 (NASA fact sheet Earth), shoudn’t the reflected radiation be 104.1 and the resulting absorbed radiation about 236.3? Has the albedo changed, maybe from too many parking lots?
To Physics: Thanks, again very informative. Makes sense that the blackbody curve is compilation of all the atmospheric emission coupled by frequency shift due to particle motion with a peak that corresponds to the average temperature (motion) of the molecules.
I guess my question boils down to this: if O2 and N2 absorb heat from direct contact with the surface and with other molecules (increasing their average kinetic energy), then when they collide they emit radiation (from the NASA article I previously quoted), wouldn’t their emissions be part of the blackbody pattern recorded at the TOA?
Ray: “So the coefficient (5.35 or other) is determined from mathematically comparing measurements of CO2 levels with measurements of back radiation over a span of time?”
No, The study Dave Burton links to uses surface radiation, and as Dave Burton states that is not the same as top-of-atmosphere (TOA) radiation response. It is an error to assume the two are the same. It is a serious error that has continued to be made for many years (cf. Sherwood Idso), and I was taught not to make it in the 1980s as a grad student..
The ln(CO2) equation is an approximation for a global average. Estimates are typically based on detailed radiation transfer codes such as MODTRAN or HITRAN, and global 3-d models (atmospheric temperature values vary spatially), etc.
Thanks- is the approximation then based on radiation measured at the TOA and compared to the CO2 levels? What is compared to come up with the equation? Is it just global temperatures vs CO2 levels?
Ray: the fundamental radiative transfer equations governing spectral radiation through gases can be confirmed by measurements in a laboratory and field measurements in the atmosphere. The radiative transfer is well-known and well-defined – including the effect of CO2.
The global temperature response is less well-defined. Although we can pretty confidently say “doubling CO2, with no other changes, causes a radiative forcing of X”, determining a temperature response requires models of much more than just radiation. Climate models.
Even the paper referred to above requires models. In the abstract, they say “The time series of forcing at the two locations … are derived from Atmospheric Emitted Radiance Interferometer spectra together with ancillary measurements and thoroughly corroborated radiative transfer calculations.” [Emphasis mine]
It is extremely unusual for any complex set of scientific equations to be verified all in one fell swoop from a single set of measurements. Various components of the theory will be tested independently, through a combination of controlled and uncontrolled experiments. Any new work will not repeat all the measurements that went into every previously-confirmed component.
Thanks, just trying to wrap my brain around this. The radiative transfer equations- I assume that means radiation absorbed and emitted by CO2 (and other GHG’s)- is proven in the lab. That makes sense. It is known how much CO2 absorbs and emits.
You said “The global temperature response is less well-defined. Although we can pretty confidently say ‘doubling CO2, with no other changes, causes a radiative forcing of X'”. I assume that means when CO2 is doubled, it causes more radiation to be absorbed so that the rate of escape into space is slowed at certain wavelengths. Also tested in the lab I assume.
So is the radiative forcing based on that lab leading to the equation ΔF = α·ln(C/C₀) W/m² ? So that the forcing is well demonstrated, but the temperature response of the Earth is a separate, less defined issue?
For the temperature response, is it estimated using computer climate models that try to include other factors? Is it also compared to the temperature rise that has already occurred and the CO2 rise that has already occurred, or is that not factored in?
Thanks for your patience, just trying to see what is considered in the process.
Ray,
As Bob mentioned, the effect of changing atmospheric CO2 is done by line-by-line radiation transfer codes. However, this is informed by laboratory experiments of how different molecules abosrb and emit radiation. Also, we have satellite observations of the outgoing spectrum, which can also be used to test the calculations.
Yes, what we expect is consistent with what we’ve observed. The change in forcing – to date – is about 2.5 W/m^2. The equilibrium response to that would be about 2C +- 0.6C (roughly). However, it takes a long time to reach equilibrium, so it’s more appropriate to use the transient response, which would 1.2 +- 0.5C. So, the warming to date of around 1.1C is very close to what we’d expect.
Thanks,I feel like you all have given me a better idea of what’s behind the equation.
Other question I don’t think anyone has responded to yet: if O2 and N2 absorb heat from direct contact with the surface and with other molecules (increasing their average kinetic energy), then when they collide they emit radiation (from the NASA article I previously quoted), wouldn’t their emissions be part of the blackbody pattern recorded at the TOA?
Ray:
You’re basically asking for an entire course in factors affecting climate.
Radiation transfer involves both absorption and emission of radiation. It is also a spectral characteristic – i.e., wavelength dependent. Yes, it can be tested in a lab, and in fact much laboratory measurement uses the principles to measure quantities of substances. You can buy off-the-shelf infrared gas analyzers to measure many different gas concentrations in air. Choose the correct wavelength, and you can measure many different gases because of their different spectral responses. CO2, water vapour, ozone. The US military did a lot of research on atmospheric IR transfer in the 1950s and ’60s so that heat-seeking missiles would work.
Climate depends on more than just radiation transfer – all energy flows need to be considered. Climate models put it all together, to varying levels of complexity.
I am going to suggest a couple of sources. Spencer Weart’s The Discovery of Global Warming provides a history of the science:
https://history.aip.org/climate/index.htm
and here is a link to a simple description of how climate models work
http://nas-sites.org/climate-change/climatemodeling/
Thanks, that’s great. I appreciate the sources and the info. I do feel like you all have covered what I was asking about up to this point, (what factors into the equations) but I don’t think I’m asking about all the factors affecting climate. My last question is just “if O2 and N2 absorb heat from direct contact with the surface and with other molecules (increasing their average kinetic energy), and when they collide they emit radiation (from the NASA article I previously quoted), would their emissions be part of the blackbody pattern recorded at the TOA?”
Ray,
I think the answer to your question is essentially. However, it will depend on the altitude. The radiation only escapes to space when emitted from an altitude where it wont be re-absorbed by the atmosphere. However, if you look at the figure in the post, you can image the outgoing spectrum as being made up of blackbody spectra coming from different levels in the atmosphere and, in some bands, from the surface. All the molecules and will be contributing to that spectrum.
Thanks! I get the altitude corresponds to amplitude concept, very cool. If the ground emits some radiation at around 12 microns (which shouldn’t get intercepted by GHG’s through the atmosphere) and an air molecule through collision (and/or the Doppler effect?) also emits radiation upward at 12 microns, would that have an additive effect on the amplitude at TOA?
Ray,
Yes, but the flux is quite strongly dependent on temperature. So, in the bands where the surface can radiate to space, this will be dominated by emission from the surface, because the emission from within the atmosphere will be from layers that are colder than the surface, and hence are emitting much less.
Wow thanks. Questions keep coming to mind, I’m trying to make it stop, but would the total area under the spectrum curve (all the amplitudes added up), if it equals the area under a specific smooth blackbody curve- would that blackbody curve with the same area be equal to the average temperature of the column below the measuring device from the ground to the TOA?
Ray,
Yes, that’s essentially the point. We know how much energy the Earth is absorbing from the Sun. It’s equivalent to the flux from a blackbody at temperature of 255K. Hence, the amount of energy we emit into space must also be equivalent to a blackbody of temperature 255 K. However, since some of this is coming from within the atmosphere, and since the atmospheric temperature decreases with altitude, in order for this to be the case, the temperature of the surface must be greater than 255 K (i.e., in order for the area under the spectrum to be the same as that under a 255K blackbody spectrum the surface must be > 255 K).
Just wanted to say thanks for a really interesting blog.
My position previously has been sceptical, mostly because of the emotion surrounding this issue and often very unclear explanations of the ‘warming mechanisms’. I hate being ‘bounced’ to accept things I don’t understand.
As far as I see it it is the CO2 IR window that is critical and the EEH in this window is the basic AGW mechanism, driving the effective ‘Blackbody’ surface upwards to a cooler height.
This mechanism is NOT well explained in general CC literature.
And, both frustrating and fascinating, it is really complicated to describe, especially with the lapse-rate being so important!
So, just a vote of thanks having a really interesting Physics site in this wonderfully complex arena of ideas. I’ve been making some inane comments on the SoD site and Clive’s site while trying to makes sense of this, but I am finally happy I have a mechanism for AGW that makes sense.
Peter,
There’s a very good description of this explanation for the Greenhouse effect in this Realclimate post, which includes this animation.
Thankyou.
The animation is really simple isn’t it? Which tends to be the hallmark of someone that understands something.
I now need to turn my momentum of previous scepticism (mostly because many folk seemed to be talking confused obscurantism ) to (reluctant) acceptance of the ideas, (and who knows, even climate zealotry in time !)
It’s good to be in an area that offers a clear opinion, yet objective view of science rather than what seems to have become a sort of witch-hunt against ideological difference. Ideas live and die by how good they are, don’t they?
Climate thermodynamics are fascinating and really complicated with so many feedbacks and such a matrix of influences and parameters that it is easy to lose sight of the significant mechanisms.
I now to make sense of the water vapour feedback, which seems less clear … can’t get rid of all the old scepticism at once ! I’m pretty satisfied that there is a clear mechanism by which more CO2 DOES impede atmospheric cooling (ergo creates warming).
Peter, Ken is too modest. His explanation of the so-called “greenhouse effect” is much better than Ray Bradley’s explanation in that RealClimate post.
Bradley/RC (and SkS, and many others) err by describing emission height as a single number. In fact, it is a function of wavelength. If you oversimplify it as some sort of average, it no longer “works” to describe how emissions and temperatures change with changes in CO2 concentration.
Most sources, including Bradley/RC & SkS, get that wrong, but Ken gets it right:
That “boundary” is called the tropopause, because that’s where the temperature lapse rate pauses. (One nit: the wavelength range over which CO2’s emission height is approximately the tropopause is a bit narrower than Ken describes; it’s about 14.2 to 15.8 µm rather than 13 to 17 µm.)
The tropopause is the coldest altitude in either the troposphere or stratosphere. The lapse rate there is zero, and the temperature does not continue to decrease with increasing altitude.
Adding CO2 to the atmosphere raises emission heights, over the full CO2 emission band, but for emissions between about 14.2 µm to 15.8 µm (i.e., most of CO2’s emissions), raising emission height does not lower emission temperature, so it doesn’t reduce emission intensity, and has no “greenhouse warming” effect.
It is only at the fringes of CO2’s emission band, where CO2 absorbs (and emits) weakly, that CO2’s emission heights are below the tropopause. Within those fringes, raising emission heights lowers emission temperatures, which reduces radiative emissions and causes the so-called “greenhouse warming” effect. Additional CO2 does not deepen the “15 µm CO2 notch” in Earth’s emission spectrum, but it does broaden the notch slightly:
You can see that in this graph is from van Wijingaarden and Happer (2021), which is derived from line-by-line spectral calculations. The black trace is the emission curve for CO2 = 400 ppmv. The red trace is for CO2 = 800 ppmv. (I added the flashing purple ovals.)
The difference between the red and black traces is the calculated effect at the mesopause (i.e., approx. TOA) of a doubling of CO2 concentration.
As you can see, the difference is about 277 – 274 = 3 W/m². They give a more precise figure of 2.97 W/m² in their Table 2:
To put that into perspective, it is calculated that a uniform global temperature increase of 1°C would increase radiant heat loss from the surface of the Earth by about 1.4% (variously estimated to be 3.1 to 3.7 W/m² or 3.1 to 3.3 W/m² in the CMIP5 models (the 8th column) — it’s complicated).
Dave,
Your comment reminded me of this cartoon. It’s always tricky to explain complex scientific concepts in a way that is both accessible and that captures the complexity. People have different views about this, and that some might have explained it in ways that others disagree with doesn’t necessarily mean anything other than they regarded their explanation as being more suitable for the audience they were trying to reach.