Ocean Acidification by Carbon Dioxide

We often read in the media that increasing carbon dioxide in the atmosphere will make the oceans too acidic, and dissolve or otherwise harm carbonate-shelled marine fauna. These writers or reporters seem ignorant of the fact that these marine fauna evolved when the atmospheric CO2 concentration was more than 10 times higher than the current level.(1) Ironically, a recent New York Times article was fretting that the ocean is not absorbing enough carbon dioxide to act as a good carbon “sink.”

pHscaleThe metric for acidity/alkalinity is called pH. The pH is defined as the negative logarithm of the hydrogen ion concentration (or the logarithm of 1 divided by the hydrogen ion concentration). The pH scale goes from zero to 14 with pH of 7 being neutral, lower than 7 is acidic, and higher than 7 alkaline.

Two factors control the amount of carbon dioxide in the ocean: ocean temperature and amount of carbon dioxide in the atmosphere, i.e., its partial pressure. Cooler oceans and higher atmospheric CO2 should result in more carbon dioxide in the oceans.

Henry’s law states that the concentration of a gas in a liquid is proportional to the partial pressure of the gas in equilibrium above the liquid. It stands to reason that more CO2 in the atmosphere would translate to more in the ocean. However, Henry’s law assumes constant temperature. If the temperature changes, then the absorption changes. If the oceans warm, CO2 will leave the ocean and return to the atmosphere. Cold liquids can hold more dissolved gas than warm liquids. Just think of what happens to a carbonated beverage left to warm to room temperature.

It has been estimated that current ocean pH is 0.1 pH unit less alkaline than it was in recent pre-industrial time, and some climate models predict a further decrease of 0.7 pH units by 2300.(2) However, proxy reconstructions of ocean acidity, based on fossil and modern corals, show that ocean pH has oscillated between pH of 7.91 and 8.29 during the past seven thousand years.(3) That cyclic variation is nearly four times larger than the 0.1 decrease alarmists are whining about, and even if the model predicted decrease of 0.7 units occurs, the water will still be alkaline.

An independent reconstruction, again based on corals, shows that between 1708 and 1988, there was a clear interdecadal oscillation of pH, (between 7.9 and 8.2 pH units) which is synchronous with the Interdecadal Pacific Oscillation of water temperature.(4) During this time, atmospheric CO2 concentration increased by about 100 parts per million. If more CO2 is dissolved in the ocean, the added carbonate (to build the calcium carbonate shells) will more than offset the decreasing alkalinity. (5) The effect of increased CO2 seems benign to other small sea creatures, including corals. (6)

The specter of acidification seems irrelevant to carbonate-shelled animals. What of fish and fish larvae? A study by Munday et al. (7) found CO2 acidification had no detectable effect on embryonic duration, egg survival and size at hatching. As for adult fish, they found that most shallow-water fish tested to date appear to compensate fully their acid-base balance within several days of exposure to elevated CO2 concentrations.

Recent claims by climate change alarmists have raised the possibility that terrestrial ecosystems and particularly the oceans have started losing part of their ability to absorb a large proportion of man-made CO2 emissions. However, a new study combines data from ice cores, direct atmospheric measurements, and emission inventories to show that the fraction of human emitted CO2 that remains in the atmosphere has stayed constant over the past 160 years, at least within the limits of measurement uncertainty. (8)

Can the oceans ever become very acidic? There is no evidence that the oceans were ever acidic during the past 500 million years, even when atmospheric concentration of carbon dioxide was more than 10 times current levels. This implies that besides temperature and partial-pressure, there is a third controlling factor. That factor is the buffering effect of carbonic acid reaction with the basaltic oceanic crustal rocks. This process uses up excess carbon dioxide.

Ocean acidification is just another scary scenario, a phantom menace.


1. Berner, R.A. and Kothavala, Z., 2001, A revised model of atmospheric CO2 over Phanerozoic time: Am. J. Sci., v. 301, p. 182-204.

2. Caldeira, K. and Wickett, M.E. 2003. Anthropogenic carbon and ocean pH. Nature 425: 365.

3. Liu, Y., Liu, W., Peng, Z., Xiao, Y., Wei, G., Sun, W., He, J. Liu, G. and Chou, C.-L. 2009. Instability of seawater pH in the South China Sea during the mid-late Holocene: Evidence from boron isotopic composition of corals. Geochimica et Cosmochimica Acta 73: 1264-1272.

4. Pelejero, C., Calvo, E., McCulloch, M.T., Marshall, J.F., Gagan, M.K., Lough, J.M. and Opdyke, B.N. 2005. Preindustrial to modern interdecadal variability in coral reef pH. Science 309: 2204-2207.

5. Gutowska, M.A., Pörtner, H.O. and Melzner, F. 2008. Growth and calcification in the cephalopod Sepia officinalis under elevated seawater pCO2. Marine Ecology Progress Series 373: 303-309

6. Kurihara, H., Ishimatsu, A. and Shirayama, Y. 2007. Effects of elevated seawater CO2 concentration of the meiofauna. Journal of Marine Science and Technology 15: 17-22

7. Munday, P.L., Donelson, J.M., Dixson, D.L. and Endo, G.G.K. 2009. Effects of ocean acidification on the early life history of a tropical marine fish. Proceedings of the Royal Society B 276: 3275-3283.

8. Knorr, W. (2009), Is the airborne fraction of anthropogenic CO2 emissions increasing?, Geophys. Res. Lett., 36, L21710, doi:10.1029/2009GL040613.


  1. Incorrect logic as always. You imply that if ocean pH as varied over geologic time, then no harm would befall the corals and other oceanic species. You are forgetting evolution as you pick and choose your evidence to support your unwavering anger at the majority of earth scientists in the world. Of course oceanic species adapt to changes in ocean pH. Certain things will be limited in their growth or die off as is currently indicated with relatively new studies examining these effects (http://www.sciencemag.org/cgi/content/abstract/318/5857/1737), and other species will increase or new species will likely develop. Climate change is not just about potential die offs but the altered environment that us and all biological species will need to adapt to, as we have already seen with new evolutionary changes. Its time for you to stop fighting a discussion that ended in the scientific community over a decade ago. Climate change is occurring as it always has (even with the underlying decadal and multi-decadal influences that influence our environment) and the current change is being modified by our influence. The question now is whether we want to continue providing this influence and how would we adapt if the influence continues as is or is it better to take actions to reduce the influence and provide us with more time to adapt.

  2. The discussion has ended? Must be consensus.
    Well J, I know it is futile to argue with a true believer because to them facts don’t matter.
    The paper your link refers to, “Coral Reefs Under Rapid Climate Change and Ocean Acidification” is mainly a computer simulation based on questionable assumptions – GIGO.
    The first sentence of the abstract reads [emphasis added]:
    “Atmospheric carbon dioxide concentration is expected to exceed 500 parts per million and global temperatures to rise by at least 2°C by 2050 to 2100, values that significantly exceed those of at least the past 420,000 years during which most extant marine organisms evolved.”
    Most families of marine organisms evolved during the early Paleozoic Era more that 320 million years ago. Scleractinian corals, which are the major builders of the reefs of today, first appeared during mid-Triassic time 210 million years ago, when the earth was considerably warmer .   Do you want to quibble about subspecies?
    The reference of lower carbon dioxide levels during the past 420,000 is code for ice core data, data which, incidentally shows that temperature changes preceded changes in atmospheric carbon dioxide.
    However, carbon dioxide data from ice cores is suspect because it assumes that carbon dioxide content of entrapped air bubbles accurately reflects that of the ancient atmosphere, but there is no proof of that. In fact, there is good evidence that, with increasing pressure and time, the bubbles undergo chemical and physical changes that deplete CO2, so it is unlikely that they contain true ancient atmospheric compositions. Furthermore, the ice core composition data disagree with other proxies.
    I will deal with corals in more detail in a future post.

  3. Jonathan,
    Yes, there is a consensus in the scientific community that climate change is occurring and we are having an influence. If you spent any time at an earth science conference or going through the literature, you will see that this is true. Obviously, there many, many indicators that are reacting differently. The earth system is very dynamic and complex.
    I see that you are now a better judge of the scientific merit of studies than the authors and the reviews at Science (based on dismissing the Science article). Of course there are assumptions! Science is based on assumptions. Not sure what to make of your additional post. It appears that you are arguing that corals of today have not changed in the past 420,000 years?! Also, yes things change with time. You are still not making any valid argument. Your article implied that changes to ocean pH are irrelevant and just another scare tactic. There is no basis to your argument to continue to stick your head in the sand about climate change. Continuing to find small discrepancies and enlarge them to dismiss climate change is scientifically invalid. Simply pointing to a weakness of one indicator cannot be used to dismiss the entire body of evidence that is overwhelming pervasive. Before dismissing someone as a “believer”, a bit of self reflection as to your motivation would be beneficial to your state of mind.

    1. I think you are mis-reading my posts and phrases like “unwavering anger” seem rather extreme.  I wonder who’s really angry.  My posts are based on observed and measurable data, not computer models.  My posts show that there has always been natural climate  change. Read the series on geological history of Arizona for instance.  We can influence local climate by land use changes, but there is no empirical evidence showing that our carbon dioxide emissions are significantly changing the climate.  If you can present some such evidence, I would be glad to see it.

      As for pH, my articles imply that it changes over a small range that is well-handled by the majority of species, and that our increasing carbon dioxide emissions don’t seem to have any effect on ocean pH.

  4. Unbelievable for you to say that there is no empirical evidence that carbon dioxide emissions are affecting climate. To make a claim, you would have to discount carbon as a greenhouse gas. Proven and accepted over and over. Why do we talk about historical climate change in relation to carbon, particular in reference to volcanic emissions? I recommend you do some reading, because there is ample evidence in all major earth science journals about carbon dioxide emmissions and their effect on climate. There is a reason we are calling this epoch the Anthropocene. Stop burying your head. Typical economic geologist. Bought and paid for by industry with obvious strong bias for the use of carbon. Its deniers such as yourself that contribute to the hate that circulates in the political discussion surrounding this issue.

    1. Carbon dioxide, not carbon, is a green house gas, but a very weak one compared to water vapor or methane.  Again show me some evidence that human carbon dioxide emissions have had a significant effect on global temperature.

  5. I’m not qualified to determine whether the information you present is valid and relevant to the issue at hand, but I gotta admire you for your doggedness, Jonathan.  And you’re directly addressing the issue, not just attacking the opposition.

  6. Sorry Jonathan. Didn’t mean to confuse you. I used carbon as a general indicator because methane is simply the reduced form of carbon in the atmosphere and is a prevalent constituent in anthropogenic emissions (plus it has 25 times the effect of carbon dioxide as a greenhouse gas). You are still avoiding the issue. If you agree that carbon acts as a greenhouse in the atmosphere, how do you discount the continuing mass of carbon building in the atmosphere from our emissions and the natural flux of carbon through the various components of the carbon cycle. I have found your articles to simply be strawman diversions that attempt to divert people’s attention from the basis of the discussion. Your use of terms like “phantom menace” clearly point to an emotional plea and not a scientific analysis.
    Since I don’t think you have the background to follow many of scientific journal articles, you should start by reading the UN IPCC reports. They are written for the general public and provide a good synthesis of the current understanding of the anthropogenic influences as they relate to climate change. You will find a multitude of references to the question you pose. There is a reason why the major scientific and governmental agencies across the globe are currently discussing possible actions to reduce our effect on the climate. Again, the question is not whether it is happening, but how do we want to address it?

    1. By studying the geologic history of this planet, I see that carbon dioxide, although a weak greenhouse gas, has never been a major driver of climate.
      Your faith in the IPCC is perhaps misplaced, since the IPCC is primarily a political body rather than a scientific one – who else would publish a Summary for Policy Makers months before the underlying papers were written. They also unscientifically ignored research that did not support their agenda.
      See: http://tucsoncitizen.com/wryheat/2009/06/27/the-assumed-authority/
      IPCC modeling of the climate assumes there is positive feedback with water vapor, but observations show that the feedback is negative, therefore, the models make predictions which are not found in nature: see http://tucsoncitizen.com/wryheat/2009/06/17/a-basic-error-in-climate-models/
      You seem to be unaware of the events of the past few weeks which revealed that the data which formed the basis of IPCC modeling scenarios was manipulated to show a warming bias, and thus does not show the true state of the climate.
      You, like others in the carbon camp, keep saying that there is plenty of evidence that human carbon emissions have a significant effect on temperature, but when asked, you don’t produce any. Which specific papers do you think prove your case?

  7. Hey Johathon,
    False. Carbon dioxide has been a major driver of climate change throughout Earth’s history. Pick up any basic earth science journal or textbook for a refresher (and of course, don’t forget methane, also carbon). Of course water vapor provides a variable feedback. Increased temperatures increase water vapor from increased evaporation. It is one of the difficult topics within the climate change field. Particularly since increase water vapor would create more clouds, which can have a dampening effect. Of course the atmosphere cannot be viewed as a monolithic body and these effects will be variable across the globe.
    I grow weary of this tiresome discussion. It is very apparent that you have political beliefs that significantly cloud any potential scientific objectivity. The IPCC reports are not published by politicians and are  a compilation of scientific work from around the world by many of the top earth scientists in a multitude of countries. Their work is summarized and synthesized within the IPCC reports where you find tons and tons of references for you to examine concerning carbon emissions and our changing climate. If you are not even willing to look at such work, there is no point in attempting to discuss this issue with you. It is apparent that you simply are a fraud. It is a disservice to the readers that you have been given this forum to promote a political belief disguised as a scientific discussion.
    If you can’t look at the IPCC reports, simply go to the any major earth science journal as I have repeatedly suggested. The work is there, you are just choosing to ignore it.

  8. That is the spirit Jona-charlatan! If you ignore the science, it can’t be true, right? I really like how you are willing to discount the findings from top earth scientists from all over the world, whose work is shown in the IPCC reports, but cite your political blog as scientific reference. Keep up the political fight. I know the Luddites and Flat-Earthers are rooting for you!
    I have an idea for your next blog. Why not mock those thousands of earth scientists from all over the world at the AGU Fall Meeting (premier earth science organization) who are currently presenting loads of studies describing the effects climate change related to change in carbon in the atmosphere. Such foolish scientists must be found to be part of some great conspiracy that only Jona-charlatan could uncover.
    Best wishes in your political ramblings!

  9. Wish you wouldn’t keep your head in the sand Jona-charlatan. The world is moving ahead without you. It is just a shame that you have been given a forum to display your psuedo-science to promote a political agenda. Your knowledge of the earth sciences seems to be stuck back in the 1960s. You should enter the 21st century and discard your biases. This is a world-wide issue and the ongoings in Copenhagen are a significant point in our history. Instead of trying to spread disinformation, it would be best to educate yourself and be a positive force.

  10. When one feels a need to resort to name calling it is apparent that they have already lost the argument.

  11. It is not name calling, but a simple fact. Jona-charlatan is passing himself off as a scientist in touch with issues concerning climate change. He uses biased information from political sites to support claims that have been proven to be false. His unwillingness to objectively examine the issue and deny the knowledge we have about the various earth systems makes him a fraud. It is just unfortunate that his political motivation is being hidden behind a psuedo-science format. He could really use a climate science class as UA to catch him up on the our understanding of the atmosphere and it relation to the hydrosphere and geosphere. You should never stop learning and let biases intercede in your thought process on issues so important to our country and standard of living.

    1. J – when you call a man a charlatan it is most certainly name calling and has no place in a scientific discussion. Could YOU please refer to your notes from your UA climate science class and cite the evidence that shows carbon dioxide to be a major factor in driving the climate? If your statements have merit then surely you must be willing to back them up.
      I believe that Jonathan has provided his résumé to this group before. Would you care to do the same?

  12. Hey G,
    There is not a scientific discussion going on in this forum. It is a political discussion being promoted as psuedo science. I simply refer you to the UN’s IPCC report for the current understanding of climate change as these reports synthesize the best research ongoing from across the globe. There is a reason that the world’s leaders are currently in Copenhagen to address our influence on climate change. It is accepted in the scientific community that carbon in the atmosphere plays a significant role in the climate change. It is typical for a political blogger to call the UN reports political, but they are simply a compilation of scientific work by other scientists under the World Meterological Organization and and the UN Environmental Programme. Yes, I am a earth scientist and actually perform work in my field. I am not a political blogger. Believe what you will as is even one’s right, but I find it unfortunately that a political blog is being promoted as science under the technology section of this news outlet. As readers of this blog appear to whole heartedly accept whatever psuedo-science is being promoted for a political agenda, I will leave you to your fantasy world.

  13. J – I challenge your asssertion that “It is accepted in the scientific community that carbon in the atmosphere plays a significant role in the climate change.”.At the top of this article Jonathan cited eight sources for his article. Could you please do the same in order to substantiate your opinions. Having had courses in Meteorology, Climatology, Oceanography, Ocean Geology, Sedimentation and Stratigraphy, among others, I may be able to read your citations with a modicum of understanding. Politicians settle questions by taking a vote. Scientists tend to use Thesis, Antithesis and Synthesis. Let’s try that route.

  14. Yet another religious debate posing as science.  It would be lovely if all the oddbods that think that carbon dioxide rising leading to climate change is a furphy, would simply admit it’s based on faith not evidence.

    The reality is here now staring you all in the face.  It’s no longer merely a warning by intelligent people, it’s already happening. 

    Try as you will to make it not happen by making up lies, it won’t stop.  Sorry Jonathan, I think you’d better go back to school and learn some climate science.

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