Aug 04 2008
Trends in Atmospheric CO2 Trends
Talking about the concentration of CO2 in the atmosphere seems to be cool this week. [1], [2], [3] It was brought up at one of the sites that the increase we’ve since the beginning of the Mauna Loa record may not be anthropogenic. First, I’ll outline using simply cartoons why it has to be anthropogenic.
Consider the amount of carbon dioxide in the atmosphere prior to the industrial revolution. Assume that it is in a steady-state equilibrium, and that all sources and sinks are natural. Use a bathtub as an analogy. If I add 3 buckets of water to the tub per hour, then the amount of water in the tub will steadily increase. However, if suddenly a friend starts taking water out of the tub at the same rate I add it, the water will retain the same level.
Prior to the industrial revolution, the primary sources and sinks of CO2 into the atmospheric bathtub were natural, and they were balanced such that there remained a trace amount of CO2 (about 280 parts per million by volume). This is idealized in the cartoon below.
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The amount of carbon dioxide added to the atmosphere (Sp; source, pre-industrial) equal the amount exiting the atmospheric reservoir (Qp). Therefore, the amount of CO2 in the reservoir remains constant. However, when humans started burning thing (particularly fossil fuels) they added another source into the reservoir.
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In addition to the natural source of CO2, I’ve added another arrow that represents the rate at which humans are adding CO2. The exact rate is inconsequential for this discussion, but as long as there is an extra source of CO2 into the reservoir, the quantity of CO2 in the reservoir will increase if the rate of CO2 exiting the reservoir through the sinks remains the same.
Let’s look at how much CO2 there is in the atmosphere.
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It should be clear that it is increasing. The difference colored lines indicate the different months of the year. In a recent post, Anthony Watts noted that the CO2 concentration in July 2008 was less than the concentration in January 2008, and that was the first time the Mauna Loa CO2 has exhibited that behavior. I’m not exactly sure what that means, other than the July value maybe low or the January value may be high. There is a yearly cycle to the concentration of CO2, so comparing absolute values between months is odd.
Instead, I’ll look at how the yearly changes in CO2 have changed throughout the last 50 years. Note that the title of the post refers to trends. No actual trends were computed, nor harmed, during the making of this post. What I did was simply subtract one months value from the previous years value, to give an indication how much change we can expect during a month.
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The yearly changes in concentration are roughly Gaussian with a mean of 1.41 ppmv/yr. The July 2008 CO2 concentration was 384.93 ppmv. So if the concentration was increasing linearly with time, in July of next year one would expect it to be 384.93 + 1.41 ppmv (+/- 0.71). But what if the concentration of CO2 is not increasing at a linear rate?
I used the same analysis as above - looking at how monthly values of CO2 concentrations change from one year to the next, but instead of displaying them in one histogram, I sorted them by decade.
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One can clearly see that the concentration of CO2 in one month compared to the previous year has accelerated. In the 1960s, the mean value was only 0.88 ppm/yr, but the mean value for the 2000s is double that at 1.92 ppm/yr. I’ve plotted the histograms vertically and on the same scales so that comparisons would be easier.
While these histograms do not depict actual trends, they do show that CO2 is accumulating in the atmosphere at an increasing rate.
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24 Responses to “Trends in Atmospheric CO2 Trends”
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The cat looks like it would prefer not being in the tub while you are conducting your demonstration!! 8>)
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XYZ — you should read this guy named Gary at desmogblog.com — he’s an AGW-denier-bot who spells really, really badly. I wonder what that means for the AGW-denier side. Actually, let me answer: it means nothing.
XYZ,
I’ve followed TCO for some time. He is a “lukewarmer” I think. He just gets really frustrated when the guys on the denial side get so screwed up and are so easily skewered.
TCO, you retired for a while to read and ponder. Welcome back.
The signal to noise ratio on Steve’s blog is really low. I just checked out his latest post and there’s literally 4 paragraphs about “how he decided to look at something” before the beginning of any discussion of a phenomena itself. Some drive by “team snark” (much of it tangential to even his main point) mixed in as well, of course. It’s such a dreary, preaching to the choir, hothouse flower type of thing.
If he can’t or won’t distill his points down to real papers (at least white papers) then it’s NOT WORTH looking at the stuff. I mean it certainly shows a disdain for any audience that he does not do so. And it shows sloppy thinking on his own part. Mixed in of course is a bunch of precious Latin and other pompous, brittle language.
The whole thing blows, because the issues are actually interesting. But following this crap for 3 years is a waste of time. This BLOWS.
I’m gonna go off and read some sports blogs or Volokh.com or Steve Pinker or something like that. Something with a point and with real analysis.
While I already knew that Watts should basically stick to taking pictures of surface stations and out of analysis, one thing you wrote really sticks with me….
“Assume that it is in a steady-state equilibrium, and that all sources and sinks are natural.”
While I don’t know if we can make this assumption in real life with absolute certainty, I do know there was absolutely no point to the rest of your post after that. Your assumptions proved your point, and without them, you have proven nothing. So any analysis after your assumption was basically superfluous because the qualities you described are inherint to “a steady-state equilibrium” of atmospheric CO2.
Other than that, I agree with TCO and lets get back to something more, um, proactivly analytical and not a reply/rebuttal to someone else’s crap.
Go to a good dictionary and look up the words “empirical” and “evidence”.
What Wade said.
I’ve seen this Bathtub “argument” several times in recent years. The assumption provides the answer. It’s like you assume 2+2=4 and then “prove” 2+2=4.
Where is the validation for the assumption? Consider for example the estimates for the magnitudes of the natural carbon flows and then compare those with the estimates for the human contributions. Tiny fractions of percentages.
The gas transfers between the atmosphere and the oceans are at best WAGs. The gas transfer coefficients are basically unknown due to the extreme complexity of the thermal-hydrodynamic states of the atmosphere-ocean interface. Turbulence is only a small part of the problem, and we know how big a problem turbulence is.
CO2 sources/sinks are indeed difficult to track, but we have the ice cores as evidence that the increase we’re seeing now is something other than natural. Is it possible that some natural source or sink has gone off the rails for the first time in multiple interglacials and is a major component in the present rise? In principle, sure, but there’s the problem of the complete lack of any evidence for such a thing, to say nothing of a hypothesis about how it would be possible.
dhogaza,
What does “empirical” and “evidence” have to do with the logic of this post?
Do you believe in *infinity*? If so, prove it with empirical evidence. Now try *zero*.
You realize almost all post-high-school mathematics is done using zero emperical evidence? Look up “proof by induction” sometime. And as far as I know, mathematics is still a science, isn’t it?
In Atmoz case, his assumption doesn’t allow for non-natural increases in CO2. Therefore any increase is unnatural because it invalidates the assumption. Since it’s unnatural, it “follows” (loosely) that it must be anthropogenic. QEDish.
Wikipedia on steady state: “a steady state is a situation in which all state variables are constant in spite of ongoing processes that strive to change them”
Wikipedia on chemical equilibrium: “in a system at chemical equilibrium, the net reaction rate is zero…”
For those that say they wanted more sciency topics, I point you to yesterdays post, that like most of the more technical things I’ve posted, has received a less than good response. If readers want a certain type of post, show that by responding with your comments. A simple “nice post” is enough to let me know that you enjoyed reading it. However, since those types of post generally have lower readership, and less comments, I’ve interpreted that to mean that people aren’t interested in them. And those are the posts that take longer to write, so I don’t want to waste my time on them if nobody reads or understands them. I appreciate the comments, but let me know what you would be interested in reading, not what doesn’t interest you.
Thanks.
Wade,
My model did allow for increases in natural sources. I had two other cartoons, but decided not to include them for simplicity. It’s just that we know that non-natural sources of CO2 have increased from the combustion of fossil fuels. If you don’t think that CO2 is a byproduct of combustion, then there’s not much I can say to make you think otherwise.
Atmoz, I think I left out my personal feelings about the topic when trying to point out I didn’t like the M.O. of the article, that being that I totally agree with your final conclusion, just not every part of the method.
I’m very particular when assumptions are used because…well…they’re assumptions. Regardless, I agree that the the drastic CO2 increase is anthropogenic from combustion, I just didn’t like the assumption (nitpicky, I know).
You may enjoy this paper on emissions, particulates, and combustion with some meteorological anomolies: http://www.wvdep.org/Docs/15050_BlueHaze-May2008.pdf
Maybe you can shed a little light on how a coal plant can massively outweigh even large chem plants in terms of emissions.
Isn’t there some line about lawyers straining at gnats and swallowing camels?
We know that during the past few glacial/interglacial cycles, CO2 never rose above 300 ppmv. We also know that it’s now at ~385 ppmv and rising.
We further know that, through land use changes and fossil fuel combustion, we’re adding [X] Gt y-1 of CO2 to the atmosphere.
Given those, which inference is more logical?
(1) The CO2 we’re emitting is responsible for the rise in atmospheric CO2 we’re observing;
or
(2) The CO2 we’re emitting is being magically removed by some unknown phenomenon, while, coincidentally, some other unknown phenomenon is simultaneously adding CO2 to the atmosphere in a way that never occurred in the past 850,000 years.
Ok, last try. I reread what I wrote, and I still don’t think I’m conveying my point….
So, pretend I’m your teacher, and you submitted this for review. I would tell you to drop the assumption line, put in a paragraph or two on why you believe the steady-state thing, then I’d sign-off on it as perfectly acceptable.
Does that clear it up at all? I’m not very good at writing what I’m thinking, which is why I don’t have my own blog!
Also, thanks for what you do on here, keep up the good work.
WRT science-y vs chatty, I don’t read a lot of primary literature on climate and I generally don’t work with the data very much — I think this means that presenting something known in a slightly different way (like you have with the distributions by decade) is very much entertaining and valuable to someone like me. Thanks. (And I, too, keep hoping more people will comment at the previous post.)
I think you meant
Instead, I’ll look at how the yearly changes in CO2 mixing ratios have changed throughout the last 50 years.
Rather than
Instead, I’ll look at how the yearly changes in temperature have changed throughout the last 50 years.
You may delete this
For those quoting ice core data to support the historic levels of CO2, I would remind them we have absolutely 0 (zilch, nada, nill) empirical evidence equating the readings from deeper (older) levels of the ice cores with actual atmospheric conditions.
Please read the literature about how they theorize the relationships. Also look to the new AIRS data to see how we have less than “Well Mixed” GG’s in the atmosphere.
Someone should have woken up when the data started showing interesting artifacts like Methane clouds over tropical forests. Sadly climate scientists are still working with the “well Mixed” mythology.
Atmoz,
sorry, but how do you take into account natural sources like the Champagne Field:
http://www.sciencedaily.com/releases/2005/01/050104114942.htm
How many cars worth of CO2 do you think these natural LIQUID CO2 sources equate to?? Maybe I should be suggesting coal fired power plants??
We should see some interesting research from these areas on acidification and decalcification in the next few years also!!
Just for fun, here is some more unknown data from the oceans. Wonder what the total energy input to the oceans comes to now??
http://environment.newscientist.com/article/dn14456
http://www.sciencedaily.com/releases/2008/01/080109173830.htm
The climate types have consistently underestimated the natural inputs to the system. They finally adjusted the models to take into account the changes in TSI. When will they seriously start looking into the geo heat and co2, which has been ignored, like the sun, as negligible??
[Reply: Let's assume that your source of new CO2 just happened to form at the turn of the industrial revolution, and that's it is of the magnitude needed to increase CO2 levels as observed. (Neither is likely to be true.) Please tell me where the CO2 produced by humans is going. That is, what carbon sink magically appeared at the same time, and of the same magnitude, as your new natural source such that it is offsetting anthropic CO2?
In the absence of an addition natural sink, your hypothesis fails because CO2 should be rising faster than presently observed. There is actually a missing carbon sink. All else equal, with the amount of CO2 being emitted by humans, we would expect the atmospheric CO2 to be rising at a faster rate than observed. And that is without the addition of an additional source.
In the presence of an additional natural sink, your hypothesis fails because it is no different than the first cartoon shown in the above post, where natural sources equal natural sinks. Therefore, your hypothesis isn't wrong - it's not even wrong. The suggestion that the rise in atmospheric CO2 isn't of anthropogenic origin doesn't make any sense.]
Good post.
However, the cat is not angry enough. For one of those, see story & pictures:
http://www.mandm.ws/cat.html
Where was the missing carbon sink when the world was in carbon cycle equilibrium in pre-industrial times?
It was always there. It’s only been ‘missing’ in that it’s extremely hard to measure global carbon fluxes.
I understood that “missing” was code for not clearly defined. But if it were always there, doesn’t that make the pre-industrial equilibrium a bit out of equilibrium?
Sun at most active in 1200 years, oceans warm, CO2 released, not to hard to get your head round.
“It will without doubt have come to your Lordship’s knowledge that a considerable change of climate, inexplicable at present to us, must have taken place in the Circumpolar Regions, by which the severity of the cold that has for centuries past enclosed the seas in the high northern latitudes in an impenetrable barrier of ice has been during the last two years, greatly abated.
(This) affords ample proof that new sources of warmth have been opened and give us leave to hope that the Arctic Seas may at this time be more accessible than they have been for centuries past, and that discoveries may now be made in them not only interesting to the advancement of science but also to the future intercourse of mankind and the commerce of distant nations.”
President of the Royal Society, London, to the Admiralty, 20th November, 1817