Home/BlogI continue to get blog comments and e-mails from well-intentioned folks who still don’t understand what determines temperature.
More specifically, I’m talking about those who claim that the atmosphere cannot influence the temperature of the surface because the atmosphere is (usually) colder than the surface. You know who you are. 😉
Their argument goes like this…since net heat flow must be from warmer to colder temperatures (the 2nd Law of Thermodynamics), the presence of the cold atmosphere cannot cause “heating” of the surface. I understand the source of this confusion, and it’s partly a matter of semantics: rather than saying that the “atmosphere heats the surface”, it would be less confusing to say that the “atmosphere reduces the ability of the surface to cool”.
To examine the issue, I’m going to keep the discussion as simple as I possibly can without sacrificing accuracy. Let’s return to one of my favorite examples, an open pot of warm water on the stove. Let’s assume the stove is set on low, and the water has reached a rather warm temperature.
Now, we all know from personal experience that if you put a lid on the pot, you can cause the water’s temperature to rise.
But how can that be, if the lid is colder than the water?
It’s because temperature is determined by both the rates of energy gain AND energy loss, and the lid reduces the water’s ability to cool to its surroundings. It doesn’t matter what the specific mechanism of energy loss is: conductive, convective, evaporative, or radiative.
When we put a lid on the pot, we reduce the rate of evaporative and convective heat loss, as well as radiative loss from the water surface, and the water’s temperature rises until the pot once again reaches a state of energy equilibrium. Convective and radiative energy losses increase with the water’s increasing temperature compared to its surroundings. In a sense, the lid further insulates the warm water from its cooler surroundings, where “insulates” means reducing heat flow in a general sense.
The same is true of the atmosphere. Greenhouse gases in the atmosphere represent a sort of “radiative lid”, reducing the rate at which the Earth’s surface cools to outer space.
One of the major points I am making is that you cannot determine equilibrium temperature based upon the rate of energy input alone: it’s a function of rates of energy gain AND energy loss.
An extreme example is the Sun. At the core of the Sun, “weak nuclear force” reactions produce energy (so I am told) at a rate even less what the human body produces…yet temperatures in the core reach an estimated 15,000,000 deg. C. The reason why the temperature reaches such extreme values is that energy LOSS outward from the Sun’s core is so inefficient.
The everyday examples of the presence of cooler objects keeping things warmer than they would otherwise be are everywhere. For example, coffee in a cold Styrofoam cup. Stack a second cup with the first, and the temperature of the coffee will stay warmer than it would otherwise be.
In fact, everything I can think of that has a heated warm core has its equilibrium temperature controlled by cooler materials surrounding that core. A blanket over your body, etc.
No doubt my detractors will claim I am making absurd comparisons, between a pot of water and the climate system. No, the basic principles of heat flow are the same. If you pump energy into an object, no matter what it is, its temperature will increase until it’s mechanisms of energy LOSS increase to the point where they equal the rate of energy gain. The temperature will then stabilize.
But those mechanisms of energy loss routinely involve materials with cooler temperatures than the warm object itself, materials which reduce the rate of energy loss.
I’ve purposely stayed away from arguments over the specific ways in which infrared radiation courses through the atmosphere so that I can make the more general point.
This issue is so basic I cannot fathom how seemingly intelligent people refuse to accept it, and are so militant in their attempts to refute it. I sometimes wonder whether they are funded by global warming alarmists to waste my time. 😉
“The same is true of the atmosphere. Greenhouse gases in the atmosphere represent a sort of “radiative lid”, reducing the rate at which the Earth’s surface cools to outer space.”
Please explain the phrase: ‘sort of “radiative lid”‘.
As I see it, the so called “greenhouse” gasses do not represent a lid of any kind. They selectively absorb long wavelength radiation and then transfer that energy to neighboring atmospheric molecules. The atmosphere becomes warmer and by the gas laws becomes less dense. That reduction of density allows the hotter air to rise and to be replaced with more dense colder air. Which becomes involved with exactly the same mechanism. This is not a lid, it is a surface cooling mechanism. The surface will remain at the same temperature or increase in temperature only if it receives more energy.
Now it is true that the convection part of the cooling mechanism is much slower than the radiative part, but it is none the less a cooling mechanism. All that means is that there is a slight lag in the temperature drop of the surface after the source of its energy is removed. Note the rapid drop in environmental temperature when the sun is eclipsed by clouds, the moon, or by dropping below the horizon. There is a small impact in that rate of heat loss by the presence of water vapor but it is still a cooling mechanism and not even close to a lid! It is not in the same universe of mechanisms as an actual greenhouse. There is no “sort of lid”.
Geez, Lionell…if you actually read the whole post and did not understand the point(s) I was making, we must be speaking different languages.
Then why use the phrase “sort of a lid”? It is as misleading and as much a lie as the anti-concept “greenhouse effect”.
There is NO lid and there is NO greenhouse in the atmosphere. ALL you have is energy exchange via radiation, conduction, convection, and latent heat transformations. They each occur at different rates, different times, and different proportions of energy transferred per mechanism. The use of the “lid” and “greenhouse” terms do nothing but distort and distract from your point. Why use them unless your purpose is to mislead and to try to appear to both agree and disagree with the alarmists? I find no honor nor honesty in such an attempt.
Come on now. Reality is real. It is what it is and isn’t what it is not. Drop all those inadequate, misleading analogies and speak to what actually is! I suggest your message will get through far more clearly.
OK, then forget the terms “lid” and “greenhouse effect”, since they seem to be getting in the way of the main point of my post.
Do you agree that the presence of the atmosphere reduces the radiative cooling rate of the surface, compared to if the atmosphere was not there?
Because if you agree with that, then you are also agreeing that the presence of the (cooler) atmosphere raises the (warmer) surface temperature.
Because the presence of the cooling effect of the atmosphere by all mechanisms, the temperature of the surface is lower than it would have been without the atmosphere. Thus the rate of radiative loss in full sunlight is less with than without the atmosphere BECAUSE of its lowered temperature. See the temperature of the surface of the moon in full sunlight compared to the earth for a case in point.
Please try to hold context. All mechanisms are functioning all the time and at the same time. They have interactions that determine the end result depending upon many details. Simply choosing one mechanism to the exclusion of all the others and attributing a theoretical but unmeasurable independent result from that exclusion is erroneous.
The consequential result of all mechanisms of energy transfer is that the surface is much cooler in full sunshine with the atmosphere than it would have been without the atmosphere. THAT lowered temperature causes the lower rate of radiative loss but that lowered rate cannot cause an “increase” in temperature – even metaphorically. You have confused cause and effect to preserve your wished for interpretation. The three laws of thermodynamics apply in spite of your apparent wish to evade them.
The important point here seems to be that a Mr. Wood, early in the twentieth century, was generally believed to have refuted the greenhouse effect by pointing out that greenhouses were warmer due to convection rather radiating heat. AGWers have to defeat his case. I don’t see that you have. The cooler atmosphere does not raise the temperature of the Earth, it only reduces the cooling rate compared with the yet cooler vacuum of space.
Hi Lionell,
You should note in the interest of honesty and full disclosure that the high lunar daytime temperature (approximately 100 degrees centigrade to a maximum of 120 degrees centigrade) results greatly from slow lunar rotation and the long length of a lunar day, around 27 to 28 earth days. In addition, daytime temperatures vary greatly based on the angle of incident sun light. At high latitudes temperatures fall to 8 degrees centigrade. Night time temperatures will drop to -153 degrees centigrade, and in some craters -250 degrees centigrade or less. Average lunar temperatures fall far short of earth temperatures.
“Note the rapid drop in environmental temperature when the sun is eclipsed by clouds”
That’s an illusion. In windy conditions you won’t really notice the drop as the air is well mixed. In relatively still conditions, the air mass below the cloud is moving with the cloud. Thus when the cloud moves overhead, the air mass that has been in shade for some time also moves overhead, and is colder.
I think Lionel is pointing out that other cooling mechanisms prevent GHGs from working as a lid.
In the absence of such other mechanisms then of course GHGs could have the effect of reducing the rate of cooling and I don’t think Lionel intended to deny that.
It is not clear to me that the GHG’s have an effect of reducing the rate of cooling. They actually account for more of the cooling per molecule than the so called non GHG gasses. All they can do is shift the proportion of energy transferred by the different mechanisms. Again, consider the context that ALL mechanisms are at work all the time and at the same time. Their rates and directions of transfer of energy will depend upon specific circumstances that cannot be in violation of the three laws of thermodynamics, the gas laws, nor the laws of radiation.
However the net effect of the atmosphere is that it cools rather than heats. This general principle can only be violated when the cooling results in a situation where the atmosphere is warmed in in one area and blown to another area in which the surface is cooler. Then and only then is the surface warmed by the atmosphere. This effect is essentially due to local situations and not global ones.
I agree that GHGs might not reduce the rate of cooling anyway because they provide an extra radiative window to space not provided by non GHGs and help shift the energy around as you say but I didn’t see any need to mention that for the purposes of discussing Roy’s analogy.
As for the net effect of an entire atmosphere being cooling then we cannot agree for the reasons set out in one of my other posts.
Quite simply planets with atmospheres are always warmer than those without because an atmosphere presents resistance to the radiative flows of energy in and out. However that resistance is due to mass and not radiative characteristics.
Roy asks:
“Do you agree that the presence of the atmosphere reduces the radiative cooling rate of the surface, compared to if the atmosphere was not there?”
Interesting queston because it implies a recognition that it is the entire mass of the atmosphere that reduces the radiative cooling rate of the surface and with that I would wholeheartedly concur.
The real issue is whether the radiative characteristics of constituent molecules can have any additional such effect given the wide range of non radiative processes available to prevent it.
I’m going to upset virtually everyone with this! Most physical scientists fail to understand the Stefan-Boltzmann equation or the mechanism by which greenhouse gases cause the atmosphere to warm.
The monochromatic volume-specific rate of gain of heat qdot by matter from incident EM energy is the negative of the divergence of the monochromatic flux density vector.
This means net qdot = -(integral over all wavelengths(vector sum of Poynting Vectors at a point in space)). PV is the power transferred by a monochromatic wavefront.
A single body does not transfer real radiative energy; you need its radiation field to interact with that from another body. Hence the S-B flux is a potential energy flux from a body at T> 0 °K to a body at 0 °K not an energy flow or a stream of photons as many physicists believe.
It gets more complex with the atmosphere because it is semi-transparent. Of 160 W/m^2 average SW energy to the surface you get 17 convection, 80 evapo-transpiration, 23 absorbed by GHGs [non self-absorbed water vapour sidebands plus trace gases) and 40 to space by the atmospheric window (2009 Energy budget, which is surprisingly accurate). Forget about the 396 ‘black body IR’, that is ludicrous, as is ‘back radiation’.
The Ramanathan ‘clear sky greenhouse factor = 396 – 238.5 = 157.5 W/m^2 exaggerates GHG absorption of IR by 6.85x.
The 23 W/m^ real average GHG absorption cannot be thermalised directly because the atmosphere is at Local Thermodynamic Equilibrium. The absorbed photon is entering a filled IR density of states so another photon is ejected from the volume to be thermalised at heterogeneities, particularly clouds but also to space.
There can be no GHG blanket. Most energy is transferred via convection up to about 6 km where that changes to radiation. None of that going upwards can be thermalised so it mostly goes to space. OLR is misinterpreted because the CO2 15 µm band is self-absorbed so it comes from ~6 km not 220 °k as the simple comparison with S-B gives.
As for the GHE, most is from gravity – adiabatic lapse rate. There is some from GHGs but because there can be no significant net CO2 15 µm IR emission from the surface, there is no connection between rising CO2 and water vapour to affect lapse rate.
Hope this is some help…….:o)
Hence the net effect of the atmosphere is to cool the surface and not heat it in either full sunlight or full darkness and for almost all the time in between. That is except for local transient effects from lateral transfer of warmer atmosphere in to an area of lowered surface temperature.
All you have to do is live close to the ocean to experience the above several times a day. On shore winds cool. Off shore winds warm. Yet the global effect of each is a net cooling. What is cooled and warmed simply changes.
What you have stated does not upset me. You have more clearly defined, in more detail ONE, of the energy transfer mechanisms that work in parallel with all of the other energy transfer mechanisms. It is nothing mystical or magical. It is simply a different and a bit more obscure mechanism that some in the “climate” field try to use to accomplish impossible things.
Thank you.
It’s time someone nailed back radiation by linking to the basic physics [Goody and Yung is the source].
Basically, climate alchemy adds 134.5 W/m^2 radiative warming out of thin air by assuming the energy leaving the Earth’s surface is 3.1 times greater than that which arrives.
This is justified by 333 ‘back radiation’, which does not exist except as a potential energy flux to a sink at absolute zero. They claim they measure this by a pyrometer which internally converts the ‘temperature’ of the lower atmosphere via the S-B equation to its potential energy flux – pyrgeometers. This si a 50+ year old mistake from meteorology.
Exaggerated warming of sunlit oceans is offset by exaggerated cloud albedo so they get the ‘right temperature’ in hind-casting. Because of the exponential evaporation kinetics there is vastly increased evaporation in sunlit oceans yet average temperature seems OK. This gives the imaginary positive feedback.
They then give themselves Nobel prizes for being very good a cheating.
Lionell said:
“Because the presence of the cooling effect of the atmosphere by all mechanisms, the temperature of the surface is lower than it would have been without the atmosphere”
The effect of the atmosphere (by all mechanisms) is to lower the highest surface temperature on the day side and raise the lowest surface temperature on the night side but with overall an increase in the average temperature of the surface globally.
What happens therefore is that the atmosphere becomes warmer than the surface on the night side whilst remaining cooler than the surface on the day side but overall the former outweighs the latter so actually the atmosphere slows the cooling of the surface by being warmer than the surface (averaged globally).
If the atmosphere averaged globally were always to be colder than (or the same temperature as) the surface then the night side would lose energy just as fast as the day side gained it and the atmosphere would have no net warming effect at all.That would be the scenario with no atmosphere.
It is false to assert that the atmosphere is usually colder than the surface. Averaging globally across both night and day sides it is always warmer than the surface.
Water oceans present an extra layer of complexity but we needn’t deal with that here. For present purposes we should assume 100% land area.
The energy in delta temperature is an exponential function. The lower the temperature the lower the change in energy per degree. An average of an intensive (temperature) variable has no physical meaning. Sure it can be computed but there is no physical meaning in global average temperature there is no physical meaning. There is not much physical meaning in a single point average temperature.
This discussion has physical meaning in ONLY the dynamics of energy transfer for which temperature is a damn poor proxy.
If you want to limit the discussion to physically meaningless averages, you can but what does that have to do with anything real?
I ONLY talked about the dynamics of energy transfer.
The atmosphere does what it does and I described that for you.
What you completely evaded was the fact that heat was conducted from the surface to the subsurface during the time the sun was shining on it. That conduction further limited the rise in surface temperature. Then, during the night, that heat was conducted back to the surface and mostly carried away by the atmosphere.
Like I say, ALL the modes of energy transfer that are possible in a physical situation are going on concurrently and interact with each other. You cannot properly isolate one factor from all others, look at the result of the response to the total collection of processes, and then attribute the specific result to that one factor. Context matters and context always exist and must be accounted for.
The reason the temperature at night is elevated is the heat that was stored during the day below the surface was returned to the surface. The primary reason for the huge difference between the earth’s day and night temperature and the moons day and night temperature is the earth day/night cycle is roughly 1/27 that of the moon.
You can apply relative scales of effect to the different energy transfer mechanisms.
For a solid surface (no atmosphere) conduction makes no discernible difference to the temperature predicted from the S-B equation.
Add a gaseous or liquid atmosphere and the internal circulation of that atmosphere does make a discernible difference to the temperature predicted from the S-B equation.
AlecM said:
“As for the GHE, most is from gravity – adiabatic lapse rate”
Yes it is but gravity works on mass to create the lapse rate so we are back to mass being the relevant factor and NOT the radiative characteristics of constituent molecules.
The S-B equation can only be applied to a solid surface with no internal circulation to effect energy transfers by non radiative means.There can be a little conduction but insignificant in terms of affecting surface temperature.
As soon as one introduces a non solid surface (gas or liquid) then there is an internal circulation that removes energy from radiative to non radiative transfer mechanisms.
The latter are slower than the former so the gas or liquid introduces resistance to the flow of energy in and out which results in a temperature rise (a greenhouse effect or atmospheric thermal enhancement as referred to by Nikolov and Zeller).
That temperature rise is a result of mass and not radiative characteristics of constituent molecules hence the fact that at the same pressure the atmospheres of both Earth and Venus have much the same temperature after adjusting only for their respective distances from the sun.
The empirical evidence is that radiative characteristics of constituent molecules have no effect on the temperature of surface or atmosphere but would have a miniscule effect on the internal circulation within the gas or liquid forming an atmosphere.
That internal circulation employs non radiative energy transfer processes and will always regulate the energy flow through the system so that over time energy in equals energy out at the top of the atmosphere (however defined).
Sorry, misled you by accident.
I meant ‘Of ’33 K GHE’ claimed by Climate Alchemy, most is from adiabatic lapse rate and is independent of CO2 concentration.’
I’ve been triply awestruck by this article.
Firstly, by the sheer clarity of its explanation. I envy the brilliance of your analogy. I’ve tried to make the same point myself, elsewhere, and failed. I not only admire your choice of example, I’m small-souled enough to envy it.
Secondly, I was struck by the common-sense of the preemptive comment “No doubt my detractors will claim I am making absurd comparisons, between a pot of water and the climate system.”
Finally I was blown away by the fact that Lionell Griffith did still fail to comprehend you. He mistakenly took a clear disproof of the claim “cooler things cannot increase the heat of warmer things” as being instead a physical analogy.
Apropos of that mistake, I might well be making it myself in a separate context. The claim “that we are loading the climate dice to increase the likelihood of more extreme climate events” troubles me. As far as I know, this is not an example, but a mere assertion, an analogy that does not have any physical correspondence to the real world. I am unable to confirm or disprove my understanding.
Could you please help me? I’m asking for just a brief answer while being aware that reality is more complex than brief answers usually permit.
Is there any physical basis for that claim?
Leo, thanks for recognizing the main point of my post, which (predictably) has been ignored by those who wish to obfuscate with technical details.
The claim that we are “loading the climate dice” is indeed an assertion, although (like most things in science) not necessarily false. But when storms happen anyway, the idea that a ~1% decrease in the infrared cooling rate of the Earth (without feedbacks) is going to cause a noticeable difference is speculative at best. Remember, most “storminess” is due to the equator-to-pole temperature difference, which is supposed to be *reduced* with global warming.
Roy, with respect, the cooler object is pre determined in it’s equilibrium ‘position’ by gravity. The rest state is the adiabatic. As defined Roy, by the application of PURE PHYSICAL LOGIC, the higher state ‘always’ has greater ‘potential’ energy and if we are not nuclear then the exchange is through kinetic. Kinetic energy in a gas is thermal It’s not rocket science! ANY, ANY,ANY EXCHANGE, involving mass will answer to gravity. Period. The rest is conservation and Newtonian mechanics, which I can assure you of are entirely valid. The rest state of any atmosphere is dT/dh=-g/Cp. Where Cp acknowledges work being done on or by the thermodynamic process.
Lionell has emphasised that all modes of heat transfer answer to the instantaneous thermal gradient they ‘see’. As he has said this is valid within a ‘coupled’ thermal system. There is no deception. The manifestation of this is the ‘evolution’ of the various thermal gradients over time. Each affecting the other in filling or draining the Earth’s thermal pools.
Within the atmosphere thermalised absorption always leads to buoyancy and opacity swaps over to convection, irrespective of mechanism. Whichever mechanism succeeds, does so because of the gradient it ‘sees’. It is obvious that ‘normally’ accepted heat transfer to set isothermal equilibrium is on average ‘overwhelmed’ by the incontrovertible persistence of gravity. As proved by the ‘average’ measurement of the tropospheric thermal gradient.
As viewed from the surface, any radiative coupling occurs either spectrally or broadband across an optical depth. Vertically this addresses a mean height of atmosphere. Varying opacity addresses different heights and temperatures. Those temperatures are on average set by the gravitationally set gradient. Heat travels between the surface and the mean optical depth as a result of the temperature ‘difference’. Without the temperature ‘difference’ and a mechanism, how do you describe a sustainable exchange?
This is the result of the gravitationally set lapse rate on average. This renders net radiative flux and ‘calculated back flux’ a ‘product’ of the gravitationally set thermal gradient. As Stephen knows, all atmospheres act to restore the gravitationally set adiabatic profile.
Incidentally, the only way to increase the temperature of the core of the Sun would be to increase or decrease it’s mass . The interior of a star is the closest we have to a black body. With heat transfer totally independent of composition.
Last paragraph should read ‘ only way to ‘alter’ the temperature of the core of the Sun etc. my apologies.
I would also specifically point to that Actual warming is done by the sun and nothing else. The atmosphere as a whole warms (ie its temperature increases) only when the sun shines down on it and on the surface. If we were to put earth in the dark, no matter how many greenhouse gas there is in the atmoshere it would not warm but cool, eventually going down to zero and with atmosphere freezing out.
Yes, of course, the sun is the source of energy. But, as should be clear from my post, that fact tells you nothing about what the Earth’s temperature will be.
2lionell:
Do not forget that the atmoshere itself has pretty high heat capacity so that at around normal earth temperatures itbwould cool only about degree or two overnight, and even if one confined most cooling to boundary lyer, the temperature of srface layer of thevatmosphere would not cool more than 10 to 20 degrees centigrade, which is what really happensin drier climates; on a second ought, if the inversion layer is extremely shallow the surface may cool even more.
That does not change the fact that a free atmosphere cools a heated surface and cannot heat it when it is colder than the surface. In fact, the colder the atmosphere is with respect to the surface, the higher the rate of cooling the surface.
As for the lid of a pot “proving” a colder object can cause the temperature of a hotter object to rise, even if true (and is isn’t), it has absolutely nothing to do with the atmosphere/earth system. In fact, it is an inverted greenhouse in which the heat comes from below and the lid prevents convection from cooling the heated pot as much as a free atmosphere would without the lid. As such it doesn’t even come close to “proving” anything about the atmosphere/earth system. The good doctor has assumed what he is attempting to prove and has failed.
I acknowledge that your point is that you see Dr Spencer’s example as having ‘absolutely nothing to do with the atmosphere/earth system.’
However, in passing, you assert that it isn’t true that the lid of a pot example proves a colder object can cause the temperature of a hotter object to rise.
It is true, it does make it hotter, admit it or explain why our experience is wrong.
Hi Leo Morgan,
You claim: “However, in passing, you assert that it isn’t true that the lid of a pot example proves a colder object can cause the temperature of a hotter object to rise.
It is true, it does make it hotter, admit it or explain why our experience is wrong.”
Your statement fails to convince. Remember a mind will be only so good as the precision of it’s concepts. Most mornings I bring heated tea to work in a thermos. The “cooler” thermos prevents the tea from cooling down during the morning hours. After noon my tea remains hot and steamy. The cooler thermos never causes the temperature of my hot tea to rise. Instead it merely prevents heat from escaping the confines of the thermos to the outer environment. Dr. Spencer acknowledges this in his statement above.
The only time anyone ever observes heat energy transfer from a cooler object to a warmer object occurs when additional mass/energy performs work on the system (therefore not in conflict with the 2nd law of thermodynamics) to force such heat transfer as in the case of a refrigerator. In Roy’s example above the stove provides the additional energy and the lid additional mass to confine the energy, therefore no violation of the second law of thermodynamics occurs. The lid can only raise the water temperature in concert with additional energy from the stove’s flame. The cooler lid cannot raise water temperature in the absence of added energy or work being performed.
This clarification seems as Roy stated: “so basic I cannot fathom how seemingly intelligent people refuse to accept it, and are so militant in their attempts to refute it.”
Correction to my post above. It should have read: “The only time anyone ever observes the heat energy increase of a warmer object originating from a cooler object occurs when additional mass/energy performs work on the system (therefore not in conflict with the 2nd law of thermodynamics) to force such heat transfer as in the case of a refrigerator.”
Dr. Spencer – excellent post.
You have my sympathies WRT the many replies missing the point.
thank you, KR.
Haven’t any of the commenters here noticed the difference in how rapidly the surface air temperature cools when the sun goes down dependent on the humidity of the air?
In Dr. Spencer’s humid Alabama summers, the cooling is very gradual. In coastal California, we laugh at the Eastern tourists in the summer who are not prepared for our relatively rapid evening temperature drops and are quickly shivering in their shorts and T-shirts while we throw on our sweatshirts. In the southwestern deserts, with their very low humidity, the cooling is even more rapid.
The difference, of course, is how much water vapor there is in the air to act as a “lid” limiting how fast the “pot” of the surface land that has been heated by the sun all day can cool in the evening.
The humidity aspect arises from the ability of water vapour to store energy as latent heat.
The presence of the latent heat in water vapour does restrict the cooling rate of the surface below but that is a separate process from any effect that might arise from the radiative characteristics of molecules of water vapour or from the presence of atmospheric mass.
If one takes the atmosphere as a whole that disruption of the energy flows caused by the presence of latent heat gets dealt with by changes in circulation via winds and so overall has no net effect on the total system energy content or the average temperature of surface and atmosphere.
As Geoff wood says, all atmospheres act to restore the gravitationally set adiabatic profile.
That is a point that I have been putting forward for several years now.
If any atmosphere were to fail to restore the gravitationally set adiabatic profile for a long enough period of time then the atmosphere would either boil off to space or congeal on the surface.
The persistence of planetary atmospheres for 4 billion years (so far) is empirical proof that atmospheres succeed in restoring the gravitationally set adiabatic profile.
Curt,
I have done some studies on your issue about humid air cooling slower than dry air and I do not find this is a factual statement (though many believe it). I converted the humid air and dry air to enthalpy energy of air (humid air stores a lot more energy at the same temp as dry air). I found the humid air lost energy faster than the dry air.
Also I did a larger study on the contiguous USA using NOAA data of 118 years. The list most and least temp and percipitation and give each year a rank. I did a top 10 study of wettest and driest years. I used only summer months (June, July, August) since that is when the air would contain the most water vapor molecules (you can have a high relative humidity in winter but the number of water molecules of GHG in the air are much less).
In my study it was very conclusive (with only a couple exceptions) that the wetter summers were cooler (some the coolest of 118 years) and the drier summers (with less water vapor) were among the hottest. I can send links if you are interested to confirm what I am stating.
Norman — We are talking about different things. I am talking about the rate of cooling after the sun sets as a function of humidity. A little more generally, this could be viewed as the day/night (max/min) temperature difference as a function of humidity. But I am not talking about the absolute level of that temperature.
I do not doubt your claim (and I would be surprised if it weren’t true) that wetter summers in a given location are cooler than dry summers. But wetter summers mean more cloudiness, and in summer, with longer days than nights, more clouds mean net cooler weather.
Hi Curt,
I actually did a study of Montgomery Alabama vs Las Vegas for the rate of cooling. The more humid city does not cool slower and night time lows for desert locations do not always drop in temperature. Go to weatherunderground website, find History and put in any city you wish and do the study to see if your understanding is the correct one.
I did check typical temperature swings in the desert southwest versus the humid southeast before I posted, and found them to be larger in the southwest.
Curt,
It is more complex, you also have to take elevation into effect. I have found dinural range goes up considerably as you go up in altitude even in wetter cities.
Climate Phoenix (elevation 1117 feet)
http://www.rssweather.com/climate/Arizona/Phoenix/
Climate Mongomery, Alabama (elevation 220 feet)
http://www.rssweather.com/climate/Alabama/Montgomery/
If you look at the July temperatures for both these cities you can see Phoenix has a dinural range of 22.8F and Montgomery has a diurnal range of 21.8F not really that much difference.
Now look at what elevation does:
Climate Vail Colorado (8150 feet)
http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?covail
The diurnal range of Vail in July is 37.2F.
Las Vegas (elevation 2030 feet) diurnal range 25.9F
Barstow California (elevation 2106 feet) diurnal range 31F
From this limited study I do not know if there is sufficient evidence to formualte your conclusion.
The clear sky heat loss at night is because of two thirds of the IR emission from the surface is to space via the atmospheric window. Unchecked this will continue until the surface temperature has fallen low enough that reverse IR outside the AW equals the IR lost in the AW.
For air at 15 °C, this equilibrium is at -13.5 °C. This is how the Bedouin make ice in the desert – in pits with steep sides to maximise emissivity.
The reason why cooling is slower in humid climates is because of the release of latent heat by condensation. IR in the AW and the water cycle control diurnal temperature range. It is nothing to do with ‘back radiation’ which does not exist.
The evening cooling in a humid locale is slower than in a less humid location even before the dew point is reached and water starts condensing out of the atmosphere.
Your theories fail to explain easily observable and measurable phenomena. You really need to rethink.
Curt
If interested here is the Weatherundergound link. I have it for Mongomery, Alabama. You can put in any day of the year and go back to 1948. It gives you the entire daily temperature record on an hourly basis and tells you what the weather conditions are (sunny, cloudy, wind direction and speed). For my analysis with Las Vegas I looked for cloudless days and nights and also the lowest wind levels (not always easy to find to match up). Not the ideal but you can see if your view is a correct one. Maybe with research you will prove it is. Weatherunderground is an excellent resource to test ideas such as yours.
http://www.wunderground.com/history/airport/KMXF/2013/4/10/DailyHistory.html?req_city=Montgomery&req_state=AL&req_statename=Alabama
Your point is easily explained. The dew point is when liquid water forms. Adsorption and local liquid formation in re-entrants will take place at <100% RH.
Because the latent heat of condensation is so great, it slows the cooling rate long before visible condensation.
If you put a little water in a good tall thermos bottle and point it at the sky on a warm dry windless night the water will freeze for the same reason.
Dr. Spencer
Thank’s for talking time explaining the basics on many levels on your site. Browsing through the comments on this very basic post I see how stuck some can be in a pattern of reasoning. Die hard warmists are note alone in this respect.
It is not paranoia to suspect some posters to be trolls wanting to waste your time but hopefully some readers also got your point.
thanks, Sigmund.
“This issue is so basic I cannot fathom how seemingly intelligent people refuse to accept it, and are so militant in their attempts to refute it.”
Me either. Perhaps they don’t realize or fundamentallly understand that radiative effects are different. On an individual particle level (i.e. individually emitted photons), the direction of each can be either from warmer to colder or colder to warmer, as they have no way of distinguishing or discriminating. The only requirement for the 2nd law is that net total heat transfer must flow from warm to cold, which it does in the atmosphere.
Thank you, Dr. Spencer, for this post. Very clear, and I like your use of everyday examples.
Does Roy agree that it is the entire mass of the atmosphere that has the effect of reducing the rate of surface cooling and not just greenhouse gases ?
Thanks, Dr. Spencer.
Your clear explanations will be remembered, even if they are misunderstood by a a few.
I would like to comment on the warm water with a lid. With a lid the water will warm more than without but the lid will be as warm as the water not colder.
If you would do the experiment a little differently, say a thick lid (so it stores lots of energy) that is chilled to freezing temps and put it over the pot of warm water and measure the water temperature, you might find that the water will actually cool (even though it is being supplied a continuous heat source) until the lid warms up, then the water will heat to temperatures above the situation without a lid.
Roy,
This argument has been going on for quite some time. On your blog, WUWT, Jo Nova, Judith Curry, Science of Doom.
Can a cooler object warm a warmer one via radiation?
You suggest a thought experiment. I still ask why doesn’t anyone actually do an experiment (maybe Myth Busters would do it since no scientist seems to want to). I would do the experiments myself (experimentation is what drew me to the sciences in the first place) if I had access to a vacuum chamaber. NASA has them. Why not do the experiment. Test it and see what the actual result is. It would end the argument. Settled. Now we have people that dislike the PSI group for suggesting it will not warm the warmer object.
So many opinions. So much absoulte certainty they are correct in their understanding. So little actual experimentation to end all the debate. It would not even be an expensive experiment and could be done in a day.
Again why won’t the experiment be done. Roy don’t you have friends at NASA that would allow you to run such tests?
“Can a cooler object warm a warmer one via radiation?”
No, of course not, and nobody has suggested otherwise.
Try and read what Dr. Spencer actually wrote. It really could not be clearer.
“atmosphere reduces the ability of the surface to cool”
This is NOT in any way the same as a cooler object warming a warmer one.
steveta_uk
My question comes from other posts by Roy Spencer “Yes Virgina…” is one example. He posted a thought experiment run in a vacuum where a heated object will get warmer after another object is placed close to it (non heated). I would like the experiment to go out of the “thought” phanse and into the real phase.
I do agree atmosphere will reduce the ability of the surface to cool. But will an all nitrogen atmosphere do the same? An atmosphere would do both, keep the surface from warming too much and cooling too much. A moderating effect.
Somewhat OT, but I find it interesting that although the satellite temperature record seems to be stuck on “warm” there are certain regions (Britain, Germany, asia) that are experiencing unusual cold. I agree that regional climate sensitivity is meaningless unless you carefully define the “region” you are talking about. However, regional climate does vary as a matter of common knowledge and the relationship of regional variation to solar activity is a legitimate subject of interest, as there are important impacts on food production and energy consumption. I hope and pray that Monsanto and the other seed companies are positioning themselves for an era when cold-hardy food grains may be in demand, even though “science” remains on the AGW gravy train for now.
Dr. Spencer, of course it’s all about the flux of energy in, out, and through a medium. And because it’s hard to measure the directions and amounts simultaneously, confusion comes screaming in. Perhaps a better analogy out of the realm of physics, such as the checking account, would help because dollars are more discrete and easily tracked than are joules. I have to get back to work so I’ll leave it to you to flesh out the analogy.
I found this about the reason why humid air is warmer. Hope it helps but note that for the entire atmosphere the local and regional effects of humidity are negated by wind and circulation changes so as to restore the adiabatic lapse rate set by gravity.
“Air is composed mainly of 78% nitrogen (molecular weight 28) and 21% oxygen (molecular weight 32), with another 1% of other gases. Water vapor (molecular weight 18) is considerably lighter and when it displaces nitrogen and oxygen in the air, makes the air density lower (lighter, as you have said, than dry air at the same temperature).
The result of the absorption of energy is a higher energy state of the molecules, reflected only in increased temperature and pressure if the volume of the air is held constant. However, in the atmosphere there are no fixed boundaries to keep the air volume the same, so when the temperature of the air increases, it wants to expand (although this is slowed by the shear mass and weight of air around it), thus reducing the molecular weight of the air in the original volume. The temperature of all of the molecules increases as water vapor radiates some of its absorbed energy to neighboring nitrogen and oxygen molecules.
If your volume of air has water vapor in it, it will warm more rapidly than dry air, since water vapor is a greenhouse gas that has the capacity to absorb more energy than nitrogen and oxygen. The amount of water in the air is always small compared to the amount of nitrogen and oxygen, so a humid volume of air, though being less dense than a dry volume of air, is not an impediment to the absorption of energy by the water vapor. The only mass of any molecule in the air that is important is that of the water vapor itself. The more water vapor, the more absorption of energy is likely, irrespective of the mass of other constituents of the air.
David R. Cook
Meteorologist
Climate Research Section
Environmental Science Division
Argonne National Laboratory “
Stephen Wilde
“If your volume of air has water vapor in it, it will warm more rapidly than dry air, since water vapor is a greenhouse gas that has the capacity to absorb more energy than nitrogen and oxygen.”
I am not sure this statement is correct when looking at humid vs dry areas and temperature rise. One thing David R. Cook might consider is that humid air stores much more energy than dry air (same volume…heat capacity of water).
When Doug Cotton brought out his study of wet/dry cities I continued the research and I can’t find evidence to prove him wrong. Wet regions seem cooler than dry ones. It could be that water vapor has a cooling effect and not warming. Radiates away energy that N2 and O2 are not able to do.
Also “The temperature of all of the molecules increases as water vapor radiates some of its absorbed energy to neighboring nitrogen and oxygen molecules.” From my understanding, neither nigrogen or oxygen are IR absorbers. They are transparent to IR energy to the most part and would not absorb radiation from water vapor.
Dr. Spencer, For what it’s worth, your explanation made perfect sense and really helped me mentally model heat flow. Thank you for taking the time to provide the concise lesson.
Brian
In Holland we like skating, specially on natural ice.
In winter when it starts freezing and ice in the canals end lakes is getting thicker. But too often a big spell of snow is putting a layer on the thin ice.
Now people have to be warned for very dangerous ice conditions.
The ice hardly grows or even gets thinner.
All by the isolation of the snow.
Snow is colder then the water under the ice. But the net flow of energy is sometimes from the water to the ice.
Dr Roy,
As you will have noticed, analogies are often misleading at best, and mischievous at worst.
Pots, lids etc.
I believe you hit the nail on the head with your comment about a “heated warm core”, when referring to the atmosphere acting as a “blanket”.
The Earth’s molten interior is insulated from the close to absolute zero of outer space by the crust of solidified rock, the surface water (oceans etc), and the atmosphere.
The temperature gradient to outer space (nominally 0K), proceeds generally from the center of the Earth at some thousands of degrees K (due to original energy content at creation, plus additional energy due to weak nuclear forces to date), to nominally zero, once the outer limits of the atmosphere have been left behind.
The resultant “surface” temperature is, as you state, the resultant temperature after the various energy flows both positive and negative are taken into account.
The atmosphere does not provide any additional energy to the system, by itself, any more than a blanket does. Surrounding an inert body with CO2 will not raise its temperature at all. Not one bit. Wrapping a corpse with a blanket will not raise its temperature.
There is an instructive Toureg saying – “If I had known it was going to be this hot, I would have worn a thicker robe”. Researchers who have bothered to measure relevant temperatures in this regard, rather than conduct “thought experiments” have discovered that facts can be counter intuitive occasion.
So, the Earth is the temperature it should be. It gains energy from a variety of sources – the Sun, internal radioactive mass conversion, Man and his works, the Moon (tides etc), and all the rest.
It loses energy by means of electromagnetic radiation, and maybe other means that I know nothing about.
In conclusion, hot molten blob, cooling slowly. Congealed exterior. No mystery. It will no doubt continue to cool until it is an isothermal cold blob.
Are my “facts” open to question, or is my logic faulty?
Live well and prosper.
Mike Flynn.
If there were no greenhouse gases (no water, no CO2,
no CH4, etc)in the atmosphere the atmosphere would,
entirely cease to radiate, to space or ground.
This is BECAUSE a bad absorber such as nitrogen is a bad emitter.
Over time, the atmosphere would uniformly adopt the temperature of the solid surface (about 300 K). This surface temperature is determined at equilibrium,
solely by insolation.
This is BECAUSE the modelled blackbody temperature of about 300 K must be exactly high enough to radiate away to space any inflowing energy.
The “greenhouse effect” is genuine but completely irrelevant in the long run since it merely displaces a mechanism of conduction that would otherwise be more active.
Of course the shape of the earth, and its daily rotation, and its annual path around the sun, introduce disequilibriums for any particular place.
Wrong.
The equilibrium temperature is 255K.
“Over time, the atmosphere would uniformly adopt the temperature of the solid surface ”
Actually not because the gravitationally induced pressure gradient would still cause a lapse rate resulting in convection which would rise and fall as before.
The rest of your point is correct because any energy converted to PE as air rises comes back to KE as air falls so at equilibrium the surface would still radiate just as much as necessary to match incoming energy.
Your comment about the radiative abilities of GHGs merely displacing conduction (and convection) that would otherwise be more active is spot on as I have tried to explain previously.
Also correct is your point about local and regional disequilibria.
In the end what that all means is that GHGs affect circulation but not global equilibrium temperature.
Does the water in the pot heat up because the pressure increases when you put a lid on it? Water at a higer pressure boils at a higher temperature.The lid would just get hotter until the same heat was lost at equilibrium otherwise.
I agree with you Dr. Spencer, but I think it’s somewhat of a moot point when all is said and done. I believe there is a foundational problem here. Why use the 255K greybody temperature to solely attribute the 33K to radiation while 80% of the planetary surface is composed of a super-capacity ocean, without a diurnal cycle? The mere existence of an atmosphere insulates the ocean surface (note why the boiling temp of water decreases with altitude), and as the faint sun paradox suggests, even with cloud cover, we don’t need all that much in the way of back radiation to maintain their temperature. Without cloud cover the lit side of Earth would be receiving almost 680W/m^2…right into the oceans.
Removing all GHGes not only takes cloud cover out of the picture, but it also leaves Oxygen absorbing in the UV spectrum, the atmosphere becoming isothermal as surface temperatures initially cool and the upper atmosphere heats up, thus we lose all convective cooling as the atmosphere now cannot radiate to space at all… and the oceans are now taking in much more in the way of SW radiation, plus and surface temps are now swinging wildly from day to night, conducting to a non-emitting, isothermal atmosphere.
The only thing for the temperature to do at that point is warm. I think the 33K figure being attributed solely to radiation is silly, it is a combination of factors including Earth’s rotation rate, thermal capacity, and radiative/conductive insulation of the surface.
Dr No says 255K
Perhaps, we are both wrong.
With no greenhouse gases at all there would be no water
vapour to form clouds, and the albedo of the earth would
be near zero (actually zero, if we are modelling it as a
true black-body). Therefore the insolation would be 43% greater, and the equilibrium temperature would be 10%
higher than 255 K – i.e. 279 K. The average temperature of the earth (I am told) is 287 K and so the net effect of all changes induced by greenhouse gases, including water, is perhaps +8 K.
This talk about averages, for various varieties
of “equilibrium earth” – which are merely posited –
seems a bit pointless.
Since blackbody radiation is a function of the fourth
power of temperature; and an average temperature, by
definition, tells one nothing about the fluctuations
in time and space of temperature; the actual uncertainty
must increase as of the fourth power of these unknown (or,
at least, extremely complicated) matters.
Roy.
It is quite true that the temperature at the base of the atmosphere “supports” the surface temperature, though this has little to do with any “lid” effect, because you cannot stop the overall tendency for radiative balance in the total “Earth + atmosphere” system as seen from outer space. There’s been plenty of water vapour around for a long time doing about a thousand times what all the carbon dioxide can do, and yet measurements show no net radiative imbalance at TOA when temperatures are reasonably level as they have been since 1998, and will continue not to rise until 2028.
If anything were going to provide a “lid” on the atmosphere it would be water vapour, but you have no evidence of it doing so and causing any radiative imbalance. And the only real world evidence is that more water vapour produces lower surface temperatures, not higher ones.
There is no analogy with your pot on the stove because the overall physics of the atmosphere is more complex and, in particular, the effect of gravity over the height of the troposphere is far more significant than in the height of your pot of water, where it can be neglected.
The underlying base temperature is established by the need for this radiative balance (which sets the mean level of temperatures in the whole system) and the thermal gradient (aka effective lapse rate) which is established by diffusion of kinetic energy at the molecular level, following the concepts of Kinetic Theory as used by Einstein – see Wikipedia.
The surface temperature is supported by the fact that the temperature at the base of the atmosphere is in fact itself supported by the above mechanism. This is very evident on Venus, where direct Solar insolation could not possibly produce the observed surface temperature of over 720K.
The warm base of the atmosphere does this supporting through a ratchet effect between day and night. The base temperature slows down the rate of cooling (both by radiative and non-radiative processes) as the temperature gap narrows late at night. That’s why it doesn’t keep cooling at the same rate as it did in the late afternoon. This then assists the Sun to warm the surface more the next day than it could have if the surface had cooled more the previous night.
But the daily warming is a marginal effect, and so too is the slowing of surface cooling by both radiative and non-radiative processes. Water vapour and carbon dioxide do slow the radiative cooling, but the more significant effect which they have is to reduce the thermal gradient by intra-molecular radiation. This sets a lower base surface temperature, and this is why real world data shows that similar regions have higher daily maximum and minimum temperatures when the air is drier than when it is moist.
So, you are correct in some ways, but you are incorrect in assuming that there is any transfer of thermal energy from a cooler atmosphere to a warmer surface by radiation. The only such transfers are by “heat creep” in the non-radiative process of diffusion and (downward) convection, but these processes are restricted to not exceeding the effective thermal gradient set by gravity g and mean specific heat Cp and reduced by about a third by intra-molecular radiation between H2O and CO2 etc. You can read plenty about this in my papers, articles and forum comments on the Principia Scientific International website.
For more on this see my three comments starting here …
http://www.drroyspencer.com/2013/04/direct-evidence-of-earths-greenhouse-effect/#comment-74240
Doug Cotton
Your pot only boils at night, Roy.
If you check out the net energy diagram by NASA you see that 16% +3% = 19% of incident Solar radiation is absorbed by the atmosphere and clouds. Then only 15% is absorbed from the surface radiation. Of course, during the day more than twice as much is absorbed on its downward path compared with that going back up. At night it is nearly all upward radiation that is absorbed. (If you prefer to use those diagrams with back radiation, just deduct the back radiation from the upwelling radiation to get the net amount absorbed.)
This is why the Earth does not get as hot as the Moon during the day, nor as cold as the Moon at night.
So your pot only boils at night, Roy. During the day you could draw an analogy with a pot in the Sun filled with ice. Place the lid on the pot and the ice melts more slowly than it would in direct sunlight.
Furthermore, the 24 hour mean favours the ice bucket slightly more than the pot on the stove.
As you say, Roy, “This issue is so basic I cannot fathom how seemingly intelligent people refuse to accept it.”
>>This issue is so basic I cannot fathom how seemingly intelligent people refuse to accept it, and are so militant in their attempts to refute it. I sometimes wonder whether they are funded by global warming alarmists to waste my time.<<
I would call it "Ecological Piety", the ilk of which the Scarlet Letter 'A' was made. There is nothing more dangerous then men and women who feel righteous and 'none so blind as those who will not see.'
I have to say I have a hard time following all that is being reported without a scientific background, but I appreciate the effort and muddle through. SO, I'm glad you take the time to give another view.
To be exceedingly simple, just think of the atmosphere as a thermos bottle.
And to be a little less simple-minded, think of all those oxygen and nitrogen molecules (with a little help from water vapour and CO2 etc) acting as a blanket at night and a slightly more effective umbrella by day.
But if you really wish to find an accurate explanation for all planetary surface, crust, mantle and core temperatures – an explanation backed up by empirical evidence – then you need to be somewhat less simple-minded, my friend, and dig deeply into the physics of the situation into realms not yet widely known, let alone understood. Heat transfer mechanisms are a complex study at the forefront of modern physics, I would suggest – not a place “to be exceedingly simple.”
PS See this comment.
“An extreme example is the Sun. At the core of the Sun, “weak nuclear force” reactions produce energy (so I am told) at a rate even less what the human body produces…yet temperatures in the core reach an estimated 15,000,000 deg. C. The reason why the temperature reaches such extreme values is that energy LOSS outward from the Sun’s core is so inefficient.” ~Roy
Uh… the core is radiating into an environment at nearly the same temperature, isn’t it?
Using the SB law equation properly makes this clear:
P = εσA(Th⁴ – Tc⁴)
If Th is close to Tc, P will not be large.
_______________________________________________
In another post above I saw it stated that the Earth radiates more than it receives?
“It is an empirical fact that the earth’s surface emits far more power than it obtains from the sun. Yet the earth is not rapidly cooling. Where does the balancing power come from? (You seem to object to analyses that say that the earth’s surface radiates more than twice what it receives from the sun — I see no factor of two issue in the 1st law.)” ~Curt
Hmmm, the illuminated half of the Earth receives 1.22×10^17 Watts from the Sun, and I’m pretty sure the day and night side emit around 5.11×10^16 Watts each, for a total of 1.22×10^17 Watts absorbed and emitted.
Just to add, it seems almost as though you’re saying the temperature is a result of the comparitively low energy transfer through radiation emitted by the core to the outer layers, as though you could trigger nuclear fusion with an arbitrarily low input as long as you had sufficiently effective insulation?
You’re making it sound like you could have a chunk of solar core material next to you with no issues because it’s “only giving off around 276 W/m^3″… when the only reason that value is so low is, as I noted above, Th is close to Tc, in the case where Th is vastly higher than Tc (like a 15 million K hunk of fusing hydrogen and typical temperatures found here on Earth) then P would be much higher.
I can’t find a BB calculator online which doesn’t laugh at me when I put those values in, though.
You’ll find a valid explanation of planetary core temperatures in my paper “Planetary Core and Surface Temperatures.” After all, what;s in a name.
However, a star (and even a shrinking gaseous planet) have another source of heat, namely kinetic energy coming from potential energy as the total size of the sphere shrinks. This happens with Jupiter, causing radiative energy imbalance, but not Earth or Venus of course. I am not saying it is the only internal source of energy in the Sun, but it is a significant source relatively speaking in Jupiter.
As for Earth’s surface, NASA net diagrams show about 51% of incident Solar radiation entering the surface, which then exits the surface as …
Thermal energy to atmosphere by evaporative cooling 23%
Thermal energy to atmosphere by conduction 7%
Thermal energy to atmosphere by radiation 15%
Thermal energy to space through window 7%
It seems to me that 23 + 7 + 15 + 6 = 51%
Energy in = energy out, so what’s the problem? You see, radiation transferring electro-magnetic energy is not the same as thermal energy transfer.
Again, you perhaps seem to think I’m endorsing greenhouse effect nonsense, and your posts thus have an antagonistic approach towards me.
If you’re right your argument will stand on its own merits, but simply declaring that you’ve found the one true way isn’t science, it’s just another permutation of faith.
Good information. Lucky me I found your site by chance (stumbleupon).
I’ve bookmarked it for later!
The point which I was trying to make (badly, I now see)
is that “the greenhouse effect”, to the extent we consider
it PURELY, PURELY in terms of radiative flows (i.e. to a first approximation)
(a) WILL increase the heat in the solid parts of a
rocky (no H2O) earth’s skin;
(b) will NOT change the heat and temperature of an
atmosphere.
The reasoning is simple. I assume that all the sun’s energy
is delivered as short-wave radiation to the surface rocks of the earth through an atmosphere which is transparent to all radiation. Then the earth’ skin, at equilibrium, will adopt an effective temperature of, say, 280 K which is sufficient to radiate away energy at the same rate as the sun delivers it. And the atmosphere will be cold ( assuming no conduction). Now introduce a perfect greenhouse gas (one which absorbs – and emits -all infrared, but no short wavelengths). Calculations of radiation balance show the system will attain equilibrium again when the temperature of the physical skin of the surface of the earth is higher than 280 K, and the temperature of the greenhouse gas, and thus of the whole atmosphere IS 280 K. The atmosphere has to be 280 K because it is now the sole effective radiator to space.
To be the radiator for the whole system, the atmosphere
has to be cooler than the solid earth but at no higher
temperature than the solid earth was before.
Theoretically then , as a result of these processes alone,
an increase in greenhouse gases should warm the soles of the feet but not one’s nose up in the air.
Therefore: People, who “just do not see” how the
greenhouse warming principle can be “right”, may be correctly, if incoherently, picking up on SOMETHING wrong in the usual statement of it. And the wrong bit is the assumption that the temperature of ALL parts of the system can be increased in this way. The temperature of the part that is radiating to space is limited, in equilibrium, by
the solar input.
Imagine a blackbody radiating:
outward
radiation
!!!!!!
solar input—-> ——— 280 K
Barrier
below
Put another blackbody close above it at 280 K:
outward
radiation
Flow A up !!!!!
———- 280 K
Flow B down !!!!!
Flow C up !!!!!
solar input—-> ———- 280 K
Flow A = Flow B = Flow C as they come from radiation
across surfaces at the same temperature. C and B cancel
each other and the lower body starts to warm to more than
280 K. Flow A is the net outflow from both the system and the upper body, which starts to COOL to less than 280K.
This is disequilibrium of course, but it is obvious how equilibrium will be reached.
The above assumes a barrier to heat flowing “below” the surface of the earth. But in the longer run, excess heat
HAS been going into this enormous sink. A comparison of the records of the Challenger voyages, of 120 years ago, with modern records shows that the surface of the Ocean has warmed some 0.6 C in that time; the water, 1000 meters down, has warmed 0.4 C; and the bottom water has warmed
(perhaps) 0.1 C.
The above facts set a limit for calculating the historical surface warming rate – namely 1/100 C, per year.
My nice little diagram was mangled in the upload
!!!!
solar input –> ——– 280 K
A up !!!!!!
——– 280 K
B down !!!!!!
C up !!!!!!
solar input –> ——– 280 K
Sigh. Still mangled. The exclamation marks !!! are
meant to be coming in and out of plate-like black bodies
——-
Double sigh.
The exclamation marks are meant to show RADIATION
coming in and out of plate-like blackbodies.
Also: When I wrote “0.4 C rise in temperature at 1000
meters depth” in the sea, this should have been “1000
FEET depth.”
So; 99% [my simple calculation] of the “excess heat” of
the last 120 years has gone into the middle-deep waters of the oceans – where it has made the temperature soar by 0.4 C. Presumably that heat sink will work similarly over the next 120 years. Is there really any reason for precipitate actions?
“… 1/100 C per year… ”
should have been 1/200 C per year.
Roy your physics gets worse and worse
You write “It’s because temperature is determined by both the rates of energy gain AND energy loss, and the lid reduces the water’s ability to cool to its surroundings. It doesn’t matter what the specific mechanism of energy loss is: conductive, convective, evaporative, or radiative.”
The pot is receiving energy at a rate which is capable of raising its temperature to boiling point or more.
In contrast, the direct Solar radiation which the Earth’s surface is receiving is only capable of raising its temperature to the proverbial 255K – which is in fact a little inaccurate because we don’t live on a flat Earth, but it is certainly a value less than 288K.
The surface of Venus receives only about 10% of the direct Solar radiation that Earth’s surface receives, so on that planet the Sun can only raise its surface temperature by direct radiation to something colder than about 150K – which is certainly hundreds of degrees less than its actual surface temperature.
The explanation as to what really happens on these planets is in my paper Planetary Core and Surface Temperatures.”
Dr. Spencer,
You certainly have a lot of patience. I would have given up trying to explain the basics of heat movement a long time ago.
I really do admire your efforts at trying to educate the public.
Years ago, I attempted to explain to people what would happen when electronics became cheap enough for people to start creating and storing digital images. They just didn’t get it. I wonder if most understand the concept today.
Please keep up your efforts. I learn something every time I visit.
Regards
Fascinating sequence of debatable ideas, even for an amateur whose major interest is in the logic (and its occasional foundering).
Thank you Roy for this, and so much more.
However, your initial challenge was to explain the difference in temperature between pointing at the sky and pointing at the cloud.
The cloud is warmer than the sky. Several factors have been mentioned that account for that. An hypothesised greenhouse effect in the atmosphere appears not to be required to explain that temperature difference.
Cheers
Ian
I’ll try to say this as simply as I can, before wading
through 91-plus comments:
The 2nd Law of Thermodynamics only governs *direction
of net heat flow*. It says nothing about *rate of heat
flow*, especially when adding a barrier can change the
rate.
And when a barrier is selectively barrier to heat
outgo and not to heat income for some object, then
that object gets warmer.
For example: Adding insulation to the exterior walls
of a building during wintertime. The interior of the
building will get warmer, even though the insulation is
cooler than the building is. The insulation does not
change the heat capacity of the building’s furnace.
Or, throwing on a blanket when sleeping while your
bedroom is chilly. The blanket will make your skin
warmer, even though the blanket is cooler than your
skin. The blanket does not reduce your body’s
ability to produce heat as needed.
And as I have heard Spencer said, putting a lid on a
pot makes the pot’s contents warmer, even though the
lid is cooler than the pot’s contents. The lid does
not affect ability of the stovetop to heat the pot.
This does not change when the additive is a barrier
to outgoing thermal radiation from Earth’s surface.
Greenhouse gas molecules absorb photons of outgoing
thermal radiation, and have a (usually lesser) but
nonzero rate of emitting ones of their own. Half
of those new emitted photons are emitted towards the
surface. The greenhouse gas molecules only have to
be warmer than absolute zero to return downwards a
fraction of the energy that they absorb.
Yet, greenhouse gas molecules are not a barrier to
most incoming solar radiation, because that mostly
has different wavelengths not absorbed by greenhouse
gas molecules.
For that matter, glass greenhouses have their
interiors warmer than their exteriors, despite the
glass being cooler than the interiors. I consider
it a matter of debate *how* the glass is a barrier
to outgoing heat. (Convection at convection-favorable
times of the day, or radiation? It could be more a barrier to convectional than to radiational heat loss.)
Yet, the glass makes the interior warmer, while the
glass is cooler than the interior.
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