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Ocean acidification: Global warming's evil twin

Posted on 7 April 2010 by John Cook

While there's much focus on the impacts from warming temperatures, there's another more direct effect from the burning of fossil fuels and deforestation. More than 30% of the carbon dioxide emitted by humans is dissolved into the oceans, gradually turning ocean water more acidic. Coral reef researcher Ove Hoegh-Guldberg explains the threat of ocean acidification: "Evidence gathered by scientists around the world over the last few years suggests that ocean acidification could represent an equal – or perhaps even greater threat – to the biology of our planet than global warming". Thus a new paper Paleo-perspectives on ocean acidification (Pelejero et al 2010) labels ocean acidification the 'evil twin' of global warming.

As CO2 dissolves in the oceans, it leads to a drop in pH. This change in seawater chemistry affects marine organisms and ecosystems in several ways, especially organisms like corals and shellfish whose shells or skeletons are made from calcium carbonate. Today, the surface waters of the oceans have already acidified by an average of 0.1 pH units from pre-industrial levels and we're seeing signs of its impact even in the deep oceans.

The past gives us an insight into future effects of ocean acidification, as we continue to emit more CO2 and acidify the ocean even further. Ice cores give us accurate data on the evolution of CO2 in the atmosphere over the last 800,000 years. These reconstructions, together with data derived from foraminifera, find that the pH of ocean surface water was lower during interglacials (high levels of atmospheric CO2). Seawater pH was also higher during glacial periods  when atmospheric CO2 was low. Correspondingly, foraminifera seem to have grown thicker or thinner shells over glacial–interglacial timescales in time with changing CO2 levels.


Figure 1: Glacial–interglacial variability in surface water pH (filled blue symbols, note the reversed axis), superimposed on atmospheric CO2 concentration during the last 800,000 years (magenta curve) (Pelejero 2010).

Current atmospheric CO2 are at greater levels than seen over the last 800,000 years. Similarly, pH levels are already more extreme than those experienced by the oceans over this same period. By the end of the 21st century, the projected decline in seawater pH is expected to be three times larger than any change in pH observed as the Earth’s climate has oscillated between glacial and interglacial periods. The times when seawater pH changed fastest was during glacial terminations when the Earth came out of an ice age. The change in seawater pH over the 21st Century is projected to be around 100 times faster than this rate.

What will be the effect of seawater pH falling to such levels? Let's look further back at periods when pH fell to the levels projected for the end of the 21st Century. There have been several periods where pulses of CO2 have been injected into the atmosphere, from volcanic activity or melting of methane hydrates. One well known example is the Paleocene-Eocene Thermal Maximum (PETM), which occurred around 55 million years ago. During this event, global temperatures increased by over 5°C over a time frame less than 10,000 years. This coincided with a massive release of carbon dioxide into the atmosphere, which led to ocean acidification. This change caused a series of biological responses, including the mass extinction of benthic foraminifera.

Looking further back, there are other examples of mass-extinctions coinciding with global warming and increases in atmospheric carbon dioxide.  Examination of the mass extinction that occured 251 million years ago during the end-Permian find that the patterns of mortality are consistent with the physiological effects of elevated CO2 concentrations (along with the effects of global warming). 205 million years ago at the Triassic–Jurassic boundary, a sudden rise in the levels of atmospheric CO2 coincided with a major suppression of carbonate sedimentation, very likely related to ocean acidification. A similar situation occurred 65 million years ago during the Cretaceous–Tertiary extinction event. Most of the planktonic calcifying species became rare or disappeared.

Future acidification depends on how much CO2 humans emit over the 21st century. By the year 2100, various projections indicate that the oceans will have acidified by a further 0.3 to 0.4 pH units, more than many organisms like corals can stand. This will create conditions not seen on Earth for at least 40 million years.

A highly recommended website is Climate Shifts, run by one of the coauthors of Pelejero 2010. with a strong emphasis on coral reefs. For more peer-reviewed research on ocean acidification, check out AGW Observer's Papers on Ocean Acidification.

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Comments 1 to 50 out of 70:

  1. In all such a long article that JC has not entered the ocean pH will have for 100 x ? years. And ... will always be a > 7 ... I’m looking - maybe on number of the fossils calcareous Ammonites genera in Triassic/Jurassic/Cretaceous (W.J. Kennedy 1977 in Patterns of Evolution, Amsterdam) and The Bahamas Banks, and comparison with carbon dioxide concentration in T/J/C oceanic (probably even > 4 x higher than It is a modern) and air (see: for example http://upload.wikimedia.org/wikipedia/commons/7/76/Phanerozoic_Carbon_Dioxide.png) and temperature in this period (perhaps http://www.nzetc.org/etexts/Bio16Tuat01/Bio16Tuat01_004a.jpg) I can see great correlations in this older geological period: higher p.CO2, temperature = higher calcareous biomasses …, specifically by Ammonites: ~215 millions years BP = maximum - ~ 180 of genera, and 600 - 2100 ppmv CO2 , ~110 m. years BP = maximum - 180 of genera, and 500 - 2300 ppmv CO2,; similarly what about a temperature. In the Triassic/Jurassic/Cretaceous a calcareous organisms are like warm… What about modern times? M. D. Iglesias-Rodriguez et al, in: Phytoplankton Calcification in a High-CO2 World - Science, 18.04.2008 (downloadable from http://www.sb-roscoff.fr/Phyto/index.php?option=com_docman&task=doc_details&gid=418&Itemid=112); say: “From the mid-Mesozoic, coccolithophores have been major calcium carbonate producers in the world's oceans, today accounting for about a third of the total marine CaCO3 production.” “Field evidence from the deep ocean is consistent with these laboratory conclusions, indicating that over the past 220 years there has been a 40% increase in average coccolith mass.” I remind You same important papers (as I think) from Idso: “In a study of calcification rates of massive Porites coral colonies from the Great Barrier Reef (GBR), Lough and Barnes (1997) found that "the 20th century has witnessed the second highest period of above average calcification in the past 237 years." “Buddemeier et al. (2004) have continued to claim that the ongoing rise in the air's CO 2 content and its predicted ability to lower surface ocean water pH (which is also a key claim of Orr et al .) will dramatically decrease coral calcification rates, which they say could lead to "a slow-down or reversal of reef-building and the potential loss of reef structures in the future." However, they have been forced to acknowledge that "temperature and calcification rates are correlated, and [real-world] corals have so far responded more to increases in water temperature (growing faster through increased metabolism and the increased photosynthetic rates of their zooxanthellae) than to decreases in carbonate ion concentration."
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  2. Thanks for an interesting post, John. I had not seen the Pelejero 2010 paper before. One small note. John Cook writes: A similar situation occurred 65 million years ago during the Cretaceous–Tertiary extinction event. Most of the planktonic calcifying species became rare or disappeared. Readers might wonder why a mass extinction caused a comet impact would show signals of ocean acidification. It was initially assumed that the main impact (pun not intended) of the K-T event would have been rapid global cooling caused by the injection of dust and aerosols into the stratosphere. But in recent years geoscientists have realized that the carbonate rocks at the site of the Chicxulub crater would have provided a massive pulse of carbon into the atmosphere. This would initially have been primarily in the form of CO, which would have rapidly evolved into tropospheric ozone, CH4, and ultimately CO2. The result would be a very rapid and intense warming -- RF probably peaked around 8 W/m2, dropping to 2 W/m2 by year 10 as the CO, O3, and CH4 evolved into CO2. From year 10 on, the warming episode would have persisted for centuries thanks to the long lifetime of the CO2 pulse. Fig. 6 from Kawaragi et al. 2009. (a) Temporal evolutions of change in abundances of CO, CH4, O3, and OH after the Chicxulub impact. The amounts of CO and NO released into the atmosphere are assumed to be 2.8 × 1016 mol and 5.0 × 1013 mol, respectively. (b) Temporal evolutions of radiative forcing of tropospheric O3, CH4, CO2, and their total. The radiative forcing of CO2 is the sum of contribution of CO2 oxidized from CO through photochemical reactions and shock-induced CO2. Right vertical axis represents the increase in surface temperature corresponding to the radiative forcing. That long-lived pulse of CO2 from carbonate rocks at Chicxulub is presumably the explanation for the signs of ocean acidification at the K-T impact. Massive flood basalt outbreaks at the Deccan Traps would also have released a lot of CO2, and is also widely suspected to be implicated.
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  3. I wrote: a mass extinction caused a comet impact [...] Er, that obviously should have been "a mass extinction caused by a comet impact" The mass extinction did not in fact cause the comet impact.
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  4. 1. Neutral water has a pH of 7, below 7 we call it acid, above 7 it is alkaline. With a pH of 8.1 we cannot speak of acidification. The ocean remains alkaline, though slightly less al-kaline. 2. Just as a global temperature, 'the' global ocean pH does not exist. We have only calcula-tions of the average of various separate measurements. The accuracy of such an average can be estimated at 0.15 pH-units. This means, that the pH shift that is found now, is only slightly more than the error in the measurement. Statisticians have an expression for such a difference: ‘not significant’. 3. The oceans have a huge buffering capacity. Excess CO2 is neutralized by chemical and biological mechanisms. Calcification by phytoplankton removes a lot of CO2, which is stored in the cell walls, and deposited to the bottom after death of the plankton cells. Maybe these buffering mechanisms are is the reason that the pH – as found in ice-cores – has never decreased below 8.1, nor has it risen above 8.3 in the past 800,000 years. 4. By the way, I would not simply accept pH-measurements in 800,000 year old ice cores. The assumption that the chemical composition of the ice cap and the air bubbles within it has not changed for 800,000 years – under hundreds of bars of pressure – is unproven. CO2-measurements in ice caps conflict with stomata-indices, that show that 10,000 years ago the CO2-concentration was higher than today. Nevertheless no biological disasters happened at that time. 5. A shift of the pH from 8.3 to 8.1 is not serious for most organism. An optimum pH-range of 0.5 to 1.0 pH-units is normal. I myself studied the growth of mushroom mycelium, and found optimal growth in the pH range from 6.5 to 7.5. Small shifts in pH are biologically insignificant. 6. Predictions of a further drop in pH by 0.3 or 0.4 units are highly speculative, as long as the buffer mechanisms of the oceans are insufficiently understood.
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  5. fydijkstra, it seems this word "acidification" touches a hot button for a lot of folks, perhaps the same way as does thinking of C02 as a pollutant. When the relative pH number is reduced, a solution is said to be "acidified." It's a convention in our language you're not going to be able to change. It's the same deal as speaking of relative temperature. A gas at 2,500 degrees C is said to "cool" if its temperature is later found to be at 2,400 degrees centigrade. It's not cool by any means, but it has cooled. Easy, eh? Getting hung up on this point does the rest of your post no credit.
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  6. fydijkstra wrote
    "2. Just as a global temperature, 'the' global ocean pH does not exist. We have only calculations of the average of various separate measurements. The accuracy of such an average can be estimated at 0.15 pH-units. This means, that the pH shift that is found now, is only slightly more than the error in the measurement. Statisticians have an expression for such a difference: ‘not significant’."
    Of course both "global temperature" and "global ocean pH" are expressed as averages. Your misinterpretation of the standard uses of those terms is just as pointless and distracting as your misinterpretation of the term "acidification," as Doug pointed out. Regarding the "accuracy" of the average pH measurement: Randomly distributed errors in the individual measurements cancel each other, increasing confidence in the average measurement as the number of measurements increases. Read about the Law of Large Numbers. Statistical significance is not calculated as simply as you described.
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  7. fydijkstra wrote "3. The oceans have a huge buffering capacity." Of course. But actual measurements reveal that the buffering is insufficient, because the pH has changed despite that buffering. That's not speculation, it is measurement. You wrote "5. A shift of the pH from 8.3 to 8.1 is not serious for most organism." Your statement is too vague to be useful, or even meaningful. If you actually read the actual scientific papers you will see highly specific descriptions of exactly what the consequences are expected to be, not just for individual species directly affected by such pH changes, but also for other species affected by the cascading effects such as disruption of the food chain.
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  8. I was going to comment on what acidification means, but Doug did that. Then I was going to post about averaging large numbers but Tom did that. All I can do is to back up Tom's point with a link to Taminos. John
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  9. "there are other examples of mass-extinctions coinciding with global warming and increases in atmospheric carbon dioxide" If I am not mistaken, in previous posts, arguments have been made against anthropogenic global warming as being faster than historically warmer periods produced solely by nature. Here is a switch that simply proves mankind is just as much a part of nature as anything else.
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    Response: The one example of time-frames used above is the PETM which occured over a time-frame of thousands of years. This is substantially slower (at least an order of magnitude) than current warming. It's not just the amount of CO2 that we're emitting that is the problem with global warming - the rate is also important because climate is changing faster than nature is able to adapt. So while there have been other past periods where climate changed faster than nature could adapt, current conditions are even worse.

    The primary lesson when looking at past climate change is that it gives us insights into how the planet responds to changes such as more atmospheric CO2 and/or disturbances in energy balance. And what we learn is that the planet is highly sensitive to changes in energy imbalance and that extinction rates increase when the climate change is more rapid.
  10. When the term "surface water" is used in relation to the oceans, it is generally used to identify a specific zone within the ocean. However it seems in this thread that the terms Ocean pH and surface water pH are both being used and interchanged, even in the OP graph. When surface water pH is mentioned, what depth of water is it referring to? When Ocean pH is mentioned does this refer to the full depth of the entire ocean or just different terminology that actually means surface water pH? For clarity perhaps it needs to be defined what each refers to, especially when pH values are being mentioned.
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  11. RSVP, there's a fundamental difference between us and much of the rest of nature. Unlike a large rock following a deterministic Newtonian existence leading to an orbital rendezvous with Earth, we're not mindless, we have some iota of influence on our destiny. We've sprung from nature, but for better or worse we've transcended a limitation shared by most other features of the natural world and have got a least a few levers of control in our hands. We're not supposed to be "dumb as a rock"; to be mindless is no longer in our nature.
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  12. Figure 1 suggests that dissolved CO2 in the ocean is historically in near equilibrium with atmospheric CO2. That makes sense given the rather large contact area. But it raises a huge question for me, one that must have been answered somewhere but I've so far not stumbled on it. What is the actual form of the carbon sink that interchanges with the atmosphere to form the Milankovitch-driven glacial cycle? My understanding is that in the slow cooling phase of the cycle, carbon is sequestered at the bottom of the ocean via the "rain" of dead organisms. If that understanding is correct, how does that reverse during the (relatively fast) warming phase of the cycle?
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  13. Ah, at least part of the answer to my question at 13 is likely to be related to the answer to johnd's questions at 11 regarding the definition of "surface".
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  14. GFW: Part of your answer is that during ice ages, carbon is sequestered in the land in the form of dead vegetation. As the ice then recedes the vegetation can decay and CO2 is released. Regards, John
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  15. RSVP writes: "there are other examples of mass-extinctions coinciding with global warming and increases in atmospheric carbon dioxide" If I am not mistaken, in previous posts, arguments have been made against anthropogenic global warming as being faster than historically warmer periods produced solely by nature. Here is a switch that simply proves mankind is just as much a part of nature as anything else. You're right. In the 4.5 billion year history of the Earth, there have been six or more brief episodes of extreme climate change that each killed off a large fraction of life on the planet. If you use that as your yardstick, then our impact on the planet is not unprecedented in magnitude. I'm not sure what the policy relevance of this is, however. Does the fact that AGW won't be worse than a comet slamming into Yucatan mean that we shouldn't bother trying to prevent or reduce the impact of AGW? That's setting a pretty high bar for action, IMHO.
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  16. So the K-T impact caused cooling or warming? Or to be more explicit, what happened , a "Nuclear Winter" or a "Greenhouse Oven"? Dinosaurs died frozen or cooked?
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  17. The solubility of carbon dioxide in water varies greatly with temperature and pressure. At the surface of the ocean, [760 mm Hg] the solubility in grams of CO2 in 100 g (pure water)is .3346 @ 0 C, .2318 @ 10 C, .1688 @ 20 C, .1257 @ 30 C, etc. Global warming warms the ocean surface causing release of CO2. Global cooling allows the ocean to absorb CO2 as the ocean cools. But in the deep oceans there are lakes of almost pure CO2. Presumably, much of this is from under sea volcanoes where the pressure is high enough for CO2 to liquefy, and being denser the water, fall to the ocean floor. Slowly, this CO2 does migrate to the ocean surface. During the global cooling from 2004 to 2009, our oceans did absorb more CO2 resulting in a decrease in pH. Now that our globe is again warming, I expect the oceans to release vast quantities of CO2 and thus increase the pH of the ocean's surface. During of period of global warming, the amount of oceanic release of CO2 can be greater then all from all the power plants and vehicles man has made.
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  18. I found some common misconceptions over the internet and here in the comments. The first, and the least important, is the use of the word acidification. Doug already clarified the meaning and its use; but neverthless, it's obviously irrelevant. Call it de-alkalinization or pH change, it doesn't matter, what's important is the effect. Some people think that CO2 in water forms HCO3- plus H+, the former then decomposes into CO3-- plus H+ and then increasing CO2 will increase CO3--. If true, it would favour the formation of calcium carbonate. Unfortunately, the opposite is true. The buffering effect to CO2 induced pH reduction consists in limiting the H+ concentration increase by formation of more HCO3- at the expenses of CO3--. Calcification is then limited not by availability of Ca++ but by CO3-- concentration, which is declining along with pH. pH has the same fate as CO2 in the sense that skeptics claim, for example, that it's not true that pH reduction influences corals growth, the latter being related to temperature. Did anyone ever say that corals growth is governed just by pH? Corals, as well as other shell forming organisms, respond (among other things) to temperature, true; but a reduced pH will increase their stress and limit the resilience to increasing temperature. Other human induced stresses (pollution) come also into play and clearly more stress means less resilience. Similarly, no one ever said that all species are getting into trouble, at least not in the short run. For example, some organisms (e.g. foraminifera) form calcite while others (e.g. corals) aragonite structures. The latter is more soluble than the former, so it is expected that aragonite forming organisms will be more vulnerable to pH reductions. And this is not the whole story. Some organisms, for example, are able to use different chemical paths to form their shells making them much more resilient to water acidification. The last myth that comes to my mind is that you need to have an acidic water (pH<7) to have any impact on calcium carbonate dissolution. This is not true, any alteration of a chemical equilibrium brings the reaction one way or another.
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  19. JRuss, can you supply a pointer showing where we may read about naturally occurring pools of liquid C02 in the deep ocean?
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  20. JRuss, #18: "in the deep oceans there are lakes of almost pure CO2." I think you're mistaken. Do you have a reference for this?
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  21. An important point, often overlooked, is the use of CO2-only figures in papers such as Pelejero et al (2010). However, most policy-makers use the term "carbon dioxide equivalents", rather than CO2-only targets, when discussing stabilisation targets for climate change. For example, targets for stabilizing temperature rises between 450-550 ppm "carbon dioxide equivalents" generally include all components of the atmosphere affecting global temperature rises, including CO2, other greenhouse gases and the cooling effects of aerosols. For further discussion, see: http://www.climateshifts.org/?p=683 John, this could be the subject of a useful post from you clarifying the differences between CO2-only and CO2-equivalents targets.
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  22. "Dinosaurs died frozen or cooked?" Does it really matter? The climate changed faster than the plants could adapt to the change, so the dinosaurs starved.
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  23. I find the level of analogy between the skeptic arguments regarding ocean acidification and those already debunked regarding climate to be remarkable. Er, perhaps the are homologous. Anyway, in comment #4, which I otherwise thought was a waste of time, the sixth point about buffer systems not being very well understood was worth adding to. Being a fish guy, I like this story, and so will you: "Fish an 'ally' against climate change." I haven't read enough papers on this topic yet, but I like the fourth one on Ari's CC Observer page Wooten et al (2008) pdf, particularly figures 1B and 2B. These show that things are already changing. A friend in the scallop farming industry tells me that there's been trouble with low pH so far this year. I can't help but think that the observed reduction in pH on the coast of the Pacific Northwest is too fast to be due directly to anthropogenic CO2 emissions (though those certainly can't help). I think I read somewhere or heard that changing wind patterns are bringing more ancient CO2 into surface waters than used to occur. Anyway, the changes in coastal invertebrate communities (like those shown in the Wooten et al paper) at this early stage are probably a bit of a window into the kinds of changes we'll be seeing in the open ocean in the next few decades.
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  24. From Peru at #17: Both. Actually, not just frozen then fried, but fried then frozen then fried, as I understand it (no citations, so take it with a grain a salt). I believe one consequence of a large impact is an enormous amount of debris which spreads out over most of the planet, much of which is very hot (incandescant?) when it hits the ground, causing very widespread fires. There's your first fry-up. Of course, this also releases a *lot* of CO2 & aerosols. The aerosols (from the impact & subsequent burning) then have an enormous negative radiative forcing, causing the big freeze. As these aerosols settle out, though, over a relatively short period of time, the forcing from the massive GHG pulse becomes dominant, and the temperature heads north again. On the one hand, this GHG contribution would tend to prevent an impact from causing a snowball earth. On the other hand, such drastic climatic swings would almost certainly lead to mass extinctions. Sorry I don't have any references - this is just pulled from memory, but I'd love to read a paper examining climatic consequences of large impacts, if anyone knows of one (or more).
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  25. JRuss wrote : During the global cooling from 2004 to 2009, our oceans did absorb more CO2 resulting in a decrease in pH. Do you have any figures or references for that global cooling in association with that decrease in pH ? How significant are the trends and the relationship between the two ?
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  26. Local diurnal/seasonal/interdecadal pH variability is rather larege comparedt to projected changes. Therefore marine ecosystems must have been evolved to deal with such excursions. Response to Comment on "Preindustrial to Modern Interdecadal Variability in Coral Reef pH" Pelejero & al. Science 27 October 2006: Vol. 314. no. 5799, p. 595 DOI: 10.1126/science.1128502
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  27. JRuss, in addition to the mysterious "pools of liquid CO2" comment, I'd like to highlight this, which is also incorrect: Now that our globe is again warming, I expect the oceans to release vast quantities of CO2 and thus increase the pH of the ocean's surface. As long as humans are burning large quantities of fossil fuels, the direction of the CO2 flux is from the atmosphere to the ocean. It's true that warmer waters hold less CO2, but that means the oceans will take up less CO2 from the atmosphere, not that the oceans will be a net source of CO2 to the atmosphere. See: * Sabine et al. (2004). The Oceanic Sink for Anthropogenic CO2. Science, Vol. 305. no. 5682, pp. 367 - 371. * Takahashi et al. (2009). Climatological mean and decadal change in surface ocean pCO2, and net sea–air CO2 flux over the global oceans. Deep Sea Research Part II: Topical Studies in Oceanography Volume 56, Issues 8-10, Pages 554-577.
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  28. Berényi Péter, "natural pH cycles can modulate the impact of ocean acidification on coral reef ecosystems." This is the conclusion of the original Pelejero et al 2005 paper that you did not quote. Modulation is one thing, long term decrease, eventually modulated, is another.
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  29. I am finding this discussion of "pH units" a little uncomfortable. As I understand it, pH is a logarithmic scale, so a change of 0.1 pH units means a different change in H+ concentration depending on the starting pH. Is there data on the % change of H+ concentration, or would this be misleading?
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  30. Ah, was just being stupid I think (re my comment #30). Is a 0.1 decrease in pH roughly the same as a 26% increase in H+ in the water?
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  31. The sad thing about JRuss is that he substitute teaches classes, including science classes, in public schools. The "pools of CO2 at the bottom of the ocean" and stuff like this being taught to our children? Ooof.
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  32. Answer to malcuk @31: yes.
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  33. #29 Riccardo at 22:19 PM on 8 April, 2010 Modulation is one thing, long term decrease, eventually modulated, is another Of course it is, for us. For the creatures living there it is all the same. If natural variability is high, a little drift does not make any difference.
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  34. BP writes: If natural variability is high, a little drift does not make any difference. How do you know that? Let's say a species is existing near the limit of its range in a given parameter (temperature, moisture, pH, whatever). There's some range of variation s around the mean x of that parameter which it has to be able to cope with. In other words, it has to be able to survive and reproduce through the range of conditions [x-s, x+s]. Now perturb x upward or downward to x'. That natural variability s doesn't disappear. The species is now subject to the range [x'-s, x'+s]. That's a different range of conditions and there's no guarantee the species will be able to survive under this new range. Of course, s may also change. That adds to the uncertainty. Your flat assertion that the existence of natural variability around the mean somehow immunizes the ecology to variability in the mean seems to be unjustified.
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  35. Wikipedia has an interesting chart on Ocean Acidification: ocean pH between the 1700s and the 1990s. According to Wikipedia
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  36. Again, the analogy between anthropogenic acidification denial and debunked AGW-denier arguments is remarkable. "We experience daily temperature fluctuations greater than the projected average temperature increase by 2100; therefore AGW is no big deal." Average surface water in the North Pacific will be unsaturated for Aragonite in the North Pacific by 2100? Don't worry! Small volumes are ephemerally unsaturated for Aragonite even now, and there are still pteropods.
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  37. Ned (#2 & #3), I don't know, there's a correlation there, but you can't prove causality. :-P
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  38. Chris G writes: Ned (#2 & #3), I don\'t know, there\'s a correlation there, but you can\'t prove causality. :-P My motto is "Post in haste, repent at leisure." I think my frequent mishaps and typos probably helped provoke John into adding the "Preview" button.
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  39. Ned, No worries. Actually, when I first read it, I assumed you were having a poke at the anti-AGW argument regarding the correlation of CO2 and global temps, or anything where the causation can be determined by physics, and not by simply looking at the stats. Cheers
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  40. Bern, I don't have time to back you up with real papers at the moment, but I was thinking the same thing. For a 1st-order assessment, I imagine an overlay graph of the lifetimes of sulfates, particulates, CO2, whatever, and the different rates, and opposing effects, determine that a climate roller-coaster was likely. As well, systems tend to 'wobble' for a while after a disturbance, as inertial effects often cause an overshoot of equilibrium.
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  41. I\'ve been thinking for some time that ocean acidification is potentially a bigger problem than sea-level rise, maybe even bigger than climate zone shifts. But, I haven\'t been able to bridge the gap between impacts to specific species of foraminifera and impacts to people. I\'ve read speculations that we might want to develop a taste for jellyfish, but I suspect there exists information on the food chain dependencies on the threatened foraminifera and the subset of those chains on which a lot of people are dependent for food. Any pointers? RobHon #16, my sister and I happen to have graduate degrees in psych, though I went the cognitive route (and ended up in a not in a research career) and she went social and teaches at university, your thoughts are within the realm of how I remember things in that area. I don\'t know the answer; attempts to ease the dissonance are often seen as attempts at manipulation. Defense mechanisms kick in (It\'s really hard to admit even to yourself that your actions cause harm to others.) and further attempts are most often met with hostility. Kind of like trying to force water on a dehydrated person, they don\'t feel thirsty, but you have to keep making water available.
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  42. Ah, I think I detect a pattern related to the preview pane. Look's like apostrophes are escaped as part of coping with XML(?) in the preview, but not returned to original when submitted. It's a minor defect.
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  43. #35 Ned at 00:52 AM on 9 April, 2010 Your flat assertion that the existence of natural variability around the mean somehow immunizes the ecology to variability in the mean seems to be unjustified. It would be unjustified indeed had I claimed such a thing unconditionally. However, it was not the case. I said it should not have observable effect provided shift is negligible compared to natural variability. If diurnal pH changes up to 1 pH do occur in coral reefs with no devastating consequences, a less than 0.1 pH change since 18th century is insignificant. BTW, I wonder how they figured out how much average ocean pH was 250 years ago with such accuracy.
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  44. Berényi Péter, diurnal and annual temperatures may vary a couple of tens of degree Celcius. Does it mean that the biosphere is already adapted to similar changes in average temperature? The same question can be asked for almost any physical/chemical variable. You reasoning is a huge oversimplification.
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  45. Berényi Péter #44: "BTW, I wonder how they figured out how much average ocean pH was 250 years ago with such accuracy. " I was wondering that, too. It's not easy to figure out from the link (Wikipedia).
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  46. "Examination of the mass extinction [...] are consistent with the physiological effects of elevated CO2 concentrations (along with the effects of global warming)." What exactly is your claim?
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  47. Ned "I'm not sure what the policy relevance of this is, however. Does the fact that AGW won't be worse than a comet slamming into Yucatan mean that we shouldn't bother trying to prevent or reduce the impact of AGW? " As my (non hybrid) petrol burning vehicle was idling at a red light, I was wondering why the concept of "idle" continues to exist, and why these motors cant simply stop completely as long as the vehicle is at a halt. I'm sure this is technically possible. My next thought, of course, was how much more energy it would take for such large scale retooling, and whether on the whole, this would have any benefit to the environment. While this may not be the greatest example, it illustrates the kind of problem I believe we are running into. I am not questioning whether we should bother, rather that one must be very careful in deciding what to actually do, given that almost anything you do do is likely to have a hitch.
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  48. Berényi Péter @44 and VoxRat @ 46. Sometimes we are fooled into assuming a high degree of accuracy by a high degree of resolution of the measurement in question. Cheap electronic measuring devices are an example. Just because they display units to a resolution of 0.001 unit doesn't necessarily guarantee that they are any more accurate than 1.000 unit. I think many historic reconstructions may not be able to guarantee even that same degree of accuracy. At least with cheap electronic goods there is a standard of known accuracy that they can be calibrated against. With historic reconstructions they are subject to the accuracy of any number of assumptions.
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  49. RSVP:
    As my (non hybrid) petrol burning vehicle was idling at a red light, I was wondering why the concept of "idle" continues to exist, and why these motors cant simply stop completely as long as the vehicle is at a halt. I'm sure this is technically possible
    Hybrids already do this, and automakers apparently are going to mainstream this. Another trick (in the sense in which engineers and scientists (including Phil Jones) use the word) that's already been deployed is to shut down some of the cylinders while the car is cruising at steady speed on relatively flat terrain.
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  50. Well guys, I have looked into the acidification issue a bit and found the usual pattern: not even the opposite is true. Variability of Surface Layer CO2 Parameters in the Western and Central Equatorial Pacific Masao Ishii & al. Global Environmental Change in the Ocean and on Land, Eds., M. Shiyomi et al., pp. 59~V94. © by TERRAPUB, 2004. 1. Eastern equatorial Pacific is particularly interesting 2. It is one of the regions with the lowest alkalinity in oceans (with pH sometimes as low as 7.9) 3. It is a net source of CO2 to the atmosphere (up to 1012 kg C year-1) 4. Dissolved CO2 in surface waters is highly variable, depending on ENSO phase 5. It is highest during La Nina events, lowest in strong El Nino. On the other hand we know El Nino sometimes has a really devastating effect on coastal ecosystems. La Nina is just the opposite. SeaWiFS Galapagos is in the middle of this region, so marine life there has to tolerate the great swings of ENSO. Still, it thrives in La Nina with its high CO2 concentrations and acidic waters from the deep and suffers when carbon dioxide is low in waters coming from the West Pacific warm pool. As a reality check, let us see a map of average absolute pH values of sea water (as opposed to anomalies): Thank to God, Galapagos coral reefs are still well and alive.
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