There will be large daily and seasonal variations. The annual average change should be fairly small, but not true equilibrium. Still, like local thermal equilibrium (LTE for short), it’s a useful approximation for illustrative purposes with a simple model.

Thanks for your reply.

You say that the energy in must equal energy out in any layer at equilibrium.

Is there any reason to suppose that a layer is in equilibrium at any one time. Given the complexities you mention it seems that it may be reasonable that there is a very long term equilibrium but there does not seem to be any requirement for an exact energy balance over days, weeks or even years.

I will investigate the web resources you linked to and see what I can do with them. I suspect I will find myself out of my depth rather rapidly!!!

I live in a very small Spanish village and our local library is even smaller!

It looks as though I will have to fork out some of my meager pension and buy it from Amazon. The problem at the moment is that the English pounds I receive have crashed against the euro and so it may be best to get the book from England. There are some other books I am thinking of buying and that will keep the postage costs to a reasonable level.

Do you think I will be able to follow the maths? I have not had much to do with thermodynamics since I left college. Since then my maths skills have atrophied and things like integration by parts are just a distant memory.

Am I right to assume that the only heat source involved is the earth at some chosen temperature and that solar radiation does not show up at all? Secondly, am I right to think that the temperature/pressure/composition profile is specified in advance of the calculation?

Yes to both. The atmospheric profile can be changed by selecting a different locality, Tropical, Sub-Arctic Winter, etc. If you select save data and click on the link in the lower graph, the complete tables of pressure, temperature and composition as well as emission are displayed.

Is there some rule that says the temperature must change so that up/down radiation have to be equal at each altitude? Given that there is also convection and phase changes to add/subtract energy from any given layer there does not seem to be an obvious reason why radiation alone should have to be in balance.

At equilibrium, the energy in at any altitude must equal the energy out. How the energy is transferred is much more complex in the real world compared to the simplified radiation only model, which doesn’t look at energy balance either. The atmosphere absorbs some incoming solar radiation and the surface transfers absorbed solar energy by convection and conduction as well as radiation. Increased CO2 cools the stratosphere by increasing emissivity, which is also not included in the Archer Modtran program. The lapse rate is also a function of water vapor content, but that requires an explanation of moist and dry adiabats, which is outside the scope of this thread. There are resources on the web that go into much more detail about Physical Meteorology, here for example.

The book starts with oversimplified models and progressively relaxes the simplifications. So, with regard to radiation, they begin by discussing radiation in an atmosphere with no conduction or radiation. The questions you ask about whether temperature must adjust so incoming radiation balances outgoing radiation at each level is discussed in the section on the radiative convective model. Convection does indeed modify things.

The later chapters discuss climate models in a general framework. (Newer versions may say more. But I have a 90’s version.)

Many thanks for your continuing attempts to help us understand the radiation physics. I have tried to follow some of the discussions at Climate Audit and other places but I think I am missing something very basic.

I think I have the hang of how lab type spectroscopy works in that one can see/measure emission lines from a hot gas against a dark/cool background or absorbtion lines from a cool gas against a light/hot background. It seems that in these cases the gas temperature is not usually affected by the presence of the radiation as any gain or loss of energy is compensated by gains or losses from the walls of the container or the thermal mass is generally too large for small amounts of radiation to have much effect.

I have not really worked out what is happening with the MODTRAN simulation. Am I right to assume that the only heat source involved is the earth at some chosen temperature and that solar radiation does not show up at all? Secondly, am I right to think that the temperature/pressure/composition profile is specified in advance of the calculation?

The end result being a spectral profile of the up/down radiation at a give altitude. I can see how this can show a radiative imbalance over the whole spectrum at a particular altitude but I cannot see how this imbalance is supposed to be translated into a temperature change from the originally specifed temperature profile.

Is there some rule that says the temperature must change so that up/down radiation have to be equal at each altitude? Given that there is also convection and phase changes to add/subtract energy from any given layer there does not seem to be an obvious reason why radiation alone should have to be in balance.

Perhaps it is at this point where we depart from rock solid radiation physics and calculating the resulting temperature changes is very dependent on whatever other atmospheric changes result from the changed radiative imbalance with extra CO2.

I know there seem to be some arguments about the details of radiation calculations but these seem minor compared to knowing how to turn a changed radiation imbalance at the top of the troposphere (or anywhere else) into a new surface temperature.

I read your posts. Your understanding of the physics is still incorrect. I’ll try a different approach.

Look at it this way, the surface warms the atmosphere, not the other way around. In fact, the atmosphere can’t, on average, warm the surface because it’s colder and heat flows from warm to cold. Heat flows from the sun to the atmosphere and surface, whether land or ocean. Note that your argument applies to the land surface as well as the ocean. An increase in a ghg does not warm the surface by first increasing IR emission. CO2 absorption is saturated, i.e. the absorptivity (and emissivity by Kirchhoff’s Law) are 1 to a good approximation over the band centered at about 15 micrometers. Emission from the atmosphere to the surface can not increase in the center of the band simply with increased concentration because it’s already emitting at the Planck curve limiting rate, which is a function of only temperature and wavelength (or frequency), not concentration. Emission from the wings of the band could in principle increase, but that doesn’t amount to much at the bottom of the atmosphere because of overlap with water vapor. Emission at the top of the atmosphere can, however, decrease significantly with increasing CO2 concentration because the CO2 emission to space is from CO2 molecules that are at high altitude where the optical density finally becomes low enough that the probability of emission to space exceeds the probability of absorption by a CO2 molecule at even higher altitude. Overlap with water vapor is negligible at high altitude because there isn’t much water vapor because it’s number density decreases with both pressure and temperature and the lines for CO2 and water vapor are much narrower at the lower pressure and temperatur that exists at high altitude. The lower temperature at high altitude also lowers the Planck curve. Higher concentration causes increased absorptivity in the wings of the band which means less radiation is emitted to space from the now wider band. Only an increase in temperature of the surface and the atmosphere caused by the excess heat retained can increase the emission intensity at other wavelengths and restore the balance between incoming and outgoing radiation.

In summary, the surface warms not because of increased thermal emission from the atmosphere with increasing CO2 concentration. The surface and the atmosphere warm because less heat is lost to space at any given altitude and temperature with increased CO2 concentration, all other things being equal.

I`m not interested in which negative feedbacks the IPCC has missed other than to say they must have missed some.

I agree with you that solar energy is radiated back off the earth at longer wavelengths with much of this being absorbed by CO2 and other gases creating a greenhouse effect.

I agree with you that extra energy at around 15 microns will excite the major bonds of the manmade CO2 molecules in the atmosphere and cause those molecules to vibrate. This vibration should be and is measured as a higher temp. in the atmosphere (aprox 0.3C to date).

This vibration will cause an insignificant amount of energy to be slowly transferred from the atmosphere to the ocean by conduction.(remember, if aerosols are asumed to have negligable effect, the IPCC implies that 80% of the energy trapped by extra manmade CO2 finds it`s way into the ocean).

This is where your`s and the IPCC`s narative stops and where what I`m trying to say begins. You`ve stopped too early.

After a short time the excited manmade CO2 molecules, mentioned above, stabilize. As they stabilize they reemit radiation in all directions at the same 15 micron wavelength. A large percentage of this radiation hits the ocean, and 99.99% of this is reflected as a blackbody back to the atmosphere and space. Virtually none of this energy is absorbed by the ocean. Water acts like a very efficient mirror at this wavelength as it has an absorption coefficient of 5000 cm^-1 at this wavelength.

I believe the IPCC wrongly treats this reemitted 15 micron radiation the same way they treat solar radiation which has an absorption depth of 10 metres or more. They use historical data (solar) to calculate equilibrium temps. caused by manmade CO2.(AR4 9.6.3.2).

Douglass Hoyt is well respected in this field and his link at post #6969 suports me. There is virtually no manmade CO2 induced energy in the pipeline.

The question I`ve been trying to ask, although badly, and you need to answer is this;

If conduction is too slow and radiation at 15 microns is almost totally repelled by water, by what mechanism do you propose the energy trapped by manmade CO2 gets transferred to the oceans to be stored and later released to the atmosphere?

I live in the hills of East Tennessee so I didn’t even bother to look in the local library. Based on your recommendation and the excerpt and table of contents I read on Amazon, I’m buying the paperback edition. It didn’t cost that much more than the Tomb Raider Underworld PC game I just bought.

The issue of “in the pipeline” is discussed in the IPCC report. One of the ways is by illustrating what will happen if the level of GHG’s is frozen at the current level. The IPCC just don’t use the term “in the pipeline”. I don’t know who introduced the “in the pipeline” term.

Each GCM model models has a slightly different parameterizations which results in somewhat different time constant. So each model would predict different amounts of heat “in the pipeline”.

Hansen has said it will take 25 to 75 years to reach 60% equilibrium based on the ocean uptake in surface layers but then how long will the remaining 40% take.

His 1988 temperature predictions apparently did not take this influence into account.

I note we are getting farther and farther away from the expected 3.0C per doubling trendline as time goes on. If there is not an uptick in temperatures in the next 5 years or so, the warming in the pipeline timeline will have to be extended out to perhaps over 100 years (maybe more).

While we might still reach the 3.0C doubling (and it is starting to look more and more debatable whether that will occurr), the modelers need to start being more specific with the public about the timelines expected here.

Hansen says we will be “committed” to the doubling temperature response when we get to the doubling level but if there is another 100 years or 200 years before temps do reach those levels, there is obviously more time for solutions. Maybe they have figured out the timelines but don’t want to be more specific since this might create less urgency to the issue.

(BTW. I’m pretty sure when some people incorrectly claim GCM’s assume constant humidity, it’s rooted in some past simplified non-GCM approaches where the types of models in Chapter 4 of H-S&M assumed constant relative humidity when trying to estimate feed backs. Estimates based on simplified models are totally respectable in all fields as they give a level of insight about the physics. Of course, they are estimates, but … that’s not a defect as long as one admits it’s an estimate. )

Thanks. It took me a while to get to where I understood how the whole radiation transfer thing worked.

I did leave out another key to the greenhouse effect, the decrease in temperature with altitude. In an isothermal atmosphere, there would be no greenhouse effect, or at least it would be a whole lot smaller. I don’t think an isothermal atmosphere that can emit in the thermal IR is stable, though. The top layer would be emitting more than it received from below so it would have to cool and that cooling would then propagate downwards. I keep meaning to try to calculate this effect with a layered atmosphere model, but you can’t use a simple gray atmosphere and you do have to include water vapor mixing ratios. Messy.

You clearly do not understand the physics behind the greenhouse effect. Solar energy is absorbed by the atmosphere, the ocean and the land, ~235 W/m2 on average. That energy is then, at equilibrium, radiated back to the atmosphere and eventually to space at longer wavelengths. Because the atmosphere contains molecules that absorb and emit in the thermal IR region, the surface must be warmer than the Stefan-Boltzmann equation would predict from the amount of incident solar radiation absorbed so that total energy balances at the surface. See the Kiehl and Trenberth paper for example. Increased CO2 causes less radiation to be emitted to space from the upper atmosphere at constant temperature (see the Archer link above). You can see the dip from the CO2 band in both calculated and observed IR spectra and the integrated emission drops when CO2 is increased. The surface and the atmosphere above it must then warm so that energy balance is again achieved. There is no neglected negative feedback from CO2 emission to the surface from the atmosphere as that is strictly a function of atmospheric temperature and is fully accounted for in the energy balance numbers. Unless the relative humidity is 100%, the surface of the ocean will always be cooler than the water just below the surface because of evaporation. This energy loss is also included in the energy balance numbers as sensible and latent heat transfer from the surface to the atmosphere.

While I would like to believe the Argos numbers for ocean heat content, they haven’t been collecting data long enough and are still controversial. It took quite a few years to find all the major systematic errors in the satellite MSU data reduction process, for example. They are also irrelevant to the radiation transfer physics. If they are correct, they do imply that the GCM’s are wrong. But it won’t be the radiation transfer calculations, it will be how the GCM’s account for the effects of clouds, moist convection, aerosols or some other mechanism.

Since even the IPCC admits that clouds, etc. are poorly understood, trying to attack the warmers on radiation transfer is worse than pointless because it just gives rational skeptics a bad reputation.

I agree the damping effect will be reduced over time but the oceans will still have a damping effect. This and the slowness of conduction from the atmosphere to the ocean means that the air temp. will be a good measure of the amount of energy CO2 puts into the system.

The oven has to get hot before the turkey starts to cook and this will show up in the temp. of the air in the oven.

If virtually zero CO2 reemitted radiation enters the ocean and conduction is too slow and doesn`t matter anyway then the GHG induced 2.64w/m2 already in the system should have showed up as a temp. increase of aprox. 2.3C fairly quickly.

It hasn`t, therefore, there is something desparately wrong with the IPCC`s prediction of 3C warming from 3.5w/m2.

DeWitt

I apologise for a mistake in my last post that may have misled you. ” It is worth mentioning for A=5000cm at 15 microns…” should have read ” A=5000cm-1 “. This means only a very small amount of radiated energy from CO2 is absorbed by the oceans.

It doesn`t really matter to the arguement how much of the reflected radiation makes it to space. The point is that none of the energy reemitted by CO2 enters the ocean and therefore should show up almost immediately in the air temp. record. There is virtually nothing in the pipeline.

The absorption coefficient of visible light averages 10^-3 cm^-1 and therefore penetrates water to a depth of aprox. 10 metres. the oceans are almost entirely warmed by solar radiation.

The IPCC (chapter 9.6 AR4) tries to quantify ocean lags from CO2 induced radiation by referring to history. Historical temp. lags are almost entirely due to solar radiation penetrating deep into the ocean and are completely different to energy reemitted by CO2.

Major points:
1. The 15 micron is absorbed in the upper 15 microns of the oceans.
2. This layer is cooler than the water below it, so it cannot be heating the bulk of the ocean by conduction (very slow), convection (suppressed), or radiation (opaque).
3. The extra 15 micron radiation will be re-radiated upwards and over all infreared wavelengths with a blackbody spectrum so that about 40% will escape directly to space. This can be viewed as a neglected negative feedback.
4. Compo (2008) has shown that the net flow of heat in recent years has been out of the ocean, not into it.

It is worth mentioning for A=5000 cm at 15 microns, the implied water emissivity is 0.9998 implying that of the incident radiation only 0.02% of it will be absorbed.

No. Kirchhoff’s Law applies here which means that emissivity = absorptivity so only 0.02% of the incident radiation isn’t absorbed. I suggest you go to the Archer MODTRAN site and generate and look at some calculated surface and atmospheric emission spectra. Then you will see that the atmospheric IR window covers much less than half the spectra and in the end only about 10% of the radiation emitted from the surface, on average, escapes directly to space, more at high latitudes and less in the tropics. Note that the spectra are in wavenumbers (cm-1) rather than in wavelength so the CO2 emission band is centered at 667 cm-1 and the atmospheric window is at about 800 to 1300 cm-1.