Discussion > GHG Theory step by step
Rhoda
"Now, does the surface temp set the tropopause temp, or vice versa?"
I think it works both ways, like any other equilibrium. Change one and you change the other.
If you increase insolation you increase surface temperature. The atmosphere expands and raises the tropopause.
If you increase greenhouse gases you raise the tropopause and the lapse rate then resets the equilibrium surface temperature.
"We blew up that 288K myth years ago, it just ain't so. Check the moon."
I must have missed the memo. This thread is about exploring alternatives hypotheses. Please explain your hypothesis in sufficient detail that I can check at least the basic maths for myself.
Entropic man
A little learning is a dangerous thing;We have really only begun to study the complexity of the atmosphere and the interactions therein, yet you do seem to have declared yourself an expert on it. It is curious how you can only find what you want to find, isn’t it?
Drink deep, or taste not the Pierian spring.
The atmosphere expands and raises the tropopause.Does it? Or is this yet another of the many suppositions that you continually make to prove your point? You are not interested in exploring alternative hypotheses, but emphasising your own pet one, as you have done as long as I have observed your contributions. Lapse rates occur as it is a gaseous atmosphere; the composition of the atmosphere is irrelevant – what is relevant is that the gases of the atmosphere are in contact with the heated surface. It is this heating that causes the thermal; it is the density of the atmosphere and the gas laws that determine the lapse rate of the thermal; it is gravity and the gas laws that determines the lapse rate of the environment that the thermal rises in. There will be many, many other factors involved in this, many of which might be known but may not be recognized, many will be known and ignored, some, perhaps, as they interfere with the theories; and, there may also be many that have not yet been identified. Why you should fear such ignorance, and take solace in your obsession with it all being the fault of human-produced CO2, exasperates many of us, and makes many of us fear for you.
Radical Rodent
RR, good exposition.
Now, I'm just an Oxfordshire housewife again, wishing I was back in Texas. I don't have the kind of hypothesis EM seems to require. I have a null, which I've often stated, 'nothing much is happening and if it does we can adapt.' It's for the other lot to show that theirs invalidates mine. And they seem to have big problems showing it. They can't decide whether it is DW or the newly fashionable tropopause thing. Neither work for me.
If it's DWLIR, why can't I use that energy to, say, boil an egg?
If the height of the equal radiation thingy can affect the temp at the surface, where is the energy coming from at the surface to heat anything just because the tropopause went up? No, the lapse rate works UP the gravity well, not down it IMHO.
Lastly, the 288K thing. The temperature of the moon where only insolation and SB operate, is not 255K, so we can assume that the temperature of an airless earth would not be 255K either. And the awfully convenient 33 degree difference to the 'global average' is wrong.
rhoda
Correcting a misstatement, when I say the lapse rate works up the gravity well, I don't mean the gas doesn't warm coming down but that conditions are set by the warm surface, not the top of atmosphere.
rhoda
S's Cat says
I’m suggesting a thread that builds up the process, step by step. If a step is uncontroversial we move to the next.
Stripping out everything but the one fundamental in their working hypothesis is that there would be differences between a planet with no atmosphere, a non-radiative atmosphere and a radiative atmosphere. So;
On planet B with no atmosphere, it will radiate to space from its surface. Its temperature will be that which the surface archives at radiative balance with insolation.
Add a non-radiative atmosphere, it will radiate to space from its surface. Its temperature will be that which the surface archives at radiative balance with insolation.
Change to a partially radiative atmosphere, it will radiate to space from its surface and atmosphere. Its temperature will be that which the whole achieves at radiative balance with insolation.
∴ There is an effect from radiative gas in the atmosphere.
Is that controversial?
Their working hypothesis is that, as the atmosphere is colder than the surface, it is colder than the average and therefore the surface is warmer than the average. ∴ Radiative gas in the atmosphere causes a warmer surface when the whole is at radiative balance with insolation.
Is that controversial?
ssat
Derivation of lapse rate.
https://www.climate-policy-watcher.org/aromatic-hydrocarbons/derivation-of-lapse-rate-in-troposphere.html
I don't see the need for a greenhouse gas.
Schrodinger's Cat
I've searched a number of sites and clearly we have not been the only ones discussing the lapse rate. However, from what I have found there is no doubt that a GHG free atmosphere such as nitrogen would still have a lapse rate. It is a consequence of gravity and the gas laws.
The earth surface is hot, space is cold. There is a molecular density gradient, a heat capacity gradient and a temperature gradient.
Schrodinger's Cat
Mr Cat (gender-presumptive, maybe, but… who cares?): that about sums it up (even if so many graphs seem to show space must be stinking hot!). Ssat has encapsulated the argument that Entropic man is fond of; one of the flaws in it is that we have no example of a GHG-free atmosphere to study. However, we do have two planets that have atmospheres that are almost entirely GHG – and the evil one at that, too! (Perhaps the result of human activity in the past that has since been erased from our records? Now there’s a conjecture that could lead to interesting discussion!) One would have thought that they would have surfaces that are hotter than Hades, and all could be blamed on the CO2. But no: the heat at the surface of Venus is easily explained by the massive pressure of the atmosphere, and the surface of Mars is, as Elton John explained, “cold as hell.” And, guess what? Both, it would appear, have lapse rates not too dissimilar from that of Earth’s, the only differences involved easily being explained by the density of the atmospheres. Therefore (I have no idea how to do those three dots), the composition of the atmosphere has no relevance to either of the two main lapse rates.
Radical Rodent
When you start comparing planets it is the distance from the sun that determines the temperature.
Schrodinger's Cat
I just realised that having discussed the lapse rate and distance from the sun, we have just constructed the main elements of Nikolov and Zeller's paper. They claim that for rocky planets with atmospheres, the surface temperature depends on the distance from the sun, gravity and the mass of atmosphere. the last two determine the atmospheric pressure.
It sort of makes sense. The sun heats the surface and the temperature gradient is as we discussed above. Carbon dioxide and other GHGs absorb and radiate but the main factors have already been established. It makes sense to me. The surface heats the atmosphere, not the other way round.
Sorry, I digress, but I find the gravity explanation more convincing than the alternative.
Schrodinger's Cat
Mr Cat (Jul 25, 2017 at 2:50 PM):
When you start comparing planets it is the distance from the sun that determines the temperature.Well… yes. I took that as read – in all three cases, the distance from the Sun determines the temperature at any given pressure. In the case of Venus, at altitudes where the atmospheric pressure is equivalent to that of Earth’s, the temperature is what Earth’s would be, were it the same distance from the Sun. Similar results can be found comparing Mars’ surface temperature with that found in the Earth’s atmosphere at altitudes where the pressure is equivalent to that of Mars. These are figures that can easily be calculated, even by me, a dumb… well, mousey-coloured-now-going-grey-haired person. And all three have lapse rates so similar as to be more easily explained by atmospheric density and gravity than atmospheric composition.
Radical Rodent
Mr Cat. but, but, but I recall not so long ago when I maintained that, at night, my hand could be warmed by radiation from the ground, and thus this radiation could do work, that I was beset on all sides and more or less told I was scientifically illiterate. Was I right, or have I still missed something?
Supertroll
Ravishing Rattie. How can you write that you are a "mousey-coloured-now-going-grey-haired person". Surely you mean "rattie coloured"? I, of course, am a silver fox!
Hehehe.
Supertroll
Supertroll, The heating of your hand by radiation from the ground is just a transfer of energy, is it not? The heat transferred from a hotter body to a cooler one by radiation in line with the laws of thermodynamics. No work is done. The heat gained by your hand equals the heat lost by the ground. (ignoring heat radiated elsewhere, like to the sky.)
Work involves a process such as producing or resisting a force.
Schrodinger's Cat
Mr Cat you are considering the entire system. For me I experience my hand being heated, I.e.for me work has been done. Using your argument if I burn coal to drive an engine that generates electricity that powers an electric fire that heats my hand, examining the whole system, everything ends up as heat, and ?no work is done?
Suggest you look at Wikki. There are many different forms of work, not just producing or resisting a force. Transfer of energy from yone place to another involves work being done
However I wish I hadn't started this all up again.
Supertroll
Radical rodent, rhoda
" You are not interested in exploring alternative hypotheses"
Remember Huffman. He was trying to warm Venus using energy which did not exist.
More recently there was Nikolov and Zeller's pressure warming hypothesis, which also fails for thermodynamic reasons.
Then there was Svenmark's cosmic rays, which failed the test of experiment at CERN.
I love alternative hypotheses. They are great fun to analyse. The problem is that none of them so far have made scientific sense.
Entropic man
I don't support Nikolov and Zeller, never have because they don't include length of day in their formula and we know from the moon what a difference that makes. With a very long day the SB formula with its usual assumptions doesn't quite work, with a very short day it does.
As far as Schrodinger's Cat's gender, it is both until you look.
All of our hypothetical planets fail to emulate the Earth because of all the water and its phase transitions. That's why this type of discussion always ends in circles. We (anybody at all on any side of the argument) cannot explain what controls the climate. But I seem to see that warmist claims to know soon fall down.
rhoda
rhoda - very good! I'm referring to the uncertainty principle and my @#&8&%
Schrodinger's Cat
Assuming that we now have a 97% consensus that the lapse rate doesn’t require GHGs we now have an atmosphere with carbon dioxide absorbing and emitting photons, water vapour likewise, and lots of molecular collisions, the latter much more frequent. In addition to that we have convection.
Your starter question: why does carbon dioxide control the heat loss?
Schrodinger's Cat
Schroedinger's Cat
Lots of problems to discuss with the pressure warming hypothesis, but your last question struck me.
"Your starter question: why does carbon dioxide control the heat loss?"
This will takes several posts.
First consider a non-radiative atmosphere (no GHGs).
Insolation is the amount of radiation intercepted by the planet. Some is reflected(albedo) and the remaining energy reaches the surface. The surface then radiates the same amount of energy to space as infra-red radiation, the OLR. The same applies to bodies with no atmosphere . The surface temperature stabilises at the temperature at which
Insolation -albedo = OLR
You can calculate the temperature of the surface by calculating the temperature at which OLR balances insolation-albedo.
I'll pause here for comments. Whle I'm waiting I'll try and calculate what Earth's temperature would be without GHGs. Anyone care to do the same to crosscheck?
Entropic man
Yes, Entropic man, I do remember Huffman, and I have yet to see his hypothesis debunked; all I have seen are ad hominems against the man, but nothing against his arguments. He gives all the data and formulae that he uses/used, and allows anyone to verify that by themselves; he has NEVER responded with: “Why should I give you the data? You only want to prove me wrong!” I am not sure where you get the idea that he offered warming of Venus by energy that does not exist; the best examples he gave were to compare the results of the Venusian atmosphere at altitudes where the pressure is equivalent to Earth’s with the Earth’s equivalent temperature at that distance from the Sun. Curiously, he only ever gave further examples from higher altitudes, and no-one I ever challenged has been able to reason why this should be (for what it’s worth, I have figured that one out for myself, but no-one I have challenged seems to have).
And let me correct you on one point: Svenmark's cosmic rays hypothesis failed the test of one experiment at CERN. This does not necessarily invalidate the hypothesis. I read the report, and thought, at the time, “Curious. This is a particular narrow investigation…” It really only indicates that they might be looking in the wrong place or for the wrong explanations.
Finally, it is curious to note how you completely ignore the possibility if the atmosphere primarily being warmed by conduction from the surface to the atmosphere and subsequent convection; without GHG, the surface of your world would be as cold as if there was no atmosphere, a proposition that I find utterly absurd.
Radical Rodent
Schroedinger's cat
Calculation of surface temperature for a GHG free Earth.
First a couple of assumptions. No greenhouse gases, so Earth is a dry desert with albedo 0.3 and emissivity of 1.
Solar constant is 1361W/M^2 at Earth orbit.
Total energy intercepted by Earth is 1361×πr^2.
As total energy per square metre that would be
1361×πr^2/4πr^2 =1361/4=340W/m^2.
Allowing for albedo that becomes
340×(1-0.3)= 240W/m^2.
The temperature at the surface would be such that it emits 240W/m^2.
The Stefan Boltzmann equation is
P=eAsigma(T^4-Tc^4)
P is radiated power in Watts
e is emissivity
A is area
sigma is a constant, 5.67×10^-8
T is the radiating temperature
TC is the temperature of the surroundings.
For Earth, when P =240W , eAsigma(T^4-Tc^4) becomes 1×1×5.67×10^-8×(255^4 -3^4).
T is 255C .
That is 33C cooler than the current 288C.
Entropic man
Radical rodent
I don't know how many times I have to repeat this before you catch on.. Huffman's calculation ssumed that all 2636W/m^2 (659W/m^2 of surface area) of the solar constant at Venus was absorbed by the atmosphere.
In reality 90% of that energy is reflected back into space as albedo. The amount of energy absorbed by the atmosphere is 66W/m^2, much too small to produce the effect claimed by Huffman.
Schroedinger's cat
This is also why the pressure warming hypothesis does not work.
The solar constant for Venus is nearly twice that of Earth 2636Wcompared to 1361W.
Venus' albedo is 90% compared to 30% for Earth. The result is that Earth takes up 240W/m^2 and Venus takes up 66W/m^2.
The pressure warming hypothesis is based on solar constant and ignores the effect of albedo, just as Huffman did. When you include albedo the energy budget for Venus is much smaller than Earth's, not much larger. The supposed link between energy input from the sun and temperature collapses.
Entropic man
And how many times do I have to repeat for you to catch on: the calculations Mr Huffman gives return a value at the altitude where the Venusian atmospheric pressure is the same as Earth’s that is EXACTLY the temperature of the Venusian atmosphere at that altitude. This is something that you have singularly failed to do by any other means.
Curiously – and this is something that many people have trouble accepting – Mr Huffman postulates that albedo appears to have no impact on the planetary temperature. As you will also dispute that, I suggest that you enter into discussion with Mr Huffman, himself, about it, as he will be far more capable of explaining his methodology and reasoning than I will. Somehow, I suspect that is not a path that you will choose.
Radical Rodent
Four days ago you said this:
4) The GHGs do not cause the lapse rate directly, but the conditions in which a lapse rate develops would not occur without them.
In fact the lapse rate exists without GHG, it is dependent on well-known gas laws and gravity.
Now, does the surface temp set the tropopause temp, or vice versa?
Can you derive the stefan-boltzman temperature accurately by averaging the radiation from places with different temperatures and emissivities(?)? We blew up that 288K myth years ago, it just ain't so. Check the moon.