Talk:Global warming potential

Carbon dioxide
Vicki, the global warming potential of carbon dioxide is disputed. It depends on the hypothetical positive-feedback advocated by the IPCC. --Ed


 * Disputed by whom? This is pretty standard science--it's why Venus is so hot, for example.
 * Also, it's difficult to fix real, undisputed errors--like the fact that whoever created the page can't spell "hydrofluorocarbon"--in the midst of this argument. Could you maybe take a moment to look at spelling and grammar, if you're going to dive in and revert my edits? Vicki Rosenzweig

Don't people exhale carbon dioxide? Don't plants breath carbon dioxide? This entire article should be deleted. -fr8train —Preceding unsigned comment added by 67.142.130.28 (talk) 18:14, 24 April 2008 (UTC)
 * The recommendation for deletion is not justified by the questions you pose, as you probably know by now. ( Martin | talk • contribs 18:50, 18 August 2012 (UTC))

Greenhouse effect
Vicki, I'm trying to distinguish between the "greenhouse effect", the substantial and undisputed phenomena that keeps the earth warm enough to sustain human life -- and the "greenhouse theory" (for lack of a better term) (global warming or anthropogenic global warming -- SEWilco), the hypothesis that excessive emissions will cause a runaway greenhouse effect leading to a harmful warming.

I think the term "global warming potential" describes not (a) how much a gas contributes to the greenhouse effect but (b) how much it is estimated to contribute to the hypothesized scenario of a runaway greenhouse effect. The problem is that the terms are often not clearly defined.

Please continue to help out, and I'm sorry if I reverted your edit unjustifiably. Feel free to re-revert. And thanks for adding the immigration thing to Unification Church. Ed Poor

Indeed, the OP has a very valid point. GWP, as I understand, is calculated with the integral of the applicable band of a compound's IR absorption spectrum ("greenhouse effect") coupled with some estimate for that compound's atmospheric half-life ("lifetime" is a false concept in chemistry). This data, combined with local information about concentrations of relevant gases, leads to some useful guesses about AGW - on a local scale - but is only one fragment of the complex puzzle that is climate dynamics. -ZI — Preceding unsigned comment added by 24.18.72.255 (talk) 01:21, 12 July 2014 (UTC)

Definition
Can you find the IPCC definition of GWP which seems to be unclear? ipcc.ch/Publications -- SEWilco


 * You want the radiative forcing chapter of course: http://www.grida.no/climate/ipcc_tar/wg1/247.htm

Water
What is the GWP of water vapor? About 26.26? SEWilco


 * Probably very very small, because GWP is not the total effect of the gas but some function, per molecule, of effect times lifetime, and H2O lifetime is short and the effect probably small (because of saturation). But I've never seen it explicitly calculated - perhaps because its not of much interest. (William M. Connolley 19:12, 14 Aug 2003 (UTC))


 * I've heard it is about 0.1, which indeed is quite small. However the vast amount in our skies means that it emposes a huge increase in global temperatures, (about 20°C I think), so surely it would be in our interests to calculate an exact figure? not that it is in our powers to affect its global influence. mastodon 20:05, 30 December 2005 (UTC)

I'm sorry but to state that the effect of water vapour on global warming as being irrelevent is both alarming and factually misleading for the people who will read this article. In fact water vapour is excellent at asorbing IR radiation and in a wider band than CO2, although admittedly it has a shorter lifetime as mentioned.

I agree, it would be very useful to find a GWP for water. Not sure, but it seems as if the statement that we could not directly influence water vapour levels is not true. —Preceding unsigned comment added by Energydoc (talk • contribs) 20:46, 4 February 2008 (UTC)


 * This article covers the GWP of water vapor quite well. It contributes 95% of the greenhouse effect, making CO2 and other gases insignificant. The wiki article should be edited to include water vapor's true contribution, since it's the dominate greenhouse gas. Otherwise it is not NPOV, and seriously biased in favor of the political agenda of the global warming alarmists. oward (talk) 02:28, 6 June 2008 (UTC)
 * There is just a couple of problems with that article... the first is that it isn't a reliable source, and the second is that the figures it quotes are wrong. WV is not 95% of the greenhouse effect, sorry. --Kim D. Petersen (talk) 03:20, 6 June 2008 (UTC)


 * Here's a reference from the DOE that gives the 95% number for water vapor in the troposphere vs. just 5% for CO2. oward (talk) 21:08, 6 June 2008 (UTC)
 * Jolly good, now read the surrounding text and following table D2 William M. Connolley (talk) 21:27, 6 June 2008 (UTC)
 * Can you be more specific what you mean. Text before table D2 says as referenced: "Given the present composition of the atmosphere, the contribution to the total heating rate in the troposphere is around 5 percent from carbon dioxide and around 95 percent from water vapor. In the stratosphere, the contribution is about 80 percent from carbon dioxide and about 20 percent from water vapor." I do not know what troposphere/stratosphere difference plays a significance here, but clearly as stated there, watter vapor is responible for 95% of warming effect. — Preceding unsigned comment added by 91.213.255.7 (talk) 21:51, 26 March 2012 (UTC)

This statement, as mentioned above, is clearly identified as false: "There is no possibility to directly influence atmospheric water vapour concentration." Water vapor is a product of nearly every combustion process. Twice as many water molecules as CO2 molecules are produced in the stoichiometric combustion of methane. For liquid fossil fuels, it's about 1:1, with a slight lean toward water. Coal burning is principally carbon, very little hydrogen, and as such little water is a product. Airplane contrails are a direct visual indicator that human activity can affect atmospheric water concentrations. This doesn't even consider the waste heat released by combustion engines, and the higher solubility of water vapor in air at increasing temperature. -ZI — Preceding unsigned comment added by 24.18.72.255 (talk) 01:04, 12 July 2014 (UTC)


 * See IPCC 2014 WG1 Chap 8 page 666; water vapor is variable depending on temperature, and GWP is not calculated over a molecule's lifetime, but over any given period relative to a molecule of CO2 during the same period.   There's no fixed number, since accounting methods differ, but the GWP of a molecule of water vapor "can be considered to be approximately two to three times greater" than one of CO2, over a given period of time.  The real question for climate change is how will atmospheric water vapor change.   IPCC AR5 WG1 says what we add (via irrigation, power plant cooling stacks, etc) is negligble; the real factor is that warmer air holds more water vapor (i.e., more evaporation).   Scientists therefore consider changes in water vapor as a feedback, rather than an issue of emissions.  Or so says the RS.  If you wish to pontificate.... please don't.  Instead summarize an RS.  NewsAndEventsGuy (talk) 21:52, 28 December 2014 (UTC)


 * This is accurate in the troposphere, where water vapor has a short lifetime and is dependent on temperature, HOWEVER for aircraft, water vapor is an important greenhouse gas emission (even more important than CO2) because it's emitted into the stratosphere, where water vapor residence times are orders of magnitude longer. Therefore, water vapor has very high GWP in the stratosphere. I think it'd help this article to mention GWP of water vapor as a function of altitude and/or lifetime as that would make it much easier to compare with CO2. This is, admittedly, a special case for aviation, but it'd be very helpful. Many scientific sources (including the IPCC) mention this important effect, but it's hard for the lay person to understand since it's often not portrayed in something simple and easy to understand like a multiplication factor. If anyone can find a good GWP equivalent for anthropogenic water vapor as a function of lifetime (and/or altitude) with good citations, that'd be really nice. Robotbeat (talk) 18:39, 31 July 2020 (UTC)

Who defines GWP?
The article currently says that the IPCC are the authors of the definition of GWP. I'm not sure that is true, though it might be. Previously the article said that the defintion of GWP could be found in the IPCC report. (William M. Connolley 09:16, 25 Aug 2004 (UTC))
 * TAR gives a reference to the First Assesment report which is not online. I'll try and dig it out of the UL sometime but it will have to wait...--NHSavage 20:25, 19 January 2006 (UTC)

Global warming potential looks like a possible subsection of greenhouse gas?
Rd232 suggested that Global warming potential looks like a possible subsection of greenhouse gas. I'm not so sure. GWP is a thing in itself. There is scope for more in the article - like how it gets calc and stuff. OTOH it could be a redirect into the GWP discussion of GHG... I'm not sure. William M. Connolley 23:04:33, 2005-07-17 (UTC).
 * Thanks for putting this note. I see Greenhouse effect, greenhouse gas and global warming potential as overlapping somewhat, in a way that I'm not sure is helpful for the average reader. I'm not disputing that GWP is a thing in itself, but why not merge GWP into one of the other two articles for now - it can always be recreated if/when the material justifies it. (I think in general it's better to keep related material together, to avoid duplication, encourage clear structure, maintain context, and ultimately encourage better quality editing.) Rd232 21:38, 20 July 2005 (UTC)

Super greenhouse gas

 * trifluoromethyl sulfur pentafluoride has a GWP of 18,000 recently dubbed a super greenhouse gas[1]. The source is anthropogenic but the research shows the source is not sulfur hexafluoride

This looks like rubbish to me, I don't want to remove it until I'm sure. --Demiurge


 * I wasn't sure, but its link is broken, so I removed it. The page isn't supposed to be an exhaustive list anyway. William M. Connolley 17:34, 18 September 2005 (UTC).


 * I'll look into it. Some of the work on this seems to have been done by a former colleague of mine (W. Sturges). The real question is whether it is important enough to go into this article or not. --NHSavage 18:25, 18 January 2006 (UTC)
 * OK - the key paper is one from Science in 2000 - the abstract doesn't mention the GWP but according to BBC News GWP is 18,000 (no timescale mentioned....) but Bill says its concentrations are too low to worry about at present and likely to remain that way as the growth rate is only 6% per annum. I think this is probably too insignificant given the low concs and the fact that the GWP is less than SF6 to warrant inclusion here.

Valueless GWP?
Just a detail - the 20 year GWP methane figure differs in article para 1, section under Values and under Importance of Time Horizon Elfie10 (talk) 13:03, 7 September 2011 (UTC) 7 September 2011

From following some discussion on GWP at the page on Talk:Methane I think we need to make a couple of things clearer about this concept. Firstly that the timescale over which GWP is calculated is critical and therefore whenever GWP is given the timescale must be indicated. Secondly that it depends on how the decay over time is calculated and so there is not one definitive value for a given gas - it depends on the way the lifetime is calculated and given that the oxidising capapity of the Earth changes from year to year and decade to decade can never have a single undisputed number in the way that Pi has for example. This means that when you give a GWP you must always give the reference. I will also try and include the equation for GWP from the TAR when I get time.--NHSavage 08:53, 18 January 2006 (UTC)


 * The point about timescale is already made on the page, and the source (IPCC) is given. The point about no-exact-number is fair enough. William M. Connolley 09:26, 18 January 2006 (UTC).
 * I just think it needs to be a bit clearer. I'll try and work on this. It has caused much confusion over at methane.--NHSavage 09:55, 18 January 2006 (UTC)
 * OK. Feel free to clarify. I may have a go too. We don't want confusion... William M. Connolley 16:39, 18 January 2006 (UTC).
 * Had a go. Feel free to edit my edits though! Next stop is to clear up the misunderstanding over at methane.--NHSavage 18:21, 18 January 2006 (UTC)

Looks OK, thanks for the math. I changed the bit about WV: the article said it was small. I don't know a source for that. I think its not calculated, on the grounds that WV is reactive not active; this is gone over at greenhouse gas. The comment here may be too cryptic perhaps... William M. Connolley 23:01, 18 January 2006 (UTC).

SAR values?
Someone with a stuck CAPS key wrote:


 * COMMENT: IT IS IMPORTANT TO POINT OUT HERE THAT UNDER THE KYOTO POLITICAL PROCESS AND MOST OTHER PROCESSES (CCX, RGGI, ETC.), THE SAR GWP VALUES ARE STILL USED.

I don't know if this is true or not. It probably belongs in KP rather than here? What is CCX (contraction and convergence?), RGGI (regional greenhouse gas inventory?) William M. Connolley 15:55, 20 January 2006 (UTC).
 * I don't know if it is true or not but it is already in the article: For converting the various greenhouse gas emissions into comparable CO2 equivalents under the Kyoto protocol, the Conference of the Parties decided decision 2/CP.3 that the older GWP values from the IPCC Second Assessment Report are to be used to compute overall emissions by sources or removals by sinks. I'll stick a citation needed on it.--NHSavage 17:07, 20 January 2006 (UTC)

I think the original comment is important. Kyoto will continue to use SAR GWP values until 2012. All voluntary programs I'm aware of (The Climate Registry, Climate Action Reserve, Voluntary Carbon Standard) use SAR values, as did the Chicago Climate Exchange (CCX). North American regulatory programs, including California AB32 and RGGI, and the recent EPA GHG Reporting Rule program use SAR. See http://www.epa.gov/climatechange/emissions/downloads09/GHG-MRR-Full%20Version.pdf (Table A-1). Therefore, I think the OP's comment was that the table of GWP values should include SAR because they are the mostly widely used, and because almost everyone having to report GHG emissions will need the SAR values. I think AR4 are also relevant, and I'm not sure if TAR values are relevant.

I would suggest changing the table of GWP values, so that SAR and AR4 values have equal emphasis, include a prominent footnote about the wide use of SAR values, and omit the TAR values. Any thoughts? Pjwst6 (talk) 15:22, 22 April 2011 (UTC)

Non-linearity
I removed the "non-linearity" section as follows:


 * ''The above equation is a rather simplistic model since it implicitly assumes that the effects are linear over the range of concentrations concerned, whereas in reality this is not the case.


 * Beers-Lambert Law tells us that this is essentially a logrithmic relationship and therefore the absorption varies with the concentration of the gas present. As the concentration of the gas rises, less and less of the light remains to be absorbed. Simply put, doubling the gas concentration will no longer double the energy absorbed.


 * In the case the greenhouse gases, methane is still at very low concentrations where such a linear approximation is fairly accurate, however carbon dioxide is now (2007) at a level which places it well into the non-linear region, at levels at which it will absorb nearly all of the energy of the wavelengths where it is active. Increasing concentrations will have less and less effect.


 * This means that the above equation is only valid for small variations of concentration around the static values on which the calculations are initially based. Over longer periods where the concentrations are expected to change significantly, or for large short-term changes in the levels of gas present, the variation of absorption with concentration must be reagarded as variable and any calculation based on the simple model must be regarded as inaccurate.


 * This approximation has the effect of playing down the importance of changes in the other greenhouse gases and

underlines the danger of focusing on carbon dioxide as is frequently the case in the media and public perceptions where the greenhouse effect is CO2.''

This was based on reading the IPCC as saying it was for the release of 1 kg of gas, which is small. But OTOH given the time horizons involved, in the real world the GHG concs will change... in fact the TAR linked form the page says ''The radiative efficiencies ar and ax are not necessarily constant over time. While the absorption of infrared radiation by many greenhouse gases varies linearly with their abundance, a few important ones display non-linear behaviour for current and likely future abundances (e.g., CO2, CH4, and N2O). For those gases, the relative radiative forcing will depend upon abundance and hence upon the future scenario adopted. These issues were discussed in detail and some sensitivities to chosen scenarios were presented in IPCC (l994).''

So: my initial reason for removing the text was wrong. But given the text about a_x being time-variable, I don't see how This means that the above equation is only valid for small variations of concentration around the static values on which the calculations are initially based can be correct. But we should point out that the GWPs are scenario-dependent. William M. Connolley 09:46, 6 February 2007 (UTC)

OK, thanks for the explaination. Maybe you should have read up on the subject before deleting my entry wholesale. It also seems you misunderstood the meaning of whatever IPCC article you read about 1kg of gas. Do you have a scientific background?


 * Maybe you should read up on my userpage William M. Connolley 18:40, 6 February 2007 (UTC)

I will look into the non-lineararity of methane. While no absorption curve is truely linear, it is a case of required precision as to how far a gas can be approximated by linear absoption. As my entry explained atmospheric methane is in an approximately linear region, maybe this needs qualifying. CO2 is not in such a region and as such the GWPs are crude approximations that can be misleading.


 * Please remember that you can't say that as your personal opinion - it counts as Original Research and is forbidden. OTOH if you can find a reputable source to say the same then its fine. If you *can't* find such a source you should wonder why not William M. Connolley 18:40, 6 February 2007 (UTC)

The key fact to get accross is that if the whole world is going to try to control climage change based on trading CO2 tickets we need to look closely at these "equivalents" and emphasise that greenhouse is not a synonym for CO2.

This means that the above equation is only valid for small variations of concentration around the static values on which the calculations are initially based

If the variations are small around a know valid datum it can again be approximated as linear in that region. In short the GWPs will never be valid over the range and in the context in which they are used. That does not make my comment above incorrect.

Now you have a better understanding of the subject is there anything you think I should clarify in this topic before putting it back in?


 * Please don't put it back in. You have missed the point that I quoted - that the values are scenario dependent. The calculations don't assume static values for the other GHGs. At least, thats how I read the IPCC text. How do you read it? William M. Connolley 18:40, 6 February 2007 (UTC)

Your point about it being senario dependant is entirely valid but nothing to do with the point I am making. I even think you are now confusing senario (ie strategies of levels we maintain) and duration of the GWP calculations : 20,100 or 500 years.

The values cannot be senario dependant beyond maybe applying a different fixed value. Whatever the fixed value the forumla in the article will be simplistic and inaccurate.

Please give me an exacty reference of the text you would like me to read.


 * http://www.grida.no/climate/ipcc_tar/wg1/247.htm. As I said, its linked form the page. Its where the defn comes from William M. Connolley 20:08, 6 February 2007 (UTC)

The values of a sub x and a sub r clearly are constants in that equation and not fuctions or time or concentration. How do you manage to read this otherwise? Is that not the equation used ?


 * Why are a_x and a_r constant? the IPCC text says The radiative efficiencies ar and ax are not necessarily constant over time.  William M. Connolley 20:08, 6 February 2007 (UTC)

Exactly my point! Despite the report clearly stating they are not constant over time, the formula used to calculate the GWPs DOES use a constant value and IS simplistic.

You will note that none of this dicussion refers to the non-linearity that is the essential nature of spectral absorption and thus is irrelevant to your mistaken motive for removing my entire entry in the first place.

It seems clear from your posting so far that you are not familiar with this subject and are simply going from what you think you have gleaned from the IPCC text.

I do have relevant expertise in spectroscopy and physics.

I dont have the time to make a lengthy discussion on on this. Unless you can come up with a clear, well-founded, scientific disproof of what I posted I shall resubmit it.

Thanks for your comments.


 * Why do you think that the values a_x and a_r are constant in the formula? Nowhere does it say they *are* constant; in fact it explicitly says they aren't; yet you insist they are. This seems weird. I am indeed going from the IPCC text which defines the GWP. It seems that you are not familiar with the text either. Knowing a lot about radiative physics doesn't help if you don't know what the values in the equation are William M. Connolley 21:30, 6 February 2007 (UTC)

While the general discussion points out the non-linearity the explaination of the term in the equation is this: ax is the radiative efficiency due to a unit increase in atmospheric abundance of the substance in question

It is also defined as studying the pulse responce to the release of a very small quantity of gas.

This equation is clearly intended to study uniquely the effects of decay of the gases over time. That's all it does.

simplified measures to estimate in an approximate fashion the relative effects of emissions of different gases

Though it is not the job of Wikipedia entries to tow the party line as far as the IPCC is concerned, I dont see anything in the text you refer me to that contradicts what I posted originally.


 * It says, perfectly clearly, that the a_x may not be constant. The text you've added seems to be entirely your own personal opinion, and doesn't agree with the IPCC page that the defn is sourced from. Please find a proper source for what you want to add, if you want to add it. —The preceding unsigned comment was added by William M. Connolley (talk • contribs) 10:12, 7 February 2007 (UTC).

If that integral was taking into account the fact that concentration and hence absoption was changing during the time interval indicated by the bounds of the integral then a_x would be have to be shown as a funtion of time. It is not.


 * This is just plain silly. Just because a variable doesn't have a (t) after it doesn't mean it doesn't vary with time, especially when the text explicitly say it does William M. Connolley 13:57, 7 February 2007 (UTC)

Your profile indicates you have a maths background I really should not have to explain this to you (nor should I have waste hours googling for a reference to justify what is basic science before you will stop deleting my contributions wholesale).

The page this refers IS one acreditted justification for my comments.

>> The radiative efficiencies ar and ax are not necessarily constant over time. While the absorption of infrared radiation by many greenhouse gases varies linearly with their abundance, a few important ones display non-linear behaviour for current and likely future abundances (e.g., CO2, CH4, and N2O). For those gases, the relative radiative forcing will depend upon abundance and hence upon the future scenario adopted. These issues were discussed in detail and some sensitivities to chosen scenarios were presented in IPCC (l994). >>

They publish a simplistic formula with no time dependancy in these terms. They clearly indictate that the indices it produces are "simple" "approximage" "estimates". They also confirm the non-linear absoption issue. What more do you want?


 * If all you want to do is quote from that IPCC page, then fine: I have no problem with that. If it contains what you need, then great. Just don't add your own unwarratned extrapolations William M. Connolley 13:57, 7 February 2007 (UTC)

Unfortunately, one of the failings of IPCC is the lack of rigourous scientific referencing of sources. Simply avoiding explaination with a vague reference to "IPCC (1994)" is of little use. I tried find what this refers to but could not.


 * Then you're being rather pathetic. Permit me to spoon feed you: see http://www.ipcc.ch/pub/reports.htm. Or, you could have found it via the references section for that chapter: http://www.grida.no/climate/ipcc_tar/wg1/259.htm. You assert expertise but are incapable of a basic reference lookup? This is very odd William M. Connolley 13:57, 7 February 2007 (UTC)

Neither does the report give any way of reproducing the data shown in the table or verifying the method. Again this is bad science.

You contradict yourself with your postition here. At one stage you say non-linear does not apply because it's a small peturbation but you also say these terms are variable and take non-linearity into account.


 * My initial impression was that it didn't matter because it was a small perturbation. But I explicitly retracted that when I realised I was wrong. You know that. Do pay attention. William M. Connolley 13:57, 7 February 2007 (UTC) But then I carelessly reverted back to the small-erpturbation text I originally put in. Sorry. Will fix... William M. Connolley 14:01, 7 February 2007 (UTC)

Is it simply this question of whether these values are constants that is your issue here ?


 * As far as I can tell, the problem is you refusing to admit that a_x can vary with time William M. Connolley 13:57, 7 February 2007 (UTC)

NO! I am insisting that it does varies with time but that this is not taken into account if the GWP formula. Will you now please address this issue specifically?

a_x is not shown as a function of time in that integral.

Are you maintaining that in fact it is a function of time but that this is not correctly shown, or that the table of results comes from some other formula where the time dependancy is taken into account.

What seems to be your position upto now is that'' a_x. x(t) dt is the same thing as a_x(t). x(t) dt''. Is that in fact what you are maintaining?


 * OK then, As far as I can tell, the problem is you refusing to admit that a_x can vary with time in the formula given, jsut because the dependence on t isn't shown explicitly. I do indeed maintain that the absence of a (t) after a_x does not imply that a_x is constant especially (all together now...) since the text says it can vary. If you want to be sure, you'd have to look up the more detailed calcs in IPCC 1994, whose exact ref I've helpfully provided you after you failed to find it yourself, but of course you didn't thank me for that William M. Connolley 15:32, 7 February 2007 (UTC)

Why is it that when you have a different interpretation to someone else it the other "refusing to admit"? By your own admission you have already made a couple of errors in handling this, your estimed opinion is clearly not beyond question.

Well this may seem "silly" to you but I was taught that mathematics was a precise language. A mathematical formula does not have "implicit" time dependancies hidden in a time integration that are explained two paragraphs further on in prose. Your position is completely unscientific, it seems it is you who is refusing to admit what is in black and white in the IPCC document.

This is a simplistic, approximation. The paper says as much, I have already quoted the authors on that but you, once again, think you know better and chose to delete the entry.

The comment that these terms are variable is there to point out the limitations of the simple form of the GPW calculation. It is well acknowleged that a GPW value has to be qualified by the time period over which it is calculated. I have yet to see anyone quote GPW with a reference to the IPCC senario they are based on. This is simple not the case. They are to quote the authors (all together now) "simple, approximate estimations" which do not take the non-lineararity into account.

That is why the authors deemed it necessary to add the qualifying comment. That does not change the maths.

Not only are you trying to censor any comment on the precision of the IPCC formula but you are not even prepared to see the qualifications and limitations published by the authors of the document appear in the Wikipedia entry. A strange approach for someone involved in scientific research.

Difference with CO2e?
I think it would be beneficial to include what makes GWP different from CO2-e, they both relate global warmin potential to that of carbon dioxide.
 * They are the same, really. Except for the lifetime, which can be implied for either William M. Connolley 20:16, 24 May 2007 (UTC)
 * It looks to me like GWP is the quantity, and CO2e the unit. GWP is commonly measured relative to CO2, but from the name, it could be measured relative to some other gas. Often enough quantities have a unit so common, we forget that they have a unit. Well, also that in any case the time scale being used should be indicated, which isn't always done. Gah4 (talk) 17:14, 15 May 2020 (UTC)
 * It looks to me like GWP is the quantity, and CO2e the unit. GWP is commonly measured relative to CO2, but from the name, it could be measured relative to some other gas. Often enough quantities have a unit so common, we forget that they have a unit. Well, also that in any case the time scale being used should be indicated, which isn't always done. Gah4 (talk) 17:14, 15 May 2020 (UTC)
 * It looks to me like GWP is the quantity, and CO2e the unit. GWP is commonly measured relative to CO2, but from the name, it could be measured relative to some other gas. Often enough quantities have a unit so common, we forget that they have a unit. Well, also that in any case the time scale being used should be indicated, which isn't always done. Gah4 (talk) 17:14, 15 May 2020 (UTC)

Suggest merge from Greenhouse warming potential
I just created the article linked above, unaware that this article already existed as Global warming potential. Please import any relevant information that's not already covered in the article. Then (and only then) make a redirect. Thank you. Shalom (Hello • Peace) 17:46, 21 November 2007 (UTC)

Wikiproject Earth
Hello i have recently proposed the Wikiproject Earth. This Wikiproject`s scope includes this article. This wikiproject will overview the continents, oceans, atsmophere and global warming Please Voice your opinion by clicking anywhere on this comment except for my name. --IwilledituTalk :)Contributions —Preceding comment was added at 15:37, 30 March 2008 (UTC)

Nitrogen trifluoride
Used as an etchant in microelectronics, is a potent greenhouse gas, with a global warming potential (GWP) 17,200 times greater than that of carbon dioxide when compared over a 100 year period. Its GWP would place it second only to Sulfur hexafluoride in the group of Kyoto-recognised greenhouse gases, although is not currently included in that grouping. It has an estimated atmospheric lifetime of 740 years, although recent work suggests a slightly shorter lifetime of 550 years (and a GWP of 16,800).

Industrial applications routinely break down NF3, whereas the regulated compounds SF6 and PFCs are released. Although the impact of NF3 is difficult to project, based on 2008 production levels of 4000 tons, could prove to be more significant than PFCs or, and greater than that of the largest coal-fired power stations.

In 2008, about three-quarters of the chemical is now used to manufacture computer microchips; the rest is used to make LCD panels.

World production of NF3 is expected to reach 8,000 tons a year by 2010. Currently at least 2% is ultimately released into the atmosphere; perhaps substantially more, but there is not good independent data about releases, nor measurements of atmospheric concentration. -69.87.203.92 (talk) 19:33, 10 July 2008 (UTC)


 * Very good, why does it belong in the article? See-also William M. Connolley (talk) 21:33, 10 July 2008 (UTC)

GWPs in Table
The table shows nitrous oxide as 310 for 20 years. The IPCC source shows 289. This seems to need correction unless I'm missing something? Other numbers seem OK (though I didn't check the ones in parentheses).

Why only these few items? Table would benefit at least from a note that CFCs and dozens of other compounds are available in the source table.Numbersinstitute (talk) 18:14, 12 December 2008 (UTC)


 * The AR5 values shown include climate-carbon feedbacks, which are not part of the recommended values in Table 8.A.1. If the article is going to show these values they should be in addition to the values without climate-carbon feedbacks and should also include reference the the higher uncertainty in results with cc feedbacks (Schivlg (talk) 15:26, 6 March 2014 (UTC))


 * This has been an issue for a while, I think the current state of the article is misleading. There is a short table we could add, at page 87 of the synthesis report. Chtfn (talk) 06:55, 18 July 2017 (UTC)

I standardized the tables so the same items in the most recent IPCC are also compared for previous years. The 2 tables could be combined if other editors agree. Making them sortable by source lets readers see each group from the same source together, or all estimates for a gas together. It also allows inclusion of other reputable estimates, like the PFTBA and latest methane data. Numbersinstitute (talk) 23:36, 1 July 2019 (UTC)

History of GWP's
I don't have time right now - but I think this article needs one paragraph on where GWP's came from. How long they have been around for, who was the first to write down the calculations. Chur. —Preceding unsigned comment added by 202.50.184.138 (talk) 03:55, 1 May 2009 (UTC)

GWP of Sulfur Hexafluoride over time
The section on the importance of the time horizon says:

The GWP value depends on how the gas concentration decays over time in the atmosphere.

Sulfur Hexafluoride has a long half-life and its GWP increases with longer time horizons, unlike the other chemicals. The reason for this is not clearly stated in the article though. If the reason is that the Sulfur Hexafluoride has a longer half-life than Carbon Dioxide, then we could say:

The GWP value depends on how the gas concentration decays over time in the atmosphere compared with the decay in the concentration of Carbon Dioxide.

This would explain the odd behaviour a bit more clearly. But is something else going on like the transformation of Sulfur Hexafluoride into an even more potent GW chemical? Recent Runes (talk) 15:46, 24 September 2009 (UTC)

Article probation
Please note that, by a decision of the Wikipedia community, this article and others relating to climate change (broadly construed) has been placed under article probation. Editors making disruptive edits may be blocked temporarily from editing the encyclopedia, or subject to other administrative remedies, according to standards that may be higher than elsewhere on Wikipedia. Please see General sanctions/Climate change probation for full information and to review the decision. -- ChrisO (talk) 19:38, 2 January 2010 (UTC)
 * Is the probation indefinite? 99.181.147.10 (talk) 05:11, 1 April 2011 (UTC)

Add Global warming potential (GWP) is often used in conjunction with a compound's Ozone depletion potential?
Add Global warming potential (GWP)is often used in conjunction with a compound's Ozone depletion potential? 209.255.78.138 (talk) 17:46, 7 April 2011 (UTC)
 * Source?  — Arthur Rubin  (talk) 19:40, 7 April 2011 (UTC)
 * Refrigerants discusses these together. General search on google backed up the OP assertion.Pjwst6 (talk) 14:50, 26 April 2011 (UTC)

See Talk:Ozone depletion potential's 209.255.78.138 (talk) 20:09, 7 April 2011 (UTC)
 * There currently is an issue with that Talk, see Ozone depletion potential maybe? 99.181.133.155 (talk) 04:01, 16 April 2011 (UTC)
 * Something is strange with Talk:Ozone depletion potential? 99.181.143.101 (talk) 05:51, 16 April 2011 (UTC)

Is the 20 year GWP of methane 56 or 72?
"the global warming potential of methane over a 20 year time period is 72" from here: http://en.wikipedia.org/wiki/Atmospheric_methane#Methane_as_a_greenhouse_gas vs "For example, the 20 year GWP of methane is 56" on this page. 101.98.150.115 (talk) 15:07, 19 May 2012 (UTC)


 * It's 72 according to the 2007 IPCC report. I have updated the reference. However, this number may still be disputed, as more recent research (Shindell, 2009) indicates that the GWP of methane may have been underestimated, and the 100-year GWP of methane is likely closer to 33 than 25 as stated in IPCC AR4, and the 20-year GWP is correspondingly higher at 105 rather than the 72 reported in IPCC AR4. I don't have time to make this change right now but intend to in the future as it is crucially important to understand that GWPs of various shorter-lived gases are somewhat contested even today.

--129.67.199.19 (talk) 21:51, 24 May 2012 (UTC)

Talk:Natural_gas The Wikipedia article on natural gas seems to me to say that methane has 2x the 100 year effect of CO2, or possibly 3, not 30. ? ( Martin | talk • contribs 18:56, 18 August 2012 (UTC))

Regarding the replacement of what was there with this sentence "If you started with 1 tonne of methane which has a GWP of 25, after combustion you have 2.75 tonnes of CO2, each tonne of which has a GWP of 1. The effect of this burning is to reduce the Global warming effect of the gas released in the ratio 25:2.75 or by about 9."

You guys may or may not consider running the math on the effect of burning methane to Co2 to be original work. But it is just arithmetic and pre uni science. Molecular weights of methane and Co2 are just facts. hence mass of Co2 produce from burning Ch4 is yr11(17yr old student) chem. the GWP of the original mass of Ch4 or larger mass of Co2 then has an effect in the ratio 1x25:2.75x1. (mass X GWP) — Preceding unsigned comment added by 202.164.205.96 (talk) 05:53, 3 November 2012 (UTC)

"Lifetime" of Methane
Methane has a half life of roughly 7 years in the atmosphere, why does this say it has a lifetime of 12? Roughly 30% of the methane would still be in the atmosphere at that point in time.174.101.99.191 (talk) 01:20, 20 November 2015 (UTC) I followed the lifetime link, I haven't taken chemistry for a long time, but I am really not familiar with that. Maybe this is not a concern, but I do think that sources might be good here. If I understand this currectly, half-life isn't used because of natural occurances of the molecules? 174.101.99.191 (talk) 01:29, 20 November 2015 (UTC)
 * Atmospheric methane states 29 on 100 yrs, did not checked sources. 7 GWP might refer to 10 yrs period or something. prokaryotes (talk) 13:55, 28 December 2015 (UTC)

Requested move 28 December 2015

 * The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section. 

The result of the move request was: moved. Jenks24 (talk) 10:12, 5 January 2016 (UTC)

Global-warming potential → Global warming potential – Page was moved from global warming potential to global-warming potential in 2011 without discussion. Besides that "global warming" is unhyphenated and so "global warming potential" should be as well, I have been unable to find even a single source using the hyphenated "global-warming potential". The unhyphenated form on the other hand is used by, well, everyone, from the IPCC to the UNFCCC to the EPA. Kolbasz (talk) 13:31, 28 December 2015 (UTC)
 * Support. Makes sense. prokaryotes (talk) 13:53, 28 December 2015 (UTC)
 * Support per nom's sources. Zarcadia (talk) 14:13, 28 December 2015 (UTC)


 * The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.

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The part about perfluorotributylamine (PFTBA) is incorrect and should be removed
In the Values section, there's a paragraph that talks about perfluorotributylamine (PFTBA). It claims PFTBA is the most potent greenhouse gas yet discovered (i.e. it has the highest GWP), according to a source that's worth about as much as any random blog. If you go to the source for the 2013 values of GWP, on page 733 it gives the GWP(20) of sulfur hexaflouride as 17,500. The stated GWP(20) of PFTBA is only 7100. Last time I checked, 17,500 was larger. The source itself makes the claim that PFTBA is the most potent gas in the world, so the error seems to be from picking a terrible rag as a source, as well as not doing any fact-checking.

Mama told me

not to cite dirt

seventeen five

SF6 you have to insert

2602:306:3788:590:A966:5932:9B4:C343 (talk) 01:27, 8 May 2017 (UTC)


 * That's correct. The source itself emphasizes that the PFTBA concentrations are low. There are no estimations about the amount of emission levels according to Hong. So I think there is no point why PFTBA should be featured with an own paragraph here. It seems just as relevant as dozens of other special substances. I have removed the paragraph but will include a more general remark on those unregulated gases with high GWPs. Hedgehoque (talk) 21:29, 3 March 2021 (UTC)
 * I suspect it depends on counting by mass or moles. Most often they are counted by mass, but maybe not always. Gah4 (talk) 22:07, 19 January 2022 (UTC)
 * I suspect it depends on counting by mass or moles. Most often they are counted by mass, but maybe not always. Gah4 (talk) 22:07, 19 January 2022 (UTC)

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Merger proposal
I propose to merge Carbon dioxide equivalent into Global warming potential.

Carbon dioxide equivalent is an extremely confusing article. For example it defines CO2eq as CO2e is defined by the United States Environmental Protection Agency and defined by The Guardian newspaper and it defines CO2e as something else.

If I google "difference between CO2eq and CO2e" I cannot find anything that I can understand which explains it.

After the merger we can delete the section about CO2e as it only has one citation which (without registering) does not actually mention CO2e.

We can also then add "Carbon dioxide equivalent" to Glossary of climate change with the CO2eq definition. Chidgk1 (talk) 17:48, 20 June 2020 (UTC)


 * Agree CO2e article is quite small. We need to have good definitions and arrange this article to be understandable to non-specialists. I've made an attempt at that. Some people distinguish between "radiative forcing" and "atmospheric warming", which the article does not distinguish. It also needs to explain climate feedback effects. Numbersinstitute (talk) 19:31, 20 June 2020 (UTC)


 * Agree - me too. There's not much at CO2e it would be good to consolidate William M. Connolley (talk) 19:41, 20 June 2020 (UTC)

Lede wording and past GWP
Lede now refers to "gases subject to restrictions under the Paris Agreement are either rapidly increasing their concentrations in Earth's atmosphere or have a large GWP.", where it previously said "under the Kyoto Protocol". I'm not sure the Paris Agreement has "restrictions." There must be a list of gases covered by the Paris Agreement, since it came into force when the producers of enough of these gases ratified it. I haven't found that list to see if they all are "rapidly increasing their concentrations in Earth's atmosphere or have a large GWP." I agree the sentence should no longer refer to Kyoto Protocol. We need to check if it's true, or maybe it can be deleted, and the Paris Agreement article can address it if needed. Numbersinstitute (talk) 23:12, 1 July 2020 (UTC)


 * I suggest it would be best to put the 2001 GWP numbers back in, and even the 1997 numbers. The value is to see how stable or unstable they are over time., which lets readers judge the reliability, and even understand writings from that time. I haven't put them back yet, since I wanted to ask if there's any reason to keep the 2 tables separate? If together, they can be sorted by gas or by year. Sorting by year makes it easy to see an overview of all the most recent values for all gases (which should be the default). Sorting by gas makes it easy to see the history of any particular gas. The table can be collapsed to save space. Another idea is to have the most recent numbers in one table, not collapsed, and all numbers, from oldest to newest in another collapsed table. Numbersinstitute (talk) 19:56, 2 July 2020 (UTC)


 * I don't have an opinion - go ahead and do as you think best Chidgk1 (talk) 06:28, 3 July 2020 (UTC)

Is hydrogen GWP still correct?
I ask as source says there had been very few studies by 2018. Chidgk1 (talk) 17:42, 13 September 2020 (UTC)


 * This recent UK government study suggests Hydrogen has an average GWP (100 years) of 11 ± 5, rather than 4.7 (or, as the article suggests has commonly been quoted in the past from a 2001 study, 5.8), so is ‘twice as powerful a greenhouse gas as previously thought’: UK government study
 * Should the figure for Hydrogen in the table be updated therefore, quoting and linking to the source report, released on 8th April 2022, namely 'Atmospheric Implications of Increased Hydrogen Use'?  Buyani Nyoni (talk) 19:44, 13 April 2022 (UTC)Buyani Nyoni (talk) 19:59, 13 April 2022 (UTC)

Tons or metric tons?
The article makes many references to "tons" and "tonnes" but it's not clear whether they're short tons, metric tonnes, or something else. Can anyone clear up the ambiguity on the page?

--Error9312 (talk) 01:10, 6 October 2020 (UTC)


 * They are all metric and should remain so. As I see you are American it would be great if you could change them all to be whichever word would be clearest to, say, a high school student in the USA. Chidgk1 (talk) 06:49, 6 October 2020 (UTC)
 * How often is the difference important? Often enough, tons is a convenient large unit for something that might have a large enough uncertainty to include all of them. Gah4 (talk) 20:06, 19 January 2022 (UTC)
 * How often is the difference important? Often enough, tons is a convenient large unit for something that might have a large enough uncertainty to include all of them. Gah4 (talk) 20:06, 19 January 2022 (UTC)

Calculating CO2e
Hey team. I went ahead and removed text referring to calculating CO2e by multiplying gas concentration in ppm by GWP. That's incorrect since GWP is a ratio of mass (not molar concentration) and seemed like a bit of an emergency to fix. Calculating the CO2e of the ppm of GHG in the atmosphere is more complex and needs to involve the molar masses of the gases to link concentration to mass in order to use their (mass ratio) GWPs. Let me know if I can explain more. I think the references are still fine? Eccentricorbit (talk) 17:40, 19 January 2022 (UTC)
 * ppm is also a ratio of mass, though if parts makes you think about counting molecules, I can see why you might have thought different. If it actually said moles (or mM or micromole) then it would be obviously wrong. Gah4 (talk) 20:04, 19 January 2022 (UTC)
 * Thanks for responding. I think in this context (CO2 atmospheric concentrations) ppm is always molar? Here's how NOAA measures GHG concentrations on Mauna Loa.. They refer to it as the dry air mole fraction. Eccentricorbit (talk) 05:36, 20 January 2022 (UTC)
 * In the NOAA paper, and in Carbon_dioxide_in_Earth's_atmosphere it specifically says that it is molar ppm. As well as I know, in chemistry it is commonly mass. Well, since chemistry is most often done in solution, and solutions most often in molarity, there would be M, mM, or μM. But as Parts-per_notation notes, it is best to say which one is used. Each field has its favorite. That said, I didn't figure out which one was in the delepted data. Gah4 (talk) 22:50, 20 January 2022 (UTC)
 * More general (drop "CO2"), ppm is molar in atmospheric contexts. This is so universally true that there is no doubt if not explicitly stated (as usual).--Rainald62 (talk) 11:46, 22 January 2022 (UTC)
 * I suspect so, but not all of us are atmospheric scientists. As noted in the linked article, different fields use different conventions. Since it sounds like chemistry, some might assume chemistry conventions. Gah4 (talk) 05:10, 23 January 2022 (UTC)
 * In the NOAA paper, and in Carbon_dioxide_in_Earth's_atmosphere it specifically says that it is molar ppm. As well as I know, in chemistry it is commonly mass. Well, since chemistry is most often done in solution, and solutions most often in molarity, there would be M, mM, or μM. But as Parts-per_notation notes, it is best to say which one is used. Each field has its favorite. That said, I didn't figure out which one was in the delepted data. Gah4 (talk) 22:50, 20 January 2022 (UTC)
 * More general (drop "CO2"), ppm is molar in atmospheric contexts. This is so universally true that there is no doubt if not explicitly stated (as usual).--Rainald62 (talk) 11:46, 22 January 2022 (UTC)
 * I suspect so, but not all of us are atmospheric scientists. As noted in the linked article, different fields use different conventions. Since it sounds like chemistry, some might assume chemistry conventions. Gah4 (talk) 05:10, 23 January 2022 (UTC)
 * I suspect so, but not all of us are atmospheric scientists. As noted in the linked article, different fields use different conventions. Since it sounds like chemistry, some might assume chemistry conventions. Gah4 (talk) 05:10, 23 January 2022 (UTC)
 * I suspect so, but not all of us are atmospheric scientists. As noted in the linked article, different fields use different conventions. Since it sounds like chemistry, some might assume chemistry conventions. Gah4 (talk) 05:10, 23 January 2022 (UTC)

Image for the lead?
I've just added an image to the lead as there was none so far. Pinging User:RCraig09: what do you think of this image or do you have a better one at your fingertips for this article? Thanks. EMsmile (talk) 08:22, 10 July 2023 (UTC)
 * I haven't made any more appropriate graphics than File:1979-_Radiative_forcing_-_climate_change_-_global_warming_-_EPA_NOAA.svg, but a Google image search of "GWP site:commons.wikimedia.org" turned up some possibilities. Checking corrsponding non-English-language Wikipedia articles might have other relevant images. — RCraig09 (talk) 14:52, 10 July 2023 (UTC)
 * I've now found one image at the Swedish Wikipedia and one more from OWID that was already in Wikimedia Commons. I have added those two bar charts. I guess the charts for GWP are inherently quite boring because it's just bars with differing heights but nothing that would change over time. EMsmile (talk) 12:26, 18 December 2023 (UTC)

Sulphur Hexafluoride SF6 GWP100 values shown are out of date with latest IPCC AR6 report
Am I correct that an SF6 GWP100 of 25,184 CO2e should be added to the tables to bring it inline with the latest IPCC AR6 WGIII Annex II (Table 9, page 1,831)? Source https://www.ipcc.ch/report/ar6/wg3/downloads/report/IPCC_AR6_WGIII_Annex-II.pdf Samfalmouth (talk) 10:53, 10 July 2024 (UTC)