Talk:Greenhouse gas

Atmospheric Lifetime

The following statement in section 6.2 contradicts the preceding definition of lifetime and should be deleted: "The atmospheric lifetime of CO2 is often incorrectly stated to be only a few years because that is the average time for any CO2 molecule to stay in the atmosphere before being removed by mixing into the ocean, photosynthesis, or other processes. However, this ignores the balancing fluxes of CO2 into the atmosphere from the other reservoirs. It is the net concentration changes of the various greenhouse gases by all sources and sinks that determines atmospheric lifetime, not just the removal processes." If the inputs are included to balance out the outputs, then the lifetime for any gas with a stable concentration would equate to infinity (divide by zero). This is clearly wrong and it is the flux or flow of the substance through the atmosphere which is the denominator not the difference between the inputs and outputs. For a stable concentration the input equals the output, but as per water vapor, that does not mean that it has an infinite lifetime. This misunderstanding has propagated numerous incorrect statements such as "Recent work indicates that recovery from a large input of atmospheric CO2 from burning fossil fuels will result in an effective lifetime of tens of thousands of years." in the following section. It is quite apparent from the amplitude of the yearly CO2 concentration cycle that it's Lifetime is relatively short. The only way it could get to tens of thousands of years would be in situations like "snow ball earth" with no plants and no plankton etc. I suggest the above statement be replaced with "The atmospheric lifetime of CO2 is often incorrectly stated to be thousands of years or more, due to substituting the net input minus output flux through the atmosphere in place of the output flux. The atmospheric lifetime of CO2 is actually only a few years because that is the average time for any CO2 molecule to stay in the atmosphere before being removed by mixing into the ocean, photosynthesis, or other processes." — Preceding unsigned comment added by BFhybrid (talk • contribs) 13:13, 7 June 2011 (UTC)

The correct definition of atmospheric lifetime in the context of greenhouse gases is defined by what the literature states, and not what we as editors judge to be the correct definition. I've spent a bit of time looking in the TAR for its definition (which can be found here), and that one contradicts your personal definition of molecule lifetime, and is similar to the definition in 6.2. So that is the one that the preponderance of the literature seems to support. If you disagree, then i suggest that you find sources of equivalent merit to support yours. (suggestion: The U.S. Global Change Research Program or the AR4 might be a place to look) --Kim D. Petersen (talk) 15:59, 7 June 2011 (UTC)

The definition that I am discussing is not 'my personal definition' as you make out, it is the clear definition that is already referenced in 6.2 to Jacob, and includes the equation with explanations of each variable; maths is the universal language and it is unambiguous. I found no definition of atmospheric lifetime in your link, only one oblique reference to lifetime, in the obvious statement that well mixed gases have longer lifetimes. You have not addressed my objection that the second paragraph is contradicting the first paragraph, and the statement you are supporting is already tagged with 'citation needed'. What I don't understand is your claim that the definition you found in the TAR (what is this?) is similar to the definition in 6.2. Perhaps you could just extract the definition you are referring to from the TAR and post it here? Here is the first internet reference I found on Google on this issue BFhybrid (talk) 12:47, 8 June 2011 (UTC)

BFhybrid, you are absolutely correct. But I caution you not to pursue this matter because you will just get more frustrated. If you go back into the archives you'll see contributions from me on this subject. Physicists and engineers use half-lifes to describe exponentially decaying processes, and don't generally use the simple term "lifetime" except in casual conversation. Authors writing about greenhouse gas/effect make up their own definitions; you won't find a consistent definition. Indeed if someone attempted to create one, it would be torn to shreds or just ignored by others who have preconceived notions of what the end result should be. I've read some of the papers that assert lifetimes of the order of 100,000 years for CO2 in the atmosphere. While they may make some attempt to descibe how they arrive at a figure, they're not precise in describing where they set the concentration threshold on the way to an infinitely long lifetime. As for my understanding of the matter, when the terms are shifted to those physicists would use, the half-life of CO2 in the atmosphere (sources cease, decay only) is somewhere near three months (if I remember correctly). The more interesting observations that can be made are about the mechanisms. CO2 removal is a largely a surface effect, depending on how you view H2O condensation and the mass transport of CO2 to the surface by precipitation. H2O removal is a volume effect for the most part. Water vapor condenses at temperatures commonly found in the atmosphere; CO2 does not change state at temperatures found in the atmosphere. These are the underlying reasons why CO2 leaves the atmosphere far more slowly than H2O. blackcloak (talk) 09:37, 5 August 2011 (UTC)

Potency claim for CH4 versus CO2

Article claims that as a greenhouse gas, CH4 is eighty times more potent on a molecule to molecule basis, according to reference 8. I followed citation given for reference 8, and the link I arrived at is below.

http://iopscience.iop.org/0034-4885/68/6/R02/

I downloaded the .pdf, and all I can find is a statement on pg 1362 that states CH4 is EIGHT times more potent.

If the author can show where the "eighty" statement came from it should stay, otherwise the potency should be decimated.

Stevew139 (talk) 08:54, 9 June 2011 (UTC)

I replaced that citation with the IPCC cite used later in the article for the same factoid, and modified the text according to what IPCC AR4 said, which was, that over 20 years methane has 72x the warming potential of CO2. If has a much lower potential over a 100 year time frame. (If we're only talking about the methane itself, and not the warming due to indirect effects of the methane in the atmosphere.) NewsAndEventsGuy (talk) 02:10, 29 June 2011 (UTC)

Outline organization

Today I attempted to sort out what I viewed as a jumbled up organization of the text with respect to section headings. IMO that task is not yet done, but I'll stop for now to let other editors chime in. If you want to do more, great, and if you think my reorganization attempt was misguided, revert is welcome but please explain why here in TALK. NewsAndEventsGuy (talk) 17:18, 11 July 2011 (UTC)

Resource data ...

Resource for comparative data on carbon emissions in the United States, China, and India from the United States Energy Information Administration ... http://www.eia.gov/oiaf/ieo/pdf/ieorefcase.pdf 216.250.156.66 (talk) 20:18, 28 July 2011 (UTC)

History of scientific research

There is a link in this section ( http://www.oppapers.com/essays/Global-Warming-Opposing-Viewpoints-Paper/733173?topic ) with a pay wall, it is to a purely commercial organisation trying to sell "teach you how to write". There is no access to samples of what they do or anything of that sort and it certainly does not have anything to say about GH gases unless you pay first. I will be removing this shortly unless a good argument is presented. --Damorbel (talk) 11:08, 12 September 2011 (UTC)

I created this link in this edit today. Previously the reference was "Opposing Viewpoints Resource Center. Detroit: Thomson Gale, 2005. From Opposing Viewpoints Resource Center" with no links. I have no idea who or what 'Opposing Viewpoints' is either. The problem is that the statements it provides a source for are self-evidently true. What we need is a better reference for this level of historical summary. --Nigelj (talk) 16:49, 12 September 2011 (UTC)

Typo in image

The image on the page has a typo in the bottom left-hand corner: "Absorbation" - instead of "Absorption"?

File:The_green_house_effect.svg

Can we fix it?

Drdrperry (talk) 00:22, 15 September 2011 (UTC)

"Absorbs and emits"?

Atmospheric absorption and scattering at different electromagnetic wavelengths. The largest absorption band of carbon dioxide is in the infrared.

The article begins, "A greenhouse gas (sometimes abbreviated GHG) is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range." Why do we have "emits" in there? The characteristic of a GHG is the existence of absorption bands in the IR region of the spectrum equivalent to the surface temperatures of the planet, so absorb is definitely right.

Does not any gas emit IR radiation equivalent to its blackbody temperature? I may not be correct here, as other gasses will be transparent and I'm not sure if transparent things emit IR like blackbodies, so this really is a question, not yet a suggestion and certainly not a criticism. Whichever is right, I didn't find the answer in the article. Maybe I missed it, or maybe we can improve something here. --Nigelj (talk) 18:49, 2 October 2011 (UTC)

The current phrasing is correct. Not all gases emit in the infrared when heated. For example, if you were to look at a heat gun through an infrared camera, you would not be able to see anything leaving the gun. This is because the primary components of air (oxygen and nitrogen) do not emit radiation in the infrared. However, if you were to introduce CO₂ into the heat gun intake, you'd very clearly see it show up on the infrared display because CO₂ does emit in that range. So it's very much correct to make the distinction that only some gases absorb energy and emit in the infrared. --Sean 130.253.30.70 (talk) 21:38, 2 October 2011 (UTC)