Guest Post by Reed Coray
On Dec. 6, 2011 12:12 am Lord Monckton posted a comment on a thread entitled Monckton on sensitivity training at Durban that appeared on this blog on Dec. 5, 2011. In that comment he wrote:
“First, it is not difficult to calculate that the Earth’s characteristic-emission temperature is 255 K. That is the temperature that would obtain at the surface in the absence of any greenhouse gases in the atmosphere. Since today’s surface temperature is 288 K, the presence as opposed to absence of all the greenhouse gases causes a warming of 33 K”.
Since I’m not sure what the definition of the “Earth’s characteristic-emission temperature” is, I can’t disagree with his claim that its value is 255 K. However, I can and do disagree with his claim that 255 K is “the temperature that would obtain at the surface in the absence of any greenhouse gases in the atmosphere”.
When computing the Earth’s surface temperature difference in “the presence as opposed to the absence of all greenhouse gases”, (i) two temperatures (A and B) must be measured/estimated and (ii) the difference in those temperatures computed. The first temperature, A, is the temperature of the Earth’s surface in the presence of an atmosphere that contains both greenhouse gases and non-greenhouse gases. The second temperature, B, is the temperature of the Earth’s surface in the presence of an atmosphere that contains non-greenhouse gases only–i.e., an atmosphere that contains non-greenhouse gases but is devoid of greenhouse gases.
For temperature A almost everyone uses a “measured average” of temperatures over the surface of the Earth. Although issues may exist regarding the algorithm used to compute a “measured average” Earth surface temperature, for the purposes of this discussion I’ll ignore all such issues and accept the value of 288 K as the value of temperature A (the temperature of the Earth’s surface in the presence of an atmosphere that contains both greenhouse gases and non-greenhouse gases).
Thus, we are left with coming up with a way to measure/estimate temperature B (the temperature of the Earth’s surface in the presence of an atmosphere that contains non-greenhouse gases only). We can’t directly measure B because we can’t remove greenhouse gases from the Earth’s atmosphere. This means we must use an algorithm (a model) to estimate B. I believe the algorithm most commonly used to compute the 255 K temperature estimate of B does NOT correspond to a model of “the temperature of the Earth’s surface in the presence of an atmosphere that contains non-greenhouse gases only”. As will be evident by my description (see below) of the commonly used algorithm, if anything that algorithm is more representative of a model of “the temperature of the Earth’s surface in the presence of an atmosphere that contains both greenhouse gases and non-greenhouse gases” than it is representative of a model of “the temperature of the Earth’s surface in the presence of an atmosphere that contains non-greenhouse gases only.”
If I am correct, then the use of 255 K in the computation of the Earth surface temperature difference with and without greenhouse gases is invalid.
Although there are many algorithms that can potentially lead to a 255 K temperature estimate of B, I now present the algorithm that I believe is most commonly used, and discuss why that algorithm does NOT represent “the temperature of the Earth’s surface in the presence of an atmosphere that is devoid of greenhouse gases”. I believe the algorithm described below represents the fundamental equation of radiative transfer for the Earth/Sun system assuming (a) an Earth absorption albedo of 0.3, and (b) an Earth emissivity of 1.
(1) The “effective temperature” of the Sun [i.e., the temperature of a sun-size spherical blackbody for which the radiated electromagnetic power (a) is representative of the total solar radiated power, and (b) has a power spectral density similar to the solar power spectral density] is approximately 5,778 K.
(2) For a spherical blackbody of radius 6.96×10^8 meters (the approximate radius of the sun) at a uniform surface temperature of 5,778 K, (a) the total radiated power is approximately 3.85×10^26 Watts, and (b) the radiated power density at a distance of 1.5×10^11 meters from the center of the blackbody (the approximate distance between the center of the Sun and the center of the Earth) is approximately 1,367 Watts per square meter.
(3) If the center of a sphere of radius 6.44×10^6 meters (the approximate radius of the Earth) is placed at a distance of 1.5×10^11 meters from the center of the Sun, to a good approximation the “effective absorbing area” of that sphere for blackbody radiation from the Sun is 1.3×10^14 square meters; and hence the solar power incident on the effective absorbing area of the sphere of radius 6.44×10^6 meters is approximately 1.78×10^17 Watts (1.3×10^14 square meters x 1,367 Watts per square meter).
(4) If the sphere of radius 6.44×10^6 meters absorbs electromagnetic energy with an “effective absorption albedo” of 0.3, then the solar power absorbed by the sphere is 1.25×10^17 Watts [1.78×10^17 Watts x (1 – 0.3)].
(5) A spherical blackbody (i.e., a spherical body whose surface radiates like a surface having an emissivity of 1) of radius 6.44×10^6 meters and at a temperature 254.87 K (hereafter rounded to 255 K) will radiate energy at the approximate rate of 1.25×10^17 Watts.
(6) If independent of the direction of energy incident on a sphere, the surface temperature of the sphere at any instant in time is everywhere the same, then the sphere possesses the property of perfect-thermal-conduction. Thus, for (a) an inert (no internal thermal energy source) perfect-thermal-conduction spherical body of radius 6.44×10^6 meters and uniform surface temperature 255 K whose center is placed at a distance of 1.5×10^11 meters from the center of an active (internal thermal energy source) spherical blackbody of radius 6.96×10^8 meters and uniform surface temperature 5,778 K, and (b) the inert perfect-thermal-conduction spherical body (i) absorbs electromagnetic energy with an effective absorption albedo of 0.3, and (ii) radiates electromagnetic energy with an emissivity of 1 then the perfect-thermal-conduction inert spherical body at temperature 255 K will be in radiation rate equilibrium with the active spherical blackbody at temperature 5,778 K. If the phrase “inert perfect-thermal-conduction spherical body of radius 6.44×10^6 meters” is replaced with the word “Earth,” and the phrase ” active spherical blackbody of radius 6.96×10^8 meters and uniform surface temperature 5,778 K” is replaced with the word “Sun”, it can be concluded that: If (a) an “Earth” at temperature 255 K is placed at a distance of 1.5×10^11 meters from the “Sun” and (b) the “Earth” (i) absorbs electromagnetic energy with an effective absorption albedo of 0.3, and (ii) radiates energy with an emissivity of 1, then the “Earth” will be in radiation rate equilibrium with the “Sun.” For the above conditions, the temperature of the “Earth” in radiation rate equilibrium with the “Sun” will be 255 K.
This completes the algorithm that I believe is commonly used to arrive at an “Earth’s characteristic-emission temperature” of 255 K, and hence is used to compute the 33 K temperature difference.
Even ignoring the facts that (1) it is incorrect to use the “average surface temperature” when computing radiation energy loss from a surface, and (2) in the presence of an atmosphere, (a) the blackbody radiation formula may not apply, and (b) blackbody radiation from the surface of the Earth is not the only mechanism for Earth energy loss to space (the atmosphere even without greenhouse gases will be heated by conduction from the Earth surface and both conduction and convection will cause that thermal energy to be distributed throughout the atmosphere, and the heated atmosphere will also radiate energy to space), the problem with using the 255 K temperature computed above to determine the difference between the Earth’s temperature with and without greenhouse gases is that the effective Earth absorption albedo of 0.3 used to generate the 255 K temperature is in part (mainly?) due to clouds in the atmosphere, and atmospheric clouds are created from water vapor, which is a greenhouse gas.
Thus an effective absorption albedo of 0.3 is based on the presence of a greenhouse gas–water vapor. It is illogical to compute a difference between two temperatures both of whose values are based on the presence of greenhouse gases and then claim that temperature difference represents the temperature difference with and without greenhouse gases. Without water vapor, there won’t be any clouds as we know them. Without clouds, the effective absorption albedo of the Earth will likely not be 0.3, and hence without the greenhouse gas water vapor, the Earth’s surface temperature in the absence of greenhouse gases is likely to be something other than 255 K. Thus, the 255 K “Earth characteristic-emission temperature” as computed using the algorithm above is NOT relevant to a discussion of the Earth surface temperature difference for an atmosphere that does and an atmosphere that does not contain greenhouse gases. Only if 0.3 is the effective absorption albedo of the Earth in the presence of an atmosphere devoid of all greenhouse gases is it fair to claim the presence of greenhouse gases increases the temperature of the Earth by 33 K.
Because clouds reflect a significant amount of incoming solar power, without water vapor I believe the effective absorption albedo of the Earth will be less than 0.3. If true, then more of the Sun’s energy will be absorbed by an Earth whose atmosphere is devoid of greenhouse gases than by an Earth whose atmosphere contains clouds formed from the greenhouse gas water vapor. This implies a higher Earth surface temperature in the absence of water vapor than the “Earth’s characteristic-emission temperature of 255 K”.
For an effective absorption albedo of 0, the temperature of the Earth in radiation rate equilibrium with the Sun will be approximately 278.64 K (hereafter rounded to 279 K). If this value is used as the Earth temperature in the presence of an atmosphere devoid of greenhouse gases, then it can be argued that the presence of greenhouse gases introduces a warming of approximately 9 K (288 Kelvin minus 279 K).
In summation, using the simplified arguments that I believe are also used to arrive at the 33 K temperature difference (i.e., assumed perfect-thermal-conduction Earth, blackbody Earth emission, greybody Earth absorption with an effective absorption albedo between 0 and 0.3, and ignoring atmospheric radiation to space for an Earth atmosphere devoid of greenhouse gases), I conclude the presence of greenhouse gases in the Earth’s atmosphere increases the Earth’s temperature by somewhere between 9 K and 33 K. Thus, I believe the claim that the presence of atmospheric greenhouse gases increases the temperature of the Earth by 33 K is based on an argument that has little relevance to the Earth’s temperature in the presence of an atmosphere devoid of greenhouse gases; and hence at best is misleading and at worst incorrect.
Note: Upon first publication – the guest author Reed Coray was accidentally and unintentionally omitted.
There are a few additional thoughts to add to this already “interesting” notion of removing GHGs, and that has to do with what exactly what you’re defining as the “temperature” of the planet, and the role that greenhouse gases play in providing a temperature in the atmosphere at various levels. If the Earth were simply a rock spinning in space (much like the moon), without an atmosphere at all, then what exactly would you mean by its temperature?
The temperature right at the ground (0m), or 1m above the ground, or 1m below? These would all be different. SW radiation striking the ground will either be absorbed by the ground and/or reflected back into space. Once absorbed by the ground, it will converted to LW. Some of that LW will be reemitted back toward space. Of course, without greenhouse gases it will transfer instantly to space as there would be intervening gases for it to be absorbed by. Additionally of course is the dramatic diurnal change that you’d see on an Earth devoid of GH gases, such that the very notion of an “average” becomes suspect.
@Bomber_the_Cat says:
December 27, 2011 at 8:35 am
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Bomber the Cat
I have had this argument for years with car tyres.
When you inflate the tyres, the air inside heats in relation to the pressure. After inflation, the air in the tyres is hot. However, although the rubber is a fairly good insulator eventually, the heat from the air inside the tyre is lost by conduction and radiation.
In a static condition there is nothing replenishing the heat so eventually the air inside the tyres cools to ambient garage temperature. If on the other hand, immediately following inflating the tyres whilst the air temperature inside the tyres was still hot from the pressure brought about by the inflation, you were to drive on the tyres, the very slight flexing of the side walls would be sufficient to maintain the heat inside the tyres. The flexing of the side walls does not create very much pressure but the work being done is sufficient to maintain the temperature of the air inside the tyres. If you could drive indefinitely you would maintain the temperature indefinitely,
The point is that you need some external input of energy to maintain the temperature.
Reverting to the Earth. The Earth has two such external sources of energy that maintain the temperature caused by the pressure of the Earth’s atmosphere. First, there is the sun. Some of the solar energy is absorbed by the atmosphere. Second, the atmosphere flexes just like the side walls of the tyre (when you are driving on the tyre). As you are no doubt aware there is an atmospheric/diurnal bulge which is constantly fluctuating. These inputs taken together are sufficient to maintain the temperature caused by the pressure of the atmosphere.
@Bomber_the_Cat says:
December 27, 2011 at 8:35 am
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Bomber the Cat
I have had this argument for years with car tyres.
When you inflate the tyres, the air inside heats in relation to the pressure. After inflation, the air in the tyres is hot. However, although the rubber is a fairly good insulator eventually, the heat from the air inside the tyre is lost by conduction and radiation.
In a static condition there is nothing replenishing the heat so eventually the air inside the tyres cools to ambient garage temperature. If on the other hand, immediately following inflating the tyres whilst the air temperature inside the tyres was still hot from the pressure brought about by the inflation, you were to drive on the tyres, the very slight flexing of the side walls would be sufficient to maintain the heat inside the tyres. The flexing of the side walls does not create very much pressure but the work being done is sufficient to maintain the temperature of the air inside the tyres. If you could drive indefinitely you would maintain the temperature indefinitely,
The point is that you need some external input of energy to maintain the temperature.
Reverting to the Earth. The Earth has two such external sources of energy that maintain the temperature caused by the pressure of the Earth’s atmosphere. First, there is the sun. Some of the solar energy is absorbed by the atmosphere. Second, the atmosphere flexes just like the side walls of the tyre (when you are driving on the tyre). As you are no doubt aware there is an atmospheric/diurnal bulge which is constantly fluctuating. These inputs taken together are sufficient to maintain the temperature caused by the pressure of the atmosphere.
@richard M says:
December 27, 2011 at 7:41 am
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The temperature in the first instance is created by the gravitaional pressure. Thereafter, there is heat loss from the system. You need some external input which need not be sufficient to create the remperature brought baout by the gravitional process (in our case circa 288K) but rather that which is sufficient to cover/make good the heat loss from the system.
Obviously, the sun is one such source. A second source is work done in the atmoshere itself. The atmosphere is dynamic and in constant flux. Work is being done and a by product of this is to heat the atmosphere at any rate to the extent necessary to cover/replenish the heat loss.
I would not definitely rule out some heat trapping effect caused by GHGs but there is in practice no need to resort to such a theory to explain the temperature of the Earth. Gas pressure alone is quite capable of explaining why the Earth is sufficiently warm for life to flourish.
Great post for showing how the most elemental “fact” is neither certain nor settled! The probable best response is to ask what the purpose of the question of the Earth’s non-GHG temperature is: to eliminate the oceans as part of the removal of GHG is to change what the Earth is, so the answer becomes suitable to a non-Earth. As with other variations on the calculation.
The question in the CAGW story is used to give a background to either the great warming of GHG gases, and hence their danger (the warmist side), or that total GHGs give 33C of heating, so how much change can only 300 ppm of CO2 bring (the skeptic side)?
As for the non-atmospheric temperature of the planet (any planet): I’m a geologist, and I’ve been struggling to figure that out, although I have access to almost 300,000 temperature readings (in Alberta alone) at various depths in the Western Canadian Sedimentary Basin. The loss of heat at the surface is sudden and rapid; fifty meters down most places (outside remnant glacially cooled areas) it is about 16*C. Another sudden change happens at the continental crust contact of 1000 or more meters. Both the air and the sedimentary covers have a strong cooling effect, i.e. have high thermal conductivity. Elsewhere, the Greenland ice cores seem to show that, at the base of the ice sheets, the rock is – 9*C, while in Antarctica there are buried liquid lakes of 0*C. So what is even the non-solar insolation temperature of the planet?
Mars has an apparent surface temperature averaging – 60*C. But what is it 200 m down? The moon is – 272*C on the dark side and +250*C (pardon the inexactitudes; the details are not the point here). Same question: the Apollo boys did a little digging and left some instruments for temperature monitoring, but I couldn’t figure out where the surficial rapid cooling equalled the deeper radiative heat loss. Which is why I started to try to figure out what temperature the planet – any planet – would be at in the absence of an atmosphere.
The question that in a strict physicist’s way needs answering is: for a rock surface average of Earth, where the only two ways of temperature are 1) the present cooling of a central core through a thermally conductive surrounding medium like the Earth, and 2) the different rates of warming and cooling of the average dry surface rock averaged through the day, night and orbital variations, what would the surface of the planet be?
I can’t figure out what the planetary rock should be, but I THINK, it might be 18*C. Which is higher than the 14.5*C it is supposed to be, which then says that the atmosphere COOLS the planet. What does the warming/cooling differential of solar insolation have, considering the thermal conductivity of rock? What if there were a ball of rock at 3K, a billion years ago, with a billion years of sunshine falling on it at Earth’s orbital distance, and it is now in equibilbrium with the energy pouring down on it? Would that be the blackbody radiation of 255K? So, you add the 18C, or 281K, to the 255K and you get … hell, I don’t know.
The more you think about what you think you know, the more you know you know less about what you think you know than you thought you know. And then you have to consider the question. What are we really asking?
I don’t understand this entire argument about characteristic emission temperature. If you want to understand what the Earth would be like without any atmosphere…..
Apollo 17 heat flow experiment.
http://www.ehartwell.com/afj/Reports/Apollo_17/Mission_report/4.0_Lunar_Surface_Science#4.3_Heat_flow_experiment
Remember that compared to the Earth, the Moon has far less internal heat. Also remember that the surface of the Moon is essentially an insulator against heat, it retains very little of it after dark. This can be seen in this paper of a reanalysis of the Apollo surface temperature record from Apollo 15 and 17.
After dark the temperatures falls almost instantaneously to about 110 degrees k (Apollo 15 and 17 were at low lunar latitudes). The slow decline in temperatures over the next 720 hours down to the ~75k level is from residual heat radiated from the Moon. The statement that if the Moon had a 24 hour rotational period the temperatures would be much higher is shown to be false by the data shown in figure 3.
http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1682.pdf
Thus ANY Atmosphere provides a “greenhouse” effect.
Fools and children in the climate change world simply don’t get out of their little box to find out what the world is actually like.
Oh, by the way, a major climate skeptic is one of the people (Dr. Harrison Schmidt), who installed one of these two experiments and who is the only professional geologist to visit the Moon.
Doug Proctor – do you have any data on how temps change with depth below the seabed? Presumably this is data that offshore drilling people will know?
John Eggert is asking an interesting question here:
http://johneggert.wordpress.com/2011/11/06/more-on-why-is-the-ocean-so-cold/
First, I want to thank Anthony for “Guest Posting” my thoughts.
Second, I want to thank all commenters–both pro and con. Many valid points have been raised. Some commenters have asked: What’s the issue? The answer is clear and it is “X”. The problem is, the commenters don’t agree on “X”. We each have our own personal experiences, educational backgrounds, and biases. What is “correct” to one person is an absolute “falsehood” to someone else. We (and I am especially including myself) should realize that nature (which includes mankind) will behave according to a set of laws that we may or may not understand. Those laws, not opinion pieces, will determine what happens. This is not to say we shouldn’t try to understand those laws and base our actions on our understanding of their implications. It does, however, say that our “understanding of their implications” may be incorrect, and hence our actions may worsen not help the situation. As Humphrey Bogart said in the movie The African Queen: “You pays your money and takes your chances.”
Third, it was never my intent to quantify the temperature effects of greenhouse gases on the Earth’s temperature (surface, subsurface, water, land, atmosphere at any altitude, etc.). Nor was it my intent to discuss the “Greenhouse EFFECT”, whatever that means. My intents were to (a) describe the algorithm I believed is widely used to claim a 33 K “Earth temperature difference with and without greenhouse GASES”, and (b) describe why I believed that algorithm’s treatment of greenhouse gases is internally inconsistent–specifically the algorithm computes two temperatures each of which is a function of and requires the presence of greenhouse gases, and thus to claim the difference of those two temperatures represents the temperature difference with and without greenhouse gases is internally inconsistent and hence illogical.
Thank you all.
Reed Coray
richard verney says:
December 27, 2011 at 9:52 am:
“These inputs taken together are sufficient to maintain the temperature caused by the pressure of the atmosphere.”
pV=nRT
Which comes first – the temperature of the atmosphere or its pressure?
@jim Masterson says:
December 27, 2011 at 7:03 am
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Jim
Others have hinted at the point that you so clearly have made and you are right to point this out. Regrettably, seeking to compare apples and pears is a common meme in the world of climate science.
The majority of the data is significantly flawed and not fit for purpose. It should have huge error bars and yet proponents of AGW would have one believe that the position is certain and measurements can be made to one hundredth of a degree!
They always use averages despite the fact that in the real world, the average condition is rarely encountered and tells us little about what is in reality going on. If a process is unknown or complex, it is either ignored or some fudge factor applied.
The Earth is nothing like a Blackbody so why would one expect a BB calculation to be accurate? Indeed, one point often overlooked is that we have no idea as to the area of the Earth. We look at it as if it were a uniformly smooth sphere of constant radius when we know that is not the case! What is the surface area of the Earth with all its valleys and peaks? I do not know but to give insight, the coastal distance of Norway is approximately the same as the circumference of the Earth, (ie., approximately 25,000 miles). Norway is just a small country and occupies only a small part of the circumference of the Earth and yet its coast line is equal in distance to the circumference!
The point I make is that the surface area of the Earth is nothing like that calculated from a uniformly smooth sphere (it is far larger) and each point has differences in emissivity, absorption etc such that the Earth is nothing like a Blackbody.
There are fundamental issues with the entire concepts behind the GHG theory. Now that observational data and models have ‘decoupled’, there are reasons to suspect that these fundamental issues are material and that the GHG theory is unsound. Whether this unsoundness is merely a matter of degree or more significant will no doubt become apparent the longer the ‘divergence’ continues between observational data and model projections. The heat is on to find the ‘missing heat’ or perhaps it is merely an apparition and is not missing because it was never there.
slow to follow says:
December 27, 2011 at 11:24 am
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Obviously, it is a matter of some conjecture but it is likely that the temperature comes first in that it is all part of the process of how the planet was formed (out gassing of gases built up in the cooling core/mantle which gases would have been very warm) . Thus, when the Earth was cool enough to sustain an atmosphere, the atmosphere probably in its initial state would have been very warm since although the sun may have been somewhat cooler than today the Earth was hot. At this early stage, the amount of heat being radiated was high and thus over time the atmosphere cooled to the temperatures that the Earth has experienced these past billion years.
Anthony, your credibility and that of your site remain unchanged. Sincerely. Keep up the good work.
slow to follow says:
December 27, 2011 at 11:13 am
Doug Proctor – do you have any data on how temps change with depth below the seabed? Presumably this is data that offshore drilling people will know?
John Eggert is asking an interesting question here:
http://johneggert.wordpress.com/2011/11/06/more-on-why-is-the-ocean-so-cold/
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About a year ago, I posed similar questions on this site as to whether the seabed helped warm the deep oceans. I enquired what if the oceans were drained, what would be the temperature at the valley floor (ie., at the deepest ridges of the now dry seabed)? In this regard, the average depth is just over 12,000 ft and the deepest depth somewhat over 36,000 ft. First, there would be more air pressure and hence more adiabatic heat. Second, one would, because of the depth of the valley, be standing nearer the mantle/core such that one may expect more heat to be conducted from the surface of the now dry seabed (this second point being relevant to whether the seabed heats the deep ocean). Third, the ocean crust is very much thinner (approximately on average 4 miles thick whereas continental crust is on average 25 to 30 miles thick) again meaning that seabed is far nearer the mantle/core such that perhaps more heat is being conducted from the mantle/crust. The latter two points suggested to me that if the oceans were to be drained, the now dry seabed would be warmer to the touch than would continental land such that the seabed if ever so slightly warm may to limited extent be warming the deep oceans from below.
Unfortunately I never got a satisfactory answer but I when I did some research I came across some borehole data which suggested that the continental crust has a temperature profile of about 25 to 30 deg C per kilometer depth and the ocean crust has a higher temperature profile. Unfortunately, since I have moved house, I cannot locate the relevant paper and borehole data. I do come across it, I will provide a link.
Let’s forget those rotating plates, black bodies and insulation integrals from north to south.
Why is our day colder than Moon’s day? Simply because
– air cools the surface and goes up, allowing cold air to sink and cool the surface
– water (condensed “greenhouse gas”) cools the surface by evaporation
– clouds (condensed “greenhouse gas”) shield the surface against the sunlight
– ice/snow (solidified “greenhouse gas”) reflects almost all sunlight, so the iced surface does not warm the atmosphere.
Result: our day is COLDER than Moon or black body thanks to presence of bulk atmosphere and water with its hydrological cycle and three states. So the “+33K” difference, even much more because our day is colder, must occur during the night.
Why is our night much warmer than Moon’s night?
If I go outside during the night, I am warmed by direct contact between my skin and warm bulk atmosphere. Bulk atmosphere holds the daily heat. Bulk atmosphere is nitrogen and oxygen, which got warmed during the day by conduction and convection. If they radiate IR (they should, since every object with >0 K temperature radiates something), they warm us, and there are 999,900 N2 and O2 radiating molecules per 100 anthropogenic CO2 molecules. If they do not radiate (as some of you claim), then they just hold the daily heat, effectively warming the night to much higher temperature as without their presence. Simple as that.
“Greenhouse gas” does nothing, if there is not a bulk atmosphere. NOTHING. Mars blackbody and practical temperature is the same 210K, despite its thin atmosphere contains 95% CO2, or 6,000 ppm. The point is, it does not have the bulk atmosphere.
http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html
richard verney says:
“First, there would be more air pressure and hence more adiabatic heat.”
You need to decide whether we keep the same volume of gas or would you increase the volume to account for the volume of the oceans. If the former then some areas would see a drop in temperature as there would be a thinner layer over what are now continents. If the latter then yes, the Marianas Trench would be warm indeed.
Juraj V. said:
Why is our night much warmer than Moon’s night?
If I go outside during the night, I am warmed by direct contact between my skin and warm bulk atmosphere. Bulk atmosphere holds the daily heat. Bulk atmosphere is nitrogen and oxygen, which got warmed during the day by conduction and convection. If they radiate IR (they should, since every object with >0 K temperature radiates something), they warm us, and there are 999,900 N2 and O2 radiating molecules per 100 anthropogenic CO2 molecules. If they do not radiate (as some of you claim), then they just hold the daily heat, effectively warming the night to much higher temperature as without their presence. Simple as that.
“Greenhouse gas” does nothing, if there is not a bulk atmosphere. NOTHING. Mars blackbody and practical temperature is the same 210K, despite its thin atmosphere contains 95% CO2, or 6,000 ppm. The point is, it does not have the bulk atmosphere.
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N2 and O2 have no absorption or emission in the IR range at all. It is the greenhouse properties of water vapor, CO2, and to a lessor extent, N2O and methane that hold all the IR, or as you call it, the “daily heat” in and keep it warmer at night. Considering what a small fraction all these are of the bulk atmosphere, their effect is remarkable. If you’ve ever spent any time in the desert at night, you can appreciate the potency of water vapor as a greenhouse gas, for even though the bulk atmosphere over a desert is not significantly different (certainly N2 and O2 are the same) than over a more moist region, the little bit of extra water vapor in the air makes a huge difference. The diurnal temperature change in deserts is far more extreme than in more moist regions because of the water vapor. Take it to an extreme, and keep the N2 and O2, (the majority of the bulk atmosphere) but take away all the greenhouse gases and the diunral temperature change gets even more extreme. Greenhouse gases do the heavy lifiting in moderating the diurnal temperture changes.
Juraj V. says:
December 27, 2011 at 1:13 pm
“Why is our day colder than Moon’s day?”
“Why is our night much warmer than Moon’s night?”
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Juraj is asking the right questions.
During the day it is clear that convective and evaporative processes keep the earth cooler than it would otherwise be.
During the night however there is a real greenhouse effect keeping the surface temperature warmer than it would be without an atmosphere. A real greenhouse or glass house works primarily by providing a barrier to convection. There is a very small additional effect as the glass also provides a barrier to outgoing IR. Earth’s atmosphere is the same. Restricted convection coupled with the limited ability of oxygen and nitrogen to radiate IR is what keeps earth warm at night. The so called greenhouse gases play a more limited role. In a real green house convection is restricted by glass panes. In Earth’s atmosphere the restriction to convection is provided by the inertia of millions of tonnes of air. The primary greenhouse gasses in the atmosphere are therefore nitrogen and oxygen. The condensing and non-condensing trace gasses such as water vapour and CO2 may actually play a greater role in cooling than they do in insulating.
“In Earth’s atmosphere the restriction to convection is provided by the inertia of millions of tonnes of air.”
Not so.
The restriction to convection is provided by the temperature inversion at the tropopause which is a consequence of solar heating of ozone in the stratosphere.
In my view the height of the tropopause especially the slope of that height between pole and equator is critical because that dictates the entire surface air pressure distribution, the positions, sizes and intensities of the permanent climate zones and thus the rate of energy flow from surface to stratosphere.
There we have the key to cloudiness and global albedo changes with an effect on the quantity of solar energy able to get into the oceans to fuel the climate system.
Solar activity levels appear to have the ability to raise and lower the height of the tropopause especially at the poles.
The likely cause is variations in the mix of particles and wavelengths from the sun differentially affecting ozone quantities at different levels.
Stephen – I thought bulk surface air pressure distribution would be dictated by static equilibrium and gravity with the height of the troposphere being dictated by temperature which, in turn, is largely a function of latitude?
@R. Gates says:
December 27, 2011 at 2:40 pm
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Mr Gates
You are right to point out the effectiveness of water vapour. In pointing this out, one can see how little warming/heat retention CO2 plays. However, the position is very complicated and we do not know precisely how everything interplays.
Let us assume the following: (i) that N2 and O2 cannot radiate heat and therefore can only give up heat by way of convection or conduction; (ii) that there is no CO2 nor water vapour in the atmosphere and the atmosphere consists only of N2 and O2; (iii) at the end of the day the N2 and O2 molecules are at a temperature of about 40degC (this being the air temperature measured in the shade in the usual way say 1.5m above the ground); (iv) it is a windless night; and (v) there is very thick cloud cover at say 50ft extending miles high which has a temperature of say 39 deg C on the desert side and below freezing on the space side (an unlikely scenario over a desert but since we are looking at theoretical compositions of the atmosphere a legitimate exercise).
In this scenario, the night air temperature cannot quickly cool since the thick cloud cover acts like a lid and hinders convection. The warm air (consisting of only N2 and O2) is trapped between the desert surface and low lying cloud (likewise the low lying cloud acts as a barrier to the coldness of space). The N2 and O2 unable to radiate away heat such that the air remains warm all night long.
Now what happens if we add CO2 to the mix?
Is the night air cooled by the addition of CO2 in this scenario since the N2 and O2 molecules whether by collision, conduction or what have you can transfer/give up their heat to a CO2 molecule which can then radiate away the heat (some going up, some going side ways and some going down – materially some going up and through the cloud thereby escaping out to space)?
What happens as we add more and more CO2? Obviously the greater concentration of CO2 the easier it will be for the N2 and O2 molecules to impart their energy onto the CO2 molecules and the more CO2 molecules the more radiators that are present to dissipate the heat.
I welcome your views.
slow to follow,
It would, unless the temperature of the stratosphere is affected by a top down process.
A change in troposphere height can be effected by temperature changes from above OR below.
Mr Gates
Further to my last post in which I agreed with you that water vapour makes a significant difference, perhaps I should have observed that whether this is due to the greenhouse properties of water vapour, or whether it is due to the fact that in moist air there is much more latent heat such that it obviously takes longer to cool since there is much more energy to give up/dissipate, or whether dry air convects quicker than moist air, or whether it is combination of more than one or all of these factors is a moot point.
In my view, the moderating of the diurnal range is primarily brought about by the oceans and not by GHGs. Far away from the oceans such as in deserts, the middle of Antarctica large diurnal ranges are experienced. To a lesser extent it is moderated by cloud cover which hinders convection (clouds in turn being a factor of the oceans).
Stephen Wilde says:
December 27, 2011 at 3:25 pm
Stephen, I think you have misunderstood my meaning. I am not suggesting that inertia is providing an absolute barrier to convection as in the glass of a greenhouse or the temperature inversion at the tropopause. Rather I am saying that inertia restricts the speed at which convection can remove heat from the surface. It is not necessary to have a total restriction of convection to experience a greenhouse effect. A green house with several panes of glass removed from the roof will still be warmer than one in which all the panes are removed.
shouldn’t it be fairlyeasy to create a model that also reflects the earths distance from teh sun and it’s rotation on it’s axis (and wobble) and breaks the surface down into 10k x 10k chunks. We would see that using a general number for the total surface is way out when we start looking at the actual energy loss/gain on each sector throughout not just a 24 hour day but a 365 day year and longer.
Stephen Wilde says:
December 27, 2011 at 3:58 pm
“A change in troposphere height can be effected by temperature changes from above OR below.”
Thanks Stephen – do you have any references you can point me towards?