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Unforced variations: Sept. 2013

Filed under: — group @ 2 September 2013

This month’s open thread… Expect pre-IPCC report discussion (SPM due on Sep 27, full report (pre-copy-editing) Sep 30th), analysis of this years Arctic ice cover minimum, and a host of the usual distractions.

296 Responses to “Unforced variations: Sept. 2013”

  1. 151
    prokaryotes says:

    Climate sensitivity extracted from Pleistocene climate change is thus inherently partly subjective as it depends on how much weight is given to mutually inconsistent estimates of glacial-to-interglacial global temperature change. Our initial assessment is a fast-feedback sensitivity of 3±1°C for 2×CO2, corresponding to an LGM cooling of 4.5°C, similar to the 2.2–4.8°C estimate of PALAEOSENS [99]. This sensitivity is higher than estimated by Schmittner et al. [94], partly because they included natural aerosol changes as a forcing. In addition, we note that their proxies for LGM sea surface cooling exclude planktic foraminifera data, which suggest larger cooling [126], and, as noted by Schneider von Deimling et al. [95], regions that are not sampled tend to be ones where the largest cooling is expected. It should be possible to gain consensus on a narrower range for climate sensitivity via a community project for the LGM analogous to PRISM Pliocene data reconstruction [97,98] and PlioMIP model intercomparisons [67,68].

    However, we suggest that an even more fruitful approach would be a focused effort to define the glacial-to-interglacial climate change of the Eemian period (MIS-5e). The Eemian avoids the possibility of significant human-made effects, which may be a factor in the Holocene. Ruddiman [127] suggests that deforestation and agricultural activities affected CO2 and CH4 in the Holocene, and Hansen et al. [91] argue that human-made aerosols were probably important. Given the level of Eemian warmth, approximately +1.8°C relative to 1880–1920, with a climate forcing similar to that for LGM–Holocene (figure 5), we conclude that this relatively clean empirical assessment yields a fast-feedback climate sensitivity in the upper part of the range suggested by the LGM–Holocene climate change, i.e. a sensitivity of 3–4°C for 2×CO2. Detailed study is especially warranted because Eemian warmth is anticipated to recur in the near term.


  2. 152
    prokaryotes says:

    So basically it appears that climate sensitivity is not a constant but a dynamic factor, state dependent on feedbacks and forcing.

  3. 153

    #146–Thanks for reminding us, Hank–that was indeed a good piece. It seems unlikely that the events of the last week or so have done anything to soften Mr.–Dr?–Doesken’s feelings on this topic.

  4. 154
    sidd says:

    I am indebted to

    for a reference to Previdi et al. in
    Q. J. R. Meteorol. Soc. 139: 1121–1131, July 2013 A
    available freely at

    pretty much agreeing with Hansen(2013) (in Phil. Trans. Roy. Soc. A, referred to earlier) for climate state dependent sensitivity. Implications of considering full earth system sensitivity (about twice the fast feedback sensitivity) are beginning to take hold among the Great and the Wise. Look at the authors on the Previdi paper, includes Hansen, LeQuere, Levitus and Ramaswamy.


  5. 155
    wili says:

    The Hansen, Sato et al. article that prok just linked to is well worth a careful read. Here’s some discussion of it over at CP:

    “Hansen Study: Climate Sensitivity Is High, Burning All Fossil Fuels Would Make Most Of Planet ‘Uninhabitable’

    James Hansen, the country’s most prescient climatologist, is out with another must-read paper, “Climate sensitivity, sea level and atmospheric carbon dioxide.” The paper, co-authored by a number of Hansen’s former colleagues at NASA, is an antidote to the rosy scenarios the mainstream media have recently been pushing.

    The key findings are

    The Earth’s actual sensitivity to a doubling of CO2 levels from preindustrial levels (to 550 ppm) — including slow feedbacks — is likely to be larger than 3–4°C (5.4-7.2°F).
    Given that we are headed towards a tripling (820 ppm) or quadrupling (1100 ppm) of atmospheric CO2 levels, inaction is untenable.
    “Burning all fossil fuels” would warm land areas on average about 20°C (36°F) and warm the poles a stunning 30°C (54°F). This “would make most of the planet uninhabitable by humans, thus calling into question strategies that emphasize adaptation to climate change.”

    Burning all or even most fossil fuels would be a true scorched Earth policy.

    Given that James Hansen has been right about global warming for more than 3 decades, his climate warnings need to be taken seriously…

    if we ultimately burn all of fossil fuels, Hansen et al find almost unimaginable consequences:

    Our calculated global warming in this case is 16°C, with warming at the poles approximately 30°C. Calculated warming over land areas averages approximately 20°C. Such temperatures would eliminate grain production in almost all agricultural regions in the world. Increased stratospheric water vapour would diminish the stratospheric ozone layer.

    More ominously, global warming of that magnitude would make most of the planet uninhabitable by humans. The human body generates about 100 W of metabolic heat that must be carried away to maintain a core body temperature near 37°C, which implies that sustained wet bulb temperatures above 35°C can result in lethal hyperthermia…

    A warming of [u]10–12°C[/u] would put most of today’s world population in regions with wet a bulb temperature above 35°C….

    …we are headed towards CO2 levels in 2100 last seen when the Earth was 29°F (16°C) hotter.”

  6. 156
    Jay Castor says:

    [moved to open thread]

    This may be somewhat off-topic, though not completely. I’m a member of the “lay public.” You know, the as of yet silent majority that you must convince of the direness of AGW if you really want anything done about it. Here’s my question. In the past I have read AGW “naysayers” who claim AGW theory violates the Second Law of Thermodynamics. No one has ever explained to me the reasons for that, whether true or false. Could someone here do so? Thank you in advance.

  7. 157

    #156–Jay, I’ve debated this with one particular denier repeatedly and in consequence have done a fair bit of reading on the topic, so I’ll take a crack at your question.

    Basically, the Second Law argument is misdirected. It stems mainly from a paper by Gerhard and Tscheuschner which claims to ‘falsify’ the greenhouse effect. But G & T–as clearly revealed by the bibliography of their paper, which cites *no* modern work on the greenhouse effect–do not understand the theory they seek to ‘falsify.’

    Their argument is, basically, that the atmosphere cannot warm the Earth’s surface, since the latter is warmer than the former, and ‘heat won’t pass from a cooler to a hotter,’ as Flanders and Swan popularized the Second Law. QED.

    They are wrong, however–a better formulation of the process is not that the atmosphere heats the surface, but that the atmosphere slows the rate at which the surface can cool. (That is the basis of the famous ‘blanket analogy,’ used in the SkS discussion linked below.)

    Another problem with G & T is that their argument utterly ignores actual observations of the energy fluxes between sun, surface, and atmosphere, of which there is an enormous volume, going back two centuries. I’ve written about that aspect of the question here:

    And here:

  8. 158
    Lennart van der Linde says:

    Two quotes from the new paper by Hansen et al 2013 that are particularly noteworthy, at least to me, living in Holland:

    “The empirical data support a high sensitivity of the sea level to global temperature change, and they provide strong evidence against the seeming lethargy and large hysteresis effects that occur in at least some ice sheet models [p.22].”

    “The amount of CO2 required to melt most of Antarctica in the MMCO [Middle Miocene Climatic Optimum, about 16 million years ago] was only approximately 450–500 ppm, conceivably only about 400 ppm. These CO2 amounts are smaller than suggested by ice sheet/climate models, providing further indication that the ice sheet models are excessively lethargic, i.e. resistant to climate change [p.23].”

    So we could be very close to melting all of the ice on Earth, resulting in about 70m of SLR. Maybe that would take as little as a few millennia and could be very hard to stop, if we don’t succeed in decarbonizing our economy very fast and/or in geoengineering our way out of this prospect. About 10m of SLR, including contributions from EAIS, could be possible in the coming three centuries, which may be inevitable in the longer term anyhow, but could still be slowed down substantially by fast decarbonization.

    How Holland and the world could or would adapt to 10m of SLR over the coming centuries is an interesting question, but it looks like it would be a lot more expensive than rapidly decarbonizing. Which of course would also mitigate the need for adaptation to earlier and maybe even more urgent pressures, like food and water shortages, heat waves, droughts, fires, storms, floods, diseases, migration and conflicts over all kinds of resources.

  9. 159
    Ray Ladbury says:

    Kevin and Jay,
    Anyone who makes the entropy argument against the greenhouse effect is either deluded, stupid or disingenuous. First, as Kevin notes, the problem goes away when you look at it as the atmosphere decreasing the cooling of the surface by trapping outgoing IR photons. However, it also goes away when you look at the physics–the surface is warm, and so emits a very large flux of IR photons over a more-or-less blackbody spectrum. Greenhouse gasses take a big bite out of that outgoing spectrum and are warmed by the absorbed radiation. The greenhouse gasses share this added energy with the rest of the atmosphere via collisional relaxation with them.

    The thing is that the gasses in the atmosphere will also emit IR photons–and at a higher rate than they would have if they hadn’t been warmed. Some of those extra IR photons will reach the ground. Now how are you going to keep the ground from absorbing that IR photon and warming up as a result? Quantum mechanics says photons are indistinguishable partiles?

    Moreover, we know with 100% certainty that there is a greenhouse effect. We know with 100% certainty that greenhouse gasses work by absorbing IR–hell, we can see it in satellite measurements of the emitted IR spectrum. We know with 100% certainty that CO2 is a greenhouse gas.

    This argument has to be the absolute stupidest advanced by the denialists.

  10. 160
    Steve Fish says:

    Re- Comment by SecularAnimist — 18 Sep 2013 @ 4:12 PM

    I am curious about your “empirical evidence” comment. My various dictionaries pretty much agree with the following definition of empirical: Relying on experience or observation alone without proper regard for considerations of system, science, and theory. It is just unverified opinion or data that might be correct, or not. Empirical evidence can be an interesting hypothesis to study, or used as a debating tactic by denialists.


  11. 161
    Hank Roberts says:

    The people SA is arguing with aren’t participating here.

  12. 162
    Rick Brown says:

    Steve Fish @160 re empirical.

    There are many here far more qualified to comment than I, but I think you should check more dictionaries. Empirical has multiple meanings, for example from

    1.derived from or guided by experience or experiment.
    2.depending upon experience or observation alone, without using scientific method or theory, especially as in medicine.
    3.provable or verifiable by experience or experiment.

    When I first encountered empirical as used by physicians (and you, and per 2. above) I was confused because they were clearly referring to an inferior form of evidence. Elsewhere in science the term is used as in 1. and 2. above – it’s the result of experimentation, it’s the real deal. I’m confident SA was using this connotation.


  13. 163
    prokaryotes says:

    Thank you wili for linking the open access study on CS!

    Traditionally, only fast feedbacks have been considered (with the other feedbacks either ignored or treated as forcing), which has led to estimates of the climate sensitivity for doubled CO2 concentrations of about 3◦ C. The 2×CO2 Earth system sensitivity is higher than this, being ∼4–6◦ C if the ice sheet/vegetation albedo feedback is included in addition to the fast feedbacks, and higher still if climate–GHG feedbacks are also included.


    Here we go! This finding means – mandatory actions.

  14. 164
    Mal Adapted says:


    Hank Roberts wrote: “Point is, for each of us — no matter how sure our hearts are in the right place, no matter that we’re deeply sincere — we can be fooled.”

    That’s a good description of people who believe that ginger or turmeric cannot possibly have any medicinal value, regardless of the mountains of empirical evidence showing that they do…

    I’m a little surprised to see that from you. Anyone with a commitment to genuine scepticism knows that it’s the quality, not the quantity of evidence that matters. Telling the difference requires Science, because “the first rule is not to fool yourself, and you are the easiest person to fool.” Hank has the right of it:

    Big money is being spent to fool us and divide people, to empty out the center where policy change can occur, to sell crap.

    That’s as true for “conventional” as for “alternative” medicine. More skepticism is needed, not less.

    In any case, isn’t it common knowledge that “herbal medicine” is the source of much of the modern materia medica?

  15. 165
    SecularAnimist says:

    Steve Fish:

    Empiricism is what distinguishes science from other approaches to understanding the phenomenal world.

    Plenty of pre-scientific approaches relied on theory, hypothesis and reason. Medieval theologians employed impeccable “reasoning” and rigorous “logic” based on systematic and elegant “theories” when they argued about how many angels could dance on the head of a pin. What they did not do was to look at the head of a pin under a microscope and count the dancing angels.

    Empiricism simply means “if you want to know how things are, look and see”.

  16. 166
    Hank Roberts says:

    > in addition to the fast feedbacks
    So you’re adding those to the fast feedbacks list;
    do you also remove them from the slow list? Same total amount of ice goes away in the end.

    Can annual snow persist, longterm, in winters?

    What else is still on a slow list?
    Geochemical changes, I guess.

    Subduction events must still be on the very slow list.
    One hopes.

  17. 167
    Hank Roberts says:

    want to see global trends for varieties of plankton?
    We ain’t close to having data for that yet.

    In the early years of a better understanding:

    The dataset used for Plankton Portal comes a period of just three days in
    Fall 2010. In three days, they collected so much data that would take more
    than three years to analyze it themselves. That’s why they need your help!
    A computer will probably be able to tell the difference between major classes of organisms, such as a shrimp versus a jellyfish, but to distinguish different species within an order or family, that is still best done by the human eye.

    If you want to help, you can visit

  18. 168
    prokaryotes says:

    “Can annual snow persist, longterm, in winters?”

    Depends on the climate state.

    “What else is still on a slow list?”

    Slow feedbacks, especially change of ice sheet size and atmospheric CO2, amplify the total Earth system sensitivity by an amount that depends on the time scale considered.

    fast-feedback climate sensitivity depends on the initial climate state. Fast feedbacks include water vapour, clouds, aerosols and sea ice changes


    The geo-response is still not identified probably, but relates to the sea level sensitivity(which is part of the earth system sensitivity).

    “Geochemical changes”

    Are ocean acidification, ocean anoxia, ocean saturation, ocean circulation…

  19. 169
    Steve Fish says:


    Re- Comment by Rick Brown — 19 Sep 2013 @ 1:15 PM

    What you have presented just verifies what I said. As we both have said, empirical evidence is just data. A scientific study compiles empirical data in a systematic manner relative to previous research and theory. Until a scientific study is performed and a publication in a peer reviewed journal is performed it is just conjecture. Even a single scientific study is subject to criticism until it is verified by further science. Empirical evidence can’t be trusted until it passes through this process because iIt is just opinion that has yet to be verified.

    For example: When a weatherman in a local TV station questions global warming because it is very cold in his region, this is empirical evidence. When a weatherman looks at land temperature monitoring stations and claims, without any reasonable analysis, that global temperature is biased, this is just empirical evidence. This a major problem in the health industry when MDs and alternative medicine practitioners make claims based on personal experience of themselves and others because it is just the opinion of biased individuals. Asking these people to show their evidence in a testable format is what good scientific skepticism is all about.


  20. 170
    prokaryotes says:

    saturation = stratification.

  21. 171
    Steve Fish says:

    Re- Comment by SecularAnimist — 19 Sep 2013 @ 3:01 PM

    Pre-scientific approaches didn’t provide data and an analysis that allowed others to test their conclusions and, in any case, there was no community that was capable of evaluating what they proclaimed. “[I]f you want to know how things are, look and see” is what we all do to solve our everyday problems, but this is a very bad scheme for trying to understand complicated issues such as climate science, evolutionary theory, or what medicinal products or practices are good or bad. Empirical evidence it just unverified opinion, maybe right, maybe wrong.


  22. 172
    prokaryotes says:

    Stratification of ocean water is a naturally occurring phenomenon that is important to the structure, circulation and productivity of the oceans.1-3 The formation of vertical stratification in the water column is a consequence of water masses with different densities. Water density is strongly influenced by temperature and salinity; with less dense, warmer surface waters floating on top of denser, colder waters. The boundary between the warmer and cold waters is called the thermocline. Water is unable to passively mix across this layer, but wind, upwelling, down-welling and storms help move water across the boundary. For instance, winter storms create turbulent mixing between water layers. Mixing is critical for ecosystem productivity because it brings nutrients to the surface and oxygen to deeper waters. During springtime warming, the waters stratify, trapping phytoplankton near the surface, resulting in a spring bloom in the nutrient rich water. The spring bloom in turn provides food for many marine animals and plays an important role in the global carbon cycle.4-6

    While stratification of the water column is important, prolonged or strengthened stratification can have negative impacts. As the temperature of coastal waters increase, the thermocline becomes a more powerful boundary, making it more difficult for the nutrient rich waters to reach the surface. This potential reduction in upwelling and mixing can result in local or widespread biomass loss and changes in species composition. Between 1951 and 1993 zooplankton biomass off Southern California decreased by 80% as a result of warming surface waters. In some areas the water temperature rose by 1.5oC and restricted coastal upwelling and nutrient availability.7


    Now this study from 1985 describes a large impact event, but is it correct that they essentially describe a stratified water column?

    A decrease of up to 3°/oo in the δ13 C values of planktic skeletons has been systematically observed across the Cretaceous/Tertiary boundary; the benthic skeletons show no corresponding changes. We interpret this decrease as a manifestation of the elimination of the surface-to-bottom carbon isotope gradient in ocean waters at a time when carbon fractionation by a photosynthesis-respiration mechanism became ineffective. A concurrent release of excess CO2 from a nearly barren ocean to the atmosphere could have caused global warming.


    Would it be correct to call future stratification “Strangelove ocean”? (An ocean, which primary production decreases considerably). Maybe this large impact event during the “Cretaceous/Tertiary boundary” was in a nutshell, an extreme ocean response we can expect today? Though some studies later conclude that this event wasn’t actually that long, until production restarted.

    Maybe someone can check the paper out or post a link to the paper??

  23. 173
    Mal Adapted says:


    Empiricism is what distinguishes science from other approaches to understanding the phenomenal world.

    Steve Fish, in response to SA:

    Pre-scientific approaches didn’t provide data and an analysis that allowed others to test their conclusions and, in any case, there was no community that was capable of evaluating what they proclaimed.

    IMHO, Steve’s point can’t be over-emphasized: above all, “Science is a way of trying not to fool yourself. The first rule is not to fool yourself, and you are the easiest person to fool.” Empiricism is a foundation of of Science, but intersubjective verification is even more fundamental. Until your evidence has passed the unsparing scrutiny of other trained scientists, you have no way to know whether you’re fooling yourself or not.

  24. 174
    Hank Roberts says:

    > some studies later conclude

    citations would be helpful to the “some studies later”
    if you know what they are.
    If you don’t know what theyare,
    what’s your source for the “some studies”?

  25. 175
    flxible says:

    When a weatherman in a local TV station questions global warming because it is very cold in his region, this is empirical evidence.

    Wrong. The [limited/incomplete] “empirical evidence” is the recorded temperature, the conclusions drawn from that are an opinion, and your hypothetical weatherman obviously doesn’t understand the difference between regional weather and global climate.

  26. 176
    Hank Roberts says:

    Phil Plait of “Bad Astronomy” quotes a Congressman: Let me be clear: What he said here is complete nonsense.

  27. 177
    Steve Fish says:

    Re- Comment by Mal Adapted — 20 Sep 2013 @ 7:39 AM

    I strongly agree. The “don’t fool yourself” imperative was drummed into my head in my graduate program and later I observed embarrassing instances where others had made this mistake. Correcting these mistakes can promote success for bright postdocs and occasional grad students.


  28. 178
    SecularAnimist says:

    Steve Fish wrote: “Empirical evidence it just unverified opinion”

    Sorry, but that’s just plain wrong — of course, if you want to make up a new definition for the word “empirical” that is pretty much the exact opposite of the dictionary definition, you are free to do that.

    Empirical: “derived from or guided by experience or experiment, depending upon experience or observation alone, provable or verifiable by experience or experiment“.

    Steve Fish wrote: “Pre-scientific approaches didn’t provide data and an analysis that allowed others to test their conclusions and, in any case, there was no community that was capable of evaluating what they proclaimed.”

    On the contrary, pre-scientific approaches provided PLENTY of “analysis” and there was always a learned community capable of evaluating that “analysis” based on principles of pure logic, pure reason, theology, what Aristotle said, or whatever.

    What that community did NOT do was to test “analysis” by deriving testable predictions from it, and then actually testing those predictions against actual observation, which is the ONLY way we ever obtain “data”.

    Mal Adapted wrote: “Empiricism is a foundation of of Science, but intersubjective verification is even more fundamental.”

    Well, as Bohr’s one-sentence summary of the Copenhagen Interpretation (which represents the truly radical empiricist epistemology that quantum theory requires) put it, “It is sufficient that we can unambiguously communicate the results of our observations”.

    Yes, of course, scientific empiricism must be rigorous, careful, precise, preferably quantitative, and subject to verification by multiple observers. Science sets a very high standard for empirical observation, but what is most “fundamental” is the recognition that actual observation is the ultimate test of truth; indeed, that it is the definition of truth.

  29. 179
  30. 180
    Hank Roberts says:

    > this study from 1985 … but is it correct that
    > they essentially describe a stratified water column?

    Can you ask your question differently? I can’t figure out what you mean to ask. Citing studies may help explain what they’re describing:,5&hl=en

  31. 181
    Hank Roberts says:

    That list of the citing studies leads to, e.g.:

    Long-term legacy of massive carbon input to the Earth system: Anthropocene vs. Eocene — RE Zeebe, JC Zachos

    Here, we discuss the long-term legacy of massive carbon release into the Earth’s surface reservoirs, comparing the Anthropocene with a past analogue,the Palaeocene–Eocene Thermal Maximum (PETM,approx. 56Ma).
    We examine the natural processes and time scales of CO2 neutralization that determine the atmospheric lifetime of CO2 in response to carbon release. We compare the duration of carbon release during the Anthropocene versus PETM and the ensuing effects on ocean acidification and marine calcifying organisms. We also discuss the conundrum that the observed duration of the PETM appears to be much longer than predicted by models that use first order assumptions. Finally, we comment on past and future mass extinctions and recovery times ….

  32. 182
  33. 183
    Hank Roberts says:

    A chunk from Zeebee and Zachos:

    Rapidly increasing CO2 levels over a few hundred years because of fossil fuel burning cannot be stabilized by natural feedbacks such as dissolution of deep-sea carbonates or weathering of terrestrial carbonate and silicate rocks. These natural feedbacks operate on time scales of tens to hundreds of thousands of years and are too slow to mitigate ocean acidification on time scales of decades to centuries. But could natural feedbacks have mitigated ocean acidification during the PETM? …
    …. Our results show that if the proposed PETM scenario roughly resembles the actual conditions during the onset of the event, then the effects on ocean chemistry, including surface ocean saturation state, were less severe during the PETM than expected for the future[65,66]. As shown by Zeebe et al.[4], not only the magnitude but also the time scale of the carbon input is critical for its effect on ocean carbonate chemistry.

  34. 184
    Steve Fish says:

    Re- Comment by SecularAnimist — 20 Sep 2013 @ 12:28 PM

    Empirical evidence is just that, but assemble it into a peer reviewed study in a reputable journal and I will take a look. I will even pay attention if you show me ten articles on a subject.


  35. 185
    john byatt says:

    You should be able to get behind The Australian’s Curry concern troll opinion piece by google….. Consensus distorts the climate picture

    worked for me

  36. 186
    john byatt says:

    Open access

    the editorial The Australian

    CONSENSUS has its strengths and weaknesses. In politics it can sometimes be a useful model; in other spheres, not so. Until recently it was not a term we associated with science, where the testing of provable facts takes precedence. The fact, for instance, that Nicolaus Copernicus failed to win a public consensus during his lifetime did not alter the reality of his postulations that the Earth was not at the centre of the universe. Likewise, the Earth was a sphere long before the flat Earth consensus dissipated. In that seminal study on such matters, Monty Python’s Life of Brian, the point is clarified. An idolising crowd is told they should not follow Brian as the Messiah, but think for themselves. “You’re all individuals,” Brian tells them. “Yes,” the crowd responds in unison. “We are all individuals.” Then a lone voice pipes up. “I’m not.” In this case, the consensus was wrong; as was the dissenter. – See more at:

    [Response: This is written as if discussing the science and coming to a consensus on what is known, what is uncertain and how this might be quantified is some kind of tyranny. It isn’t – it is simply what people do; this demonisation of agreement is verging on the ridiculous. – gavin]

  37. 187
    prokaryotes says:

    Hank, Can you ask your question differently? I can’t figure out what you mean to ask. Citing studies may help explain what they’re describing.

    I wonder if this wiki entry is correct (i made some edits)

    All the studies there appear to describe “Euxinia” Though it would be great maybe to get some clarification from Peter Ward (who commented before here at RC) or someone else. And maybe a post from RC on this subject, which could focus on SLR sensitiviy and ocean impacts.

    Also see Peter Ward Our Future In a World Without Ice Caps (April 2013)

    Re Zachos,
    Ocean Acidification in Earth’s Past: Insights to the Future – James Zachos
    (June 2013)

  38. 188
    prokaryotes says:

    Also relevant

    Conditions required for oceanic anoxia/euxinia: Constraints from a one-dimensional ocean biogeochemical cycle model

    Widespread black shale depositional intervals termed oceanic anoxic events (OAEs) occurred repeatedly during the Phanerozoic Eon. Here we developed a new vertical one-dimensional ocean biogeochemical cycle model that involves several chemical reactions in an oxic–anoxic–sulfidic water column. To explore the theoretical constraints for global oceanic anoxia/euxinia quantitatively and systematically, we conducted sensitivity analyses of the proposed causal mechanisms, including elevated rates of riverine phosphorus (P) input, ocean stagnation, and lowered oxygen solubility due to climate warming. We gave special attention to the vertical chemical structure of the ocean and also to the characteristic behaviors of the marine P cycle under anoxic conditions, because the relationship between the depth of anoxia and the benthic phosphorus flux could be important for the occurrence of oceanic anoxia/euxinia. Steady-state simulations indicated that (1) a decrease in ocean stagnation or oxygen solubility is not enough by itself to achieve widespread anoxia with the present reactive P river input rate, and (2) shallow water anoxia followed by massive P liberation from surface sediments can lead to widespread eutrophication and anoxia/euxinia. We conclude that elevated riverine flux of reactive P is the most important factor for triggering global anoxic events via a positive feedback loop among ocean anoxia, phosphorus regeneration, and surface biological productivity.


    Massive release of hydrogen sulfide to the surface ocean and atmosphere during intervals of oceanic anoxia

  39. 189
    David B. Benson says:

    SecularAnimist @178 — You put it too strongly or rather, unconditionally. For a nuanced view, read The Unreasonable Effectiveness of Mathematics in the Natural Sciences

  40. 190
    prokaryotes says:

    Oh this seems to be the missing link

    Reconstructing the history of euxinia in a coastal sea (Current Issue Sep 2013)

    Areas of the coastal ocean where oxygen is low or absent in bottom waters, so-called dead zones, are expanding worldwide (Diaz and Rosenberg, 2008). Increased inputs of nutrients from land are enhancing algal blooms, and the sinking of this organic matter to the seafloor and subsequent decay leads to a high oxygen demand in bottom waters. Depending on the physical characteristics of the coastal system, this may initiate periodic or permanent water column anoxia and euxinia, with the latter term implying the presence of free sulfide (Kemp et al., 2009). Global warming is expected to exacerbate the situation, through its effects on oxygen solubility and water column stratification. In many modern coastal systems, anthropogenic changes are superimposed on natural variation and lack of knowledge of such variation makes the prediction of future changes in water column oxygen challenging (e.g., Grantham et al., 2004). That natural drivers alone can be the cause of widespread coastal anoxia is evident from studies of greenhouse periods in Earth’s past, including the oceanic anoxic events of the Cretaceous and Toarcian (Jenkyns, 2010).


  41. 191
  42. 192
    prokaryotes says:

    Updated (working) link from #168

    July 2013 Climate sensitivity in the Anthropocene
    M. Previdi, a *B.G.Liepert, b D. Peteet, a,c ,J.Hansen, c,d D. J. Beerling, e A. J. Broccoli, f S. Frolking, g J. N. Galloway, h M. Heimann, i C. Le Qu ́ er ́ e, j S. Levitus k and V. Ramaswamy

  43. 193
    Hank Roberts says:

    > prokaryotes says:
    > 20 Sep 2013 at 8:42 PM
    > Hank, Can you ask your question differently?
    > I can’t figure out what you mean to ask.

    What? You’re echoing what I asked you, but I’m not sure why.

    Never mind, I’ll just watch for a while.
    Let someone else figure it out.

  44. 194
    Hank Roberts says:

    Prokaryotes, you copy material from other links, put it on your own climate blog, then post here pointing to your copies.

    You’re taking something — attention — from the people who did the original work, by taking credit for the copy.

    The Zachos lecture Prokaryotes points to is a copy of one of a large set — available from the Metcalf Institute,

    Doesn’t pointing to the original seem somehow more appropriate than copying to your own site and pointing to your copy?

  45. 195
    Susan Anderson says:

    I don’t think practical observation from daily life should be summarily dismissed. If the general population is to be activated to get past our deadlock, observation of consequences to extreme weather and overall seasons, for example, do more than any number of scientific studies. We’ve had an uptick in understanding because the idea of blocked weather patterns is possible for laypeople to grasp. Trying to put this in perspective is helpful and indicating scale and timespan helps with that.

    I realize I’m going a little sideways from the point at issue, but anecdotal evidence from farmers and old-timers can be useful. Our memories can be short, and life may be an illusion (a persistent one, as Einstein said), but for most people that’s what they believe most. Of course they mostly believe in some rather odd forms of deity as well, but we have to take the rough with the smooth.

    (ps, KR@113 (13 Sept) if you’re around, thanks for the link on von Storch. That was interesting and indicated the line of country. The assertions from the other side of the moon seem to have died out.)

  46. 196
    SecularAnimist says:

    Steve Fish wrote: “Empirical evidence is just that, but assemble it into a peer reviewed study in a reputable journal and I will take a look.”

    Yes, of course, the quality and reliability of empirical evidence can vary widely, particularly regarding phenomena that are in principle or practice difficult to observe. And one of the strengths of science is that it sets very high standards for empirical observation — we must define precisely what and how we are observing, observations must be replicable and preferably quantitative, etc.

  47. 197
    prokaryotes says:

    Hank, my earlier question “but is it correct that they essentially describe a stratified water column?”
    Has been resolved for the most part. The events described are related to ocean anoxia and ocean euxinia. With the latter being anoxia in the presence of hydrogen sulphide. I wonder now why experts rarely use the terms. I only found out about euxinia by reading the cited papers. And that is strange because so many popular scientist talk about it. The scenario is popular known as “Under a Green sky”.

  48. 198
    prokaryotes says:

    Global Warming Amplified by reduced Sulfur Fluxes as a result of Ocean Acidification

    Climate change and decreasing seawater pH (ocean acidification)1 have widely been considered as uncoupled consequences of the anthropogenic CO2 perturbation2, 3. Recently, experiments in seawater enclosures (mesocosms) showed that concentrations of dimethylsulphide (DMS), a biogenic sulphur compound, were markedly lower in a low-pH environment4. Marine DMS emissions are the largest natural source of atmospheric sulphur5 and changes in their strength have the potential to alter the Earth’s radiation budget6. Here we establish observational-based relationships between pH changes and DMS concentrations to estimate changes in future DMS emissions with Earth system model7 climate simulations. Global DMS emissions decrease by about 18(±3)% in 2100 compared with pre-industrial times as a result of the combined effects of ocean acidification and climate change. The reduced DMS emissions induce a significant additional radiative forcing, of which 83% is attributed to the impact of ocean acidification, tantamount to an equilibrium temperature response between 0.23 and 0.48 K. Our results indicate that ocean acidification has the potential to exacerbate anthropogenic warming through a mechanism that is not considered at present in projections of future climate change.


  49. 199
    sidd says:

    Re:ocean euxinia

    I believe I have previously referred to Kidder and Worsley who had a freely available summary in GSA (doi: 10.1130/G131A.1). I find their treatment quite plausible, and repeat my question: what is a possible time frame for the Red Sea or Med to go euxinic ? I suspect the answer is larger than a millenium or three although they list a number of feedback timescales in Table 2 which are uncomfortably small (10^2 yr) and which include warm-brine sinking and polar upwelling of desert-belt generated brine. They suggest global hothouse climate initiation in 10^4 or 10^5 yr but I have no physical intuition for the timescale for euxinia in enclosed oceans. I would appreciate some insight.


  50. 200
    sidd says:

    I see from one of the links above to Slomp(2013) from prokaryotes at
    (which is unfortunately no working for me at the moment)

    that the timescale for the Black Sea to go euxinic was on the order of 10^3 yr. This is uncomfortably small.