Talk:Greenhouse effect/Archive 5

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Citation needed

This concerns the most recent (July 14) two edits of the article as shown at the article's history.

Experience with solar ovens of the kind invented by Horace de Saussure in 1767, confirmed by similar experiments done at the Smithsonian Astronomical Observatory in November 1897, show that it is essential to keep them well sealed to maintain their high temperature. Based on this experimental evidence, there can be no question that greenhouses retain their heat the same way as solar ovens, namely by good sealing. (The role if any played by opacity of glass to IR is irrelevant here.) The windows used by greenhouse operators to prevent greenhouses from overheating lend further support to this theory. So far so good.

However can we then infer that air not trapped in a greenhouse rises? If thermals, the bubbles of heated air that eagles and gliders soar on as they rise, were ubiquitous this would be a no-brainer. Now radiosondes are not instrumented to correlate thermals with terrain, but manned gliders are, namely with the observational abilities of their human pilots. At the article Lift (soaring) we read "Typical locations to find thermals are over towns, freshly ploughed fields and asphalt roads," with the obvious qualification that thermals are hard to associate with any feature on the ground. The article gives two other examples, exhaust gases from power stations and fires. Agriculture (except in its ploughed state) and horticulture (except for flower beds and vegetable gardens in towns) are not mentioned as sources of thermals.

Thinking back to high school physics one might suppose that all heated air rises. While this is fine for classroom experiments, the classic text Meteorology Today by C. Donald Ahrens paints a more nuanced picture for the atmosphere. On pp.150-154 of the 9th (2008) edition we read that there is a notion of stable vs unstable atmosphere, which is defined in terms of the lapse rate induced by the warming: the stronger the warming on the ground, the faster temperature decreases with altitude. When the actual or environmental lapse rate (ELR) is below the moist adiabatic lapse rate (one ideal) the atmosphere is stable. As the ELR crosses the range between the moist and dry adiabatic lapse rates (the other ideal), namely from 5 to 10 °C/km, it becomes progressively less stable, and eventually forms a bubble of hot air that breaks away from the ground to form a rising thermal. As the thermal rises it cools partly adiabatically (by decompressing) and partly isothermally (by losing heat to the surrounding even cooler air), gradually losing its identity in the process to become assimilated in the atmosphere. The cooler air displaced by the thermal sinks to replace it at the surface.

But this only happens over terrain subject to thermals, which got me to wondering about the edit made by User:Raymond arritt on 12 Jan 08. In clarifying an earlier version, Ray wrote "The air continues to heat because it is confined within the greenhouse, unlike the environment outside the greenhouse where warm air near the surface rises and mixes with cooler air aloft."

When I first read this I thought it was so obvious as to need no citation. But now that I understand the subtleties better I'm not so sure. So I put a citation-needed tag on the statement with an edit summary making as much of the above reasoning as would fit in a summary, focusing on the Lift (soaring) observations. This tag was removed by User:Short Brigade Harvester Boris a few hours later with the edit summary "srsly, does this need a citation???", the previous edit summary notwithstanding. Rather than get into an edit war over this, especially in light of the article's disputed status, I've brought it up here.

Now I interpret SBHB as agreeing with me about overly zealous requests for citations when he pointed out elsewhere the example of someone requesting a source for the statement that hands have five fingers, which was removed four days later with an edit summary in much the same vein as SBHB's removal just now. (The article Proof (truth) I wrote recently was challenged in this way by someone who went through and put gratuitous citation-needed tags on even the most obvious statements so I'm very sympathetic to those who feel unjustly challenged. When I tried removing what I felt was the most egregious tag, which questioned no particular statement but simply said vaguely that the article lacked sources, I was firmly told by User:Moonriddengirl that "the tag should not be removed until the issue is addressed," despite my protestation that there was no specific challenge to address.)

It seems to me that challenging a specific statement on the basis of an apparent discrepancy with the known facts is a stronger reason to require a source than either the vague statement that "the article needs sources," or questioning the number of fingers on a hand. There are enough inconsistencies here between the conventional high school wisdom about hot air and meteorology that it is surely wrong to claim that heated air over agriculture and horticulture necessarily rises without a basis stronger than "it's obvious."

Sorry this is so long, if I had more time I'd edit it down to something shorter. --Vaughan Pratt (talk) 19:36, 14 July 2010 (UTC)

All hot air rises IF the air above it is more dense. For a sail plane, the question is "How high does it rise". If the air only rises a few hundred feet, then it is not useful for soaring. As a result, they look for sources that produce very strong thermals, hot spots in the general landscape. That is the difference between green fields and parking lots. They may both produce thermals, but the very large difference in surface temperatures produces different strength thermals. Q Science (talk) 20:10, 14 July 2010 (UTC)
Good point. So what you're claiming is that a rise of a few hundred feet is all that's needed here. A source for the cooling effect of a few hundred feet of circulation ought to be fine then. Note that the moist dry adiabatic lapse rate (DALR) per hundred feet is around 0.16 0.3 °C, which the source would need to address. (Ahrens p.153: "Rising air cools at the DALR and the dew point falls but not as rapidly." When they meet, condensation and cloud formation set in and further cooling is at the moist rate. Falling air, at least from above the condensation level, is dry and warms at the DALR, tending to reduce the quantity of heat carried up in a cycle.) --Vaughan Pratt (talk) 20:17, 14 July 2010 (UTC)
Pretty much any textbook that contains the phrase "lapse rate" explains this. (Including the one you quoted above.) As a result, a simple wikilink is good enough. As a rule, if it is in several textbooks, then it does not need a specific reference. That said, any sailplane manual also explains this. The next page explains how to use a Slant-T chart to determine exactly how far above ground level (AGL) a thermal will rise and to predict whether or not clouds will form. Q Science (talk) 05:29, 15 July 2010 (UTC)

Good, that's got some interesting material in it. However that article is all about how unstable air behaves: note that the second sentence of that reference reads "A certain amount of instability is desirable for glider pilots, since without it, thermals would not develop." Lift (soaring) indicates what kinds of areas destabilize the air, but agriculture and horticulture don't seem to be among them and the air over them might well be stable. What's needed here is a source that confirms that (a) air over cultivated land of the kind one would put a greenhouse on top of for additional warmth rises during the day, (b) to a sufficient extent as to make a greenhouse worth the bother. The lack of any sources for the sentence in question is additional reason to doubt it, besides the reasons above.

Air is stable if it gets warmer with height. When air at the surface is less dense (usually meaning warmer) than the air above it, then the atmosphere is unstable and the less dense air rises. It is all about the density. Over plants it is more complicated because humid air is less dense than dry air at the same temperature. Also, plants reflect more light and use a large part of the absorbed heat to evaporate water. Thus, plants tend to not get as hot as roads. Q Science (talk) 21:10, 15 July 2010 (UTC)

There is the additional thought that a greenhouse is most useful on cooler days, but those are precisely when the air is least likely to rise. This casts further doubt on the theory that greenhouses are there to stop the warm air from rising: there is no warm air to rise on a cold day. Putting glass over cultivation on a cold day only makes matters worse, by reflecting 8-16% of the sunlight depending on whether one uses single or double glazing.

It's a very interesting question in its own right, so I went looking for sources myself. Turbulence in air over forests came up a fair bit, but nothing I was able to find addressed the impact of air motion, either vertical or horizontal, on temperature of the air at the surface. As Ray's rewrite makes clear, vertical motion is likely to have the bigger impact (the version he replaced said nothing about upward motion). Ray's thinking was sound in that regard, but with all due respect to Ray's expertise in this area it may be that we have a bit of folklore here. Not to say that's bad, folklore's fine in Wikipedia, just so long as it's labeled as folklore and does not pretend to have been scientifically confirmed. --Vaughan Pratt (talk) 17:07, 15 July 2010 (UTC)

Your comments (way above) make an interesting point, "What happens at night". During the day, the glass stops convection. At night the surface cools by radiation and the atmosphere becomes inverted (warm air above cold). Perhaps you can provide data showing a 24 hr cycle. Q Science (talk) 21:10, 15 July 2010 (UTC)

This may be interesting. Search for the phrase "closed during the night in order to prevent warm air from rising and cooling against the cold glass roof." But I thought you were the data guy, I'm just an amateur theorist. --Vaughan Pratt (talk) 04:39, 16 July 2010 (UTC)

Nice article. Seems to confirm that Greenhouses work by stopping convection, though, at night, shades inside the Greenhouse help.
That wasn't in contention. It's not an either-or thing. --Vaughan Pratt (talk) 07:49, 16 July 2010 (UTC)
You have a page where you indicate that you are collecting data. I just thought that a full days data might be more useful than just the daytime peak. There may be something that both Wood and Abbot missed. Q Science (talk) 05:52, 16 July 2010 (UTC)

So far I only have data relevant to duplication of Wood's experiment, which he did not do at night. Moreover his temperature of 55 C would kill anything in a greenhouse, all he was trying to prove was that rock salt worked just as well as glass as a general principle. (Which he didn't in the end, since the additional glass he placed over the rock salt would itself have heated up, and the back radiation from that glass would then go straight through the IR-transparent rock salt back into the box, which neither Wood nor Abbot thought to factor in. Effectively both the boxes were acting as glass greenhouses to varying degrees, with the rock salt only helping to contain convection. Wood's experiment was not carefully thought out.) However we have a large vegetable garden and I've been thinking of doing a real glasshouse experiment with a vegetable patch when I get time, to see how much of a role mixing via convection plays, for which night data becomes much more interesting. Not currently a high priority. --Vaughan Pratt (talk) 18:02, 16 July 2010 (UTC)

Craig Bohren on "How do greenhouses work?"

Nice article by Penn State meteorology professor Craig Bohren that can be read in its entirety by googling "The atmospheric science community seems to be divided" (must be in quotes). Kirby Hanson's example of a greenhouse that averaged 2.4 °F lower inside than out during January 1961 bears out the point that greenhouses can sometimes prevent solar warming (though Bohren advances as the explanation only the suppression of air mixing, neglecting reflection which for a typical double-glazed polyethylene greenhouse is a considerable 16%).

The bottom line is that one cannot dogmatically take either side, since the operation of a greenhouse depends heavily on circumstances. The article's mistake is to take one side dogmatically, with sources supporting just that side, when the other side is just as valid. --Vaughan Pratt (talk) 20:45, 15 July 2010 (UTC)

On further reflection I think Bohren is right to focus on mixing instead of reflection. The reason is that mixing is variable and unpredictable while reflection is very constant and predictable from the index of refraction and number of panes. The greenhouse effect for greenhouses is as constant and predictable from the spectra for glass and plastic as reflection, and their combined effect can be calculated very accurately. Mixing on the other hand is heavily dependent on wind speed, air stability, and air temperature, and therefore would be the component to focus on when looking for an explanation of the variability of temperature delta between inside and outside of greenhouses. --Vaughan Pratt (talk) 17:31, 16 July 2010 (UTC)

Glass houses and how they work

I have assumed that the term Green House Gas came about because the upper atmosphere behaved like the glass in a greenhouse. As far as I am aware, from being a principal climatic engineer, solar radiation and terrestrial radiation in the infrared spectrum have different frequencies, the former seeing glass as transparent and the latter seeing glass as opaque, thus allowing the inside of the greenhouse to warm up during sunshine, but not allowing the heat from the greenhouse to escape at night, during the terrestrial radiation phase of the diurnal cycle.

Furthermore, warm air will not escape if you simply open a window in the top of a greenhouse. Warm air cannot do anything of its own volition, but must be moved by the imposition of colder, therefore denser, air around it so there must be a way for cold air to get under the warm air to displace it upwards. Maybe insufficient air sealing or an open door assisted a greenhouse to lose its warm air when a window in its roof was opened, but as we all know (and were taught by Isaac Newton), nothing that is stationary moves unless a force is applied to it. IN this case it is called buoyancy and nothing will float without water underneath it. A ship floats because it is less dense than the water it displaces. Warm air will remain exactly where it is unless cold air is allowed to get under it.Percussim (talk) 15:25, 17 August 2010 (UTC)

Your first point is obviously true, and the arguments against it in the article are fallacious as I've pointed out earlier. I also agree in principle with the reasoning in your second point, but with the following caveats.
1. If you also open a door or a second window well away from the first, and there is even a small breeze outside, any resulting pressure difference between the two openings will result in a draft that will rapidly replace the warm inside with cool air from outside (in the case where it is indeed cooler outside).
2. Even with only one exit for the air there will be effects, primarily eddies but also a little conduction, that while relatively small will in the course of a day have enough cooling effect for the purpose of fine tuning the temperature.
3. With a sufficiently large window and a sufficient temperature differential, hot air can rise up in bulk (convect) through one portion of the window and cold down through another. You'd probably have more intuition than I into what parameters would suffice for a significant flow. --Vaughan Pratt (talk) 17:04, 17 August 2010 (UTC)
I have assumed that the term Green House Gas came about because the upper atmosphere behaved like the glass in a greenhouse - they do. But the difference is (as the article explains) that this isn't the mechanism that (mostly) heats a greenhouse. There is rather extensive discussion of this point on the talk page already William M. Connolley (talk) 14:08, 25 September 2010 (UTC)
Those who've taken the trouble to follow the pointers in this extensive discussion, in particular the nice piece by Penn State meteorology professor Craig Bohren, will have learned that according to John Kessler, a physics professor at the University of Arizona, both sides to this controversy have merit. The relative contributions of convection suppression and radiation trapping depend very much on the greenhouse and its environment. The thicker the glass and the stiller the air, the more important is radiation trapping. The greater the wind speed and the thinner the glass, however, the less important it is.
Contrary to what you claim, the analogy is quite sound. First, most of the Earth's heat does not come from infrared trapping, it comes from the absence of exchange of matter between Earth and cooler bodies, which keeps the Earth warm to a greater extent than radiation trapping. The analogous absence of exchange of warm air inside the greenhouse with cooler air outside likewise keeps the greenhouse warm. Radiation trapping is a secondary but nontrivial effect for both Earth and greenhouses. When looked at from that perspective the analogy is excellent.
Given that this question was hotly debated in Journal of Applied Meteorology in 1974 and again in Optical Spectra in 1975, leading to yet further discussion at the time in Science, New Scientist, and Popular Science, doesn't it strike you as one-sided that the article refers only to one 1.5 page paper in 1909, containing only two numbers, 65 and 55 degrees C, with no numeric information whatsoever about the apparatus, and not to any of the more detailed papers and discussions since then that have taken the opposite position? Furthermore this remarkably content-free 1909 article was by someone who contributed two papers to Phil.Mag. in that year (respectively February and November), the second much longer and more detailed, both of which were rebutted in the same journal in the same year. It very strange that Wikipedia would prefer the judgment of one author a century ago, who moreover was striking out repeatedly in 1909, over that of the many other authors who have written during the century since on the matter.
The only other evidence besides the 1909 paper for the article's strenuous denial of any connection with greenhouses is an unsourced argument made up by a WP editor based on the fallacy that hot air must rise. My request for such a source was immediately deleted by that editor, contrary to WP policy. If his argument were sound, snow would be at the bottom of mountains instead of the top. As any climatologist will tell you, hot air does not rise until it creates a temperature gradient greater than the prevailing lapse rate, which it does not do in circumstances where a greenhouse offers any warming benefit. --Vaughan Pratt (talk) 19:47, 3 October 2010 (UTC)

This is really hard to read

I have a degree yet I'm finding this article far to laden with jargon and excessively long sentences. I understand it but it is hard work. If I'm finding this hard then I don't expect Joe Bloggs to be able to read this, which is the point of Wikipedia. Please fix. (talk) 21:39, 18 November 2010 (UTC)

WP:SOFIXIT ;-). Please be more specific or fix it yourself. But keep Einstein in mind: "As simple as possible, but not simpler." --Stephan Schulz (talk) 22:25, 18 November 2010 (UTC)
...that said, the intro is fairly horrible. I rewrote the first paragraph, but there is more potential for improvement. --Stephan Schulz (talk) 22:51, 18 November 2010 (UTC)
No, don't fix it. Let it stay the way it is- a fine example of error, poor writing, improperly placed detail, irrelevant dribble, poor organization, and a testament to unfettered group what-goes-for think. And next time, tell us what YOU really think. blackcloak (talk) 06:31, 24 November 2010 (UTC)

Basic Mechanism

In this section we see the following sentence: "Thus the presence of the atmosphere results in the surface receiving more radiation than it would were the atmosphere absent; and it is thus warmer than it would otherwise be." The premise does not justify the conclusion. Now that I've pointed out the problem, is anyone up to the challenge of explaning why? blackcloak (talk) 08:39, 23 November 2010 (UTC)

The answer is pretty simple. The atmosphere does not generate any radiation of its own, THUS atmosphere or no atmosphere the amount of radiation the earth receives is not dependent on its atmosphere. The determining factors for the amount of radiation the surface of the Earth receives are its distance from the sun, the temperature on the surface of the sun, the surface area of the Earth, the strength / weakness of the Earth's magnetic field, and the Earth's atmospheric albedo. Note that a higher atmospheric albedo reduces the amount of radiation that the Earth's surface receives. (talk) —Preceding undated comment added 02:56, 3 December 2010 (UTC).
Yes it does. Of course only if you take the preceding discussion (referenced via "thus") into account. --Stephan Schulz (talk) 08:42, 23 November 2010 (UTC)
First let me translate your three word sentence. I presume you are saying 'Yes, the premise does justify the conclusion.' If that is the case, you are wrong. Need a hint? Or do you want to think about it a bit more? blackcloak (talk) 09:01, 23 November 2010 (UTC)
Blackcloak, if you have a problem with a section of article text, please say explicitly what is wrong with it and say how the problem could be fixed, ideally by proposing better wording yourself.
As far as I can see the text you are objecting to is OK, but your style of posting "There's a problem here - guess what it is..." comments is unhelpful, and to my mind patronising to the point of incivility. Please stop it. Squiddy | (squirt ink?) 10:42, 23 November 2010 (UTC)
If you were really interested in the truth, you would not have responded this way. I've learned from too many years on WP that I can't tell anyone on WP what the truth is. Each individual editor must come to the truth all by him/herself. That requires thinking, and getting editors to think is my goal. If my style does not resonate with you, just say so. An unmindful tongue-lashing is pointless. I equate it to screaming at another driver from a car with all the windows shut. And BTW, I didn't ask anyone to guess. Your use of words is intended to trivialize the process and to insult me. Here is a general rule of thumb that you might find helpful: When you choose to exagerate with your words, you should expect a similarly phrased response. I hope other readers will notice that my response is considerably toned down from yours. blackcloak (talk) 18:20, 23 November 2010 (UTC)
If you are into koans, consider seeing your nearest Buddhist monastery. If you want to help improve Wikipedia, see WP:TPG. In particular, if in doubt, make the extra effort so that other people understand you. Being friendly is a great help. It is always a good idea to explain your views; it is less helpful for you to voice an opinion on something and not explain why you hold it. Explaining why you have a certain opinion helps to demonstrate its validity to others and reach consensus. Assume for a moment that you are wrong. If that's the case, how should we figure out where your misunderstanding is if we cannot see your argument? --Stephan Schulz (talk) 21:32, 23 November 2010 (UTC)

Change to point in Basic Mechanism

The first bullet point in the Basic mechanism section contains the claim: This is mostly "visible" light;… I don't believe this statement is accurate, as it implies that substantially more than half the insolation is visible. That is contradicted by the reference I will add. [1]

I have changed the sentence to read: Almost half the radiation is in the form of "visible" light, which our eyes are adapted to use. I'm open to improved wording for the end of the sentence, my main edit is to correct the error regarding the proportion of the incoming radiation that is visible.

(As an aside , the first bullet point starts: The incoming radiation from the Sun is mostly in the form of visible light and nearby wavelengths…. I'm not entirely comfortable with the imprecision of the word "nearby", but I'm leaving that as is.)--SPhilbrickT 13:47, 15 October 2010 (UTC)

Taking T to be 5778 K (the nominal temperature of the Sun) and integrating I(\nu,T)d\nu in Planck's Law over the intervals [0,400] nm (UV), [400,700] nm (visible), and [700,infinity] (IR) gives respectively 12%, 37%, and 51% as the TOA (top of atmosphere) percentages. You can look this up in the table in reference 21 (Lowen and Blanch) of Planck's Law (citable), or the table in Planck's Law#Percentiles (not citable), or you can integrate the formula numerically yourself by copying the formula into your favorite programming language and adding up its values with d\nu set as small as you want (arguably citable as a "routine calculation" under WP:OR#Routine_calculations). --Vaughan Pratt (talk) 01:16, 25 October 2010 (UTC)

I also added an image supporting the first bullet point. My only concern is wp:weight; given that the section makes a number of points, an image illustrating only two of them might be problematic, but it is quite on point to illustrate both the spectrum distribution of all light, and the proportion that is visible.--SPhilbrickT 14:08, 15 October 2010 (UTC)

I don't think weight is a problem. The difference between incoming radiation (maximal in the visible, where most atmospheric gases are nearly transparent) and outgoing radiation (maximal in the infrared, where greenhouse gases are anything but transparent) is the key idea, so illustrating part of that is well worth it. --Stephan Schulz (talk) 14:16, 15 October 2010 (UTC)
I would like to add another suggestion for change. Consider this paragraph.
"Each layer of atmosphere with greenhouses gases absorbs some of the heat being radiated upwards from lower layers. To maintain its own equilibrium, it re-radiates the absorbed heat in all directions, both upwards and downwards. This results in more warmth below, while still radiating enough heat back out into deep space from the upper layers to maintain overall thermal equilibrium. Increasing the concentration of the gases increases the amount of absorption and re-radiation, and thereby further warms the layers and ultimately the surface below.[7]"
In the first sentence it says that greenhouse gases absorb heat radiated from lower layers. In the second it says that greenhouse gases re-radiate heat in all directions. Can you see the contradiction here? The first sentence implies that a layer receives no heat transfer from layers above it, but the second sentence implies that a layer radiates heat down towards the layer below it.
It is my understanding that the reason that the Earth's atmosphere retains the energy that is radiated from the surface is because the speed of energy transmission is slowed. Thermal energy (infra red radiation) leaves the Earth's surface at the speed of light. With no greenhouse gases in the atmosphere the infrared energy would quickly be released into space - .000537 sec travel time from Earths surface to outer edge of atmosphere (approx 100 miles up). With greenhouse gases present this travel time increases significantly because when electromagnetic energy strikes a greenhouse gas, that energy is converted to kinetic energy of the atoms within the greenhouse gas molecules. The bonds between the atoms are stretched and relaxed by the incoming infra red radiation. Also, as these molecules strike each other and other gas molecules within the atmosphere the kinetic energy is effectively shared by all atmospheric components. This kinetic energy progresses much more slowly up through the atmosphere and a portion of the energy is effectively retained by the atmosphere beyond the diurnal and seasonal cycles. (talk)
People often get confused by muddling 'heat transfer' with 'net heat transfer'. This paragraph tries to keep things simple. There is radiant heat transfer from colder to hotter objects, but there is far more from hotter to colder ones, so the net heat transfer is from hotter to colder (one transfer rate minus the other). The net heat transfer that we are discussing here (i.e. the long-wave IR radiation that cools the Earth/ocean/atmosphere system) is from the lower atmospheric layers to the ones above, but there is some transfer back down as well. If any layer interrupts the outward radiation and turns it into local heat (describing stretching bonds and kinetic energy is just another way of describing 'heat' in a gas), then this slightly warmer gas now radiates back down more than it would if it was not there or if it was not hot. There's no contradiction here: the first sentence does not say there is no heat coming from above, just that there is heat coming from below. In a discussion, you have to start somewhere; it's no good starting at both ends of the argument at once, that will just confuse people more. The heat from below is the net direction of heat flow anyway, so it's the best place to start.
The important point in that paragraph is the one about maintaining thermal equilibrium. The Earth, in a steady state, has to re-radiate away all the energy it receives, and it has to do that from the outermost layers of the atmosphere (those visible from space at whatever frequency we are considering). In order to maintain enough temperature in the outer layers to do this, with all the downward radiation (i.e. subtractions from net heat flow) going on on the way up, the lower layers and the surface have to be noticeably warmer than they would need to be if there were no subtractions going on in the atmosphere. It's not much like a (series of) blanket(s) over a sleeping person, as in that case there is no equilibrium requirement from the outer surface, as the primary heat source is inside, not outside the layer(s). But it is more like that than it is about the speed of light, slowing things up or about conduction (one molecule striking another) within the gases. Regarding seasonal and diurnal cycles, most of the radiant heat input to any piece of ground is in the day and in the summer. The escape of this heat through the atmosphere happens all the time, though it is obviously more significant (especially more significant than the input) during the night and in the winter. --Nigelj (talk) 17:47, 25 November 2010 (UTC)

Nigel, I am indeed confused at this point. My understanding was that radiation comming from a colder body would just get reflected at a warmer body and may be absorbed only by a still colder body. Are you a physicist, or do we have a physicist to confirm the fact that some radiation comming from colder body is absorbed by the warmer body? Lars B R (talk) 10:12, 21 December 2010 (UTC)

Nigel, the speed of energy transmission plays a role for an object to warm up over time and stay warm (that is why I mention the diurnal and seasonal cycles). Supposing there was no atmosphere at all (like the moon), all solar energy received and emitted by the moon's surface is quickly lost because infrared radiation progresses through space at the speed of light, hence the wide swing between daylight and nighttime surface temperatures on the moon. I know that heat transfer should be looked at on a net basis (net flow of heat is from warm body to cold), but you must also look at how quickly that heat energy travels through the atmosphere on its arrival and its departure. There are 3 different heat flow rates (dQ / dt), one for radiative heat transfer, one for conductive heat transfer, and one for convective heat transfer. Obviously radiative heat transfer happens more quickly than conductive, which is the point I was trying to make. Once infrared energy strikes a greenhouse gas molecule, the energy transfer mechanism between it and the surrounding molecules is a mix of radiation (electromagnetic energy) AND conduction (kinetic energy). —Preceding unsigned comment added by (talk) 12:37, 30 December 2010 (UTC)
Well, I only got an (unused) minor in physics, but of course a warmer body will absorb the same radiation coming from a colder or from a warmer body, equally. Photons have no history, so how would a mechanism work that depended not on qualities of the radiation, but on qualities of the emitter? The spectrum of radiation changes with temperature, of course, but that is a large part of the mechanism of the greenhouse effect. --Stephan Schulz (talk) 10:29, 21 December 2010 (UTC)
"Photons have no history". Photons have energy E = hv which is entirely dependent on the source of photons. If you have in mind black body radiation then the average energy of the photons emitted is a linear function of its temperature (wien's displacement law) for this reason another body in the same photon 'field' will have the same temperature. In his 1862 paper Kirchhoff identified this case when he generalised from a black cavity to an arbitrary cavity at temperature T. --Damorbel (talk) 12:03, 21 December 2010 (UTC)
An individual photon does not have an "average energy", but one particular energy. Two blackbody emitters of different temperature will both emit photons over a large range of frequencies. What differs is the distribution of the frequencies. But photons of the same frequency will be absorbed (or not) with the same probability, whether emitted by a warmer or a colder body. I'm not entirely certain what you mean by "photon 'field'". In a closed system in thermodynamic equilibrium, two bodies able to exchange energy will be of the same temperature. But that does not apply to an open system into which the sun pumps 3.846×1026 Joules every second. --Stephan Schulz (talk) 12:34, 21 December 2010 (UTC)
"An individual photon does not have an "average energy"" Why ever not? If they come from a monochromatic source such as a laser then all photons have the same energy and the same polarisation, they also will have the same phase.
"I'm not entirely certain what you mean by "photon 'field'"" In a cavity with a known temperature there will be an equilibrium condition where the temperature of all objects are the same - it is reasonable to call this a photon field. Since the Earth is treated as a sphere in most calculations of its temperature the calculation is in fact done as if it was immersed in a uniform radiation (photon) field.
"an open system into which the sun pumps 3.846×1026 Joules every second". I don't think the semantics of thermodynamics should get in the way but an open thermodynamic system can exchange matter as well as energy. The Earth intercepts only a fraction of the Sun's photon output according to the inverse square law. The photons still have energy derived from the 5780K source, that is why they can split O2 molecules in the troposphere and make ozone (O3). However, because the rate of photon intercepts is reduced (inverse square law) the power is reduced in proportion, so the Earth (as a disc) receives 1,366W/m^2 or 342W/m^2 as a sphere. If you are really interested you can recover the original 5780K using a mirror or lens to focus an image of the Sun. Because of losses you are unlikely to get close to 5780K but you can start a fire. Other applications of this technology are Solar furnaces, they get quite hot!. --Damorbel (talk) 13:28, 21 December 2010 (UTC)
There's a good example of this at Thermal radiation: "In a practical situation and room-temperature setting, humans lose considerable energy due to thermal radiation. However, the energy lost by emitting infrared heat is partially regained by absorbing the heat of surrounding objects (the remainder resulting from generated heat through metabolism). Human skin has an emissivity of very close to 1.0. Using the formulas below then shows a human being, roughly 2 square meter in area, and about 307 kelvins in temperature, continuously radiates about 1000 watts. However, if people are indoors, surrounded by surfaces at 296 K, they receive back about 900 watts from the wall, ceiling, and other surroundings, so the net loss is only about 100 watts." I'm sure there are examples all over the place in textbooks etc, as this is fundamental to thermodynamics. --Nigelj (talk) 12:47, 21 December 2010 (UTC)

Error: Only tri and higher atomic molecules exhibit green house effects

There is an obvious error in the claim:

"The majority of the atmosphere—in particular, O2 and N2 which together form more than 99% of the dry atmosphere—is transparent to infrared radiation. Only triatomic (and higher) gases interact with infrared. However, due to intermolecular collisions, the energy absorbed and emitted by the greenhouse gases is effectively shared by the non-radiatively active gases."

Carbon monoxide, a diatomic molecule, is a strong green house gas, cf. e.g.:

It's not a large contributor to climate change since it breaks down to CO2. It is, however, a much stronger green house gas than CO2 and has high absorption in the small atmospheric window.

Best regards,

/Per Nostell —Preceding unsigned comment added by (talk) 17:29, 2 December 2010 (UTC)

What is that graph? I don't see an obvious error or contradiction, since I don't see any clear claims about CO. Dicklyon (talk) 22:50, 21 December 2010 (UTC)

"the planet's actual blackbody temperature"

What is the intended meaning of "the planet's actual blackbody temperature" and "the blackbody temperature" in the lead? The number given, and its dependence on albedo, suggests that the intended meaning is what the planet's effective temperature would be if there were no atmospheric greenhouse effect. Can we find a more clear way to say that, or a source that supports the way it's described now? Dicklyon (talk) 22:46, 21 December 2010 (UTC)

I fixed it, I think. Comments? Dicklyon (talk) 06:23, 24 December 2010 (UTC)
That’s definitely easier to read and understand. Good work. CurtisSwain (talk) 07:43, 24 December 2010 (UTC)

Greenhouse Gas Warming vs Atmospheric Warming

The articles starts, "The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases," So this is explicitly stating that the greenhouse effect is identified by the warming due to greenhouse gases.

Later in the blackbody section, "The mechanism that produces this difference between the actual surface temperature and the effective temperature is due to the atmosphere and is known as the greenhouse effect." This is contrasting an earth with no atmosphere with the actual and saying the difference is due to the greenhouse effect.

To further support the above the following quote exists at NASA's EarthObservatory site, "The natural greenhouse effect raises the Earth’s surface temperature to about 15 degrees Celsius on average—more than 30 degrees warmer than it would be if it didn’t have an atmosphere." This provides similar numbers and explicitly states the contrast is with an earth that doesn't have an atmosphere (any atmophere).

I can see two problems here,

1. What is the greenhouse effect? Is it the sum of all warming that occurs as a result of having an atmosphere, or is it warming which results from the atmosphere's constituent gases which fall into the greenhouse category? (those that absorb reflected IR).

2. In the blackbody paragraph no reference is made, as is made in the NASA article regarding the quoted temperature figures, that the low case is where no atmosphere exists (as opposed to an atmosphere which does not contain greenhouse gases). Considering the first sentence of the page tells us greenhouse effect is tied to greenhouse gases I can see a reader incorrectly thinking the low temperature case results when there is an absence of greenhouse gases only and not as it is the absence of the atmosphere in its entirety.

I would be happy, or content at least for the definition of the greenhouse effect to remain a fuzzy amalgamation of greenhouse gas and general atmospheric warming as that seems to reflect the reality. However do feel that point number 2 should be addressed to ensure the reader knows the quoted -18 degree figure is true for an earth devoid of atmosphere and not one devoid of greenhouse gases. Possibly also add a reference to the greenhouse effect's dual meaning, general and specific. --DavidM —Preceding unsigned comment added by (talk) 14:55, 12 April 2011 (UTC)

The crux of your point seems to be that there would be some 'atmospheric warming' even on a planet whose atmosphere had no greenhouse properties at all. (The greenhouse properties that I mean here are entirely caused by absorption bands in the IR region that is relevant to the planet's surface temperature.) I'm not sure that's true. Wouldn't such an atmosphere, if it were possible (and I really don't know enough about the IR spectrum of every gas to know if it's possible/unlikely/common), be totally two-way transparent and so have no effect on the black body energy balance of the underlying planet, just like if it wasn't there? --Nigelj (talk) 08:19, 22 April 2011 (UTC)

Change to discussion of fundamental mechanics

The article tries to argue that the fundamental mechanics of a greenhouse and Earth's ability to retain heat are fundamentally different, since a greenhouse does so by hindering convection: "This mechanism is fundamentally different from that of an actual greenhouse, which works by isolating warm air inside the structure so that heat is not lost by convection." However the earth's heat loss by convection is negligible, and only happens as single atoms and molecules escape from the thermosphere and earth's gravity field, and may, or may not end up interacting with the atmosphere of another planet. This heat loss is negligible and earth's presence in a partial vacuum in space can therefore be said to affect it's ability to retain its thermal energy, similar to a greenhouse. It shouldn't make a difference whether the vacuum in space is created by the expansion of space-time, and that the glass for the greenhouse comes from a factory in detroit. They still show these same mechanics. When it comes to the radiance bit; the glass in the greenhouse has similar function to co2 in our atmosphere, in that it is transparent in the visible spectrum and opaque in the infra red, re-radiating energy back into the greenhouse.

I would formally like to suggest that this bit "This mechanism is fundamentally different from that of an actual greenhouse, which works by isolating warm air inside the structure so that heat is not lost by convection." is taken out, as it is inaccurate; the earth's convection insulation is just as important for its thermal equilibrium as it is for a greenhouse.--Harald Veland, Bergen, Norway 26 December 2010 —Preceding unsigned comment added by (talk) 16:19, 26 December 2010 (UTC)

What you're talking about might be true, but it's not what's called the greenhouse effect, which is an effect about radiative heat loss. This greenhouse effect is pretty much unrelated to convective effects. Dicklyon (talk) 22:17, 26 December 2010 (UTC)
But the function that warms the air inside the greenhouse is in fact the same function as with greenhouse gases! The trapping of air does not make it warm inside the greenhouse; only the windows that let visible light through, and traps infra red light has the power to actually heat the air on the inside. Hindering convection only stops that hot air from escaping. The earth's atmosphere is insulated, as is the greenhouse. What makes it warm in both cases is the trapping of infrared radiation. -- (talk) 16:23, 28 December 2010 (UTC)
I understood the sources to say that the real greenhouse doesn't have any significant effect from trapping of infrared radiation. Are we reading it differently? The "greenhouse effect" is all about radiative heat transfer, and real greenhouses are all about convection, yes? Dicklyon (talk) 18:31, 28 December 2010 (UTC)
Could you direct me to that specific source? Reading about this issue in the archives (discussions), there were conflicting opinions from various sources, and as far as I could tell the call was eventually made by the editors of the page. To paraphrase one specific opinion on the issue, one scientist who stated "of course its all about radiation. I don't know why this is even being discussed" -speaking on greenhouses. —Preceding unsigned comment added by (talk) 03:54, 29 December 2010 (UTC)
See the source that's cited and linked in the section in question (I had added it there just a few days ago, in response to your questioning). Dicklyon (talk) 07:59, 29 December 2010 (UTC)
The link cites another wikipedia page, which is itself not cited. This alone should bring the section into question. Further, the article does claim that the radiative forcing from the windows is negligible compared to convection, a claim backed up by the phenomenon that if you let the air out, you get temperature change. I guess this would happen with the entire atmosphere too if some hypothetical factor made it able of convection with the atmosphere of Io... What that has to do with anything is beyond me. Again; what traps the heat within the greenhouse IS radiative forcing. Trapping air does not have a heating effect all of its own. If you close a plastic bottle, its interiors maintains the outside temperature. -Not true of a glass bottle. -- (talk) 23:40, 29 December 2010 (UTC)
I was referring to the cited reference, not a wiki link. Read it. Dicklyon (talk) 00:19, 30 December 2010 (UTC), I wouldn't waste time trying to argue your point here. On the Internet both sides of the global warming debate behave as though the basic science was settled in their favor. My experience has been that essentially all of them lack the sort of physics background that would allow them to critically examine arguments for and against global warming. They don't understand where the peak of Wien's displacement law is, or what proportion of CO2 absorption lines are still open, or how to derive Arrhenius's logarithmic dependence of surface temperature on CO2, or whether it's even true, or how OLR is divided up between emission from the surface vs. the atmosphere, or the extent to which the feedback between CO2 and water vapor is changing cloud cover, or which of ground water or precipitation cools the Earth's surface more via evaporation, or how back radiation bears quantitatively on climate sensitivity, or how to apportion global temperature fluctations between natural and anthropogenic causes, and so on for all sorts of things without which both affirmation and denial of global warming are just two competing religions.
Liberals and conservatives argue with each other in much the same way, with both sides claiming they're right. On both sides, some bloggers are polite, some are impatient, some are incredibly rude (on both sides), but almost all seem incapable of stepping back in order to critically examine the premises of their beliefs, which they all uniformly treat as written on tablets carried down from a mountain top. Journalist Gregg Easterbrook (skeptic geologist Don Easterbrook's cousin) and the Economist are among the very few flexible media-oriented sources in that regard.
You'll be better off corresponding by email with real climate scientists, who you'll find much more open minded about these things because they have the background to evaluate the logical soundness of both their own arguments and those of their colleagues, a necessary skill given the continual evolution of the subject. Better yet, if you have any in your neighborhood chat them up in person.
It's pointless arguing these things on the Internet, where you'll be extremely lucky to find these skills anywhere (though tiny pockets exist if you know where to look, certainly not here however). With extremely few exceptions these people simply don't have a lot of practice at arguing at the frontiers of science where even the most famous scientists occasionally have to back down from some deeply felt belief. --Vaughan Pratt (talk) 06:49, 1 April 2011 (UTC)
Incidentally did you follow up on Dicklyon's recommendation to read reference [25] of the article? This is the book "Favorite demonstrations for college science: an NSTA Press journals collection," a collection of articles from the Journal of College Science Teaching describing various science experiments that have been devised for classroom use. The article in question is by David P. Martin titled "Demonstrating the 'Greenhouse Effect': Illustrating Variations on an Atmospheric Phenomenon" and originally appeared in the Dec. 1995/Jan. 1996 issue of that journal. I'll describe the demonstration so people can decide whether as a source it supports the article's claim that salt and glass boxes warm about equally when exposed to shortwave radiation and therefore do not model the atmospheric greenhouse effect.
The goal of the article is to demonstrate the greenhouse effect in the lab. To this end it simulates the joint action of the Sun (as a source of shortwavelength radiation), the Earth (as an absorber of sunlight), gravity (in its role of preventing the massive "convection" that would result in its absence), and the atmosphere (in its role of reflecting some of Earth's OLR back to Earth while transmitting the rest to space). For the Sun, Martin uses the high-temperature (3300 K for a typical OHP bulb) radiation from an overhead projector. For the Earth he uses aluminum foil painted black to absorb the OHP radiation and reradiate it as infrared. For gravity he uses an airtight optically clear salt box containing the foil; salt allows the IR from the "Earth" to escape to the "atmosphere" placed around the box, while airtightness not only confines the air to one place but also allows pressure, measured by a liquid barometer, to be used as a proxy for temperature. This proxy has two advantages over a thermometer: it is very sensitive when a thin bore is used, and it measures temperature averaged over the whole interior of the salt box instead of at one point, which may not be representative (one of several flaws in Wood's experiment).
Three atmospheres are provided, each in the form of a box open on the bottom (so as not to have to slide that side under the salt box, which sits on a table) and one side (to admit the light from the projector), with the remaining four sides enclosing the salt box. The first atmosphere is an IR-transparent plastic film. The second is aluminum foil painted black on both sides. The third is like the second but with the exterior left unpainted and hence shiny.
The demonstration is conducted by putting the first atmosphere in place, turning on the light, and waiting for the temperature to equilibrate. The first atmosphere is then replaced by the second, and the temperature noted. Then the third replaces the second, and the temperature is again noted.
The idea is that the first atmosphere does not warm significantly but passes all the IR from the Earth to "space" (the room). The second intercepts the IR, warms, and radiates half back to Earth and half to space. The third behaves like the second but with no significant radiation to space.
The result was that each rise in temperature was on the order of 1 °C. This is on the same order as the rise in global temperature over the past century.
Left unanswered was the question, if Wood's experiment showed no significant temperature difference between salt and glass boxes, why go to the trouble of procuring, cutting, and grinding fragments of halite to make optically clear panes for a salt box when it would have been easier to construct the box from glass? My answer to that is that there were enough errors in the methodology of Wood's experiment as to render his conclusion meaningless, and that 4 mm thick glass is at least as effective at trapping IR as 400 ppmv of atmospheric CO2, while 4 mm optically clear salt is completely transparent to IR below 18 microns. --Vaughan Pratt (talk) 17:07, 4 April 2011 (UTC)
I deleted this unsupported assertion : This mechanism is fundamentally different from that of an actual greenhouse, which works by isolating warm air inside the structure so that heat is not lost by convection. If anyone wants to put that back, then be sure to include a verifiable citation why solar gain has nothing to do with it and if the only thing that's involved is preventing convection, then why won't a hermetically sealed box on the cold dark side of the moon warm up inside? NewsAndEventsGuy (talk) 15:50, 4 June 2011 (UTC)
Aaaaaaaaaarrrrrrrrggghhhhhhhhhh.... I give up. Goodbye Wikipedia. Short Brigade Harvester Boris (talk) 17:12, 5 June 2011 (UTC)
Dear NewsAndEventsGuy, you're wrong and your edit was not an improvement. I've restored the earlier wording, and tried to add some clarifications that may overcome your confusion: note the source, which is now provided in a convenient html link rather than having to read a pdf. Please make proposals on the talk page rather than trying to push through such drastic changes. . . dave souza, talk 18:28, 5 June 2011 (UTC)
Also, please check sources before making silly changes. "This is called the greenhouse effect. The glass walls in a greenhouse reduce airflow and increase the temperature of the air inside. Analogously, but through a different physical process, the Earth’s greenhouse effect warms the surface of the planet." It's a fundamentally different process, more explanation is given in the first section of the article. As for the convection point, we already have lots of nice sources in the Real greenhouses section so I've cited a couple. . dave souza, talk 19:06, 5 June 2011 (UTC) oops, revised as cited sources, 19:18, 5 June 2011 (UTC)
Well if I was naughty it was editing before I read the entire piece, in which case I would have seen the real greenhouse section. So I'll apologize for haste. And I thank you moving some of those citations to the LEDE, so in substance, that's done for now. However, its not fair to bite my good intentions after you switched out the citations. The SPECIFIC citation I moved was a PULLQUOTE PINPOINT citation that did not support the second half of the sentence, so I moved it to comport with what the pullquote said without overreaching. That's proper editing, and you don't have to be PhD in a field to draw such a conclusion.
So now the article is improved because I did something... conceptually mistaken but inspired due to the articles status at the time. You corrected my mistake and improved the article. Ain't that what it's about? NewsAndEventsGuy (talk) 00:50, 6 June 2011 (UTC)

Merger proposal

Is there a reason to have separate pages for greenhouse gas and greenhouse effect? IMO, the greenhouse gas page should be merged into this one. It could organized to talk (A) greenhouse physics in general, (B) earth's greenhouse, and (C) exoplanet greenhouse issues. NewsAndEventsGuy (talk) 23:53, 2 June 2011 (UTC)

  • Support. This makes sense. It's hard to discuss the greenhouse effect without discussing greenhouse gases, and vice versa. A merged article would be stronger than the two separate ones. Short Brigade Harvester Boris (talk) 01:49, 3 June 2011 (UTC)
  • partially Oppose. The problem with merging them is that greenhouse gas is long, and could almost stand to be split up, while the greenhouse effect is generic and also applies to green houses, which involve a different process. - Parejkoj (talk) 03:43, 3 June 2011 (UTC)
  • Oppose -- The articles are both long with not too much overlap. Dicklyon (talk) 17:37, 5 June 2011 (UTC)
  • Oppose -- I am opposing my own idea, because I proposed this during a fit of delusion, i.e., before I appreciated the fact that the atmosphere process and real greenhouse process are considered different. Now that I've been corrected, I'm oppposed to my original merger concept. I may come back with a revised idea later. Also, as a matter of housekeeping, I'm a new editor. I've got no idea when it is appropriate to close this, but I'm willing to do the work when it becomes appropriate, in keeping whatever the consensus might finally turn out to be, with future input, if any. Maybe someone would be kind enough to visit my talk page with a request, whenever its time? NewsAndEventsGuy (talk) 20:52, 7 June 2011 (UTC)

Contribution in french, because I don't speak very good english

However, if someone can do the translation...


When posting on Talk pages on the English wiki, please use English.
See Wikipedia:Talk_page_guidelines#Good_practices NewsAndEventsGuy (talk) 12:08, 9 July 2011 (UTC)

Effet de serre et Fondamentaux du dérèglement climatique

Lorsqu'ensemble, nous recherchons la vérité et que nous n'insultons personne, - nous respectons forcément tout le monde, - nous défendons l'intérêt général et, ainsi, chacun des intérêts individuels bien compris.

– Critique pure : raison du doute

David HUME : « Ce n'est pas parce-qu'un événement A est suivi d'un événement B qu'il y a un lien de cause à effet entre-eux », « ce lien peut être le produit de notre imagination »... Il suffit, par exemple, qu'un événement C soit la cause commune des 2 évènements A et B séparément pour justifier notre prudence quant à certaines affirmations.

Vers 1780 cette mise en garde a été précisée par Emmanuel KANT de la façon suivante : « Seule une loi universelle [régulièrement vérifiée par le calcul à la manière de Copernic] transforme le rapport de simple succession en celui de cause à effet ».

– Problème du protocole scientifique suivi pour accréditer les « gaz à effet de serre » (GES)

Les relevés de températures effectués depuis 2 siècles, dans les airs, sur les mers et sur les continents, n'ont pas les qualités statistiques pour représenter, en réduction, les différents champs de mesures. Ainsi n'étant qu'un biais de la réalité, ils ne peuvent être utilisés pour établir des moyennes sur des périodes couvrant des centaines de millénaires. Certains scientifiques essaient de réduire cette erreur de méthode en multipliant le nombre de points de mesure depuis quelques décennies. - La seule courbe de la température moyenne des basses couches de l'atmosphère tracée à partir de ces «moyennes» n'offre ainsi que l'illusion de la précision et de la rigueur scientifique. - La courbe de la concentration moyenne du CO2 au cours du temps établie à partir d'une dizaine de carottes de glace en 2 régions particulières du globe repose sur de trop nombreuses hypothèses.

- Conclusion

    - donc il n'y a pas de courbe fiable, 
    - donc il n'y a pas de loi entre le forçage radiatif des «gaz à effet de serre» et leurs concentrations, 
    - donc il ne peut y avoir de modèle mathématique.

Si dans les programmes universitaires, comme dans ceux des classes préparatoires, cette loi est inconnue, heureusement, d'autres lois abordées dès le lycée sont universellement validées. A défaut d'un objectif et d'une méthode globale, (Si le problème s'avérait mal posé, il ne pourrait recevoir que de mauvaises solutions), voici une série de...

- Questions préparatoires

– Rigueur des arguments ?

    La question :
  * Pourquoi le forçage radiatif additionnel annoncé du CO2 ≈ 1 W / m2, correspond-il à l'énergie qui
    suffit pour élever la température de tout l'atmosphère de 1°C en 4 mois alors qu'il peine à faire la 
    même chose sur les seules basses couches de cette atmosphère en un siècle ?
Calculation, under your control
       (CALCUL, sous votre contrôle)
– Additional heat storage
       Forçage radiatif additionnel dû à (growth) l’accroissement du (level) taux de concentration du CO2 
      «Gaz à Effet de Serre (GHS)» au 20ème siècle.

* Le forçage radiatif additionnel annoncé est de l'ordre de 1 Watt / mètre carré

* Surface de la Terre (globe) = 510 x 10¹² m² (510 millions de km2)

* Puissance radiative additionnelle terrestre de l'excédent de CO2 =

                                             = 510 x 10 ¹²  W

* Energie radiative (forçage) additionnelle annuelle : 510 x 10 ¹² W x 24 (hours_heures) x 365 (days_jours)

                  ≈ 4 500 000 x10 ¹²  Wh   
                 ≈ 4,5 x 10 ¹⁵ kWh ①
– The Earth's atmospheric mass
          Masse de l'air atmosphérique.
          La pression atmosphérique est environ celle produite par 1 kilogramme d'air sur 
          chaque centimètre carré.
          Il y a autant de kilogrammes d'air dans l'atmosphère que de cm² de surface terrestre

* Surface de la Terre (globe) = 510 x 10 ¹² m² = 5,1 x 10¹⁸ cm²

* Poids de l'air atmosphérique ≈ 5,1 x 10 ¹⁸ kg

– Heat capacity of one kg of air
       La chaleur spécifique de l'air est 0,28 Wh / kg / °C =  0,28 x 10-³ kWh / kg / °C
       Il faut une puissance de 0,00028 kilowatt pendant une heure pour élever la température 
       d'un kilogramme d'air de 1 degré centigrade (Physical property).
– Energy required to increase air atmospheric temperature one degree Celsius more
                   La capacité calorifique de tout l'air atmosphérique.
       C'est le produit de sa masse par sa chaleur spécifique : 

5,1 x 10¹⁸ x 0,28 x 10-³ ≈

                         ≈ 1,4 x 10¹⁵ kWh ➃
      Des résultats de  ① et ➃ nous déduisons que le forçage radiatif additionnel annoncé de
      l'excédent de CO2 observé au 20ème siècle ne mettrait que 0,3 (year) année -(4 months only)- 
      pour élever la température moyenne de tout l'atmosphère d'un degré centigrade. 
      (1,4 x 10¹⁵  /  4,5 x 10¹⁵ = 0,3 an).
      C'est en contradiction avec l'augmentation mesurée et calculée de 0,6 °C de la température 
       moyenne des seules basses couches de l'atmosphère sur tout un siècle.
      It's physical impossibility.
       What about the two periods from 1 to 300 times :
         - 4 months only, when we used calculation, on one side 

         - a century in reality, in other one ? 

         The other conditions are the same... energy for the same growth of temperature
         Where is the error ?

Ghgornot (talk) 08:32, 7 July 2011 (UTC)

  * Pourquoi oublie-t-on que 15 ans de toute l'énergie consommée actuellement par l'humanité 
    suffisent pour élever la température de tout l'atmosphère de 1°C ?
  Ce forçage calorifique, cette énergie produite en majorité sur des fuseaux horaires de l'hémisphère 
    Nord converge, par la circulation atmosphérique, vers le pôle Nord qu'elle échauffe et s'évacue vers
    l'espace avant d'atteindre le pôle Sud.
  * Pourquoi le CO2 retrouvé en Antarctique n'y produit-il pas un effet aussi spectaculaire que celui
    que certains voudraient lui imputer sur la banquise du pôle Nord ?

– Incohérence ?

  * Pourquoi ne pas dire que l'énergie plaquée au sol par «l'effet de serre additionnel» 
    au-dessus du glacier du Groenland mettra 4 000 ans pour le fondre ?
  * Pourquoi «l'effet de serre additionnel» mondial aura-t-il besoin d'environ 300 ans 
    (1 200 x 10¹⁵ kWh / 4,5x10¹⁵ kWh) pour élever d'un degré la température de la machine 
     thermique «océans, terres et atmosphère, hors fonte des glaciers» ?
  * Pourquoi tout le CO2, qui a une capacité calorifique globale faible (1/20ème de celle 
    des nuages) et dérisoire (1/ 3 000ème de celle de l'atmosphère, dont l'air est un isolant),
    produirait-il un « effet de serre » si décisif ?

– Explication chiffrée ?

La puissance moyenne du rayonnement solaire qui arrive au sol, après avoir joué à cache cache avec les nuages, est de l'ordre de 170 W / m².

  * Qui garantit que l'énergie solaire reçue chaque année au sol par la Terre est constante en 
    régime normal ? Sur 11 ans ? D'autres cycles ?
  * Qui peut décrypter les rôles respectifs du forçage radiatif additionnel annoncé des «GES» ~ 1 W / m² 
   et de la variation « orbitale » de ~ 7 % de la puissance solaire au sol au cours de l'année : 12 W /m²?

A Paris, sur 105 km², il est consommé l'équivalent du 1/4 de l'énergie reçue par ailleurs du soleil.

  * Des colonnes d'air chaud au-dessus de Paris comme sur d'autres villes sont-elles, à tour de rôle, 
    le battement d'aile du papillon parmi des millions d'autres, qui produit les tornades aux USA, 
    les tempêtes en Europe, les typhons en... Malaisie ?
  * Une colonne d'air chaud au-dessus de Grenoble fait-elle fondre la neige et les glaciers avoisinants ?

– Comment la loi des GES existerait-elle ?

  * Comment est mesurée la concentration du gaz carbonique (CO2 ) dans l'atmosphère ?... et où ?
  * Quel est le “mécanisme quantique” et quel est le calcul du forçage radiatif ?
  * Le réchauffement d'une molécule, d'un groupe de molécules, de CO2 par une flamme est-il de nature
    différente lorsque celui-ci est obtenu par des rayons InfraRouges (IR) ?
  * Quelle est la loi physique qui lie la concentration des « gaz à effet de serre » à la température ?

Accessoirement où peut-on trouver les formules et les calculs qui établissent que

  * la vapeur d'eau, présente dans l'atmosphère pour 0,3 % ~ 3 000 parties par million, et le CO 2 pour 
   0,037 % ~ 370 ppm, participent respectivement pour 55 % et pour 25 %, à «l'effet de serre» (passage de 
   -18°C à plus de +15°C = + 33°C de la température moyenne annuelle des couches basses ? 
  * 100 ppm de CO2 de plus pourraient accroître la température de 1 à... 6 °C ?

– Comparaison scientifique ?

L'atmosphère de Vénus, qui reçoit 2 fois plus d'énergie solaire, peut, à température égale, stocker ≈ 90 fois plus d'énergie que celle, 90 fois moins dense, de la Terre. C'est un édredon ≈ 90 fois plus isolant. La quantité de CO2 y est 200 000 fois plus importante que sur Terre, la vapeur d'eau 50 fois. Pourtant la température au sol n'est que 3,3 fois plus élevée (173+15) x 3,3 ≈ 173+450 °K (450 °C).

   * Pourquoi lorsque les molécules de «gaz à effet de serre» sont 200 000 fois plus nombreuses ne 
     sont-elles que 60 fois (3,3 ⁴/ 2) plus efficaces ?

– Anachronisme de fait ?

Les périodes chaudes repérées dans les glaciers des pôles accompagneraient systématiquement les augmentations mesurées des concentrations de «gaz à effet de serre» (CO2) depuis 400 000 ans au moins (dixit des climatologues). Ceci tend à prouver que les «gaz à effet de serre» étaient produits dans les temps anciens par une cause naturelle antérieure au réchauffement, donc non du fait de l'homme. Or nous sommes dans une période interglaciaire (de réchauffement) qui a débuté il y a 10 000 ans.

   * Pourquoi cette cause n'opère-t-elle plus depuis 10 millénaires, en ne produisant pas de 
    «gaz à effet de serre» (du CO2 en particulier) cela pour la 1ère fois ?

* etc...

   * Comment les cernes de croissance de quelques arbres donneraient-elles (au 1/10ème °C près)
    une valeur de la température moyenne des couches basses de l'atmosphère terrestre des années
    correspondantes ?
  * etc...

Ghgornot (talk) 08:00, 7 June 2011 (UTC)

This looks unrelated to improving this wp article. See fr:Effet de serre (talk) 08:15, 13 June 2011 (UTC)
This looks a lot more related to improving the article than almost all of your comments. I'm not entirely sure it's helpful, but it's at least an attempt to help. — Arthur Rubin (talk) 08:40, 13 June 2011 (UTC)
Eh bien. Google has it as:
"How the growth rings of some trees would they (1/10th ° C.) value of the average temperature of the lower layers of the atmosphere for years relevant?"
An interesting question, but it seems to lack the reliable sources we need for anything going in the article. . dave souza, talk 09:12, 13 June 2011 (UTC)
This looks like a straightforward WP:FORUM problem. The francophone editor is asking some questions about the topic rather than discussing the article. I can provide a full translation but I don't think it's worth the effort, but here is a brief summary:
Critique pure : raison du doute: correlation is not causation.
Problème du protocole scientifique suivi pour accréditer les « gaz à effet de serre » (GES): aggregating different temperature records over the past 200 years does not constitute a valid representation of global average temperature trends over the period.
Conclusion. So there is no reliable trend, hence no theory linking radiative forcing to greenhouse gas concentrations, and therefore there can be no climate models.
So, a bold head-on attack on the field. It really belongs on the author's blog. --TS 14:23, 29 June 2011 (UTC)

Edit request from, 23 June 2011

add: the atmosphere recieves many kinds of rays and waves from the sun. Some of these change into warmth. Without this process the earth would be 27 degrees farenhight cooler. however, gases from human activties are increasin this effect (talk) 21:15, 23 June 2011 (UTC)

Not done: please provide reliable sources that support the change you want to be made. Also where in the article should it go? Jnorton7558 (talk) 00:24, 24 June 2011 (UTC)


the into suggest that the surface temp of a body is dependent on the atmosphere, but disregards core temp of the body that may be fueled by radioactive decay. — Preceding unsigned comment added by (talk) 03:11, 2 August 2011 (UTC)

That is correct; the core temp is ignored in this simplified analysis; it does have an actual effect, though it's not big. Dicklyon (talk) 05:27, 2 August 2011 (UTC)
The mantle-to-crust flux should be on the order of 0.1 W/m2, roughly one order of magnitude less than global warming. In their book "The planet Venus", Marov and Grinspoon estimate the corresponding flux at 0.03 W/m2, which they describe as 2 to 3 times weaker than Earth's. (At least some of that difference can presumably be attributed to Venus's 740 K surface temperature.) --Vaughan Pratt (talk) 16:39, 17 August 2011 (UTC)

There are factual errors on this page which are misleading

I collapsed this thread, which is archivable per wiki rules. Talk pages for specific suggestions for improving the article. This thread is a debate about principles of physics, and contains only a single verifiable citation. Please debate these principles in the peer reviewed literature or appropriate science related forum. If you have specific article improvement suggestions based on verifiable citations under wiki rules, please provide some draft text and then make your case. NewsAndEventsGuy (talk) 12:17, 22 August 2011 (UTC)

Greenhouse effect and Fundamentals of climate change

IMO, while the poster may have some good ideas for improving the article, the poster's (long) presentation in this thread is archivable as disruptive because (A) as it says at the top of the page "This is not a forum for general discussion of the article's subject.", (B) the grammar used often leaves me in doubt about the posters point, (C) the poster expressed a lot of opinion about the science but provided no supporting citations for context, and (D) generally the comment lacks specific suggestions for improving the article.

I suggest the poster review their comment to identify the two ideas that could make the biggest improvement to the article, and then proceed accordingly..... please include supporting verifiable citations under wiki rules.NewsAndEventsGuy (talk) 11:20, 21 August 2011 (UTC)

"Real" Greenhouses

How greenhouses work

This is my first effort at helping Wikipedia, so I would welcome any advice.

The discussion of glass greenhouses contains misleading language. Standard soda lime glass is transparent at wavelengths below about 5 microns, but is essentially 100% opaque above about 6 microns. Therefore most of the solar thermal radiation passes through the glass, while the longer wavelength radiation from the objects in the greenhouse does not. Like in your car, the radiative thermal energy is trapped. The reference to convection is misplaced. If there is general agreement, I can write something for the article. The transmittance of glass may be found here: Gobluedebsl (talk) 17:22, 8 September 2011 (UTC)

My advice is to post your proposed text in this talk page thread, together with with verifiable citations so we can discuss something tangible. NewsAndEventsGuy (talk) 18:04, 8 September 2011 (UTC)
Goebluedebs, thanks for offering to contribute and for bringing this issue to the talk page. From the reference 27 used in the article, Brian Shmaefsky (2004). Favorite demonstrations for college science: an NSTA Press journals collection, you're right that ordinary glass is transparent to visible light but opaque to infrared, however that doesn't make a significant difference in greenhouses. As the reference confirms, an experiment with salt panes transparent to both visible and infrared light shows much the same warming: the main contribution to the warming of greenhouses is warm air being trapped instead of being removed by convection. It would be great if you could have a look at that reference and suggest improved wording to make the issue clearer in our article. You might also be able to find another reference covering the same point. Thanks again, dave souza, talk 20:26, 8 September 2011 (UTC)
The reference in question appeared in the February 1909 issue of Phil. Mag. It was rebutted by no less than the director of the Smithsonian Astronomical Observatory in the July issue.
I would love to know how any competent experimental physicist could take Wood's 1.5 page parody of bad methodology seriously. He gives no dimensions of his apparatus, neither the dimensions of the box (it could have been a two-inch cube, or a two-foot cube, or far from cubical) nor the thickness of the windows (they could have been anywhere from 2 to 8 mm, with the latter more likely given the structural weakness of optical quality salt windows).
In fact the only numbers in the entire note are two temperatures, one of which Wood decided arbitrarily was wrong and therefore discarded. How could anyone hope to duplicate his experiment with this little information about it?
Furthermore Wood said he placed glass over the salt window. Didn't he realize this will trap IR and radiate it back into the salt box, defeating the whole point of a salt window?
Wood himself points out at the end of his little note that it shouldn't be taken seriously, saying "I don't pretend to have gone very deeply into the matter." Amen to that.
Wood published two papers in the 1909 volume of Phil. Mag, issue numbers 98 and 107 respectively. The second, in November, was rebutted even faster than the first, namely in the same issue, by noted optics physicist Sir Arthur Schuster, who presumably had been the referee. While Wood had some notable successes in other years, or Schuster's report would have been grounds for rejection, 1909 was definitely not one of them.
What I find amazing is the number of people willing to ignore Wood's caveat at the end of his note and to regard his reported brief observation as the definitive word on the whole subject. Anything more BS than this would be a prime candidate for the Ignoble Prize. --Vaughan Pratt (talk) 08:14, 19 December 2011 (UTC)

Misleading text in RG section

The text

The greenhouse effect and a real greenhouse are similar in that they both limit the rate of thermal energy flowing out of the system

isn't really helpful. If you define the "system" as the Earth, then its wrong: at equilibrium, energy out = energy in. If you define the system some other way... then you'd need to explain your definition (this insight from AnotherPhilC at, of all places, WUWT) William M. Connolley (talk) 13:43, 10 March 2012 (UTC)

Sofixit. In the interim, as a sort of sticking plaster, I've looked at the cited source but my brain hurt, so simply changed the wording to "The "greenhouse effect" of the atmosphere is named by analogy to greenhouses which get warmer in sunlight, but the mechanism by which the atmosphere retains heat is different." If that or the rest of the section needs improvement, please alter it to suit. . . dave souza, talk 16:53, 10 March 2012 (UTC)
Hey, I was being all warm-n-fuzzy-carin-n-sharin :-). Anyway I think your sticking plaster looks good enough. I hadn't actually bothered read that ref before; the pic is a useful one William M. Connolley (talk) 18:33, 10 March 2012 (UTC)

Intro problems

The first sentence of the intro reads "The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions." The implication of this sentence is that the greenhouse effect does not include the idea that thermal radiation from sources other than a planetary surface is part of the dynamics of energy movement within an atmosphere. Also ignored is how the energy absorbed by a greenhouse gas heats up the atmosphere. And also ignored is how the atmosphere keeps the surface cooler than it would otherwise be in equatorial regions. That means, the last sentence in the intro is wrong because it does not specifically state that what is meant is average temperatures- temporally and spatially. It's not that hard to get this stuff right- you just have to think it through carefully provided you really understand what is going on. blackcloak (talk) 20:34, 5 December 2011 (UTC)

Clarified. You know, you could always fix it yourself rather than complaining on the talk page...... Sailsbystars (talk) 21:17, 5 December 2011 (UTC)
I no longer fix articles because I've learned that my edits won't survive the low standards of most editors. blackcloak (talk) 07:50, 9 December 2011 (UTC)
So true, at least with articles of intermediate technical complexity. Much less and what's left to argue about? Much more and no one feels competent to challenge you.
It's these intermediate-complexity articles that I've been finding the most problematic for Wikipedia, and the biggest time sink for editors with an in-depth grasp of the subject matter. --Vaughan Pratt (talk) 08:30, 19 December 2011 (UTC)
IPCC references for greenhouse effect dont explain the greenhouse effect but rather make it harder to understand. The atmosphere is not warming the surface. Instead the surface has to rise in temperature to re-emit the radiation received from the colder atmosphere where the surface is warming the atmosphere. Somewhat unbelievable the entire worlds climate scientists cannot correctly describe the effect!  :-) Andrewedwardjudd (talk) 18:07, 18 March 2012 (UTC)Andrewedwardjudd
The greenhouse gases in the atmosphere do keep the surface warmer, in the same sense that a blanket keeps a sleeping person warmer. The requirements of equilibrium are different - the planet must re-radiate all incoming heat at equilibrium, and the sleeping person must lose all their self-generated heat at equilibrium. Secondly, don't be fooled by the 'heat can't flow from the cooler to the hotter' meme - there is certainly some radiant heat energy received by any hot surface from a cooler one, provided that is above absolute zero, it's just that there is also more radiant heat transfer in the other direction. It is true that you can go into huge detail about heat flows, wavelengths, feedbacks and equilibrium conditions, but that does not make it untrue to simply say that a blanket warms a sleeper, and a greenhouse atmosphere warms a planet. Whenever you feel like you can suddenly do better in their specialist subject than all the world's greatest scientists put together, it's worth stopping for a second just to wonder if it's really true. --Nigelj (talk) 18:28, 18 March 2012 (UTC)
The issue here is you are incorrectly describing the process. You used the word energy from the atmosphere which is wrong or misleading. The energy flow is from the surface to the atmosphere. The atmosphere cannot warm the surface. The hotter surface is cooling and warming the colder atmosphere. The greenhouse effects slows down the rate of cooling which is a very different thing than saying the atmosphere in some manner warms the surface or sends warming energy. It is actually surprising that the IPCC cannot correctly describe it but there it is. Andrewedwardjudd (talk) 18:38, 18 March 2012 (UTC)andrewedwardjudd
You have not cited a single source for these changes, and some of what you are saying is flat out wrong. Please stop hacking away at the article for a minute and discuss the citable sources that you are working from. --Nigelj (talk) 18:50, 18 March 2012 (UTC)
It would be more productive if you indicated what was wrong. Andrewedwardjudd (talk) 18:58, 18 March 2012 (UTC)andrewedwardjudd
Interestingly hyperphysics is also wrong.
Andrewedwardjudd (talk) 18:58, 18 March 2012 (UTC)andrewedwardjudd
I explained the problems in my edit summary on the article - "the average surface temperature is still elevated *after* equilibrium is re-established. There is no such thing as 'cooling radiation' - that is confusing." Do you see my point that you saying that the IPCC, or whoever, is wrong, isn't much help? You have to provide a citable and reliable source that says it's wrong, and then we can discuss the WP:DUE weight to give to the alternative, or fringe, views. Your views and mine carry no weight at all round here, I'm afraid; only what's in the cited sources. --Nigelj (talk) 19:13, 18 March 2012 (UTC)
Fundamentally you assuming i am fringe when i am not.
I made it clear the greenhouse effect works. I was not saying the surface cools after equilibrium was established. If the cooling rate of the earth slows down it gets hotter and hotter until it can get rid of all of the incoming solar.
The IPCC use of warming by the atmosphere is misleading. Which is probably why so many people think the climate science is bogus. I am not saying that. We have a greenhouse effect.
Nothing i said is wrong. I just described it more correctly than the IPCC
Andrewedwardjudd (talk) 19:34, 18 March 2012 (UTC)andrewedwardjudd

I didn't much like Aej's version, but the current version was a bit horrible too, so I've revised it. Talking about it as though it were time-dependent was confusing, as was the energy bit William M. Connolley (talk) 19:26, 18 March 2012 (UTC)

You have addressed my objections to the original intro. I think you realise that the cold atmosphere cannot warm the warmer surface. And i think you realise that incoming IR is a warming IR and the outgoing is a cooling IR where these two forces are in balance at the top of the atmosphere. So any emission from the surface is a cooling emission and any absorption is a warming emission. But even so the atmospheric emissions cannot warm the surface because the surface is warming the atmosphere. Agreed? Andrewedwardjudd (talk) 19:41, 18 March 2012 (UTC)andrewedwardjudd
No, not really. All this is just words, anyway. Look at Idealised greenhouse model for the maths, which is the real bit. My own favoured explanation (it was here once, but no-one else liked it) is: "the GHE makes the sfc warmer because the sfc absorbs radiation from two things, the sun and the sky" William M. Connolley (talk) 20:13, 18 March 2012 (UTC)
A blanket cannot make a person warmer. The person makes themselves warmer because the blanket slows down their rate of cooling. If you want to believe the blanket makes you warmer, you will agree with most people. correctly says that the surface is warming the atmosphere and does not misleading say the atmosphere is warming the surface
I suspect you have not even bothered to take the time to realise that what I said was totally correct. If the surface emissions were not cooling the surface it would get hotter and hotter and typically it does not. The green house gases slow down the rate of cooling and it gets hotter until the cooling forces are again in balance with the heating forces. And it remains hotter. This process is happening every moment of the day as the water vapour content rises and falls. Some moments the surface can cool faster and seconds later it cools slower and it gets hotter till a new equilibrium balance is achieved and so forth etcAndrewedwardjudd (talk) 20:55, 18 March 2012 (UTC)andrewedwardjudd

We cannot say 'a cold greenhouse atmosphere warms a warm surface'

Recent changes

Looking at this diff, we can see that there have been a number of net changes made rather hurriedly to the article (without any new refs). I'd just like editors to have the chance to look and decide if each, any, or all of these is actually an net improvement. --Nigelj (talk) 17:51, 22 March 2012 (UTC)

My own 2p-worth:

  1. I think the changes to the first para, to "it results in an elevation of the average surface temperature above what it would be in the absence of the gases" is a less wordy way of saying the same thing, and maybe avoids some of the 'red flags' that maybe upset people bringing the 'IPCC don't understand the 2nd law' meme here. ([4] - skip the article, it's the comments that are fun)
  2. Did John Tyndall "definitively proved experimentally", or "reasoned from experimental observations"? I don't know.
  3. I don't like the third set of changes - I can't read beyond "in equilibrium between heating and cooling forces", as it's so irritating - but I think it actually makes less sense than what we had before.

--Nigelj (talk) 17:59, 22 March 2012 (UTC)

I agree. I've restored the pre-edit-war version for that third bit. I hope that if someone sees a way to improve it further they'll discuss here first, rather than go back to edit warring and convert their topic bans to blocks. Dicklyon (talk) 18:25, 22 March 2012 (UTC)

To help and to have a clear conscience, this is three examples:


Someone complained that "re-radiates" in "Most of this thermal radiation is absorbed by the atmosphere and re-radiated both upwards and downwards" is wrong. I don't think it is wrong, but there is a subtlety in there that may be worth explaining. Individual molecules absorb IR; through collision, they will pass this energy around, until it is eventually re-radiated (as a different photon, obviously, but likely with different frequency too). This could be another thing added to the "basic mechanism" section William M. Connolley (talk) 19:50, 1 April 2012 (UTC)

I think that it would be relevant to mention how many hours it takes from heat to re-radiate back into space when IR radiation is bouncing back and forwards from Greenhouse molecules. I remember that surface heat would conduct into upper atmosphere and then re-radiates back into space in eight hours, and thus there is more time for Sun to heat the surface towards the 5800 kelvin Sun's surface temperature. But I do not remember the source and not even sure if it was reliable one. Therefore my request for someone, who knows it better, to include this information, because I think that it is theoretically important bit of information. It should be also compared to Venus, where greenhouse effect is stronger.
I think also that it is misleading to say that in real greenhouses the greenhouse effect is different. Actually it is very similar, because glass in greenhouse slows down the rate on which heat is conducting from the ground and inside air into outside/space. That is, glass slows down the conduction of heat, thus it is the same thing what greenhouse gasses does in the atmosphere. --Jouni Valkonen (talk) 20:21, 1 April 2012 (UTC)
A series including Darwinian Selection – “Back Radiation” « The Science of Doom and Radiation Basics and the Imaginary Second Law of Thermodynamics « The Science of Doom as well as CO2 – An Insignificant Trace Gas? Part One « The Science of Doom covers a lot of these issues rather well, though not a rs. Some improvements may be suggested, hope to put words forward when time permits. . dave souza, talk 15:28, 6 April 2012 (UTC)
The existing version is fine but could be improved in some respects.
Part 1. Temperature.
1. Suggest change introductory sentence

The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions.


The greenhouse effect is a process by which thermal radiation from a planetary surface at one temperature is absorbed by atmospheric greenhouse gases at a lower temperature , and is re-radiated in all directions.

2. Add a sentence after 'lapse rate'. The new version would read more realistic to think of the greenhouse effect as applying to a "surface" in the mid-troposphere, which is effectively coupled to the surface by a lapse rate. Since it is much colder here than at the ground, any upward radiation from greenhouse gases at this level will be reduced compared to the original Planck radiation emitted by the ground at the same wavelength.

Justification to talk page. Although the gh effect does not act alone it is the job of Wikipedia's discussion of this topic to try to isolate the gh mechanism itself which is intimately tied up with the Scharzschild equation. The existing introductory sentence does an excellent job of describing that equation in non mathematical terms except that it fails to mention the temperature dependence of the re-radiation. Both the outward long wave radiation (OLR) and the backradiation are determined by the emission term i.e. the product of the Plank function and the emissivity of the gh gas. My suggested changes derive from the fact that the Planck function decreases as the temperature is reduced (for all wavelengths).

Geoff Wexler (talk) 10:05, 13 April 2012 (UTC)

Part 1 (a).
I suggest that this remark

The major non-gas contributor to the Earth's greenhouse effect, clouds, also absorb and emit infrared radiation and thus have an effect on radiative properties of the atmosphere.[17].

be followed with

Just as for gases, this effect depends on the clouds being significantly colder than that of the surface, which is why high clouds tend to warm more than low ones.

Suggest this paragraph

Real greenhouses .... This process may exist in real greenhouses, but is comparatively unimportant there.

is followed by a new remark i.e.

The analogy breaks down even more severely for clouds whose behaviour departs markedly from that of glass or the clear atmosphere when it comes to visible solar radiation but which nevertheless contribute significantly to the total greenhouse effect.

Geoff Wexler (talk) 15:03, 13 April 2012 (UTC)

In the bit "Just as for gases, this effect depends on the clouds being significantly colder than that of the surface", two problems: I don't see what "that of" refers to; and I don't find anything in the article that "Just as for gases" can be referring to. Clarify? Dicklyon (talk) 15:47, 13 April 2012 (UTC)
Reply to Dicklyon.
Thanks for the questions. First the two words "that of" should have been deleted (my error).
Secondly this suggestion is my third one making this sort of point about temperature; the first was in my Part 1 point 1 which inserted the new phrase "absorbed by atmospheric greenhouse gases at a lower temperature" and the second was included in my point 2 i.e. "Since it is much colder here than at the ground",
Geoff Wexler (talk) 16:18, 13 April 2012 (UTC)
Do you have sources for this stuff? Dicklyon (talk) 03:54, 14 April 2012 (UTC)
I'm finding myself a bit resistant to the colder stuff. I agree its true for Earth, but is it essential? Imagine a weird world with a thin atmos shell that absorbs, say,UV strongly and has a low emissivity in the LW. Then I think it would be possible for the atmosphere to be warmer than the sfc, but there still to be a GH effect William M. Connolley (talk) 16:23, 13 April 2012 (UTC)
Interesting and I shall consider it later, but meanwhile I don't follow properly.
What if you prepared the initial state of the atmosphere so as to have a temperature inversion and considered the effect of ordinary gh gases? I thought that would produce an anti-gh effect, i.e. gh cooling?
Are you saying that arranging to dominate the gh absorption with UV heating, as in the stratosphere, would have the effect of reversing the sign of the temperature change? In this case back to warming? Geoff Wexler (talk) 20:14, 13 April 2012 (UTC)
Lets not think of the time-dependent case, which adds complexity, at least not until we agree on the equilibrium case. What I'm saying is that if (like in the stratosphere) you have a source of heating (e.g. UV absorption) then the upper atmos can in principle be warmer than the surface. That wouldn't be stable if the atmos had unit emissivity, but if it hasn't it might work. OK, in equations (S_v = solar, visible; S_u = solar, UV; e = atmos IR emissivity, sfc emiss = 1):
Sfc: S_v = rT_s^4 + erT_a^4
Atmos: S_u + erT_s^4 = erT_a^4 * 2
which (correct me if I'm wrong) leads to:
S_v + S_u/2 = rT_s^4(1 - e/2)
S_u + eS_v = erT_a^4(2 - e)
If S_u >> S_v, and e < 1, then T_a > T_s. But there is still a GHE, because the planet is warmer than it would be in the absence of the atmosphere (assuming unit albedo in the UV for the sfc). This is a very artificial example, but I think it shows that a cooler atmosphere isn't *essential* to the GHE William M. Connolley (talk) 08:55, 14 April 2012 (UTC)
Referring back to the original post here by WMC, I think there may be some readers who might confuse re-radiate and reflect. For their benefit we may add an item to the bullet point list under 'basic mechanism' similar to the explanation given in the first post here. --Nigelj (talk) 08:51, 14 April 2012 (UTC)

It's pretty much true that you need the temperature to decrease with height to generate a traditional absorption-emission greenhouse effect, since you won't reduce the OLR to space with a radiating layer at the same temperature as the surface. It is conceivable to generate a greenhouse effect via IR reflection (rather than absorption-emission) in which case the temperature structure is less critical, since you can delay the escape of energy to space without much affecting the layer that the upwelling photon strikes, but this isn't relevant for the Earth at least. It also doesn't really matter much, to first-order, if you absorb incoming light at the surface or in the troposphere since the two are well-coupled by convection (as long as the planetary albedo in the two cases is the same). If you absorb solar radiation too strongly in the upper atmosphere though, you can generate an anti-greenhouse effect; this at least partially offsets the traditional GHE on Titan. (talk) 19:17, 23 April 2012 (UTC)Chris Colose


Use of the term "greenhouse" to describe the atmospheric phenomenon was originated in 1937 by Professor Glenn Trewartha at the University of Wisconsin, but previously the synonymous word "hothouse" had been used for this purpose. See William Safire, In Love with Norma Loquendi, page 276 (Random House Digital 2011). Perhaps a registered user would kindly insert this fact into the article? Here are some more details:

Svante Arrhenius, 1908, Das Werden der Welten, Academic Publishing House, Leipzig. (talk) 02:32, 5 August 2012 (UTC)

Incidentally, there's an article titled Greenhouse effect (judicial drift) that maybe should be in a hatnote or in the see also section of this article. (talk) 05:58, 5 August 2012 (UTC)

Simplified lead section

The current lead section is very technical and this topic is of interest far beyond technical circles, so I propose that the lead section be simplified and the technical discussion moved and reworked in the main body.

Pablo Mayrgundter (talk) 03:49, 24 October 2012 (UTC)

I don't object to simplifying the lede, but not at the loss of accuracy. Calling it "insulation" is wrong/odd. Internal heat isn't significant. "as some absorb more heat than others" is odd William M. Connolley (talk) 08:48, 24 October 2012 (UTC)

@William: I'm using the word insulation to give a simple, and I believe correct, name for what the effect is basically doing. The linked article describes "Thermal insulation provides a region of insulation in which thermal conduction is reduced or thermal radiation is reflected rather than absorbed by the lower-temperature body." Here, the atmosphere is reflecting the thermal radiation from the surface of the Earth back inwards, rather than the radiation being absorbed into lower-temperature space.

About internal heat, it doesn't change the greenhouse effect what the ultimate source of the under-atmosphere heat is, so I think it helps fully understand the concept. Also, I included it because the article introduces the concept as general to all planets, some of which will have high internal heat, e.g. Jupiter. Maybe this kind of context needs to be added? "The strength of the effect is measured by comparing a planet's expected surface temperature (in general due to insolation and internal heat and together, its black body temperature), to its actual surface temperature." or if this still seems too odd to point out, perhaps something parenthetical like "(though on Earth internal heat is relatively low compared to solar input)?"

Lastly, can you clarify what's odd about saying some gases absorb more heat than others?

Thanks for the read! Pablo Mayrgundter (talk) 17:37, 26 October 2012 (UTC)

The linked article describes "Thermal insulation... - which linked article? William M. Connolley (talk) 17:58, 26 October 2012 (UTC)

@William: in the intro sentence, the wiki-link to "insulation" is to Thermal_insulation. — Preceding unsigned comment added by Pablo Mayrgundter (talkcontribs) 22:15, 26 October 2012 (UTC)

Ah. Well the thermal - conductive - insulation bit is wrong. So presumably you mean the radiative bit? But then "reflected" is wrong; its absorbed and re-emitted William M. Connolley (talk) 22:36, 26 October 2012 (UTC)

@William: I see what you mean, though in the proposed edit I don't actually specify. Is it agreeable as-is, since insulation and its linked article support this usage? I'd like to make the change and improve from there.

Btw, I said that quickly in discussion, but I see why it's not simple (mirror-)reflection. I think that level of distinction and detail is better handled in the Mechanism section than in an intro. The intro is to orient and summarize. — Preceding unsigned comment added by Pablo Mayrgundter (talkcontribs) 21:11, 29 October 2012 (UTC)

No, its not OK to get it wrong in the introduction and correct it later William M. Connolley (talk) 21:30, 29 October 2012 (UTC)

@William: sorry for delay, I'm in the NY region and had to deal with the hurricane outages.

I don't know what you think I'm saying that is wrong in the intro at this point. I said "reflect" only in this talk page, not in the proposed edit. The proposed edit says "insulation", and the linked article supports that usage and your comment above makes mse think you agree with that. Is that right? And if so, any other objection? I think this the proposed edit is an improvement with nothing incorrect. — Preceding unsigned comment added by Pablo Mayrgundter (talkcontribs) 06:15, 8 November 2012 (UTC)

@William: I don't really understand the nature of your objection. The uses of both radiation and insulation seem both accurate and ordinary, as well as in lay terms appropriate to an introduction. What specifically do you find incorrect about it? (talk) 01:48, 18 November 2012 (UTC)Damian Phillips

Insulation is simply incorrect. The definition currently at the start of the article is incorrect too, but so deeply entrenched (even among people who should know better) that it's not worth the fight. Short Brigade Harvester Boris (talk) 02:52, 18 November 2012 (UTC)

@William and Boris, "insulation" can be achieved by multiple mechanisms. That is demonstrated by the Thermal Insulation page. But that is not of interest here, in the introduction. The effect is insulation, or a reduction of heat transfer from the surface back out into space. I think that is clearly correct. The proposed introduction doesn't use "reflected" or "conducted", etc.. I don't think either of you disagree with this, but if you do then demonstrate with actual examples of why this is not the effect. Just claiming this is incorrect doesn't really help.

The point of this edit is to simplify the introduction and move the detailed discussion of mechanism to the lower section which exists for talking about mechanism. E.g. the graphic to the right says "The ability of the atmosphere to capture and recycle energy emitted by the Earth surface is the defining characteristic of the greenhouse effect." I'd be fine with something like this too.

I'm now thinking to further simplify by not having the blackbody discussion in the intro either and will go ahead and move this to a different location.

Please don't; we've already indicated disagreement William M. Connolley (talk) 21:42, 18 November 2012 (UTC)

@William, I updated the page and didn't see your reiteration of objection before I posted it. I now see you've reverted it. I don't think you're being reasonable. The edit did not change the description of mechanism, which is all you had objected to, and I qualified "insulation" as well. I see you've been an editor here for a while and I want to respect your input, but you're not giving reasons sufficient to simply stonewall. I hope you reconsider. — Preceding unsigned comment added by Pablo Mayrgundter (talkcontribs) 22:20, 18 November 2012 (UTC)

@William and @Pablo:

I am relatively new to that topic in terms of Wikipedia. I just observed the "struggle" on the word "insulation" ... a nicer issue could be to just go to a very popular notion .. use "blanket": a woolen blanket insulates you when you are sleeping thus avoiding you getting cold just by keeping inside your warmth ... similar at Earth surface ... and you might like to use many blankets one over the other thus making a "slab atmosphere" ... :) moreover you can define the "blanket" as transparent to visible light and opaque to infrared etc.

excuse please my English - I am not a native English speaking individuum ...

Kampmannpeine (talk) 15:41, 21 February 2013 (UTC)

  1. ^ [5] "The net flow of radiant heat is still upwards from the surface to the atmosphere, because the upwards thermal emission is greater than the downwards atmospheric backradiation. This is a simple consequence of the second law of thermodynamics. The magnitude of the net flow of heat is the difference between the radiant energy flowing in each direction."
  2. ^ [6] "Skeptics sometimes claim that the explanation for global warming contradicts the second law of thermodynamics" "if you put something hot next to something cold, the hot thing won't get hotter" "So have climate scientists made an elementary mistake? Of course not! The skeptic is ignoring the fact that the Earth is being warmed by the sun, which makes all the difference" "To summarise: Heat from the sun warms the Earth, as heat from your body keeps you warm. The Earth loses heat to space, and your body loses heat to the environment. Greenhouse gases slow down the rate of heat-loss from the surface of the Earth, like a blanket that slows down the rate at which your body loses heat. The result is the same in both cases, the surface of the Earth, or of your body, gets warmer. So global warming does not violate the second law of thermodynamics"