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Post by bender on Oct 12, 2009 19:41:56 GMT
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Post by northsphinx on Oct 12, 2009 21:36:59 GMT
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Post by steve on Oct 13, 2009 8:14:16 GMT
On another thread: You have a long memory for arguments where you got the wrong end of the stick. I said "The temperature profile of the atmosphere would be, as now, warmer at the surface and cooling as you rise since this is determined by the adiabatic lapse rate (if the atmosphere continues to be convectively mixed)." There are two distinct nouns here. 1. "temperature profile of the atmosphere" 2. "adiabatic lapse rate". The former is what is measured. The latter is an idealised calculated quantity. If there is no convective mixing in the atmospher, there is little reason why there should be any relationship between the former and the latter. Eg. in the stratosphere. Hence the qualification "if the atmosphere continues to be convectively mixed". You didn't realise the difference and couldn't understand why I thought it was relevant to your discussion. I gave up when you started getting sarcastic. PS. Saying that the latter "determines" the former was a bit strong (but it was not a central point either of what I was trying to say or what you were disputing). You still cant understand it 1. The lapse rate is an observed temperature fall with altitude. It is the temperature falling rate where it is observed to fall. Much of the fall in temperature occurs because water is radiating heat out of the atmosphere that is gained at the surface. Surface conductively warmed air is observed to fall in temperature while there is water in the atmosphere. When there is almost no water in the atmosphere the atmosphere does not have a lapse rate. Instead it has a rise rate. 2. The adiabatic lapse rate is what you get when you take a parcel of air and move it upwards in the atmosphere. Therefore: 1. Is what is observed to be present due to loss of heat from the atmosphere where 98.99% of the atmosphere has no ability to radiate heat unless it is cooled by contact with 1% water or the other .01% 2. involves the word 'adiabatic' www.google.co.nz/search?hl=en&source=hp&q=define%3A+adiabatic&meta=&aq=f&oq=Adiabatic means no loss or gain of heat. Therefore there is no adiabatic lapse rate from the surface of the earth to the top of the trophosphere. There is just a fall in temperature rate called the lapse rate. Yes there is a fall in temperature leading to the observed "temperature profile of the atmosphere" (my noun 1), which I suggest is *related* to (not synonymous with) "the adiabatic lapse rate" (my noun 2) I can't believe we went around the houses so long on adiabatic lapse rate and I didn't realise your huge misconception here. Air cools when it expands whether it is humid or whether it is dry. That is from basic thermodynamics. www.tpub.com/content/aerographer/14312/css/14312_47.htmPossibly your error is in equating heat and/or energy with temperature. They are not the same thing. Temperature will fall despite no loss of heat or radiation of energy.
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Post by radiant on Oct 13, 2009 9:52:35 GMT
You still cant understand it 1. The lapse rate is an observed temperature fall with altitude. It is the temperature falling rate where it is observed to fall. Much of the fall in temperature occurs because water is radiating heat out of the atmosphere that is gained at the surface. Surface conductively warmed air is observed to fall in temperature while there is water in the atmosphere. When there is almost no water in the atmosphere the atmosphere does not have a lapse rate. Instead it has a rise rate. 2. The adiabatic lapse rate is what you get when you take a parcel of air and move it upwards in the atmosphere. Therefore: 1. Is what is observed to be present due to loss of heat from the atmosphere where 98.99% of the atmosphere has no ability to radiate heat unless it is cooled by contact with 1% water or the other .01% 2. involves the word 'adiabatic' www.google.co.nz/search?hl=en&source=hp&q=define%3A+adiabatic&meta=&aq=f&oq=Adiabatic means no loss or gain of heat. Therefore there is no adiabatic lapse rate from the surface of the earth to the top of the trophosphere. There is just a fall in temperature rate called the lapse rate. Yes there is a fall in temperature leading to the observed "temperature profile of the atmosphere" (my noun 1), which I suggest is *related* to (not synonymous with) "the adiabatic lapse rate" (my noun 2) I can't believe we went around the houses so long on adiabatic lapse rate and I didn't realise your huge misconception here. Air cools when it expands whether it is humid or whether it is dry. That is from basic thermodynamics. www.tpub.com/content/aerographer/14312/css/14312_47.htmPossibly your error is in equating heat and/or energy with temperature. They are not the same thing. Temperature will fall despite no loss of heat or radiation of energy. If you fart at 20000 feet the fart cools and that has nothing to do with the adiabatic lapse rate
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Post by steve on Oct 13, 2009 11:41:11 GMT
Lapse rate relates to a change in quantity with height. Part of the cooling of the emitted gas you refer to will, though, be adiabatic cooling because the pressure inside is higher than the pressure outside which means the "parcel of gas" will expand.
So a number of things will cause the gas to change temperature:
1. Adiabatic expansion, because pressure inside is higher than pressure outside. 2. Radiative cooling from the greenhouse gases (water vapour and methane): the temperature of the gas is warmer than the temperature from the surrounding atmosphere, so the net flow of heat will be away. 3. Some of the water vapour may condense which will release latent heat and slow the cooling. 4. Diffusion - collisions between the "warm" faster moving molecules and the "cold" slower moving molecules of the outside air will reduce the average speed of the warm molecules and cool the gas.
The term "adiabatic lapse rate" encapsulates both the adiabatic cooling with expansion *and* the rate of expansion as a parcel of air rises. That is what you are not getting.
I'm afraid the last time I was at 20000 feet it was too windy to do the experiment.
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Post by radiant on Oct 13, 2009 12:45:00 GMT
Lapse rate relates to a change in quantity with height. Part of the cooling of the emitted gas you refer to will, though, be adiabatic cooling because the pressure inside is higher than the pressure outside which means the "parcel of gas" will expand. So a number of things will cause the gas to change temperature: 1. Adiabatic expansion, because pressure inside is higher than pressure outside. 2. Radiative cooling from the greenhouse gases (water vapour and methane): the temperature of the gas is warmer than the temperature from the surrounding atmosphere, so the net flow of heat will be away. 3. Some of the water vapour may condense which will release latent heat and slow the cooling. 4. Diffusion - collisions between the "warm" faster moving molecules and the "cold" slower moving molecules of the outside air will reduce the average speed of the warm molecules and cool the gas. The term "adiabatic lapse rate" encapsulates both the adiabatic cooling with expansion *and* the rate of expansion as a parcel of air rises. That is what you are not getting. I'm afraid the last time I was at 20000 feet it was too windy to do the experiment. When you get into a glider and travel to 20,000 feet the gas expands inside your body and only slightly decreases in pressure outside of your body when released unless you are in pain. Humans who dont fart absorb the gas into the blood and then breathe the fart out thru breath and skin. At 18000 feet the gas in your body tissues is more than twice the volume it was at the surface. The issue you are not grasping is that in a temperature inversion the air gets warmer as you ascend and the reason it gets warmer is because there is only a very slight fall in temperature due to the adiabatic lapse rate For example in my living room it is noticeably warmer at the ceiling than at floor level. By your logic it would not be warmer in my living room at the ceiling or in the living rooms of other peoples houses at a distance of 4 feet above head height. You have to deal with the reality. The sun warms the earths surface where it is most warm in the atmosphere. Higher in the atmosphere or my living room it can only be significantly colder if the air is being cooled by the green house gases or some other force. Without greenhouse gases the atmosphere would behave like any public hall which is hotter at the ceiling dispite the fall in pressure. You need to consider what would happen if after millions of years the hottest air from the surface was for ever rising and there was no way ever of cooling the hotter air at altitude. If i was living at 20,000 feet would my ceiling temperature be higher than my floor temperature? why not? for what reason would it not be hotter at the ceiling? We also need to consider the meaning of higher temperature when at the limits of this ceiling or atmosphere there is almost no nearby molecules and yet each molecule is very high in energy or heat.
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Post by steve on Oct 13, 2009 14:25:57 GMT
The issue you are not grasping is that in a temperature inversion the air gets warmer as you ascend and the reason it gets warmer is because there is only a very slight fall in temperature due to the adiabatic lapse rate No you are wrong. A temperature inversion is an unusual situation that is not caused by air rising. The reason why temperature inversions are interesting is because they suppress convection. The reason they suppress convection is because if a parcel of warm air rises a bit, it cools more rapidly than the air around it, so stops rising quite quickly. The reality of a living room is that you have a large hot radiator causing convection which causes air to rise, and a *ceiling* above that stops it rising further! If the radiator were big enough and the ceiling weren't there the air would continue to rise. Yes. No no no no and again no. As a parcel of air rises it expands. The work it does to expand results in the temperature of the air reducing (even if the air does not lose any net energy - that's the "adiabatic" bit). The net change of pressure between the floor and ceiling of my lounge is small, and would adiabatically cool the air by 0.02C. No it would not. With the greenhouse gases (including water vapour) near the surface the air is (often) approximately in equilibrium (note I'm avoiding saying thermal equilibrium) in that the amount a parcel of air radiates away is approximately equal to the amount of radiation it receives from surrounding parcels of (greenhouse gas containing) air. So the net effect of the cooling from the greenhouse gases is quite small. 1. The air cools as it expands. 2. Yes there is radiative cooling *as well*. Throughout the troposphere and stratosphere, the air is close to local thermodynamic equilibrium. Oxygen and nitrogen (and water vapour and CO2 etc.) all have the same temperature.
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Post by itsthesunstupid on Oct 13, 2009 15:21:06 GMT
Steve wrote:
The reality of a living room is that you have a large hot radiator causing convection which causes air to rise, and a *ceiling* above that stops it rising further! If the radiator were big enough and the ceiling weren't there the air would continue to rise.
Wouldn't the same be true about an atmosphere chamber used to conduct CO2 experiments?
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Post by steve on Oct 13, 2009 15:47:15 GMT
Steve wrote: The reality of a living room is that you have a large hot radiator causing convection which causes air to rise, and a *ceiling* above that stops it rising further! If the radiator were big enough and the ceiling weren't there the air would continue to rise.Wouldn't the same be true about an atmosphere chamber used to conduct CO2 experiments?You can measure the spectral, and other, properties of CO2 and other gases in a lab. Using the principle of physics that the laws are the same everywhere, these can be applied elsewhere (including climate modelling). You can't really demonstrate the enhanced greenhouse effect though in a lab because you'd need a chamber bigger than my living room. Still, basic experiments + careful observations has taught us lots about the universe that could not be fully tested in a lab.
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Post by radiant on Oct 13, 2009 17:23:31 GMT
The issue you are not grasping is that in a temperature inversion the air gets warmer as you ascend and the reason it gets warmer is because there is only a very slight fall in temperature due to the adiabatic lapse rate No you are wrong. A temperature inversion is an unusual situation that is not caused by air rising. The reason why temperature inversions are interesting is because they suppress convection. The reason they suppress convection is because if a parcel of warm air rises a bit, it cools more rapidly than the air around it, so stops rising quite quickly. The reality of a living room is that you have a large hot radiator causing convection which causes air to rise, and a *ceiling* above that stops it rising further! If the radiator were big enough and the ceiling weren't there the air would continue to rise. Yes. No no no no and again no. As a parcel of air rises it expands. The work it does to expand results in the temperature of the air reducing (even if the air does not lose any net energy - that's the "adiabatic" bit). The net change of pressure between the floor and ceiling of my lounge is small, and would adiabatically cool the air by 0.02C. No it would not. With the greenhouse gases (including water vapour) near the surface the air is (often) approximately in equilibrium (note I'm avoiding saying thermal equilibrium) in that the amount a parcel of air radiates away is approximately equal to the amount of radiation it receives from surrounding parcels of (greenhouse gas containing) air. So the net effect of the cooling from the greenhouse gases is quite small. 1. The air cools as it expands. 2. Yes there is radiative cooling *as well*. Throughout the troposphere and stratosphere, the air is close to local thermodynamic equilibrium. Oxygen and nitrogen (and water vapour and CO2 etc.) all have the same temperature. Are you seriously going to argue that an atmosphere containing no greenhouse gases would be hotter at the bottom of the atmosphere than today so that it would warm the earths surface at night by conduction and give us comfortable temperatures? Surely not! If heat rises without a ceiling then it rises to the top of the atmosphere without cooling. What happens then?? Is it now going to cool?? My living room is warmer at the ceiling dispite the lower pressure. Your argument that there is a ceiling and a radiator is irrelevant since the earth radiator warms air that does not leave the earths ceiling either Hot air strongly rises and only slowly cools with altitude. None of this heat would ever leave the atmosphere without cooling or unless it found its way back to the cold surface at night 1. Hot air rises. 2. The temperature lapse rate is small and must become smaller with altitude as pressure falls. approximately the pressure halves at 18000 feet 36000 feet 720000 feet.
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Post by steve on Oct 13, 2009 20:07:55 GMT
Are you seriously going to argue that an atmosphere containing no greenhouse gases would be hotter at the bottom of the atmosphere than today so that it would warm the earths surface at night by conduction and give us comfortable temperatures? Surely not! I said in my first post on this thread and slightly qualified later as follows: The temperature profile of the atmosphere would be, as now, warmer at the surface and cooling as you rise since this is related to the adiabatic lapse rate (if the atmosphere continues to be convectively mixed). A dry parcel of air will adiabatically cool at about 10C per kilometre rise. Technically, your living room is warmer *at the radiator*. That is not a facetious comment. If you have underfloor heating, then it is warmer at the floor. But as I said, the amount of adiabatic cooling between floor and ceiling is about 0.02C which is nothing compared with the other influences on room temperature. Read this very carefully. Air will reduce in temperature as the it rises and the pressure drops *without* losing heat. That is the definition of "adiabatic". The rate of temperature drop is about 10C per kilometre rise. aren't you now saying what I've been saying? I think the confusion is as follows. You are saying that the sun warms the surface, the surface warms the atmosphere. Where does the *energy* go if there are no greenhouse gases? (lets ignore terms such as heat, temperature, adiabatic, lapse rate etc.) The heat has to go somewhere. My answer would be that if there are no greenhouse gases, then the surface will not warm the atmosphere as much as there are less greenhouse gas molecules to absorb the heat. More radiation goes directly to space, and the earth's surface temperature equalises at about 250C. Whatever amount of of energy is retained in the atmosphere will build up and up until there is enough radiation emitted by the weakly emitting non-greenhouse gases such as oxygen (which we know emits at the relatively low energy/frequency of 60Hz) - ie there may be a small greenhouse effect.
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Post by radiant on Oct 13, 2009 20:34:18 GMT
Are you seriously going to argue that an atmosphere containing no greenhouse gases would be hotter at the bottom of the atmosphere than today so that it would warm the earths surface at night by conduction and give us comfortable temperatures? Surely not! I said in my first post on this thread and slightly qualified later as follows: The temperature profile of the atmosphere would be, as now, warmer at the surface and cooling as you rise since this is related to the adiabatic lapse rate (if the atmosphere continues to be convectively mixed). A dry parcel of air will adiabatically cool at about 10C per kilometre rise. Technically, your living room is warmer *at the radiator*. That is not a facetious comment. If you have underfloor heating, then it is warmer at the floor. But as I said, the amount of adiabatic cooling between floor and ceiling is about 0.02C which is nothing compared with the other influences on room temperature. Read this very carefully. Air will reduce in temperature as the it rises and the pressure drops *without* losing heat. That is the definition of "adiabatic". The rate of temperature drop is about 10C per kilometre rise. aren't you now saying what I've been saying? I think the confusion is as follows. You are saying that the sun warms the surface, the surface warms the atmosphere. Where does the *energy* go if there are no greenhouse gases? (lets ignore terms such as heat, temperature, adiabatic, lapse rate etc.) The heat has to go somewhere. My answer would be that if there are no greenhouse gases, then the surface will not warm the atmosphere as much as there are less greenhouse gas molecules to absorb the heat. More radiation goes directly to space, and the earth's surface temperature equalises at about 250C. Whatever amount of of energy is retained in the atmosphere will build up and up until there is enough radiation emitted by the weakly emitting non-greenhouse gases such as oxygen (which we know emits at the relatively low energy/frequency of 60Hz) - ie there may be a small greenhouse effect. If you heat a molecule to 100 C and it cannot cool without warming other molecules then over time there will be more and more heat in the atmosphere that cannot cool. Only the surface of the earth could cool which would be the only way of cooling the atmosphere The adiabatic lapse rate does not mean that hot molecules must cool. it just means there are fewer of them per unit area. Hot air would rise every day until the end of the earth. Eventually all molecules at the top of the atmosphere would be as hot as they can be heated by the earth And at the surface it would be cooler because the earth cools at night. Look at it this way. Day one: a warmed parcel of air rises cools and ascends to the top of the atmosphere. Air at absolute zero preferentially replaces this air because it is heavier. Eventually there is no air at absolute zero. 'Day' two. the coldest air in the atmosphere preferentially descends each day by gravity as warm air rises. The coldest air is warmed a bit more repeat for 5 billion years Where is the descending cold air coming from now??? Hot air rises! If oxygen can totally absorb the days heating and radiate it then it must be some kind of major greenhouse gas. But apparently you tell me the greenhouse gases dont cool the atmosphere!
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Post by steve on Oct 14, 2009 8:52:04 GMT
I think the confusion is as follows. You are saying that the sun warms the surface, the surface warms the atmosphere. Where does the *energy* go if there are no greenhouse gases? (lets ignore terms such as heat, temperature, adiabatic, lapse rate etc.) The heat has to go somewhere. My answer would be that if there are no greenhouse gases, then the surface will not warm the atmosphere as much as there are less greenhouse gas molecules to absorb the heat. More radiation goes directly to space, and the earth's surface temperature equalises at about 250C. Whatever amount of of energy is retained in the atmosphere will build up and up until there is enough radiation emitted by the weakly emitting non-greenhouse gases such as oxygen (which we know emits at the relatively low energy/frequency of 60Hz) - ie there may be a small greenhouse effect. Look at it this way. Day one: a warmed parcel of air rises cools and ascends to the top of the atmosphere. Air at absolute zero preferentially replaces this air because it is heavier. Eventually there is no air at absolute zero. 'Day' two. the coldest air in the atmosphere preferentially descends each day by gravity as warm air rises. The coldest air is warmed a bit more repeat for 5 billion years Where is the descending cold air coming from now??? Hot air rises! If oxygen can totally absorb the days heating and radiate it then it must be some kind of major greenhouse gas. But apparently you tell me the greenhouse gases dont cool the atmosphere! [/quote] My solution to resolve your paradox is this. The (in)ability of oxygen to emit IR radiation is matched by its (in)ability to *absorb* IR radiation. The atmosphere *will not* warm as much as it does now. Therefore when the very slightly warmed parcel gets high up, it doesn't have to emit as much to lose what it absorbed near the surface. Now say for illustration conduction between the surface and the atmosphere were important. Then the atmosphere would warm more than it did just via radiative heating. Even then, eventually the atmosphere would get warm enough to dump the amount of heat it is getting. Furthermore, eventually the conduction between the earth and atmosphere would eventually reduce as the atmosphere approached the temperature of the surface. Then the surface would warm. Since surface radiation is proportional to temperature to the power 4 it doesn't have to warm much to radiate a lot more. And most of the radiation will pass straight through the O2 N2 atmosphere. The surface would never get much warmer than 250K on average.
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Post by radiant on Oct 14, 2009 20:16:43 GMT
My reply in yellowI think the confusion is as follows. You are saying that the sun warms the surface, the surface warms the atmosphere. Where does the *energy* go if there are no greenhouse gases? (lets ignore terms such as heat, temperature, adiabatic, lapse rate etc.) The heat has to go somewhere. My answer would be that if there are no greenhouse gases, then the surface will not warm the atmosphere as much as there are less greenhouse gas molecules to absorb the heat. More radiation goes directly to space, and the earth's surface temperature equalises at about 250C. Whatever amount of of energy is retained in the atmosphere will build up and up until there is enough radiation emitted by the weakly emitting non-greenhouse gases such as oxygen (which we know emits at the relatively low energy/frequency of 60Hz) - ie there may be a small greenhouse effect. Look at it this way. Day one: a warmed parcel of air rises cools and ascends to the top of the atmosphere. Air at absolute zero preferentially replaces this air because it is heavier. Eventually there is no air at absolute zero. 'Day' two. the coldest air in the atmosphere preferentially descends each day by gravity as warm air rises. The coldest air is warmed a bit more repeat for 5 billion years Where is the descending cold air coming from now??? Hot air rises! If oxygen can totally absorb the days heating and radiate it then it must be some kind of major greenhouse gas. But apparently you tell me the greenhouse gases dont cool the atmosphere! My solution to resolve your paradox is this. The (in)ability of oxygen to emit IR radiation is matched by its (in)ability to *absorb* IR radiation. The atmosphere *will not* warm as much as it does now. Therefore when the very slightly warmed parcel gets high up, it doesn't have to emit as much to lose what it absorbed near the surface. It sounds like a theory that air is not majorly warmed at the surface by conduction. It gets very very hot in arizona but you dont feel it is hot because there is such low humidity. Are you saying it is cold in the saraha desert with very low humidity? Maybe you need to travel in the states a bit more and go further south Now say for illustration conduction between the surface and the atmosphere were important. Then the atmosphere would warm more than it did just via radiative heating. Even then, eventually the atmosphere would get warm enough to dump the amount of heat it is getting. But we are talking about ordinary temperatures where it could not dump the heat - now you want to make out the atmosphere is ultra hot Furthermore, eventually the conduction between the earth and atmosphere would eventually reduce as the atmosphere approached the temperature of the surface. Then the surface would warm. Since surface radiation is proportional to temperature to the power 4 it doesn't have to warm much to radiate a lot more. And most of the radiation will pass straight through the O2 N2 atmosphere. Yes earth will be cooler. my point is that it will hotter higher up. at night the atmosphere would warm the earth and by day the earth would warm the atmosphere - but heat rises. The earth would be less warmed at night because once it had cooled the very lowest air layers there is no mechanism to access the warmth higher and away from the surface , but similarly the air would not be cooled much by the cool earth because the warmth would be away from the earth with this thin cold layer at the surface at night.The surface would never get much warmer than 250K on average. 1. i agree the earth would be cooler
2. I think once you can see i am allowing the earth to be cooler you will allow the atmosphere to increase in temperature with altitude
Hot air rises
Also your 10 degrees per Km makes no sense when 99.99997% of the atmosphere is under 100 kilometres and there is still atmosphere above that for hundreds and thousands of km
So 10 degrees per km needs to be quantified for a near surface temperature change or is the earth -1000 or something at altitude?
The troposphere is similar to a room with a ceiling. I doubt there is tremendous circulation of the air above the tropopause once all the convection has ended. If it can get warm in the troposphere it will progressively warm the air higher up give or take a few billion years of warming.
After 5 billion years it will be hotter away from the surface because the surface cools the air at night
Hot air rises but it can only get as hot as the hottest surface temperatures if the air neither emits or absorbs with any significance relative to the enormous surface heating and cooling each day[/quote] The surface would never get much warmer than 250K on average. What temperature do you get if you allow a real earth surface with oceans and surface moisture and a theoretical none emitting atmospheric concept?
Has anybody ever done that calculation?
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Post by steve on Oct 15, 2009 9:47:07 GMT
1. Humidity is a relative measure. When it is hot, the air can hold more water. "Dry" hot air probably holds as much water as my current surroundings (20C and 58% humidity). It is the amount of water vapour, not the humidity, that determines how effectively the air absorbs radiated heat. 2. I'm sure I've read quite often on sceptic blogs that even CO2 absorbs "to saturation" in a short distance near the surface. While it is a strawman argument I assume it may be true, and as H20 is a more effective absorber, it presumably absorbs to saturation as well. 3. Do you *know* how much heat is transferred by conduction as compared with radiation? My understanding and experience is that air is a good insulator. After all, you can fry an egg on the ground, but the air temperature may only be 35C.
No I haven't said anything about it being "ultra hot". The radiation from a material is proportional to its temperature to the power 4. That is a big exponent! And as I followed up, even if the atmosphere cannot lose heat, this means that conduction from the earth will slow down (conduction is proportional to temperature gradient). This means the earth will warm and radiate more, so bypassing the atmosphere.
I've only considered the first 10km to be honest. It was not clear to me whether you agreed that rising air would cool.
Yes it will cool at a slower rate because it is radiating less.
But an equilibrium *will* build up because eventually the surface will stop warming (at somewhere near to 250K) which means the atmosphere near the surface will stop warming which means there is no increase in the energy being transferred to the atmosphere.
At this point the *rate* of conduction to the atmosphere will be constant. The rate of net radiation transfer between surface and atmosphere will be constant (ie. the atmosphere doesn't absorb much and doesn't emit much). So the atmosphere won't warm any more.
As I said, I do not know what the properties of the upper atmosphere will be. And the properties of an atmosphere with convection will be very different from one without convection. As I've studied stellar atmospheres I know this to be true.
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