Naked Science Forum
Life Sciences => The Environment => Topic started by: Gile na Gile on 17/12/2009 15:05:33
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I find it hard to believe that every carbon molecule emitted at ground level eventually winds itself up to the atmosphere and nestles there. Is the carbon lighter than air or something? I mean, it has a mass heavier than air doesn't it? You would imagine the wind would blow most of it into land areas where it would become absorbed. Also, can we not simply send dissolvable packets of some chemical compound into the skies so that it will break up the chemical bonds of the carbon molecule thereby dissipating the effects of the greenhouse effect?
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You are right that every molecule of Carbon dioxide does not remain in the atmosphere for ever.
The carbon cycle is the conceptual model of how carbon moves around - it does not matter if this is carbon dioxide, methane or more complicated carbon based molecules.
http://maps.grida.no/go/graphic/carbon_cycle (http://maps.grida.no/go/graphic/carbon_cycle)
As the diagram shows, when CO2 is released to the atmosphere - typically by burning fossil fuel, but also by other methods such as agriculture, land use change, cement production etc. it remains their for a variable period, but overall it is thought to remain there for 50 to 200 years before being returning to the cycle.
CO2 is a very stable molecule and it difficult to breakdown, so I am afraid that a chemical approach would probably not work. Current thought is that it would be more efficient to catch the CO2 before it reaches the atmosphere. It is thought that the collected CO2 could be buried in old oil and gas fields.
typos corrected
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Thanks for the reply Mazurka.
I'm familiar with carbon capture and storage and the carbon cycle. I was more prompted by a phrase I came across in a science journal which referred to a thing called an "air fraction ratio" which was understood as the amount of carbon that would "blow away" before it reached the atmosphere. I'm curious as to whether anyone had heard of such a thing. However, I did not realise that carbon was inherently difficult to "disassemble", so my thanks again. Although, it does make a lot of sense since you often hear of the suitability of carbon as a molecule that forms the basis of life precisely because of it's durability.
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It is often hard to know what level to pitch answers on here...
I must admit that I have never heard of air fraction ratio - and a quick google later and i am still non the wiser! I will ask some chums on a weather forum i periodically frequent...
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"Blown away before it reaches the atmosphere"??
Sounds like rubbish to me. The wind is part of the atmosphere. Any CO2 gas that forms is part of the atmosphere. Where would it "blow" to? Can you remember what journal you read it in, as your current description doesn't give me enough to go on...
You refer to "carbon", pure carbon forms either diamond or graphite, both solids. It is only when carbon (containing) materials are burnt to from carbon dioxide gas (or converted into methane), and therefore form gases in the atmposphere, that the "greenhouse" effect results. If you know about the carbon cycle you presumably know that but others may not and in any case the lack of precision makes discussion almost impossible.
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"Blown away before it reaches the atmosphere"??
Sounds like rubbish to me. The wind is part of the atmosphere. Any CO2 gas that forms is part of the atmosphere. Where would it "blow" to? Can you remember what journal you read it in, as your current description doesn't give me enough to go on...
You refer to "carbon", pure carbon forms either diamond or graphite, both solids. It is only when carbon (containing) materials are burnt to from carbon dioxide gas (or converted into methane), and therefore form gases in the atmposphere, that the "greenhouse" effect results. If you know about the carbon cycle you presumably know that but others may not and in any case the lack of precision makes discussion almost impossible.
I can't recall the journal or author - though he was a ph.d writing in an Irish environmental magazine - I read an awful lot of articles and I'm not in the habit of memorising names and publications of everything that comes before me. Fortunately, I do recall the context. The article was attempting to determine how much the Global Warming Potential (GWP) of methane being released from the Western Siberian permafrost would be effected by a host of miscellaneous factors. It detailed the difference in GWP between methane and carbon, the levels of oxidisation upon release, albedo effect etc. One of the factors detailed by our writer was this "air fraction ratio", a concept which was neither footnoted nor elaborated upon and which I took to be a well known reference point for scientists in this field. Evidently, I am mistaken; it does not appear to be well known - I asked a friend of mine who was doing an MA in environmental sciences and he hadn't heard of it either so it is certainly arcane, but unlikely to be "rubbish". When I read it at first I took it to mean that in some sense the GWP of the methane was diminished somehow in it's journey through the atmosphere; through it's "fraction" in the air - is this possible, I don't know, I am not a scientist.
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Ah! I think I see what is meant.
All the gases, being gases, go into the atmosphere. But they may either go into the atmosphere in the vicinity of the emission, or they may be blown away into some other bit of the atmosphere.
I would guess that "air fraction ratio" is a intended to mean something a bit like partial pressure... perhaps refering to the proportion of the air within a certain distance of the emission which is composed of methane.
I can imagine circumstances in which relatively still condiotions, resulting of poor mixing of the released methane with the rest of the atmosphere, a significantly enhanced region of methane gas might occur over the (melting) permafrost, enhancing the warming of that particular area (rather than spreading out and enhancing the warming of the world in general). Since warming in the area of the permafropst and its trapped methae is particularly damaging in terms of the resultant vicious spiral of further methane release, that might be the sort of thing that it could be interesting and important to model if one were (as I very decidedly am not, hence I'm guessing wildly) a climate scientist.
Does that make sense in terms of what you remember of the rest of the article?
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One of the defining properties of gases is that they mix.
That includes carbon dioxide and air.
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OCEAN CARBON CYCLE
"Of all the carbon dioxide (CO2) emitted into the atmosphere, one quarter is taken up by land plants, another quarter by the oceans." http://harvardmagazine.com/2002/11/the-ocean-carbon-cycle.html
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BC- yes, but it's a process which occurs over a period of time, so it's conceivable that where mixing has not yet fully occured there might be interesting consequences. Or not. Or I may be wholly wrong about what the paper the original poster recalls is driving at...
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And.. litespeed. What is your post intended to contribute to the discussion in hand? Would you like to elaborate? You're getting a bit of a reputation for attempting to derail threads...
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rosy - You wrote: "What is your post intended to contribute to the discussion in hand? Would you like to elaborate? You're getting a bit of a reputation for attempting to derail threads..."
The entire thread is a discussion of what happens to carbon molecules released to the atmosphere. My post is entirely on topic. Specifically, it accounts for fully one half of all emitted CO2. No one else even mentioned the Oceanic Carbon Cycle. It is relevant because it reduces by half the effect atmospheric mixing might have.
Incidentally, 'Blown away before it reaches the atmosphere' is a contradiction in terms. Specifically, there is not one single smokestack high enough to emit CO2 into outer space. ALL CO2 emitted by smoke stacks gets blown away by, and mixed with, the atmosphere.
However, the current cutting-edge rage is Carbon Sequestration. In this scheme, CO2 is not sent up smokestacks to be blown away by the wind. Instead, it is in some way gathered up and 'sequesterred' from the atmosphere. I don't know. Maybe they pump back down old oil wells or something. Its something that can be done.
Further, it could be the most logical way to reduce CO2 in the atmosphere if GW actually turns out to be a bad thing. Other plans to cool the planet are simple to implement and are reversible, if they turn out badly. Piping So2 into the stratosphere like a volcano would do it. I think even Obama discussed spreading iron filings in the pacific to promote algae growth; sequestering CO2 the old fashioned way by sinking huge amounts of the stuff back to the sea bed as the algae dies off.
PS: Something like this has already been done with 'acid rain' SO2. SO2 scrubbers are standard equipment, I believe, in US power plants. Originally it was argued against as expensive. However, the produce of the scrubbers, whatever it is, turns out to have a market value itself. If I am not mistaken it is used in some way or another in the paving industry.
This is one reason I object to all the Chicken Little THE SKY IS FALLING, THE SKY IS FALLING! If time shows we really do need to reduce CO2 it can be done through sequestration. And if the climate needs to be cooled that can also be accomplished through various technologies at the same time. Just don't tell the Chinese about it. They are not interested.