2010-10-04 01:20:45Basic rebuttal #66: CO2 has a short residence time updated w.graphic



A common point of confusion for climate change skeptics is the difference between the span of time a given molecule of C02 will remain in the air versus the time needed for the total amount of extra C02 we're adding to the air to be removed. While the time a particular molecule of C02 remains in the air may be short, because C02 tends to move back and forth from the air to the ocean, the time required for excess C02 in the air to absorbed is much longer.


Whether they're byproducts of fossil fuel combustion or part of the natural carbon cycle, individual molecules of CO2 remain in the atmosphere for a brief period, about 5 years. In most cases when a molecule of CO2 leaves the atmosphere it's simply swapping places with one in the ocean, or is being recycled through biological processes. Thus, the warming potential of CO2 effectively has very little to do with the history of a particular molecule of CO2. 

What governs the long term warming potential of C02 liberated from fossil fuel combustion is how we change the proportion of CO2 in the air, not how long any given molecule of C02 remains in the air.  While C02 is involved in the life-cycle of plants and animals, on the time scale we're concerned with C02 is mostly removed by absorption into the ocean, a slow process.

With enough time most extra C02 will be soaked up by the ocean, which has a large capacity to store this gas. The problem is, a given amount of sea water can only accept a certain amount of C02. Once that limit has been reached, the water is said to be "saturated" and releases C02 at nearly the same rate it's absorbed. It's easy to see that even if an individual C02 molecule tends to make its way into the ocean after just 5 years, that's of little use in reducing the total amount of C02 in the air if the ocean is simply churning C02 molecules, releasing C02 as nearly as fast as it is absorbed.



Flow of anthropogenic CO2 into atmosphere, into and through ocean.

Once the surface of the ocean is saturated with C02, in order for it to stash away more C02 water near the surface must be replenished with less-saturated water from below. Exchange of water from the top of the ocean with water from below takes a long time, hundreds of years, leaving us in the situation where we're adding C02 to the air faster than it can be removed.  

Put another way, imagining we can predict the effects of C02 in the air by tracking particular C02 molecules is akin to thinking we can track our bank balances by recording the serial numbers of currency or checks we deposit into our bank accounts. These identities have nothing to do with our bank balance, rather it's the net amount of money entering or leaving our account that determines our financial health. 


2010-10-04 02:07:12language level still too sophisticated



As I keep ranting, for Basic-level articles I believe we need to try to achieve a reading-index level of 8th-grade: shorter (and more basic) words, shorter sentences.

I invite you to look at:


I know it's painful to do this: I'm working on another Basic-level as well, and I expect to grit my teeth. But I think we really need to make the effort.

I'm going to re-work just one paragraph of the above to show you what I'm thinking about:

"Individual molecules of CO2 have a short residence time in the atmosphere, about 5 years. However, in most cases when a molecule of CO2 leaves the atmosphere it is simply swapping places with one in the ocean, or is simply being recycled through biological processes. Thus, the warming potential of CO2 effectively has very little to do with the history of a particular molecule of C02."


"An individual molecule of CO2 doesn't stick around very long in the atmosphere - about 5 years. But mostly when it does leave, it is only changing places with another CO2 molecule in the ocean. Or maybe become part of some plant or animal. So that 5-year "residence time" for a single molecule doesn't mean very much: what matters is how long it takes to move out the bulk numbers of CO2 molecules, to reduce the concentration in the atmosphere. And that's about 1000 years, because the CO2 has to be incorporated into rock (weathering), or be absorbed into the shells of microscopic life and buried deeply in the oceans."


I think that's easier to read.

And I imagine somebody else can take it down a notch or two further.

We're competing with with the likes of the Foes of Science website, ClimateChange101: Who's ever is easier to understand will have an advantage. We start out with a disadvantage, because it's our duty to try to be faithful to the science.

2010-10-04 04:46:59


I hear, sympathize and to a certain extent will even obey, Neal! 

I'll point out, the "hard" ideas "molecule,"  "concentration," "microscopic," "weathering" and "residence time" are still there. We can get rid of those, but the item will puff up in length and then people will complain about "too long."

"Molecules" --> "substances made of different kinds of atoms"

"Concentration" --> "the amount of something versus everything else in a given volume or mass"

"microscopic" --> "too small for the eye to see"


I'm actually planning on using a money analogy.  


2010-10-04 05:18:27



Unfortunately, there is a practical limit. There is an unavoidable trade-off between a certain sophistication in vocabulary and wordiness in phrasing.

I think a good direction to go for is what gives a more vivid or concrete impression.

- "Weathering", although a technical term, has a homely feel to it; not a word that should strain anyone.

- "Concentration": It's hard to see that replacing it by the long phrase really helps.

- "Molecules": I think we're stuck with this. We're basically hiding a lot of quantum physics behind this word!

- "Residence time": But notice than when I use it in the 2nd version, it comes after the essential idea has already been explained: how long the molecule sticks around. The understanding doesn't depend on being comfortable with the word. So I hope it has less impact. The only reason I use it is that I think I've seen the term used by skeptics: So I want to reclaim the word for our side.

Also note that I have about 6 sentences to your 3, with some increase in the number of words (but not double). So the words/sentence has definitely dropped. And the syllable/word ratio has definitely dropped.

I think analogies can be very helpful, if they add to the vividness. In my next article, I'm going to use analogies between CO2 and H20 molecules blocking IR photons and military forces and hunter/gatherers. Some people might find the military comparison politically incorrect; if I hear of anything better, I'll be happy to use it. 




2010-10-04 06:02:16

Neal, thanks, this is a continuing process of education for me. Last night I managed to amputate a lot of words from the "arctic ice cycle" bit even though a few days ago I was sure it was a model of economy. Probably my key issue is words/sentence, thanks for the reminder. 
2010-10-04 09:37:49


The source of confusion is the diferent definitions of and names given to these characteristic times. Indeed, the residence time is short, as you correctly say. The adjustment time (AR4 definition) or response time is much longer and it's not unique. This is what matter for the warming potential, as again you say but do not make the distinction explicit.

2010-10-04 16:33:39



It's a trade-off: Do we introduce all these different terms for time periods, or do we find other ways of making the point? At least when we bring in new terms, we need to be aware that we're imposing a "cost" on the reader: and if the total cost is too high, the reader's not going to get the article.


2010-10-04 18:02:40



I think it is necessary to distinguish between the two. Indeed, Doug did it without naming the second kind of lifetime. People need to distinguish between the two because this is the only way to "protect" themselves from the claim we're trying to rebut.  Ideally, when reading about "residence time is  short" they should think "it doesn't matter, it's the response time that matters".

2010-10-05 00:44:32

Thanks guys and I think I can sort that without ballooning the length or causing people to collapse from mental exhaustion.
2010-10-05 00:56:34



"Ideally, when reading about 'residence time is short' they should think 'it doesn't matter, it's the response time that matters'."


In your dreams, my friend!

2010-10-05 03:28:33


Revised to incorporate Riccardo's suggestion, directly.

This could use a simple illustration. Does anybody have a suggestion?

2010-10-05 07:59:09


Ideally In my dreams ...  :)

When it's time for creative work i can't be of any help. :(

2010-10-05 08:09:52


Hmm. I spent some time looking at other sites to see what's the popular flavor of fabulous interpretation of this matter.

It seems that skeptics don't believe the turnover rate of the oceans is sufficiently proven as to demonstrate that upper layers will become saturated quickly. I'm not sure I want to touch this at this level because discussing it will require dragging in ocean circulation in more depth (hah). 


2010-10-06 07:25:31
Shirley Pulawski

I agree with the comments about simplification of the language. I find myself speaking with the loftier scientific terms I've learned to use regularly, and have noticed some eyes glazing over when I'm around non-geologists, unless they're very educated and have strong vocabulary skills. That isn't the average public, and yes, it can be really tough to lessen the language. Many of these "big words" are used to replace a paragraph of explanations. Maybe that is the way to approach the technical sounding words - can it be replaced with another simpler word or sentence, or would it take an entire paragraph to explain? If it does, then it might be worth asking how important it is to include. 

 A small point... a lot of the 'O's in CO2 are actually zeros in the original print, a pet peeve I'm guilty of unwittingly doing myself. Why did they put those two keys so close together, anyway? 

2010-10-06 08:56:27



I don't get your/their point: If the turnover rate of the ocean is slower than expected, that just reduces the rate of permanent absorption of the CO2, right? So that would mean the response time is even greater.

Whereas if CO2 saturation of the ocean is NOT the gating step, you're left with removal via the biological pump: capture of CO2 in the shells of foraminafera, and their deep-sea burials. 

So any doubts about rates of saturation should incline one towards being more pessimistic about getting rid of "extra" CO2.

Am I missing your point?



2010-10-06 08:59:48

Neal I'm in a fog of irremediable sleep deprivation. Would you mind quoting the problem phrase?
2010-10-06 09:16:05


"It seems that skeptics don't believe the turnover rate of the oceans is sufficiently proven as to demonstrate that upper layers will become saturated quickly. I'm not sure I want to touch this at this level because discussing it will require dragging in ocean circulation in more depth (hah)."

If the turnover rate of the oceans is slower, the response time will be longer => more warming to be concerned about.

2010-10-06 11:38:26


Oh, ok, not part of the article.

Yes, exactly, it's the usual situation where the skepticism dissolves as the pH of reality is lowered to neutrality. Climate skeptics thrive best in a highly (de)base(d) environment.

2010-10-06 17:12:27


Intriguingly, I picked one of the papers out at random that the Lawrence Solomon skeptical argument 'referenced' - keeling's 1973 paper "Atmospheric carbon dioxide variations at Mauna Loa Observatory, Hawaii."

According to Solomon's graph, that paper stated that the residence time of CO2 was about 8 years. I couldn't find anything in the paper about that, but coincidently the length of time of Keeling's observations was 8 years (1964-1971)

unless i missed something - i did skim.

2010-10-06 20:22:55
Paul D


I think the article repeats the same ideas to much and doesn't get to the point very quickly.

Again diagrams and even animation could reduce the need for so much text.

But even without graphics, the text could be simplified a great deal.

2010-10-07 00:00:19


I could dump the part about the biome. Show of hands?

Edit: biome focus ruthlessly killed. Sob.  

Candidate graphics for adaptation (mostly cribbed from IPCC...):







Early work



Declining sink 


Early synthesis






2010-10-09 06:07:23
Paul D


I like the last graphic, but it is probably to detailed for the article.

Are you planning to create your own version?

2010-10-09 06:17:10

Yeah, I've looked at a bunch of graphics and in general they're too general, particularly if we're trying to keep the focus on ocean recirculation of C02. 
2010-10-15 07:42:02

Ping. Suggestions for graphic welcome; point is to keep it as simple as possible, in keeping w/Neal's remarks.