Talk:Global warming potential

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[edit] 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)

[edit] 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

[edit] Definition

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

[edit] 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)

[edit] 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)

[edit] 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)

[edit] 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[1] - the abstract doesn't mention the GWP but according to BBC News[2] 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.

[edit] Valueless GWP?

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).

[edit] 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)

[edit] 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. [3] 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.

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

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.

[edit] 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)

[edit] 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)

[edit] 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)