Rhoda

If you don't think there is any greenhouse effect at all you may be right but I think there is but not by the mechanism currently popular.

Incoming solar is full spectrum and therefore includes the radiation/absorption spectrum of GHG's. If you are going to start from somewhere, why not a temperature contour in the atmosphere - at least you are dealing with a single number.

The 'trapped heat' explanation requires that an addition of CO2 to the atmosphere reduces the radiating temperature (the energy imbalance searched for from the trapped heat conclusion) which is in defiance of the S-B Law. We have that experiment running at the moment. CERES satellites can't see any discrepancy that makes sense nor can they see a trend that reflects rising CO2 concentration. For me current GH theory is a busted flush. The whole thing needs to be audited by physicist engineers (no I'm not) or better still, started from scratch.

rhoda

It is rather a circular argument using the TOA and tracing the lapse rate back down to the surface to calculate the temperature. This is where the CO2 moving TOA up and therefore theoretically increasing surface temperature argument comes from isn't it. How can you say that things like lapse rate would remain constant in that situation for example? It is all fine in giving a ballpark figure from a basic physical mechanism but has no predictive capability at all.

I've just been thinking again about the 1/5 of a cubic kilometre of ocean per person is in fact 200 million tonnes each isn't it? I could understand someone arguing that only say the top 200 metres get heated up by CO2 which is about 1/20 of that so even then each persons increased CO2 from having the aircon on has to heat up 10 million tonnes of water - clearly that is ludicrous as long as my sums were correct there. Also surely even if IR or increased surface temps could get into the ocean surely that is completely dwarfed by what the sun can dump into on a nice clear day (at some depth too)

TOA is not the same thing as average radiating height, not even close.
I haven't mentioned TOA except in this post.
The average radiating temperature is calculated from a physical Law.
Weather balloons, not climatology physics measure its height.
Lapse rates are not a controversial concept.

I bow out.

"Lapse rates are not a controversial concept."

It isn't a constant though. Do you use a dry or moist adiabat for your lapse rate, considering moisture content and vary so much in time and location.

Pity ssat is bowing out, I have always wondered about where the effective blackbody surface is located for a planet with an atmosphere.

Imagine that you are in space and you measure the radiation emitted by the earth. The SB theory lets you calculate the temperature of the earth. That suggests it is -18.

We know that the surface is about 15 degrees. The climate scientists tell us that GHG is responsible for the difference of 33 degrees.

There are a number of assumptions in this tiny bit of theory.

My apologies - I brought the frustrations of my day to a place where I generally relax.

SC. Yes, I have a problem with that tiny bit of theory too. S-B temperature for Earth with its albedo is -18. The 33 degree difference you mention, we are told, is the greenhouse effect and ascribed entirely to radiative effects within the atmosphere. However, lapse rate would add somewhere between 5 to 10 degrees/km to that. If, over a dessert, the -18 occurs at 3km above the surface then the surface (Stephenson screen height) temperature would be ~30 degrees higher and explain the greenhouse effect by an entirely different phenomenon.

Perhaps one of the commenters that Dung has encountered that don't believe we should question the science would care to explain the fault in the above? Or anybody, whatever their disposition?

Rhoda, I think this TOA thing is misleading. Assume the Earth has a constant surface (not near-surface) temperature, forget the sun but keep the radiative atmosphere. Seen from space the average radiating temperature would occur at some height in the atmosphere, would be lower than the surface temperature and the difference would be the lapse rate. No?

Rhoda, the S-B equation applies to a body at some temperature above absolute zero. For a body externally and asymmetrically heated while it is rotating, who knows if it applies. But assume it does because it is the cornerstone of GE. Let us remind ourselves of GE. From WikiP;

If an ideal thermally conductive blackbody were the same distance from the Sun as the Earth is, it would have a temperature of about 5.3 °C. However, since the Earth reflects about 30% of the incoming sunlight, this idealized planet's effective temperature (the temperature of a blackbody that would emit the same amount of radiation) would be about −18 °C. The surface temperature of this hypothetical planet is 33 °C below Earth's actual surface temperature of approximately 14 °C. The mechanism that produces this difference between the actual surface temperature and the effective temperature is due to the atmosphere and is known as the greenhouse effect.

Those numbers are all averages and come from S-B except for the 14 °C which comes from averaging of temperature measurements. So, having determined the average radiating temperature for Earth as −18 °C, the measured 14 °C at the bottom of atmosphere is declared as being a newly discovered radiative effect within the atmosphere. This is a jump of logic that I don't understand - why would the average radiating temperature be located at the bottom of atmosphere? Would it not make more sense to conclude that it exists at the average −18 °C height within it? It is so easy to check: send up a weather balloon and if the −18 °C height coincides with what might be expected by lapse rate from the Stephenson screen temperature directly below it then you have the answer that the 14 °C average is down to that phenomenon. There is no need for any other and much more complex theory.

Oh, and one more thing: S-B Law doesn't state j*=σT^4 except for CO2. It makes no exceptions at all.

So there you have it - my understanding or misunderstanding in a nutshell.

rhoda, I absolutely and completely agree with you that S-B may not apply, I said that in my second sentence. It could be the first big thing that climate science got wrong. However, if, as they have done, go on to compound that error with more error, there has to be a weak-spot that is easily attacked. There are no numbers for a planetary body that can be used for that. We simply don't know, and possibly never will directly, if your objections are apposite. Back to WikiP;

The mechanism that produces this difference between the actual surface temperature and the effective temperature is due to the atmosphere and is known as the greenhouse effect.

My objection with this is that it is linked to some idea of 'trapping heat' while other, well understood effects are ignored. This is not to say that I don't think radiative gasses have an effect - an only nitrogen atmosphere would have its average radiating height coincident with the planet surface. But add radiative gasses and it would not.

Martin A: S-B is modified for a grey body to j*=εσT^4 where ε=emissivity. It applies to absorption and radiation equally. S-B for any value of ε, including 1, requires that no heat is trapped. CO2 is not an exception.

Martin A: Trapping heat is indeed what we are told by our betters (schoolboy diffidence there) - its not my concept. I just don't buy it. A ball(oon) of CO2 in space would heat up by absorbing solar radiation at its narrow active frequencies - solar radiation is full spectrum. It would radiate at those same frequencies and attain a stable temperature when, as you say, the power it is radiating equals the power it is absorbing. For it to 'trap heat' the temperature it attains in equilibrium would have to be higher than S-B states. I don't believe it would defy S-B. Have you come across something that shows it would?

"I can't say for certain, but I remember as a lad reading that the temperature on Venus was caused by "greenhouse gases" and CO2 was the major cause - I believe a young Carl Sagan was responsible for this theory."

You can read Sagan's paper here. Sagan calculates it by determining the height of the clouds = the average altitude of emission to space, and the lapse rate. The surface is warmer than the clouds by the product of the two. That is to say, Sagan used the emission altitude/lapse rate mechanism.

"They use a geometric mean at T^4 for one number and an arithmetic mean of air temp for the other. It is not comparable, to me at least."

Quite right. The one-dimensional model is a back-of-envelope simplification that is only the starting point for understanding. To get a proper answer, you have to work out the temperature of every layer of atmosphere at every location on the globe, accounting for the opacity of the air above it, and sum. That is to say, you need a climate model.

If you want an explanation you can understand and test for yourself, it will be simplified. If you want to build your own climate model, go ahead. I'd definitely encourage people to try.

"I would not count down from TOA. I intuit that surface temps set altitude temps. I may be wrong."

First, it's not TOA, it's the average altitude of IR emission to space, which is only about 5 km up. Second, the lapse rate adjustments do actually propagate both upwards and downwards - it's more like the way the surface of a body of water with inflows and outflows approaches horizontal. So imagine a lake with a sloping bottom, with rivers pouring in at one end and another river pouring out through a narrow V-shaped channel at the other end. The V shape means the higher the water level, the faster it flows.

What determines the depth of water at any point in the lake is the slope of the lake bed (the lapse rate), and the amount of water in the lake, which is determined by the inflow (absorbed sunlight, taking account of cloudiness) and the outflow (Stefan-Boltzmann emission to space). If more water enters than can escape through the bottom of the V, the water level rises (if more heat is absorbed than emitted, the temperature rises). If less water enters than can escape through the top of the V, the water level falls (the atmosphere cools). So the depth of water in the lake at the outlet is pushed towards the point where the amount that escapes balances the input.

But the depth of water elsewhere in the lake depends on the slope of the bottom relative to the outlet, and how far from the outlet you are (the lapse rate, times the difference in altitude). It's perfectly true that all the water where you are comes from the inlets, and the levelling of the surface is driven by the water piling up close to the inlets and spreading out. But what *controls* the level is difference between input and output. The drop in level close to the output also spreads out across the surface, although the water there is flowing in the opposite direction to the influence.

"How do they establish TOA as where the up and down radiation balance? By lapse rate? Or as they should by radiative integration?"

In reality, it's not so simple because you also have horizontal energy transfer. Convection carries heat from the equator towards the poles, so at any given location you also have massive heat flows that are not accounted for radiatively. But yes, as I understand it the climate models use a joint radiative-convective approach that includes radiative integration, and no, they don't assume a fixed lapse rate, but (crudely) model the physics of convection.

"This is where the CO2 moving TOA up and therefore theoretically increasing surface temperature argument comes from isn't it. How can you say that things like lapse rate would remain constant in that situation for example?"

Because the adiabatic lapse rate is a thermodynamic property of gases. For an ideal gas, the lapse rate is equal to the acceleration due to gravity divided by the specific heat capacity of air at constant pressure. Neither of those are things that are likely to change. There is a common adjustment to account for latent heat from the condensation of water vapour, which is really a separate bit of physics but has the same sort of dependence on altitude, so it makes things simpler to merge the two effects into one number. This part of the effect depends on humidity.

The humidity *does* change, and this does indeed change the moist adiabatic lapse rate. This is in fact the putative cause of the tropical hotspot - the one that's missing. The theory is that a warmer atmosphere will be moister, which reduces the lapse rate, and the shallow curve makes levels below the average emission altitude cooler (cancelling part of the warming and therefore a negative feedback) and levels above it warmer (i.e. the hotspot). The missing hotspot is saying that the lapse rate *hasn't* changed when we expected it to - quite likely because the water vapour feedback isn't as strong as the models think.

"However, I am quite sure that there is no 'correct' temp for a body at some distance from the sun independent of its rotation rate and the conductive characteristics of the surface and thus no way to quantify 'greenhouse effect' at 33K or any other number."

True. It's an approximation.

"What I had in mind was a body where ε is a function of wavelength. For example a thin balloon containing nothing but CO2. I'm not sure that j*=σT^4 precisely for such a body."

It's not. It's an approximation. It's like asking for 'the density' of the human body, to see if a person will float in water. Different bits of the body have different densities, and thus giving any single number is always 'wrong'. But if you pick a weighted average of the many different densities involved, that will be somewhere in the middle between the highest and lowest densities, you can do the maths as if the body was all of a constant uniform density and get a valid answer. It just makes the sums easier.

To get an exact answer, you do have to integrate the absorption as a function of wavelength, which is what programs like MODTRAN do.

Martin A: I don't recall greenhouse theory concerning itself with some amplification effect of irradiated CO2 ( a greater T than suggested by S-B), rather, I thought it to be based upon CO2 (+ the rest of the GH gasses) re-radiating from the atmosphere back to the surface. If I have misunderstood that then please put me out of my misery!

As an alternative to the WikiP definition of greenhouse effect I have come to the conclusion that a planet without such an effect has its average radiating height of the S-B derived temperature coincident with its surface and a planet with such an effect has its average radiating height of the S-B derived temperature above its surface. Applying lapse rate to the second scenario would account for at least some of the additional 33°C, possibly all. Both rhoda's and your points may be germane in the real world but is that the same world that climate science inhabits?

Why am I posting on this thread (rhetorical). Basically I am asking the same question as Dung. By doing so I am trying to support him in his quest.

NiV: Isn't calculating what radiates to which inside the atmosphere just examining how greenhouse gasses distribute energy throughout the system and have in fact no bearing at all on average radiating temperature?