Talk:Greenhouse gas

Natural and anthropogenic

As someone trying to understand a little about greenhouse gases - there is a table showing Natural and anthropogenic gas ppm in the atmosphere and rediative forcing. However, the table doesn't contain water vapour which seems to be the major component of greenhouse gas. It would be useful to include this so the relevance and importance of the other gases can be understood. —Preceding unsigned comment added by 210.193.162.198 (talk) 04:52, 29 June 2009 (UTC)

Shouldn't a section titled "natural and anthropogenic sources" has some tables comparing these two sources? See http://www.geocraft.com/WVFossils/greenhouse_data.html for examples, though there may be more recent or better tables elsewhere. JesseChisholm (talk) 00:04, 20 July 2010 (UTC)

• Solar emissions seems like a fundamental for "global warming" enhanced by greenhouse gasses. Where is the evidence to show the relationship? Even NASA has very little on the subject. ?--71.245.164.83 (talk) 02:43, 3 January 2011 (UTC)

Opening sentence too vague

I'm not sure about the opening sentence of the article, "Greenhouse gases are gases in an atmosphere that absorb and emit radiation within the thermal infrared range." There is more to distinguish a greenhouse gas than that it simply "absorb[s] and emit[s] radiation within the thermal infrared range". As the diagram in the lead makes clear (as do any number of textbooks), a greenhouse gas is one that is relatively transparent to high temperature (high frequency) IR, but relatively opaque to lower temperature (lower frequency) IR. Then it produces the differential effect of letting the high-temperature solar radiation in, but interfering with some of it's loss back into space at the lower temperatures of the planet and its atmosphere. How to summarise this into one clear opening sentence? It has to be longer, with more information in it than the current sentence. How about, "Greenhouse gases are gases in an atmosphere that selectively absorb and re-emit radiation more readily within the infrared region that is equivalent to the planet's surface temperature than they do for higher temperatures."? With suitable links to other articles about infrared and maybe black-body temperature, this would be clearer, IMHO. --Nigelj (talk) 12:05, 23 August 2010 (UTC)

The opening summary is fine. If you want more details, please place them in the appropriate section. Also, "re-emit" is a common error. Even if no energy is absorbed at a given frequency, a greenhouse gas will still emit energy because of its current temperature. If fact, both water vapor and CO2 tend to emit more energy than they absorb because they are also heated by direct contact with the surface. Q Science (talk) 18:49, 23 August 2010 (UTC)

Well, the current summary includes hypothetical gases that absorb radiation right across the thermal infrared range, and those that might be opaque at high frequency IR and transparent at lower ones. Neither of these would be greenhouse gases. --Nigelj (talk) 21:31, 23 August 2010 (UTC)

Actually, it mentions 5 real gases by name. (The main article mentions several more.) It also says "thermal infrared range" which I interpret to mean "not" the high frequency range. However, that is not clarified in the body of the article, and I agree with you that it should be. Q Science (talk) 23:06, 23 August 2010 (UTC)

First Diagram

The first diagram shows solar radiation at 343 watts per sqm. Should not this be 1366 (or something similar)? See Wikip Solar Radiation Page - http://en.wikipedia.org/wiki/Solar_radiation#Solar_constant.

• Solar radiation should be a variable. Show the history that correlates. --71.245.164.83 (talk) 02:53, 3 January 2011 (UTC)

Why the discrepancy? If there is an explanation this should be stated. Oversite22 (talk) 01:38, 16 September 2010 (UTC)

The continuous TOA (Top of Atmosphere) value is 4 times larger than the average seen at the surface because the planet rotates. Q Science (talk) 02:22, 16 September 2010 (UTC)

The area of intercepted solar radiation is pi*r², the area of the planet's surface is 4pi*r², so the ratio is 1/4.

• ??? Yet the sun only shines on half of the earth, and the earth is round, not flat. So it is only the area exposed to earth that gets sunlight, or pi*r_squared. Its not the surface area (4"pi*r2) but the area exposed that matters. Edges of the earth receive less sunlight intensitty/area than those directly explosed. E.g. its less bright at sunrise and sunset. Where you got 4x factor is perplexing. Perhaps global cooling is a concern after all?... --71.245.164.83 (talk) 02:53, 3 January 2011 (UTC)

On the subject of diagrams, can we not find a better diagram than http://en.wikipedia.org/wiki/File:Atmospheric_Transmission.png? See the comments: http://en.wikipedia.org/wiki/File_talk:Atmospheric_Transmission.png Something like http://acd.ucar.edu/textbook/ch15/fig3.jpg would be much more relevant for explaining how GHGs work. 88.152.128.36 (talk) 09:20, 28 September 2010 (UTC)

Sorry, can't do that because http://acd.ucar.edu/textbook/ch15/fig3.jpg is copyrighted. In addition, it only covers infrared energy leaving the planet, as seen from above the atmosphere. That said, I agree that File:Atmospheric Transmission is completely misleading and should not be used in any article. Perhaps you can create a better, more accurate, image that we can use. Q Science (talk) 19:43, 28 September 2010 (UTC)

"A .01% increase in the total volume of CO₂ in the atmosphere"

I don't see a need for this statement considering that it repeats a point just made in ppm ("the concentration of carbon dioxide has increased by about 36% to 380 ppmv, or 100 ppmv over modern pre-industrial levels") but in a more confusing way, so I removed it from the article. I see that 68.109.66.87 (talk · contribs) has just reverted me, saying, "provides figure of comparison, e.g. water vapor is cited as 2% of the atmosphere, as opposed to 20,000 ppmv." Well I can see that as an argument for putting "(0.038%)" after the mention of 380 ppmv, but this does seem a strange full sentence to add after the mention of the 100 ppmv change. The reason we sometimes use % and sometimes ppm is because of the size of the fraction. ppm values in the tens of thousands and percentages in the thousandths of a percent are unnecessary and wrong, as would be geographic distances in inches or insect dimensions in nautical miles. I am not prepared to edit war; perhaps people would like to discuss it. --Nigelj (talk) 16:52, 25 October 2010 (UTC)

You were correct to delete it.

This amounts to a .01% increase in the total volume of CO₂ in the atmosphere since 1750.

is very confusing. A 36% increase produces a 36% increase in volume, not a 0.01% increase, which is how I read the statement. I can see what the person is trying to say, but that sentence is very confusing. I suggest removing the sentence and, if the person adding this wants to, adding a note that explains the idea in a way that is easier to understand. Q Science (talk) 18:10, 25 October 2010 (UTC)

I agree and have removed it again. As worded, it seems to be a flat contradiction of the previous sentence. Squiddy | (squirt ink?) 19:53, 25 October 2010 (UTC)

I agree, saying CO2 increased by 0.01% by volume is simply incorrect. If the total volume of the atmosphere were one million parts, then there are 280 parts preindustrial and 380 parts currently (true if "parts" are atoms, moles, exomoles, or atoms in the atmosphere). This is a 35.7% increase in the total volume of CO2 in the atmosphere. Again removing. --TeaDrinker (talk) 00:31, 26 October 2010 (UTC)

There is obvious need for the statement, otherwise I would not have added it. Although the relative change in carbon dioxide 'concentration' in the atmosphere is significant, the absolute change in volume is very small and noting this fact in the article provides needed perspective. There is nothing incorrect about the statement. Adding ppmv to the discussion of Water vapor, or adding it after 338 ppmv would also provide this type of unit comparison, however it isn't clear that one method is significantly better than the other, but any would be an improvement. The article is not improved by the deletion of this pertinent fact. The 'argument' is for providing comparable units among the various major greenhouse gasses, rather than single digit percentages in one case, and triple digit ppm's in another. Pick one and stick with it. Your choice. 128.200.157.22 (talk) 01:55, 26 October 2010 (UTC)

Thanks for the discussion here. I'm still not sure you're right. If I tell you old coke has 35mL caffeine per can, and the new coke has 45mL caffeine per can, that's an increase of 10mL or 10/35 = 28.6%. So I would say, to liken it to your sentence, A 28% increase in the total volume of caffeine in a can of Coke. --TeaDrinker (talk) 02:04, 26 October 2010 (UTC)

I would liken it more to saying that Coke is in a 1000 mL bottle, and Pepsi is in a 1 liter bottle. Parts per million is simply a way of expressing very small percentages with fewer decimal places in the figure. It's not unlike the purpose of scientific notation. To convert from parts per million to percent, one simply divides the ppm number by a million to get the fractional value, and then multiplies by 100 to convert to percent. Percent and ppmv are both ways to express a fraction of the total. ppm is in relation to a million, and percent is in relation to 100. 128.200.157.22 (talk) 02:46, 26 October 2010 (UTC)

Thanks for the illustration. I follow what you are saying and your conversion, however ppm and percent are not measures of volume, they are measures of concentration. However the increase in concentration is already mentioned in the article, which is what I think is at issue. Perhaps I am not making sense... Does this clarify it? --TeaDrinker (talk) 02:55, 26 October 2010 (UTC)

One can either express these ratios in terms of volume, or in terms of weight. The convention in this article is to use volume, hence the unit ppmv. The use of volume is precisely correct. 128.200.157.22 (talk) 03:04, 26 October 2010 (UTC)

Yes, I agree, however both are concentrations, not total volume. For example, it is not possible to convert ppm or percent into mL (a measure of total volume) or mg (a measure of total weight) without further information. Thus I don't think calling ppm or percent a measure of total volume is correct. --TeaDrinker (talk) 03:07, 26 October 2010 (UTC)

The 'v' in ppmv indicates parts per million 'volume'. However the units could just as easily be those of mass, moles, weight, or even arbitrary. But when expressed as a ratio, the units drop out of the expression. In the case of this article, the data are expressed as partial concentrations in terms of their volume - with respect either to unit volume, or to total volume. An increase in concentration of carbon dioxide per milliona parts of atmospheric volume equates to an increase in the volume of carbon dioxide in the atmosphere. It's an obvious, non-controversial point. Increasing the volume of sugar in a 100 ml can of coke from 35 ml to 45 is an increase in the volume of sugar of 10 parts per 100 because it's an increase from 35 parts per 100 to 45 parts per 100. The change in units of concentration of sugar is 10/35, but the change in volume of sugar is 10/100. I hope you can see the point. 128.200.157.22 (talk) 04:03, 26 October 2010 (UTC)

Thanks for the explanation. I'm afraid I have to disagree. 10mL/100mL is not an expression of volume, nor change in volume. It is an expression of concentration (or actually, change in concentration). I don't see how the two could be considered interchangeable terms, since they are mathematically quite distinct. I think such a use seems to be well outside common English terminology. --TeaDrinker (talk) 04:19, 26 October 2010 (UTC)

Clearly ml is a unit of volume, and a ratio is a ratio. Though this is not a point of contention in the discussion, it is a concept with which the "editor" evidently has little facility, and difficulty grasping - a difficulty which he also fails to recognize. It is an unfortunately situation for the Wikipedia article that such people establish themselves in positions of autonomous control over technical subject matter.

First, the use of ppmv is not correct. The correct expression is

A concentration of x ppm

While it is true that the numerical values of the two expressions are equal when dealing with an ideal gas, one method is correct and the other isn't. The article currently uses both expressions.

Second, nobody is saying that 0.01% is wrong. It is just that the way those two percentages are used in a single paragraph is confusing. I think that a note is the best way to include that information. Also, values less than one should always be entered with a leading zero. .01 bad, 0.01 good. Q Science (talk) 05:13, 26 October 2010 (UTC)

These observations are more typographical than conceptual in nature, and do not subvert the relevance of the deleted sentence. The reasons given for the deletion remain unfounded, and their use suggests ignorance of the fundamentals (as demonstrated in the conversation above) as well as a shameful lack of impartiality to the subject matter. 68.109.66.87 (talk) 06:05, 26 October 2010 (UTC)

I can understand your frustration, but please be assured I don't see myself as "in [a] position of autonomous control." I think everyone here has a common goal of a clear and accurate (as reflected in reliable sources) article. My concern is the use of the term "total volume." It simply does not appear to be a change in total volume. It appears to be a change in concentration, which is already included in the article. Now whether that is expressed as a change in concentration ppm, percent, or even permil, I don't think a ratio of volumes can be called a "total volume." I certainly agree the concentration went up 100ppm (which can be expressed as 0.01%, and I am happy to discuss the merits of describing it in one or the other forms), but saying the "total volume" goes up by 100ppm (or 0.01%) does not make sense to me. Expressions equivalent to ppm are simply not volume. --TeaDrinker (talk) 06:20, 26 October 2010 (UTC)

People should definitely drop the slurs on other editors' facility, impartiality, etc, particularly when defending a sentence that (at very best) is highly misleading. Saying "This amounts to a .01% increase in the total volume of CO2 in the atmosphere since 1750" reads as an assertion that the total volume of CO2 has gone up from X to X * 1.0001, whereas the figure given in the previous sentence is an increase of around 36% (ie X * 1.36). I think what you're trying to say is that the fraction of the atmosphere which is (composed of) CO2 has gone up 0.01% (not gone up by 0.01%). Wording this so that it is clear and unambiguous is tricky (I don't like the formulation I just came up with, but can't think of a better.) I also think it's superfluous, following "the concentration of carbon dioxide has increased by about 36% to 380 ppmv, or 100 ppmv over modern pre-industrial levels." Squiddy | (squirt ink?) 09:43, 26 October 2010 (UTC)

A miscalculation?

In the first paragraph (line 9)of this article (Greenhouse Gas) the temperature 33 degrees C does not correspond to 59 degrees F. It should be corrected. The two are related by the equation: F-32/180 = C/100. A temperature value of 33 C corresponds to 91.4 F. Neishapour (talk) 19:54, 30 October 2010 (UTC)

The numbers refer to a difference in temperature and are therefore correct. Mikenorton (talk) 20:02, 30 October 2010 (UTC)

In other words, the increase of 33 degrees C corresponds to 91.4-32=59.4 degrees F. Because 0 degrees C equals 32 degrees F. I understand it now. Thank you. —Preceding unsigned comment added by Neishapour (talk • contribs) 20:32, 30 October 2010 (UTC)

No cause-and-effect relationship in ice-core data.

(Updated to reflect what I've been able to discover on this..)

The AGW and 'greenhouse gas' arguments hinge on ice-core data relationships between CO₂ levels and temperature, yet as far as I can determine no cause-and-effect relationship between these has been established. Some published versions of the Vostok ice-core data would seem to show a small 'lead' in CO₂ over temperature, suggesting a cause-and-effect relationship. However, this 'lead' seems to have crept-in in the process of conversion to svg format, the original data showing the graphs to be pretty-much synchronous.

In trying to discover whether any precise relative timing can be inferred from the original graph, the answer would seem to be... No. For example, "However, because of the difficulty in precisely dating the air and water (ice) samples, it is still unknown whether GTG concentration increases precede and cause temperature increases, or vice versa--or whether they increase synchronously." from http://www.daviesand.com/Choices/Precautionary_Planning/New_Data/

This would seem to be a key question, as without relative timing information there is no way to determine whether temperature rises are an effect, or the cause of the CO₂ increase. --Anteaus (talk) 16:22, 2 December 2010 (UTC)

Simple Greenhouse Diagram

The first diagram in this article shows 343 watts per square meter from source and 343 watts per square meter reflected back into space. —Preceding unsigned comment added by Multiperspective (talk • contribs) 17:27, 2 December 2010 (UTC)

Not sure what your point is here, but for a system in thermal equilibrium, that would always be the case. Though if temperatures are slowly rising then it must be the case that radiation is less than absorbtion, but by how much I wouldn't like to say. I think it might also be added that no-one disputes the existence of the greenhouse effect, the question is whether or not small changes in CO₂ concentration drive temperature changes... or whether temperature changes drive changes in CO₂ levels. We simply don't know. And, since we don't know, it is bad science to claim that we do. --Anteaus (talk) 19:11, 3 December 2010 (UTC)

I think you'll find that in the peer-reviewed literature, and in school and university level science text books, there is a complete consensus on these basic points. Fox News and a few US politicians may not have a solid grasp of the science, but that's not the science's fault, and doesn't really warrant coverage in an encyclopedia article such as this, I don't think. --Nigelj (talk) 19:28, 3 December 2010 (UTC)

Thank you for your responses. To the first, it takes a known amount of energy to increase the temperature of the average mass of the atmosphere of about 5 quadrillion tonnes (Wikipedia). This energy must be represented in any diagram depicting the mechanisms at play, either as a change in source or a decrease of albedo and/or infrared radiation measured beyond the atmosphere. There is no geologic record of this planet ever being in thermal equilibrium. To the second response. This is highly defensive and does not speak in any way to scientific discourse. In fact, repeating the mantra of "Concensus" is the antithesis of the meaning of science which at all times must include open availability of methods and raw data. —Preceding unsigned comment added by Multiperspective (talk • contribs) 00:13, 4 December 2010 (UTC)

It does require a known amount of heat to raise the temperature a certain amount, but that is not in the drawing. The drawing shows the average values emitted by blackbodies at certain temperatures and is partly calibrated by various measurements. "The amount of heat to change the temperature" is the integral of the difference of input and output and not directly related to the values or their difference. And yes, there is consensus on that. As for "equilibrium", radiative equilibrium is obtained as soon as the temperature stops changing, typically in a few minutes, until the Sun moves to a new location or a cloud passes over. As far as the diagram is concerned, it must represent some concept of equilibrium or each day would be hotter (or colder) than the previous. There is also consensus on that. Q Science (talk) 06:58, 4 December 2010 (UTC)

"As far as the diagram is concerned, it must represent some concept of equilibrium or each day would be hotter (or colder) than the previous." This is what I am referring to. For there to be climate warming or cooling, a trend of days, years, decades, centuries,,, must be must be warmer or cooler than what preceded them. I know that sounds too simplistic but after all the modeling and calculations that is what we are talking about in greenhouse global warming or any other kind of warming or cooling, a system that is not in equilibrium. How can we have Ice Ages with sheets down to the sub-tropics and the climactic opposites in a system in equilibrium? All I am saying is that if the diagram in question is snapshot of an ideal moment of balance then that should be indicated. Being at the top of an article titled Greenhouse Gas seems inappropriate, at least without showing another depicting the net loss to space due to raising the temperature of the atmosphere. —Preceding unsigned comment added by Multiperspective (talk • contribs) 03:13, 5 December 2010 (UTC)

I see what you're saying. If you're interested in this, I think you should research how much heat energy (in joules or watts, per square meter or for the whole planet) it has taken for "global surface temperature [to have] increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 20th century." (from the Global warming article) and compare that with how much heat (in joules or watts, per square meter or for the whole planet) has arrived on the Earth from the Sun during the same period. You'll be dealing with some very big numbers, but someone must have calculated it somewhere. My guess is that the first will be a very small proportion indeed of the second figure - way too small to show up when we say "343 watts per square meter" to three significant figures. If we could find a good reference for this (without WP:OR), it would be a valuable addition to this, and maybe other articles. --Nigelj (talk) 11:27, 5 December 2010 (UTC)

I remember it as 342 w/m^2, but last digit's uncertain. I think Kiehl & Trenberth was the one who published this figure, see page 3 of pdf.[1] About a "Simple[r]" or clearer greenhouse diagram, I think there's a better diagram that's both well referenced and clearer than the one currently on this page. --CaC 174.52.224.148 (talk) 18:58, 5 December 2010 (UTC)

Water vapor as greenhouse gas

It seems relevant to include water vapor in the table discussing residence time and GWP. Thanks for listening. Lfstevens (talk) 23:57, 31 December 2010 (UTC)

Sounds like a good idea, but it may be water vapor isn't included because it is so sort lived. As stated in the Atmospheric lifetime section, water vapor "has a residence time of about nine days."--CurtisSwain (talk) 00:53, 1 January

Show reference that water vapor has a "residence time" (citation needed) of "nine days" (show some more!) --71.245.164.83 (talk) 02:45, 3 January 2011 (UTC) (UTC)

Placed ref in article.--CurtisSwain (talk) 06:37, 18 January 2011 (UTC)

The IPCC doesn't include WV in its list of GHGs (see any AR) because it is 'not influenced by human activity'(!). However IPCC considers WV to be a 'feedbacsk' mechanism.--Damorbel (talk) 13:01, 18 January 2011 (UTC)

Radiative forcing (W/m2)of water was added on Jan 17, 2011 and deleted soon after. Senior authors, if offended may interceed. —Preceding unsigned comment added by 118.172.36.9 (talk) 14:18, 19 January 2011 (UTC)

Lets not beat around the bush here. It has to have been a co-ordinated lie to be putting water vapor as only 36-72% of the greenhouse effect. How long has this lie been there and which group of people put this most transparent of lies into effect. No way its only one person putting this over on the public. An investigation is in order.

"Senior authors, if offended may interceed" This is of no importance, surely the inclusion or exclusion affects the science? Does anybody know how the IPCC does it calculations? --Damorbel (talk) 18:30, 19 January 2011 (UTC)

It might be short-lived, but there's always an awful lot of it in the atmosphere compared to CO₂. How do we know it isn't the main cause of 'global warming'? Grassynoel (talk) 08:28, 24 February 2011 (UTC)

Grassynoel-- because the systems dictating partial pressure for water vapor in the atmosphere, due to the extremely large prevalence of liquid water on the planet, are determined in an equilibrium that changes cyclically with weather patterns but is very unlikely to change significantly overall over the timetables on which global warming has been observed. If you can find a peer-reviewed study that show that natural variations in water vapor concentration (preferably explaining through Penman equations the relationship with other climatological phenomena) explain the warming trend better than a 36% increase in CO2 concentration, this might be worth adding as a factor.66.134.4.226 (talk) 20:22, 11 April 2011 (UTC)

Phases of Water

Water is somewhat of a unique substance that it can exist in our atmosphere in all 3 phases, solid, liquid, and gas.

I.E. Clouds & Fog are different than air in which the vapor has not condensed. Due to the droplet nature of the solid/liquid nature, refraction may also be an important aspect. Thus, water is an important aspect, both in cloudy sky and dry sky. I believe the IR spectrum is shifted with the different phases.

Should a chart be made to reflect the contribution of water on a cloudy day vs sunny day? Clouds with crystalline water, or a mix? Keelec (talk) 01:17, 18 January 2011 (UTC)

The IR spectra of clouds approximates a black body, water vapor does not. As a result, the effect of greenhouse gases is negligible when clouds are present. However, since only about half the planet is covered with clouds, their effect is normally ignored in the radiation balance diagrams. If you can find a chart that shows the radiation balance when clouds are present, and if that chart is not copyrighted, then we should definitely include it. Q Science (talk) 20:29, 19 January 2011 (UTC)

"The IR spectra of clouds approximates a black body". I can never understand why this is regarded as important, clouds scatter all sorts of EM radiation whether they absorb it or not. Clouds are not remotely 'a black body' since the droplets are made of water which has a refractive index >1 so any calculation based on a 'black body' assumption has got to be seriously wrong.--Damorbel (talk) 21:56, 19 January 2011 (UTC)

It is important because there are no spectral holes and, therefore, the concentration of greenhouse gases does not matter. To be clear, clouds make the atmosphere IR opaque at all IR frequencies. Q Science (talk) 23:07, 19 January 2011 (UTC)

The Lie Of Water Vapor Being About Half Of The Greenhouse Effect.

I was surprised by some propaganda outfit calling itself "The Australian Academy Of Science" making the above claim. So naturally I wondered what gave them the "plausible deniability" to put over such an outrage on the Australian public. This is the worst lie since the USGS volcanic emissions claim.

Now I traced it back to here so far. So whats going on. If something isn't done about this I will try and get hold of Mr Wales personally. Its very clear that this is not the work of one person as when the idiot known as STOAT rigged all the usual pages. This claim is so outrageous we are going to have to trace it to a co-ordinated and probably a well-funded campaign. —Preceding unsigned comment added by 110.33.41.206 (talk) 21:36, 5 March 2011 (UTC)

You are absolutely correct, water vapor is no where near half of the greenhouse effect. A 15C surface emits about 390 W/m2. Of that, the atmosphere absorbs about 303 W/m2, 282 W/m2 for water vapor and 21 W/m2 of CO2 (ignoring clouds and other greenhouse gases). From these numbers, it is obvious that water vapor is responsible for about 93% of the greenhouse effect. Q Science (talk) 07:46, 10 March 2011 (UTC)

Water vapour, the manipulated and the controlled variables (MV and CV)

There seem to be three concurrent discussions here on aspects of water vapour, so rather than pick one, I thought I'd start another :-) When you deal with a complex feedback system, it is important to sort out the inputs from the outputs. In this case, gas concentrations that humans can do something about are the inputs. The extent of the greenhouse effect, measured as a temperature anomaly, a change in energy-transfer rate, or whatever, is the output of the system. The concentration of water vapour is part of one of the feedback mechanisms (the warmer the atmosphere, the more water vapour it can (and will) hold, etc). Therefore, we must not confuse it with the inputs or the whole model becomes impossible to understand. If there were millions of people spraying water mist into the air somewhere, we might consider it as an input, but they are not and so that is not helpful.

It would not matter if it were a proven fact that 90% of the greenhouse effect were caused by water vapour, what follows would still be true. The process is that people alter the concentration of a greenhouse gas like CO₂; this causes the earth and the atmosphere to begin to warm; the warmer air causes more water from the oceans to evaporate; the extra water vapour in the air accelerates the initial warming started by the input gas; eventually a new equilibrium would be reached where the total effect of that perturbation in CO₂ concentration could be measured as an output. In practice, we never could get to the bottom of it that way as there are other feedbacks going on, such as changes in ice albedo, as well as not one but continual emissions of not just CO₂ but a whole slew of greenhouse gasses.

That, I understand, is why the IPCC and others do not either count H₂O as a greenhouse gas, nor do they run around in a panic when the popular press point out that they seem to have forgotten it. We're here to help people understand the very hard stuff that scientists are working on, not to act as an echo chamber for those who do not. --Nigelj (talk) 20:32, 6 March 2011 (UTC)

Those of us that are capable of intelligent, independent thought and critical thinking can plainly see the real reason why the IPCC and others do not count the most prevalent greenhouse gas in their calculations. The corruption on this issue is clear-cut, obvious, and disgusting. The scientific community should be ashamed of themselves for misleading the public on this issue, and you WILL be exposed. Those arguing on the side of the IPCC are either part of the corruption or easily influenced and incapable of critical thinking. I have read every IPCC report and the assumptions that models are based on are absurd. Correct scientific method suggests that to claim a "consensus" on a subject, by those in the scientific community, is in itself, proof of corruption. You people need to take a good, hard look at yourselves, and ask - "Am I a scientist, or a politician?” Charles Darwin would be rolling in his grave. Pahgcdt (talk) 00:46, 5 April 2011 (UTC)

Terminology

There is a current disagreement on terminology.

• ppm vs ppmv vs μmol/mol
• concentration vs mixing ratio vs mole fraction

In SI units, μmol/mol and mole fraction are the "correct" terminology. However, ppm is used in the IPCC documents and almost all the references.

The IPCC uses many phrases like

models project atmospheric CO2 concentrations of 540 to 970 ppm - (From WG1, page 22)

At first glance, the phrase "concentration of xx ppm" is technically wrong since "concentration" represents moles per liter. However, since the number of moles in a volume is known, "concentration" can also be interpreted as "fractions of a mole per mole" (depending on the units) which is what 540 ppm means. The titles of many of the references also use the term "concentration" with this meaning. In some references, the proper phrase is "a mixing ratio of xx ppm", though "mole fraction" is also correct. Many times, AR3 uses the term "abundance", as in phrases like "with abundances reaching 2,970 to 3,730 ppb".

From the IPCC TAR Glossary

Mixing ratio

See: Mole fraction.

Mole fraction

Mole fraction, or mixing ratio, is the ratio of the number of moles of a constituent in a given volume to the total number of moles of all constituents in that volume. It is usually reported for dry air. Typical values for long-lived greenhouse gases are in the order of mmol/mol (parts per million: ppm), nmol/mol (parts per billion: ppb), and fmol/mol (parts per trillion: ppt). Mole fraction differs from volume mixing ratio, often expressed in ppmv etc., by the corrections for non-ideality of gases. This correction is significant relative to measurement precision for many greenhouse gases. (Source: Schwartz and Warneck, 1995).

In AR3, the phrase "mole fraction" is not used very often. The following is from the caption of figure 11, page 44.

Change in CH4 abundance (mole fraction, in ppb = 10−9)

The uses of multiple phrases for the same concept indicates to me that the information is pulled from many sources and/or written by different people who use different nomenclature. At any rate, it is my opinion that changing this document to use non-standard nomenclature, even if it is "more correct", is a disservice to the readers. Q Science (talk) 20:36, 9 March 2011 (UTC)

Thanks for providing the background here. However, since this discussion has already started in the section "Ambiguous units ppm, ppb, and ppt" at Wikipedia talk:WikiProject Chemicals, it may be better to move your text onto that page? RolfSander (talk) 20:57, 9 March 2011 (UTC)

Radiation Transmitted by the atmosphere

The third chart here is very interesting. Does anybody know its source? It raises a question. It appears that the effect of CO2 has reached sort of a spectral saturation in the infrared band. That is, another 10% increase in CO2 will not increase the absorbtion of infrared, because radiation in the CO2 band is already 100% absorbed. Can somebody tell me what I'm missing here? Stevevogelnu (talk) 01:00, 13 March 2011 (UTC)

That is one of the skeptic arguments. One counter argument is that the edges of the absorption bands have a slight slope. As a result, increasing CO2 will make the bands slightly wider. There are additional arguments to counter that, and so forth. Q Science (talk) 17:19, 13 March 2011 (UTC)

The impression that I draw from your answer is that global warming is an extremely subtle affect that is not well understood. Stevevogelnu (talk) 13:51, 14 March 2011 (UTC)

Actually, this effect is quite well understood, and saturation of the CO2 absorption bands is not occurring in the thin, upper atmosphere, which is where the absorption is most important. See the following descriptions at RealClimate and Skeptical Science. Parejkoj (talk) 14:37, 14 March 2011 (UTC)

The realclimate article (which you linked to twice) claims that "higher layers ... are colder layers, so they do not radiate heat as well." Apparently, these scientists have never heard of the stratosphere. As a result, they have missed a major negative feedback. The realclimate article also ignores the fact that most of the energy absorbed by CO2 is absorbed within 20 meters of the surface. Sorry, but that is not the cold upper atmosphere. Q Science (talk) 21:19, 14 March 2011 (UTC)

I fixed the Skeptical Science link. I should have also linked their more advanced version. Please read some more on how the greenhouse effect works. What's important is not the absorption near the surface, but rather absorption in the mid-to-upper troposphere that affects the radiation balance at the top of the atmosphere. Some other references for this are Wikipedia's own page, and the included references and this page, and included references. Parejkoj (talk) 15:21, 15 March 2011 (UTC)

The skepticalscience articles are based almost entirely on a mis-interpretation of the upwelling spectra. The realclimate explanation relies heavily on Annan and Hargreaves. These researchers explain the entire temperature rise since the last glacial maximum as being caused by CO2 and ice feedback. Apparently, they have never heard of the Milankovitch cycles. I am beginning to think that the skeptics might have a point. Q Science (talk) 05:30, 16 March 2011 (UTC)

GHG intensities and other changes

I've revised the section on regional and national attribution of emissions. My main concern was the WRI GHG intensity figure which was previously included without explanation. I've added an explanation of some of the issues involved in calculating net emissions and GHG intensities.

I've rewritten the bit on cumulative emissions. In the previous revision, I made the mistake of assuming the IEA's assessment was a ranking of all countries'/regions' emissions. The IEA report does not actually state this, therefore, to present the data as a ranking is possibly misleading, i.e., some countries/regions not included by IEA may rank higher than the countries they did include. Enescot (talk) 14:50, 11 April 2011 (UTC)