Talk:Greenhouse gas

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Contents 1 Percentage increase 2 Why does the top graph go from right-to-left? 3 Dipole 4 Global warming potential (again) 5 Role of WV 6 The MOPPIT Sattilite Images 7 Heteronuclear diatomics 8 Not GA yet 9 percentage of greenhouse effect 10 ‘water vapor can not be controlled by humans’ ? 11 Greenhouses 12 General cleanup 13 Units for radiative forcing 14 Emissions by Country 15 Classroom science experiment? 16 Greenhouse Gases - human factor

[edit] Percentage increase

What does the percentage increase in the table within the section Increase of greenhouse gases refer to? 85.124.182.40 15:10, 19 August 2005 (UTC)

The 1750 baseline, which isn't given separately (the 1998 level and the change from 1750 are). It might be clearer to have the baseline as well as, or even instead of, the 1750-1998 change. Rd232 18:14, 19 August 2005 (UTC)

[edit] Why does the top graph go from right-to-left?

Didn't someone just fix that backward graph somewhere else? --James S. 19:04, 28 December 2005 (UTC)

Why not, the axis is labelled. And the net sink bit comes directly from the red/blue line crossover at abt. 1900. Seems sensible to me, what shenanegans are you referring to in that edit summary? Vsmith 21:29, 28 December 2005 (UTC)

Why are all the other graphs going in the other direction? Is there even a single peer-reviewed scientific journal in the English language which publishes time series graphs from right to left? Dragons flight is certainly capable of producing canonical graphs, and I wonder why the prominently displayed images are the only ones with reversed x-axes.

As for net sink, the system used to be in equilibrium. I'm sure you won't mind if I change that to the corresponding "net source" description of artificial sources. —James S. 00:25, 29 December 2005 (UTC)

The red/blue distinction is between fossil fuel and total change, not natural and artificial. —James S. 00:32, 29 December 2005 (UTC)

[edit] Dipole

Someone needs to change the line about dipole moments. The problem is that it should either simply say that they cannot absorb light in the IR region, or get fairly technical to explain why. The solution is to probably reference a page or a stub which goes into why. I will think about writing this, however, if it is to be done, how can the top of the page be changed?

Dipoles goes beyond me - sounds like you should be fixing it! And... go edit your user page Josh! William M. Connolley 17:34, 16 January 2006 (UTC).

[edit] Global warming potential (again)

I have come a bit late to the issue of whether GWP should be here or not. I have been trying to improve the GWP page which lead me here. I noticed that the section here was now mainly on lifetimes of GHG so I renamed the section and added a small summary on GWP with a link to that page. I think this now works better. Feel free to disagree though..--NHSavage 21:31, 19 January 2006 (UTC)

I meant to remove all the GWP figures from the section on lifetimes. I have now done this. There is a more complete table of figure on GWP in that article

[edit] Role of WV

In a comment to [1], Andrew Lacis wrote some stuff that might be useful here one day, so I'll record it before I forget where I read it:

The first statement of the punching bag quote that the combined effect of terrestrial greenhouse gases is to warm the surface of the Earth by 33 C is basically correct. The second statement that 95% of this warming is produced by water vapor is clearly erroneous. Of the 33 C greenhouse effect, about 10-11 C is due to non-volatile greenhouse gases (i.e., gases that do not precipitate out from the atmosphere for the typical range of atmospheric temperatures). These non-volatile greenhouse gases are CO2, CH4, N2O, ozone, and CFCs. If the Earth's atmosphere were totally devoid of water vapor, these non-volatile GHGs would support a surface temparature 10-11 C warmer than the -18 C equilibrium baseline (which corresponds to no atmospheric greenhouse effect). The rest of the 33 C greenhouse effect is due to feedback effects of water vapor which is a reaction to the radiative forcing due to the non-volatile GHGs and accounts for roughly half of the 33 C greenhouse effect, and clouds which provide roughly 6-7 C. As a crude analogy, the non-volatile greenhouse gases serve as a "skeleton" upon which vater vapor (and cloud) feedbacks can operate. (A horse without a skeleton upon which its muscles can exert their force would be laying sprawled out flat on the ground.) Accordingly, if the non-volatile GHGs (CO2, CH4, N2O, O3, CFCs) were removed from the atmosphere, the atmospheric water vapor and clouds would precipitate from the atmosphere, and the resulting surface temperature would drop to the basline -18 C value. In this over-simplified model, the non-volatile greenhouse gases (CO2, CH4, N2O, O3, CFCs) provide an overall radiative forcing of about 11 C. The volatile component (water vapor and clouds) operate in teh current climate system with an effective multiplicative feedback factor of 3 which multiplies the applied 11 C forcing to generate the total 33 C terrestrial greenhouse effect.

An early discussion of radiative forcing and climate sensitivity is given by Hansen et al. 1984 (Climate sensitivity: Analysis of feedback mechanisms. Geophysical Monograph 29, Maurice Ewing Vol 5, AGU, 130-163). This paper compares the radiative forcings due to doubled CO2 and to a 2% increase in solar irradiance, and provides a quantitative analysis of feedback contributions due to water vapor, cloud, lapse rate, and surface albedo changes. The paper shows that while feedback efficiencies of the different feedback processes can be compared linearly, the feedbacks combine in a non-linear fashion. In the Hansen et al. 1984 paper, the radiative forcing due to doubled CO2 was 1.2-1.3 C, with the overall feedback factor in the 3-4 range to produce a 4 C global equilibrium warming. More recent results (Hansen et al. 2005, Earth's energy imbalance: Confirmation and implications. Science 308, 1431-1435) suggest that the total global feedback effect is in the 2.1-2.3 range giving a 2.7 C global warming for doubled CO2.

Because of overlapping absorption and saturation effects, the greenhouse contributions of individual contributors depend on their atmospheric context. For example, the radiative forcing due to doubled CO2 in the current atmospheric context is about 1.2-1.3 C (with no feedbacks operating). But removal of the current CO2 amount produces a cooling of more than -7 C (with no feedbacks operating). Analytic formulas that describe the amount of radiative forcing due to different concentrations of atmospheric CO2, CH4, N2O, and CFCs can be found in Hansen et al. 1988 (Global climate changes as forecast by GISS three-dimensional model. JGR 93, 9341-9364). Again, the (applied) radiative forcing is provided by changes in the non-volatile GHGs, aerosols, or solar irradiance. Water vapor, clouds, and snow-ice albedo change in response to the applied radiative forcing and account for the overall global feedback factor which acts to magnify the applied forcing to produce the eventual equilibrium change in global surface temperature

70.134.105.203 03:43, 8 June 2006 (UTC)-- This is great! This has cleared up a lot of the global warming issue for me. Any charts for water vapor concentrations for the globe similar to the charts for the other gases? --70.134.105.203 03:43, 8 June 2006 (UTC)

[edit] The MOPPIT Sattilite Images

Do these Sattilite images dipict the difference between the seasons, or the increase over a six month period?

E-Mail me an answer at:

donald_johnston@sympatico.ca

Click Me!

[edit] Heteronuclear diatomics

The article points out, correctly, that homonuclear diatmoic don't absorb in the IR. It doesn't point out that heteronuclear diatomics such as CO or HCl absorb IR. Should it? I don't think they are very important GHG's. William M. Connolley 16:04, 9 March 2006 (UTC)

[edit] Not GA yet

This page was nominated on Wikipedia:Good articles/Nominations, but I have not added it to the list, because although the article is generally very good, the intro needs work - it's extremely confusing to quote lots of percentages and then say you can't really quote percentages anyway. Worldtraveller 00:06, 12 March 2006 (UTC)

[edit] percentage of greenhouse effect

The major natural greenhouse gases are water vapor and clouds, which causes about 36-95% of the greenhouse effect on Earth (depending on who you ask); carbon dioxide, which causes between 3.6% and 26% (again, depending on who you ask); and ozone, which causes 0-7% (again, depending on the math)(note that it is not really possible to assert that such-and-such a gas causes a certain percentage of the greenhouse effect, because the influences of the various gases are not additive. The higher ends of the ranges quoted are for the gas alone; the lower end, for the gas counting overlaps).

Obviously this needs help. "Depending on who you ask" is not appropriate for an encyclopedia. How one ascribes the greenhouse affect to various gases (and even whether that question makes sense) is going to depend on how one defines the question. We need to either formulate the range of meanings in way that explains where they are coming from and what they mean to the reader or remove them entirely. Dragons flight 20:47, 2 June 2006 (UTC)

Ah, sorry, I reverted that edit as silly before reading your more thoughtful reply William M. Connolley 21:12, 2 June 2006 (UTC)

Actually, the reverted version still has ranges that are not well explained in the text. We need to think about what the reader wants to know when he asks "How important is X to the greenhouse effect?". Dragons flight 21:21, 2 June 2006 (UTC)

Some of the numbers are sourced on greenhouse effect (which has just suffered another of the periodic additions of the 95% nonsense). Sourcing the numbers properly would be good. Answering your question depends a lot on the context; in terms of real life, people asking that question will tend to mean, "is it true wot these people having been telling me, that WV is a more important GHG than CO2"? in which case they need to find the answer, No. William M. Connolley 21:46, 2 June 2006 (UTC)

"No"? I think the answer needs to be more along the lines of "Yes, but..." myself. Dragons flight 21:59, 2 June 2006 (UTC)

Thats where the context comes in. Scientifically, the answer is yes, if by "important" you mean "causes more of the GHE". But in context, important always elides into in-the-human-context, so the answer is No, but... William M. Connolley 22:13, 2 June 2006 (UTC)

70.134.105.203 03:49, 8 June 2006 (UTC)-- As a layperson the large ranges confuse me more than clarify. Unless something more meaning full can be said, the ranges should probably just be removed from the article. The first question that arises when seeing ranges like that is how any useful climate model could be made. I didn’t see anything in the climate model articles that cleared this up. 70.134.105.203

Ah, then you have misunderstood. The ranges are not a problem for the GCMs at all. The ranges essentially come as *output* from the models, not input William M. Connolley 08:52, 8 June 2006 (UTC)

70.134.105.203This would be an excellent clarification to the article, something like “According to climate models the major natural greenhouse gases are water vapor, which causes about 36-70% … “

I was unable to find these numbers on [Global climate model] , [climate model] so I suppose this is the place for the discussion. As I read the article, greenhouse gases were know to absorb (IR) energy from the sun even before climate models, however climate models demonstrate that the cumulative interplay of the anthropogenic increase in these gases do indeed cause an overall increase in global mean temperature. However, as the ranges demonstrate the climate models don’t provide a certainty on the magnitude of the increase. Have I misunderstood? 70.134.105.203 22:52, 8 June 2006 (UTC)

[edit] ‘water vapor can not be controlled by humans’ ?

I was under the impression that for every molecule of CO2 produced combusting petroleum products, a molecule of H2O is produced, however that no H2O is produced combusting coal. I was also under the impression that petroleum products accounted for about only 25% of combustion derived CO2 and coal most of the rest, however the chart seems to suggest otherwise. May be the chemical formulas would be helpful to the article.

Does Michael Mann mean to say that water vapor can not significantly be controlled by humans? If so, does not that make the “Thus water vapor acts as a positive feedback (but not a runaway feedback) to the forcing provided by human-released greenhouse gases such as CO2.” discussion insignificant also?

The point you are missing is that excess H2O precipitates rapidly. Co2 doesn't William M. Connolley 17:19, 5 June 2006 (UTC)

[edit] Greenhouses

I am intrigued by the assertion that the mechanism for greenhouse gas warming is not the one which warms greenhouses.

My understanding of greenhouses is that the glass lets in visible light from the sun. This is then absorbed inside the greenhouse by the contents, which warm up. The contents then emit infra red light - but this is not transmitted back through the glass, which is opaque to IR light, trapping the energy inside the greenhouse and keeping it warm. This is analagous to greenhouse gases - visible light goes in, gets absorbed by the surface and re-emited as IR - but some frequencies of IR are not transmitted back out because they are absorbed by the greenhouse gases and radiated in all directions. Stephen B Streater 18:29, 28 June 2006 (UTC)

Read the greenhouse effect page (and the extensive talk page discussion, poss the archives) William M. Connolley 19:10, 28 June 2006 (UTC)

Thanks. I've added a wikilink in to help the next guy. Stephen B Streater 21:37, 28 June 2006 (UTC)

[edit] General cleanup

I've made a number of edits to remove redundant bits of text, clean up some grammatical slips and so on.

I've also changed the description of the greenhouse effect at the top of the page to one that is more accurate scientifically, though maybe too intricate for a general audience. Since this article is about GHGs as such and not the greenhouse effect, I'm sort of inclined to remove this bit altogether and just have a pointer to the main GE article. Raymond Arritt 04:34, 13 August 2006 (UTC)

Hi! I had a part in writing this bit. The most significant thing for me was the discovery outlined in the last sentence: The term is something of a misnomer, as this process is not the primary mechanism that warms greenhouses., so I'd be keener to keep this last sentence than the rest which is, as you point out, explained in its own article; a wikilink could suffice here. Stephen B Streater 17:18, 13 August 2006 (UTC)

[edit] Units for radiative forcing

Hi, I'm a bit confused by W/m² as units for radiative forcing - surely there should be a ppm component to this thing as well? Or some such? Clarification is not to be found in radiative forcing, either. Graft 19:13, 24 October 2006 (UTC)

No... the rad forcing is... well, the 1.46 W/m2 for CO2 is for the 87ppm increase over preindustrial. You could perhaps express it as 1.46/87 W/m2/ppm but it wouldn't be that accurate William M. Connolley 19:46, 24 October 2006 (UTC)

Ah. So, there's an observed forcing for the increase that has actually transpired, 1.46 w/m^2 - but is there some theoretical number, here, i.e., the general potential forcing of CO2? Cuz this is how I read that table. To me it says: given equal quantities of CO2 and methane, methane results in far less forcing than CO2 does. But this is probably not what it's saying. It's actually apportioning the amount of observed forcing attributable to various greenhouse gases. Right? So where does one find the former quantities? Graft 19:50, 2 November 2006 (UTC)

1.46 is calculated, not observed. And no, the methane forcing is smaller, but thats in total - per molecule, methane is stronger. Sorry - I though all this was obvious William M. Connolley 20:40, 2 November 2006 (UTC)

Calculated, observed, same difference - my point is, why don't we have a table of per-molecule forcing? Surely this is relevant? As to it being obvious, maybe it should be, but it could clearly be made more so. Graft 16:56, 3 November 2006 (UTC)

To be fair, since the effects are not linear (in fact logarithmic in many cases) and different gases interfere with each other through overlapping absorption bands, it isn't a trivial matter to construct such a table. Really, such a comparison is most sensibly limited to discussing the forcing associated with small changes in gases relative to the modern atmosphere. Dragons flight 23:06, 3 November 2006 (UTC)

The Expert syndrome: Knowing so much that no one else can understand a word you say. Though if there is a good table on the differential impact of various greenhouse gases relative to the modern atmosphere, I'd love to see it. For some reason, climatologists don't seem to think about greenhouse gases in the same way as physicists. Dragons flight 21:07, 2 November 2006 (UTC)

[edit] Emissions by Country

The article is quite graph-heavy already, but can anyone find an appropriate place to add this graph (from the Pollution article)?

There seems to be very little in this article (or elsewhere on Wikipedia, unless I've missed it) regarding the differing levels of greenhouse gas emissions between countries, or the differences in growth rates. -84.68.87.155 23:42, 27 October 2006 (UTC)

Go to http://www.eia.doe.gov/emeu/iea/carbon.html for a heap of countries and annual rates of emission.

Hey! How come the countries of Australia and New Zealand got lumped together in the plot?

[edit] Classroom science experiment?

Can the page suggest or link to a classroom science experiment to test the insulating properties of greenhouse gasses? For example, is there a simple test where the rate of cooling of a beaker of hot water can be measured in a standard atmosphere and then in a carbon dioxide enriched atmosphere? —The preceding unsigned comment was added by 128.250.6.243 (talk • contribs) 08:21, 5 November 2006.

Hmm... How 'bout two bell jars, two beakers of hot water, two thermometers, a source of CO2 and test. Maybe add manometers and a means of equillizing the pressure of the two bell jars as CO2 is added to one and ... then publish your findings and report back here :-)

Vsmith 14:50, 5 November 2006 (UTC)

Given that the infrared optical depth in the atmosphere is is not huge, I fear you'd need a quite high concentration of CO2 to get a measurable effect on laboratory scales (at least with classroom level equipment). Dragons flight 09:42, 6 November 2006 (UTC)

With appropriate simplifying assumptions, can a basic model be posed to predict the rate of cooling in the two scenarios?

Would a visualisation be possible? Perhaps an infrared camera could be used to observe a bar heater through a partitioned tank that has a standard atmosphere on one side and CO2 on the other.

Right, now to find some scientists that can help out! Would any science teacher and their class of budding scientists be interested in testing the hypothesis that CO2 acts as a greenhouse gas?

[edit] Greenhouse Gases - human factor

The media is making the direct link between human activity, greenhouse gases, and climate change, but can anyone out there provide a scientific link?

There is little dispute that atmospheric carbon dioxide has increased in the past century, but is human consumption of fossil fuel responsible? There is a lot of talk out there about how many tons of carbon dioxide each car and each household spews out, and how the oceans and atmosphere are at breaking point. Sure it sounds impressive, but lets look at the other side of the coin and do the maths: for each person on this plant there is a volume of ocean water (the main carbon dioxide sink) equal to 2.8 billion times each person’s volume; for each person on this planet there is a volume of atmosphere in a 5km layer (where 50% of the oxygen exists) equal to 5.3 billion times each person’s volume. That’s a lot of dilution for each of us! Even the most toxic substance is not considered by science to be potent in these minute concentrations. Wikipedia puts a human dimension on parts per billion which it equates to a drop of ink in an Olympic pool! Can our puny effect be so devastating to the plant?

Also there does not seem to be a way to compare the increase in annual CO2 emissions [World Carbon Dioxide Emissions from the Consumption and Flaring of Fossil Fuels (Million Metric Tons of Carbon Dioxide), 1980-2004] with atmospheric buildup of CO2 which is measured in ppm. For example, we know that from 1980 to 2004 total world emissions increased from 18.3 million metric tons to 27.0 million (47%), and we know that concentration increased from 330ppm to 377ppm (17%) - but what does this equate to in metric tons? Perhaps someone could find or create a conversion factor using molecular weights to convert CO2 ppm concentration into total metric tons of CO2 in the entire atmosphere. This would be useful since the measurement standard of all emissions is metric tons. A layman could then directly compare past data of CO2 annual human emission with the added load in the atmosphere. Each person could also see the relevance of the amount CO2 he was adding to/saving by his lifestyle compared to the total pool of CO2 in the 5.3 billion volumes of atmosphere of each person.

Could someone with relevant expertise verify my calculations and create an entry about the dimensions of the human factor in climate change?

EARTH SIZE

Volume sphere 1.333piR2 

Diameter =12756km/2 = 6378 radius = 1.086776 x 10 12th km3

 5km thick atmosphere (50% of all oxygen) = 6383km =1.089338 12th km3

 Difference = 2,560,376,300 km3 for 6 billion people = 0.4267 km3 per person

Average person 80kg (80liters) = 5.3 billion times each person’s volume

OCEAN VOLUME

Volume total of world’s oceans (Wikipedia) = 1.37 x 10 18th m3

for 6 billion people = .2283 km3 per person

Average person 80kg (.08m3) = 2.8 billion times each person’s volume

please go away and read Chapter 3 of IPCC TAR and then come back if you still have any questions.--NHSavage 21:59, 7 November 2006 (UTC)