The Carbon Cycle and the ‘Acidification’ of the Ocean (Part 1)

One of the few things that I have not covered before in depth is the carbon cycle.  That is the path that carbon takes in and out of the atmosphere.  For example, plants absorb CO2 from the atmosphere, but eventually that carbon will make it’s way back into the atmosphere.  The flow of carbon from one place to another is the carbon cycle.  I have been waiting for the right time to get to this topic and that has finally arrived.

Why now you ask?  Well there is a new paper that is in the news which plays on peoples lack of perspective about the carbon cycle.  It has been all over the news in the past week and it is an amazing piece of FUD.  The claim that the paper makes is that the oceans are experiencing the fastest rate of ocean acidification that has happened in the past 300 million years.  Even more disturbing is the claim that they can’t go back farther than that so what is left implied is that the Earth is currently experiencing the greatest rate of ocean acidification ever.  In addition they tie such changes to the oceans acidification to mass extinctions.  So to sum it up, the paper is saying that the Earth is potentially heading to the greatest mass extinction of life because of CO2 emissions.

Carbon Cycle Overview

The Inconvenient Skeptic

Overview of the "fast" carbon cycle. (Yellow) Natural Carbon Flows, (Red) Human Carbon Flows

I will use the NASA Earth Observatory as the source of graphics and in general I will use the numbers from them for this article.  I will specify if I am not using their numbers.

Flows to the Atmosphere:

There are three natural flows of CO2 to the atmosphere and then there are human emissions.

Ocean Exchange:      90

Plant Respiration:     60

Decomposition:        60

Human Emissions:    9


Total CO2 into atmosphere:   219

Human Contribution:         4%

So all of the human activity accounts for only 4% of the total flow into the atmosphere.  It is also the only quantity that is accurately known.  If I assume that we know the other values to within 10% accuracy, then it would be accurate to say that the natural flow of CO2 into the atmosphere is 210 +/- 21 carbon units.  Even the uncertainty in the natural flows is larger than what is known to be human caused.

This should be a very clear indicator that while mankind does indeed introduce a measurable amount of CO2 into the natural cycle, the natural portions of the cycle dwarf the human contribution.  The small scale of the mankinds contribution is tied to questions about the reliability of the past CO2 levels as I previously discussed here.  The ice cores in Greenland show a very different history than the ice cores from Antarctica.

The Inconvenient Skeptic

GISP2 CO2 ppmv data by ice core depth. The depths associated are: 1900m ~= 19,000 YPB, 1650m ~= 11,100 YBP

The records from Greenland show many times in the past when the CO2 level cycled rapidly over the course of a few hundred years by as much as 100 ppm.  This provides some evidence that such rapid cycles of CO2 change are in fact natural in origin.  Considering the scale of mankinds contribution, I consider this a realistic probability.

Flows from the Atmosphere:

There are only two paths by which CO2 exits the atmosphere.

Ocean Exchange:        92   (2 anthropogenic)

Photosynthesis:         123  (3 anthropogenic)


Total CO2 from atmosphere:   215  (5 anthropogenic)

Human Contribution:          2%

The scope of the uncertainty is equal for the amount of CO2 leaving the atmosphere at +/- 21 units, but there is also some uncertainty about the anthropogenic values, but for arguments sake I will accept these values as reasonable.  If this is the case, then the human contribution to the ocean exchange is ~2% of the natural value.

In both of these cases I have only dealt with the flows of carbon to and from the atmospheric system.  The amounts of carbon that exist in some of the systems is enormous.  The ocean surface is listed as having 1,000 units of carbon already.  Of course it only takes 11 years for the entire ocean surface to completely turn over the carbon with the atmosphere (1,000 units at 90 units per year).  While this is not quite the same as having the sprinklers on during a thunderstorm, it is pretty close.  Human contribution to the carbon cycle is little more than rounding error for the natural cycle.

It also shows the problem of treating CO2 as a pollutant.  Natural decomposition of plant material contributes more than 6 times as much CO2 to the atmosphere as all of the activity that mankind does.  The science does not support the idea that CO2 emissions are a pollutant.  The next part of the article will discuss the specifics of ocean acidification.  That mankind is at most a 2% contributor to the amount of carbon that is entering the ocean should give the reader a pretty good idea of how that will go.

Posted in Fear and Misinformation and Science Articles - Global Warming and Science Overviews by inconvenientskeptic on March 6th, 2012 at 12:25 pm.


This post has 14 comments

  1. Guy Leech Mar 7th 2012

    What about limestone rock? Surely that is by far the largest carbon sink and CO2 flows in and out of it to the atmosphere as well?

    Could you show the units you are using for the CO2 flows in the post?


  2. inconvenientskeptic Mar 7th 2012

    I will add more details in the next part, but for this section I was using the relative units used in the Earth Observatory.

    This is what is called the fast cycle. Rocks are the slow cycle as is the deep ocean.

  3. Guy Leech Mar 7th 2012

    Thanks John. I have been attempting to put the budget into a spreadsheet which doesn’t quite add up! Can I send it to you for comment without posting it?

  4. Richard Mar 8th 2012

    I have always worried that the human contribution to all of this is badly understood and under/over stated.

    Thanks for setting an overall view.

    I would be interested to know how much salt distribution in the oceans affects pH as set against any CO2 contribution (from whatever source).

  5. Rob Honeycutt Mar 9th 2012

    John… The relative amount of the human contribution of CO2 is not the issue. There is a natural carbon cycle of outputs and uptakes. Agreed? These have remained roughly in balance over the past half million years. See the EPICA Dome C data (I believe it’s thought to be the more reliable measure of atmospheric CO2.) The Dome C data shows that over the past half million years concentrations have gone from ~180 to as high as ~290 ppm along with the glacial-interglacial cycles. Right?

    So, there remains a rough balance between natural outputs and uptakes. This is part of how CO2 affect global temperature. When Milankovitch cycles change insolation the oceans warm slightly. Warmer water takes up less CO2 and thus more CO2 stays in the atmosphere, and the radiative forcing of that extra CO2 amplifies the orbitally forced warming. Are we still in agreement?

    Now, you take this system that is, again, roughly in balance and we start adding more CO2 into the atmosphere. Where does it go? Well, the natural system can actually take up a portion of that new anthropogenic CO2. But what happens is, even though we are only adding what is proportionally a small amount of CO2 to the total carbon cycle, we are throwing what was a roughly balanced system OUT of balance.

    The typical analogy is your kitchen sink. You have a drain and a faucet. You can adjust it so the sink remains roughly half full with the water flowing in matching the water going out the drain. All you have to do is change the amount of water being added just a small amount and the water in the sink will start to rise.

    Yes, anthropogenic content in the overall carbon cycle is small, but it is the balance of the carbon cycle that is being changed.

    With regards to your comment on the past 300 million years… Complex animal life has been on the planet only 550 million years. Whether CO2 concentrations changed more rapidly before that is rather a moot point.

  6. inconvenientskeptic Mar 12th 2012


    It is exactly the relative human contribution that does matter.

    Lets say that we all start using the power supply from the movie Iron Man in everything, except for me. I decide to stick with my carbon dioxide producing car.

    The relative human contribution would drop to almost nothing. As the only producer of carbon dioxide I would be insignificant in the overall picture. A house burning down would produce the same amount in a day that I would over the course of a year.

    The question is…. at what point does the human contribution become significant?

  7. Rob Honeycutt

    “When Milankovitch cycles change insolation the oceans warm slightly. Warmer water takes up less CO2 and thus more CO2 stays in the atmosphere, and the radiative forcing of that extra CO2 amplifies the orbitally forced warming.”

    Here are some links refuting that argument:

    – ‘In defense of Milankovitch’ by Gerard Roe published in ‘Geophysical Research Letters’ (2006)
    – ‘Implications of the Secondary Role of Carbon Dioxide and Methane Forcing in Climate Change: Past, Present and Future’ by Willie Soon published in ‘Physical Geography’ (2007)
    – CO2, Temperatures, and Ice Ages (Frank Lasner),Temperaturesandiceages-f.pdf
    – Nearly Half a Million Years of Climate and Co2 (CO2 Science)
    – Atmospheric Carbon Dioxide and Interglacial Warmth (Video, Co2 Science)
    – Earth may be headed into a mini Ice Age within the next decade (Hockey Schtick, Comment)

    By the way Rob, perhaps you’d care to answer Poptech’s rebuttal to one of your articles.
    Because it’s been over a year and you’ve never even acknowledged it on SkS.
    And perhaps you would care to explain why ALL of the comments by Poptech have been completely removed from your article?

  8. Rob Honeycutt Mar 12th 2012

    Adam… You’re basically laying out a case that should win you the Nobel prize for overturning 200 years of basic physics. Good luck with that.

    And, I mean, come on… Soon? Idso? Why not just give me the phone number for the CEO of ExxonMobile so I can just discuss the situation with him directly.

  9. Rob Honeycutt Mar 12th 2012
  10. inconvenientskeptic Mar 12th 2012


    I approved, but limit links to two please. This is not a debate by spamming the most content.

    Let’s keep the tone civil as well.

    For the point at hand. I will finish up the next part of the article tomorrow (my time). There will be far more detail to discuss then. Keep to the topic at hand. There are plenty of other articles to discuss other points.

  11. Rob Honeycutt

    “And, I mean, come on… Soon? Idso? Why not just give me the phone number for the CEO of ExxonMobile so I can just discuss the situation with him directly.”

    Typical. When you can’t answer the scientific points they raise you just try to smear them. Rob how about you actually look at the links I provided. Simply cutting and pasting a huge amount of links simply repeating the same argument, is hardly a credible argument. Every single one of the links I provided showed how the warmist argument of amplification was flawed.

    Can exxonmobil change the ice core data?

    And Soon’s paper was published and peer reviewed.

    P-E-E-R R-E-V-I-E-W-E-D

    You do know what that means don’t you?

    And I notice that you have completely avoided my question about Poptech’s rebuttal. Why is that?

  12. Rob Honeycutt Mar 13th 2012

    John… My apologies. I appreciate that you try to run a clean site that sticks to the scientific issue. But when I got jumped by Adam (as he now has done again) it’s hard not to lose control.

    I’ll back out at this point. Adam is not interested in a conversation on the actual science. He’s merely interested in attacking me. I don’t need it and it demeans your site.

  13. inconvenientskeptic Mar 13th 2012


    Peer Review does not mean the conclusion is correct. It means that it was reviewed by similar people for obvious errors.

    I see a great deal of semiconductor research that is amusing, but pointless. I have listed many peer reviewed articles that are in direct contrast to each other.

    It happens all the time. Peer reviewed science in many fields from the 1970’s would be laughed at today because the fields are so different. Science evolves over time.

    I like reading peer reviewed articles, but they are not the end all and be all of knowledge.

  14. inconvenientskeptic Mar 13th 2012

    The next article is up. Comments that relate to topic are welcome.

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