|This article and its editors are subject to Wikipedia general sanctions. See the description of the sanctions.|
|WikiProject Environment / Climate change||(Rated Start-class)|
- 1 Carbon dioxide
- 2 Greenhouse effect
- 3 Definition
- 4 Water
- 5 Who defines GWP?
- 6 Global warming potential looks like a possible subsection of greenhouse gas?
- 7 Super greenhouse gas
- 8 Valueless GWP?
- 9 SAR values?
- 10 Non-linearity
- 11 Difference with CO2e?
- 12 Suggest merge from Greenhouse warming potential
- 13 Wikiproject Earth
- 14 Nitrogen trifluoride
- 15 GWPs in Table
- 16 History of GWP's
- 17 GWP of Sulfur Hexafluoride over time
- 18 Article probation
- 19 Add Global warming potential (GWP) is often used in conjunction with a compound's Ozone depletion potential?
- 20 Is the 20 year GWP of methane 56 or 72?
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 126.96.36.199 (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))
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.
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 188.8.131.52 (talk) 01:21, 12 July 2014 (UTC)
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
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)
- 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 184.108.40.206 (talk) 21:51, 26 March 2012 (UTC)
- Jolly good, now read the surrounding text and following table D2 William M. Connolley (talk) 21:27, 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)
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 220.127.116.11 (talk) 01:04, 12 July 2014 (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. 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.
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)
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).
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)
|Went nowhere, degnereated into usual accusations of censorship|
I removed the "non-linearity" section as follows:
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)
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.
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.
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.
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.
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 ?
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.
While the general discussion points out the non-linearity the explaination of the term in the equation is this:
This equation is clearly intended to study uniquely the effects of decay of the gases over time. That's all it does.
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.
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?
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.
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.
Is it simply this question of whether these values are constants that is your issue here ?
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?
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)
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)
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)
Used as an etchant in microelectronics, NF
3 is a potent greenhouse gas, with a global warming potential (GWP) 17,200 times greater than that of CO
2 when compared over a 100 year period. Its GWP would place it second only to SF
6 in the group of Kyoto-recognised greenhouse gases, although NF
3 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, NF
3 could prove to be more significant than PFCs or SF
6, 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. -18.104.22.168 (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).
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))
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 22.214.171.124 (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)
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 Wikipedia:General sanctions/Climate change probation for full information and to review the decision. -- ChrisO (talk) 19:38, 2 January 2010 (UTC)
Add Global warming potential (GWP) is often used in conjunction with a compound's Ozone depletion potential?
- Source? — Arthur Rubin (talk) 19:40, 7 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. 126.96.36.199 (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.
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 188.8.131.52 (talk) 05:53, 3 November 2012 (UTC)
- Climate Change 2007: The Physical Sciences Basis, IPCC, retrieved 2008-07-03
- Robson, J.I.; Gohar, L.K., Hurley, M.D., Shine, K.P. and Wallington, T. (2006). "Revised IR spectrum, radiative efficiency and global warming potential of nitrogen trifluoride". Geophys. Res. Lett. 33. doi:10.1029/2006GL026210.
- Prather, M.J.; Hsu, J. (2008). "NF
3, the greenhouse gas missing from Kyoto". Geophys. Res. Lett. 35. doi:10.1029/2008GL034542.
- Tsai, W.-T. (2008). "Environmental and health risk analysis of nitrogen trifluoride (NF
3), a toxic and potent greenhouse gas". J. Hazard. Mat. doi:10.1016/j.jhazmat.2008.02.023.
- H. Reichardt , A. Frenzel and K. Schober (2001). "Environmentally friendly wafer production: NF
3 remote microwave plasma for chamber cleaning". Microelectronic Engineering 56. doi:10.1016/S0167-9317(00)00505-0. Text " pages 73-76" ignored (help); Unknown parameter
- M. Roosevelt (2008-07-08). "A climate threat from flat TVs, microchips".