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Communicating Science: Not Just Talking the Talk

Filed under: — group @ 16 September 2009

Michael Mann and Gavin Schmidt

The issues involved in science communication are complex and often seem intractable. We’ve seen many different approaches, but guessing which will work (An Inconvenient Truth, Field Notes from a Catastrophe) and which won’t (The Eleventh Hour) is a tricky call. Mostly this is because we aren’t the target audience and so tend to rate popularizations by different criteria than lay people. Often, we just don’t ‘get it’.

Into this void has stepped Randy Olsen with his new book “Don’t be such a scientist”. For those who don’t know Randy, he’s a rather extraordinary individual – one of the few individuals who has run the gamut from hard-core scientist to Hollywood film maker. He’s walked the walk, and can talk the talk–and when he does talk, we should be listening!

While there may be some similarities in theme with “Unscientific America” by Chris Mooney and Sheril Kirshenbaum that we reviewed previously, the two books cover very different ground. They share the recognition that there is currently a crisis in area of scientific communication. But what makes “Don’t be such a Scientist” so unique is that Olsen takes us along on his own personal journey, recounting his own experiences as he made the transition from marine biologist to movie-maker, and showing us (rather than simply telling us–you can be sure that Randy would want to draw that distinction!) what he learned along the way. The book could equally well have been titled “Confessions of a Recovering Scientist”.

More than anything else, the book attempts to show us what the community is doing wrong in our efforts to communicate our science to the public. Randy doesn’t mince words in the process. He’s fairly blunt about the fact that even when we think we’re doing a good job, we generally aren’t. We have a tendency to focus excessively on substance, when it is often as if not more important, when trying to reach the lay public, to focus on style. In other words, it’s not just what you say, but how you say it.

This is a recurring theme in Randy’s work. His 2006 film, Flock of Dodos, showed, through a combination of humor and insightful snippets of reality, why evolutionary biologists have typically failed in their efforts to directly engage and expose the “intelligent design” movement. In his 2008 film Sizzle, he attempted the same thing with the climate change debate–an example that hits closer to home for us–in this case using more of a “mockumentary”-style format (think “Best in Show” with climate scientists instead of dogs) but with rather more mixed results. Randy makes the point that the fact that Nature panned it, while Variety loved it, underlines the gulf that still exists between the worlds of science and entertainment.

However, the book is not simply a wholesale, defeatist condemnation of our efforts to communicate. What Randy has to say may be tough to hear, but its tough love. He provides some very important lessons on what works and what doesn’t, and they ring true to us in our own experience with public outreach. In short, says Randy: Tell a good story; Arouse expectations and then fulfill them; Don’t be so Cerebral; And, last but certainly not least: Don’t be so unlikeable (i.e. don’t play to the stereotype of the arrogant, dismissive academic or the nerdy absent-minded scientist). Needless to say, it’s easy for us to see our own past mistakes and flaws in Randy’s examples. And while we might quibble with Randy on some details (for example, An Inconvenient Truth didn’t get to be the success it was because of its minor inaccuracies), the basic points are well taken.

The book is not only extremely insightful and full of important lessons, it also happens to be funny and engaging, self-effacing and honest. We both agree that this book is a must read for anyone who cares about science, and the problems we have engaging the public.

If the book has a flaw, it might be the seemingly implicit message that scientists all need to take acting or comedy lessons before starting to talk – though the broader point that many of us could use some pointers in effective communication is fair. More seriously, the premise of the book is rooted in perhaps somewhat of a caricature of what a scientist is (you know, cerebral, boring, arrogant and probably unkempt). This could be seen merely as a device, but the very fact that we are being told to not be such scientists, seems at times to reinforce the stereotype (though to be fair, Randy’s explanation of the title phrase does show it to be a bit more nuanced than might initially meet the eye). Shouldn’t we instead be challenging the stereotype? And changing what it means to the public to be a scientist? Maybe this will happen if scientists spend more time not being so like stereotypical scientists – but frankly there are a lot of those atypical scientists already and the cliches still abound.

When it comes to making scientists better communicators, Greg Craven’s book “What’s the worst that can happen?” demonstrates how it can actually be done. Craven is a science teacher and is very upfront about his lack of climate science credentials but equally upfront about his role in helping normal people think about the issue in a rational way. Craven started off making YouTube videos explaining his points and this book is a further development of those including responses to many of the critiques he got originally.

Craven’s excellent use of video to discuss the implications of the science is neatly paired with the work that Peter Sinclair is doing with his “Climate Denial Crock of the Week” series. Both use arresting graphics and straightforward explanations to point out what the science really says, how the contrarians distort and misinform and take some pleasure in pointing out the frequent incoherence that passes for commentary at sites like WUWT.

Crucially, neither Craven nor Sinclair are scientists, but they are excellent communicators of science. Which brings up a point raised by both Mooney & Kirshenbaum and Olsen – what role should working scientists play in improving communications to the public? Video editing and scriptwriting (and even website design!) is probably best left to people who know how to do these things effectively, while content and context needs to be informed directly by the scientists themselves. To our mind this points to enhanced cooperation among communicators and scientists as the dominant model we should be following. We don’t all need to become film directors to make a difference!


602 Responses to “Communicating Science: Not Just Talking the Talk”

  1. 551
    Mark says:

    “Sorry Hank and Ray, but when somebody goes out of their way to write such a rude and pointless post, it is difficult to bite one’s lip.”

    Why are you talking about yourself like that Matt?

    Your post about how you trust computer engineers, and you’re sorry was either pointless or horrendously wrong.

    Pick one.

  2. 552
    Brian Dodge says:

    I’m watching the TV show “Bones” while perusing RC. The character “Dr. Brennan” just said, in response to initial misidentification of human remains as a deer, “Yet another example of the sad state of science education in this country.” If science illiteracy is making it into pop culture, maybe there’s hope that climate science won’t get completely buried by fossil fuel disinformation.

  3. 553
    Patrick 027 says:

    Brian Dodge – did you see the episode in season 1 in which Brennan was up against her former professor as expert witnesses (spoiler alert!)? A potential metaphor for the politics of AGW – her former professor was working for Exxon et al. (PS I love the episodes where she’s interacting with babies – it’s so funny).

    Hank Roberts – yes, a very good website ( I just read through http://realclimateeconomics.org/policy_mechanisms.html, though I haven’t clicked on the links to the (full?) articles yet), but no place to post an opinion. Do you remember when I posted some policy ideas a few months ago? (starting in particular at http://www.realclimate.org/index.php/archives/2009/04/aerosol-effects-and-climate-part-ii-the-role-of-nucleation-and-cosmic-rays/comment-page-5/#comment-120878 ) – there were some more details.

    I wasn’t working on numbers there, just a structure, and I was curious what you thought of it since you discussed the issue briefly in a couple of comments above. (The original part is the idea of an effect backtax.) (spending category C, mentioned in the comment to which I just linked, would include some payment or counteroffer (wind turbines, etc.) to people who had some investments in coal or deforestation who will now take a loss on that investment – of course, at least in an industrialized country, an argument to keep this to a minimum is that (many) people should have seen the policy coming; if they were betting on us never having a climate emissions regulation policy, tough cookies.)

  4. 554
    Hank Roberts says:

    Patrick, I hope you can find a climate policy blog for discussion of your ideas that aren’t about the science. I’m here trying to learn the physics and climate science stuff.

  5. 555
    Hank Roberts says:

    Here’s where they interact — Copenhagen. This model or something like it is
    ( according to Nature’s science blog,
    http://blogs.nature.com/climatefeedback/2009/10/a_simple_climate_model_to_the.html
    “A simple model to the rescue” )

    being used by most or all the parties to Copenhagen.

    http://forio.com/simulation/climate-development/index.htm

    I hope to see more discussion about this; it’d be a great chance to explain the innards of it.

  6. 556
    Hank Roberts says:

    Awww, would you look at the crap the timber industry is getting away with? This is very bad news:

    http://www.uniondemocrat.com/2009092997947/News/Local-News/Carbon-swap-plan-draws-mixed-reviews

    —-excerpt follows—-

    In the new wording, according to a handful of environment groups, the baseline is being set so low that SPI will be monetarily rewarded for its standard 17- to 20-acre clearcuts.

    “It seems to be a very similar type of logging,” said Josh Buswell, Sierra campaigner for ForestEthics, of what the report defines as “natural forest management” compared to SPI’s current clearcut methods.

    “If you can essentially do business as usual and say you are sequestering carbon, and getting rewarded for it, given that this is going to be a model for the world … I think it seems a little bit hypocritical,” he said.

    Last year, SPI and environment groups ForestEthics and Ebbetts Pass Forest Watch unleashed contradictory reports detailing how SPI’s timber-harvest practices affected carbon sequestering.

    According to the environment groups’ report, deforestation is second only to fossil fuel emissions in causing greenhouse gas emissions.

    “A clearcut is about as beneficial to the climate as a new coal-fired power plant,” said Brian Nowicki, a biologist with the Center for Biological Diversity.

    But SPI’s report concluded that “intense forest management” stored carbon at almost twice the rate of an unmanaged forest.

    “They are extremely wrong,” Pawlicki said at the time of the report. “We will offset 877,000 automobiles because of our forest practices.”

    Meanwhile, the air board is claiming a widely-approved victory with the new program’s unveiling. …

  7. 557
    Hank Roberts says:

    Matthew, google

    sea ice bet

  8. 558

    Speaking of effective communication on the GW issue, I thought this essay did rather well:

    http://blogs.edf.org/personalnature/

  9. 559
    mike roddy says:

    Mark, thanks for stepping up to support my points about the hockey sticks at Dot Earth. Your comment was precise and accurate. It won’t shut them up, but at least you defeated them for the real record.

  10. 560
  11. 561
    Patrick 027 says:

    Re my comments 357 – 359: http://www.realclimate.org/index.php/archives/2009/09/communicating-science-not-just-talking-the-talk/comment-page-8/#comment-136201

    Of course, ice-age to interglacial variations in CO2, and CH4, N2O (is that the correct nitrogen oxide – I’m afraid I could get them mixed up), as well as aerosol forcing, vegetation albedo and ice albedo feedbacks

    (the feedbacks not included in Charney sensitivity for the reason that they usually have long response times (or otherwise have more complex behavior – aerosol, vegetation (which modulates seasonal snow and cloud albedo feedbacks), and CH4 and CO2 feedback (potentially) depending on the extant mix of species and their initial distribution (potential for hysteresis), initial conditions in the ocean (potential for hysteresis), locations and potentially the minerology of mountain ranges and also the distribution of continents, etc. – well some of that might go for the snow and sea-ice, water vapor and cloud feedbacks too, but anyway… ) and so for some purposes/contexts can be approximated or are usefully treated as boundary conditions instead of variables (note that in some contexts water vapor is ascribed a radiative forcing, even though it is generally a radiative feedback on timescales much longer than a week.)
    (PS is sea ice included in the Charney sensitivity?)

    are feedbacks, generally of positive sign, for the interglacial-glacial variations in climate, at least for the most recent glaciations (the Pleistocene) – although on even longer timescales, the chemical weathering feedback is negative
    —(it may be, averaged over glacial-deglacial fluctuations, less negative or maybe(?) positive, however, when ice ages are pulsed, because each period of deglaciation leaves behind mechanically-weathered material with greater surface area, which can enhance chemical weathering; even without fluctuation, glaciers can provide sediment to rivers which can carry minerals to warmer and still wet places more favorable to chemical weathering – hence the likely role of the Himalayas (and maybe the Tibetan plateau by shaping the Asian monsoon so as to enhance precipitation on the Himalayas, etc (?)) in helping bring down atmospheric CO2 concentration over the Cenozoic Era). Also, exposure of continental shelves due to lowered sea level might enhance chemical weathering, although I wonder if it would also enhance geologic emissions (oxydation of sedimentary organic carbon). When chemical weathering is not directly forced by changes in geography, evolution, etc, then in general, an increase in geologic emission or decrease in net organic C burial would allow CO2 to accumulate SLOWLY in the atmosphere, and warming and increased CO2 would tend to enhance chemical weathering, so that a new equilibrium climate is reached when chemical weathering again balances geologic emissions minus organic C burial (however the later responds to the changes). For other forcing of climate over very long time periods, chemical weathering tends to act as a negative feedback, whose strength is modulated by geography and minerology, vegetation, etc.

    Well of course, but I wanted to be complete. And also point out:

    I have read that methane also correlates with the ~ 20,000 year precession cycle (more than the glacial-interglacial variations??) – which makes sense because, even without glacial-interglacial variations, the precession and obliquity cycles affect low-latitude monsoons (hence the wetter conditions in the Sahara desert several thousands of years ago) (See “Earth’s Climate Past and Future” by William Ruddiman (the orbital forcing also affects tropical mountain glaciation).

    Besides already going outside the range of atmospheric CO2 concentration over at least the last 600,000 or 700,000 years and likely considerably longer, the anthropogenic rate of increase in CO2 has surpassed anything seen in at least the last deglaciation (see graph in Chapter 6 of IPCC AR4 WGI).

    The positive CO2 feedback … out of time

  12. 562
    Hank Roberts says:

    > (PS is sea ice included in the
    > Charney sensitivity?)

    I doubt there’s one single answer, and I didn’t find an original Charney paper; I did look a bit
    http://www.google.com/search?q=“charney+sensitivity”+components

    and looking through those articles quickly, I don’t see sea ice listed apart from albedo generally, while land ice sheets are discussed.

    Chris Colose’s piece is good, and he links to a recent Knutti article on the subject.

    [Response: Yes it is. Only the extent and height of the land ice sheets is not. -gavin]

  13. 563

    I really enjoy reading RealClimate: Communicating Science: Not Just Talking the Talk . It’s very interesting. Hope you will post something like this again.

  14. 564

    I am so glad to have read this article on science understanding. I m just now completing my thesis on how TV affects science understanding, with global warming as a case study. It will be completed this fall and a book will follow with my publisher. My academic background is meteorology and physics and I have been a science documentary film maker for the better part of 25 years. The divergence between science and the media especially TV, has at times stretched me so thin I thought I was going to snap. This thesis is a direct result of my trying to reconcile that disconnect. Most if not all broadcasters/producers/reporters have zero interest and backgrounds in science other than for the spectacle or for anthropogenic reasons and would happier chasing ambulances than understanding science. While I do agree scientists could perhaps do a better job communicating science to the public, by far, the weight of responsibility rests on those who say they are they are in the business of informing the public, the media. In order to represent science issues and science related stories, it is ludicrous to think you can do it without understanding science, science terminology and scientific peer review. The current climate of sound bites, short pithy comments and cliches, as well as assuming journalistic method is a substitute for scientific method is plain wrong. TV is cutting science content all over the place and the current run of reality science shows masquerading as science is the equivalent of MacDonalds pretending to be health food. Most people get their science information from TV and most science on TV is over generalized and over simplified. The solution is not as simple as the criticisms. Scientists have to begin to regain control over the science content TV and the other electronic media say represents science to the masses. Leaving people who don’t care about the science in control of communicating the science message is not a good plan.

  15. 565
    Patrick 027 says:

    On the positive CO2 feedback for glacial-interglacial variations:

    It’s actually a tricky problem. It has to be a lot more than the simple temperature dependence of the amount of CO2 that water can hold for a given partial pressure, because that alone is a weak feedback. In order for the atmospheric CO2 to decrease as much as it did during glaciations, the CO2 of the upper mixed ocean would also have had to decline in concentration.

    As water has been removed from the ocean to form ice sheets, there is a smaller volume of water with higher salinity (over geologic time, oceanic composition would be affected by cycling through hydrothermal vents, etc, but that’s a slow process).

    The salinity increase would by itself tend to put a little CO2 back into the atmosphere.

    I’m not sure how the smaller ocean volume would affect things (The modern ocean has about 39,000 Gt of CO2 with an average depth near 4 km; a 120 m drop in sea level would reduce volume by 3 %, so if the average concentration of CO2 in the ocean were the same (setting aside the variation between upper mixed layer, which presumably would shrink in volume mainly by the increase in land area and not by a decrease in depth (would the average depth increase in an ice age due to greater winds or…?), and the rest of the ocean, though that shouldn’t through this calculation off by much), the shrinking ocean volume would put 1170 Gt of CO2 into the atmosphere, which is more that what is even there now.

    There may also be a net loss in the organic carbon stored on land in vegetation and soil (although one thing which occured to me is that when glaciers initially form, they may form on top of some vegetation and soil and lock those away until exposed at a moraine, where some might remain in place until warming, at which point some remaining moraine carbon and newly exposed carbon might be released ?? – this particular process, if it exists, would tend to become less important over a series of glaciations due to soil loss).

    So there would be a net loss of C from the atmosphere, land, and upper ocean, that all has to be packed into the deep ocean or sediments*, with the volume of the deep ocean having shrunk (though the deep ocean’s volume may not be much of an issue?).

    The C contents of these reservoirs according to Ruddiman, “Earth’s Climate Past and Future”, p.241, 2001 (an excellent place to go to learn some paleoclimatology, by the way):

    Gt, preindustrial amount, last glacial maximum amount (20,000 years ago), change (for going back to a glacial state), % change

    Atmosphere …………… 600 …… 420 ….. -180 ……. -30
    Vegetation and Soil ….. 2160 ….. 1630 ….. -530 ……. -25
    Ocean mixed layer ……. 1000 …… 700 ….. -300 ……. -30

    Deep ocean …………. 38000 …. 39010 …. +1010 …….. +2.7

    (* geologic emissions of C ~ 0.2 Gt / year , over 10,000 years, this would be 2000 Gt; typically nearly balanced by chemical weathering and organic C burial, where organic C burial is typically ~ 20 % of the 0.2 Gt /year, or 400 Gt over 10,000 years. A speed up or slowdown in the rate of organic C burial into sediments could play some role).

    What put all that C in the deep ocean? From Ruddiman p.245-

    1. (biological pump) “ocean carbon pump hypothesis” – greater nutrients in some places = greater photosynthesis in the surface ocean = more falling organic C (maybe also some inorganic C in shells?) into the deep ocean, most of which will be oxydized (some of the inorganic C could dissolve, too), but will not escape the water until the water mass cycles back through the upper mixed ocean = net removal of C from the upper mixed ocean and net accumulation of C in the deeper ocean.

    (Actually, though, the sinking of carbonate shells would have other effects. If carbonate shells dissolved when remaining in the surface ocean, removal of carbonate shells would reduce the ability of the surface ocean to hold CO2. However, carbonate shells might not dissolve in the surface ocean (or else we wouldn’t have coral reefs – PS can organisms build carbonate shells when they are not in chemical equilibrium, provided dissolution is slow enough? I’m really not familiar with that process.)… Anyway, though, removal of CaCO3, (or MgCO3, although that tends to form more by alteration of existing CaCO3 rock/sediment (to produce CaMg(CO3)2) so far as I know) by removing Ca(+2) along with CO3(-2), would (if my understanding is correct) leave behind whatever is left of dissolved CaCO3, bicarbonate ions and CO2 and wouldn’t pull more CO2 from the air; the act of forming solid CaCO3 from solution would tend to drive the reaction of combining bicarbonate ions to produce carbonate ions + CO2, and tend to put CO2 back in the air or reduce the ability to pull more CO2 from the air. If, however, there is a source of Ca ions such as dissolved (Ca, …)SiOx from chemical weathering, then the removal of CaCO3 from solution would ultimately be necessary to make room for the Ca ion influx, and the net process would still allow the water to continually pull CO2 from the air (although some of that would take place in the rainfall, ground moisture, and river flow); and influx of dissolved CaCO3 would allow carbonate ions to combine with dissolved CO2 to form bicarbonate and allow the water to pull more CO2 from the air, but there would be no net effect upon formation fo solid CaCO3) , and the process fhe effect of inorganic C fluxes is tricky)

    Possible causes:

    a. increased upwelling of nutrient-rich water (? wouldn’t that reduce the residence time of the C in the deep ocean, though? Well, if the organic carbon ends up sinking deeper on average than the phosphorus and nitrogen, then the P and N could be returned from upwelling of intermediate water while the the C falls into deeper water (do proteins and nucleic acids decay faster than carbohydrates and fats?) that may not even be part of that upwelling… ???; if the nutrient rich water spreads out laterally away from the upwelling then the C and nutrients could sink into water that is not soon brought back to the same upwelling region, although any increase in upwelling could still return CO2 to the air faster regardless of where the ocean flow takes the resulting organic C, so there’s a give-and-take, I’d think).

    b. upwelling of water with higher nutrient content (From Ruddiman, p.246: “Most low-latitude upwelling draws on waters from several hundred meters deep that form in the middle latitudes of the Southern Ocean. If these waters carried more nutrients during glaciations, low-latitude upwelling could tap into a larger source of nutrients.”) (But I wonder again – to the extent those nutrients came from sinking biomass, this could be (partly?) counteracted by an increased return of CO2 to the air.) (This could also be caused by upwelling drawn from different masses of water).

    c. increased delivery of dust (with Fe (if not P,N ?)) from land (by wind) to regions where biological productivity would benifit from it. This option wouldn’t require an increased rate of CO2 return to the air.

    d. (not mentioned in Ruddiman) – river nutrient supply changes ?

    2. (perhaps a variant of 1, not mentioned explicitly in Ruddiman unless I missed it; hinted at above in my elaborations): Modulation of the effect of the biological pump by changes in circulation:

    2a. same total amount of C from the surface ocean could sink into lower layers, but a change in the distribution of marine photosynthesis and food chains and/or in ocean currents, including deep currents, might allow more C to sink into regions of water that have a longer time to return to the surface, thus increasing the residence time of the C in the deep oceans.

    2b – see 3. A decrease in the sinking of surface water with lower C contents and an increase in sinking of of water with higher C contents. The C content of surface water is affected by both biotic and abiotic conditions. However, if biological activity takes CO2 and exports organic C, the water will then tend to take more CO2 from the air, so my half-educated guess is that the distribution of photosynthesis relative to where surface water is sinking into the deep ocean wouldn’t matter so much; abiotic factors, like dissolved CaCO3 (or MgCO3, etc.), salinity, and temperature, would have greater effect (and maybe seasonal timing of the sinking at high northern latitudes given the annual cycle of atmospheric concentration of CO2 – for that matter, if you could somehow get deep water formation underneath a swamp (groundwater to ocean – seems unlikely to make a big dent in anything but an interesting thought), diurnal timing could affect the net C flux.

    Past changes in biological pumping of organic C from the surface to the deep ocean can be studied using C isotopes (C-13) (see Ruddiman, pp.247-248, and for some background, pp.242 – 245). Changes in oceanic circulation can also affect the isotopes, though (see Ruddiman pp.248 – 253).

    3. Changes in oceanic circulation (see 2b.) – (see Ruddiman pp.251 – 253)

    If the water that reaches the seafloor and returns to the surface before sinking again has more dissolved CO2 or is otherwise more corrosive to carbonate minerals, it can dissolve more CaCO3, etc, which can react with the CO2 to produce bicarbonate ions, thus when the water returns to the surface, it can take more CO2 from the air before sinking again.

    Regional variations may have partly or largely canceled out, except that there is an idea that the chemistry of Antarctic water was/is particularly important. North Atlantic deep water is relatively less corrosive than some other water masses; during glaciations, the sinking water of the North Atlantic did not go so much all the way to the sea floor as it spread south, so that sources of surface Antarctic water had more dissolved CaCO3.

    What else determines the corrosiveness of the water besides CO2? (Salinity, temperature, pressure?) Would regional seafloor composition variations have an effect or would water corrosiveness have been the limiting factor? (PS if a carbonate mineral layer were sufficiently thin, one could imagine such processes eventually exhausting CaCO3 sources on a regional basis while increasing CaCO3 on the sea floor elsewhere – but perhaps that is unlikely to be significant. I wonder about direct leaching of Ca ions from silicaeous (sp?) sediments and silicate minerals…?)

    In the Cretaceous (another part of the same book), sinking of warm salty water from low latitudes may have made a larger contribution to bottom water formation than now (at present it’s actually zero contribution so far as I know).

  16. 566

    Patrick, when sea level drops, the water is normally going into the cryosphere, not the atmosphere.

  17. 567
    Patrick 027 says:

    “Patrick, when sea level drops, the water is normally going into the cryosphere, not the atmosphere.”

    Yes. Where did I imply otherwise? (Ice formation from compression of snow wouldn’t store much CO2 within it’s air bubbles, except for some amount that thankfully gives us information about a history of atmospheric CO2 variations, etc.).

  18. 568
    Patrick 027 says:

    Snow formed by deposition would trap air bubbles with a composition of the atmosphere; gas release upone freezing of liquid water would probably be enriched in CO2 relative to N2 and O2 … But I don’t think there was a large volume of bubbles trapped in the cryosphere. In so far as organic and mineral carbon trapped in the cryosphere, that was implicitly included in what I previously wrote (moraines, glacial debris, soil (permafrost is a type of soil, is it not?).

    PS When I wrote that the obliquity and precession cycles affected low-latitude monsoons, I was being very general – of course, obliquity affects seasonal monsoons, and there would be no precession effect without obliquity, but the variations in obliquity the Earth regularly experiences are small enough that precession (modulated by eccentricity) dominates in the orbital forcing of low-latitude monsoons; obliquity having greater effect at high latitudes. Some methane feedback could be associated with higher latitude ecosystems.

    I once read of a rather interesting hypothesis about bog-albedo feedback…

  19. 569
    Patrick 027 says:

    A fourier analysis would reveal clusterings of periods near the nominal periods of the orbital (Milankovitch) cycles; another way to think of it is that the three cycles’ frequencies are modulated by astronomical conditions.

    (Precession and obliquity – the sun and moon, via tidal acceleration, apply torques on the Earth via it’s equatorial bulge. The torque on the Earth caused by object x causes precession of the Earth’s axis about the normal of the plane of the orbit of Earth and x. The torque itself cycles in strength over the course of a single orbit and goes to zero as x crosses Earth’s equatorial plane. The effect depends on the Earth’s tilt relative to the orbital plane, the mass of x, the mass of equatorial bulge of the Earth (thus the rotation rate and variation of density with depth); effect might be modulated by alignment of Earth’s obliquity with respect to orbit with x and the semimajor axis of the orbit, so eccentricity could be an effect; the moon and sun are not in the same orbital plane with the Earth so each can alter the obliquity of the Earth relative to the other via precession effect relative to itself; which can then affect the rate of precession, etc, and then there is the issue of the alignment of the semimajor axes of each orbit. The climatological precession cycle depends on the direction of tilt with respect to the orbital plane about the sun and the orientation of aphelion and perihelion, which themselves regress about the sun more slowly; the effect is modulated by eccentricity; Earth’s orbital eccentricity and orientation (including the tilt of the orbit with respect to the solar system, etc., which would affect the obliquity cycle) are changed by relativistic effects and gravitational interactions among planets)…

    But the effect of the precession cycle can be potentially modulated by obliquity; either zero obliquity or zero eccentricity would remove the precession effect entirely. For large enough eccentricity, the seasons might be dominated by the eccentric orbit, so that summer and winter would occur at the same time in each hemisphere if there were zero obliquity, and then the effect of precession might be seen as being modulated by obliquity…

    If the Earth were perfectly symmetric about the equator, then the effect of precession on global averages would be a ~10,000 year cycle, analogous to the 11-year sunspot cycle, which is the half period of a full magnetic reversal cycle.

    ——

    In brief – bog albedo feedback idea: when water supply is sufficient, the climax community is not a forest but a bog; bog plants create acidity that reduces tree survival; bogs can spread and displace forest; effect of snow on surface albedo is reduced by tall plants (trees) that stick up through the snow or effectively roughen the top surface of snow; a bog forms a surface that enhances the effect of snow, thus having a cooling effect.

  20. 570
    Rod B says:

    Patrick 027, a couple of quick questions on your interesting post (565): 1.) I calculate about 5.15 x 10^18 kg x 0.058% (by mass) = 3,000,000 Gt of CO2 in the atmosphere — considerably more than 1200 Gt your retracting ocean would add in your scenario. Is your projection way wrong? Or is my math and assumptions way wrong?

    2.) When sea water freezes does it really lose all or even much of its dissolved salinity? Is sea ice the equivalent of fresh water ice?

  21. 571
    Jim Eaton says:

    Rod,

    Sea water does lose almost all of its salt when it freezes.

    http://nsidc.org/seaice/characteristics/formation.html

  22. 572
    Coder43 says:

    Institute of Museum and Library Services. ,

  23. 573
    dhogaza says:

    When sea water freezes does it really lose all or even much of its dissolved salinity? Is sea ice the equivalent of fresh water ice?

    The ice crystals, yes, they’re fresh. But the total picture’s more complex (the salt has to go somewhere, after all)…

    Typing “sea ice salinity” at Google yields a good NSIDC page on sea ice salinity.

  24. 574
    Hank Roberts says:

    >2.)
    Eventually, Rod

  25. 575
  26. 576
    Phil. Felton says:

    Rod B says:
    10 October 2009 at 3:55 PM
    2.) When sea water freezes does it really lose all or even much of its dissolved salinity? Is sea ice the equivalent of fresh water ice?

    Eventually, after a couple of years it’s fresh enough to drink.

  27. 577
    Hank Roberts says:

    First hand information–a lot here worth reading
    http://forums.steves-digicams.com/landscape-photos/139226-high-arctic-eskimo.html

    “… The ice is all around us.. take any large piece of ice and stand it up.. brush all the snow off the sides and the top.. now wait! watch. learn the Eskimo way.. that sun will beat down on that ice and you can actually WATCH the salt settle in that piece of ice !!!!!!! It doesn’t take long. then walk over to that ice with your kettle and chip that ice horizontally and fill your kettle. When melted it is the most delicious fresh water you have ever tasted”

  28. 578
    dhogaza says:

    Oh, RobB, since you still claim to be a “skeptic”, why aren’t you capable of doing the google “sea ice salinty” search on your own, rather than bother us, making clear your lack of knowledge?

    Given the kinda superior denialist airs you put on hear, I really have to wonder.

  29. 579
    Radge Havers says:

    Richard Zurawski #564

    by far, the weight of responsibility rests on those who say they are they are in the business of informing the public, the media.

    Yes, but:

    Scientists have to begin to regain control over the science content TV and the other electronic media say represents science to the masses. Leaving people who don’t care about the science in control of communicating the science message is not a good plan.

    What do you see as the best way to do that? Maybe it’s just me, but there seems to be a sort of media glass ceiling when it comes to scientists (and some other demographics as well).

    I recently saw a guy (on TV where else?) comparing TV in India and the US. His comment was that Indian programming was some times rough but widely varying, while American TV was more homogenous and tightly targeted.

    I can’t help thinking the whole business model has to change and imagine that resistance to that would be very intense. It would involve busting up massive conglomerates, perhaps? Or maybe the paradigm-bizspeak-focus-group-genie is out of the bottle, and it’s too late for that? Maybe a remaking of Business Schools or some sort of structural academic reform (put business and journalism departments under the watchful eyes of scientists)? What?

  30. 580
    Rod B says:

    Jim Eaton, thanks. I didn’t know that. I suspected the salt stayed in the ice since my highly softened water makes completely solid ice cubes. But now on close inspection they are also more “cloudy” which I deduce is caused by nano salt particles coming out of solution.

  31. 581
    Rod B says:

    Thanks too, to dhogaza.

  32. 582
    Rod B says:

    Wow! Hank and Phil. too.

    dhogaza, my thanks was for the answer of course, not the shot ;-)

  33. 583
    Hank Roberts says:

    http://www.google.com/search?q=how+does+sea+ice+form%3F
    http://www.arctic.noaa.gov/essay_wadhams.html

    “How ice forms in calm water
    In quiet conditions the first sea ice to form on the surface is a skim of separate crystals which initially are in the form of tiny discs, floating flat on the surface and of diameter less than 2-3 mm. Each disc has its c-axis vertical and grows outwards laterally. At a certain point such a disc shape becomes unstable, and the growing isolated crystals take on a hexagonal, stellar form, with long fragile arms stretching out over the surface. These crystals also have their c-axis vertical. The dendritic arms are very fragile, and soon break off, leaving a mixture of discs and arm fragments. With any kind of turbulence in the water, these fragments break up further into random-shaped small crystals which form a suspension of increasing density in the surface water, an ice type called frazil or grease ice. In quiet conditions the frazil crystals soon freeze together to form a continuous thin sheet of young ice; in its early stages, when it is still transparent, it is called nilas. When only a few centimetres thick this is transparent (dark nilas) but as the ice grows thicker the nilas takes on a grey and finally a white appearance. Once nilas has formed, a quite different growth process occurs, in which water molecules freeze on to the bottom of the existing ice sheet, a process called congelation growth. This growth process yields first-year ice, which in a single season in the Arctic reaches a thickness of 1.5-2 m.

    How ice forms in rough water
    If the initial ice formation occurs in rough water, for instance at the extreme ice edge in rough seas such as the Greenland or Bering Seas, then the high energy and turbulence in the wave field maintains the new ice as a dense suspension of frazil, rather than forming nilas. This suspension undergoes cyclic compression because of the particle orbits in the wave field, and during the compression phase the crystals can freeze together to form small coherent cakes of slush which grow larger by accretion from the frazil ice and more solid through continued freezing between the crystals. This becomes known as pancake ice because collisions between the cakes pump frazil ice suspension onto the edges of the cakes, then the water drains away to leave a raised rim of ice which gives each cake the appearance of a pancake. At the ice edge the pancakes are only a few cm in diameter, but they gradually grow in diameter and thickness with increasing distance from the ice edge, until they may reach 3-5 m diameter and 50-70 cm thickness. The surrounding frazil continues to grow and supply material to the growing pancakes.

    At greater distances inside the ice edge, where the wave field is calmed, the pancakes may begin to freeze together in groups and eventually coalesce to form first large floes, then finally a continuous sheet of first-year ice known as consolidated pancake ice. Such ice has a different bottom morphology from normal sea ice. The pancakes at the time of consolidation are jumbled together and rafted over one another, and freeze together in this way with the frazil acting as “glue”. The result is a very rough, jagged bottom, with rafted cakes doubling or tripling the normal ice thickness, and with the edges of pancakes protruding upwards to give a surface topography resembling a “stony field”. The rough bottom is an excellent substrate for algal growth and a refuge for krill. The thin ice permits much light to penetrate, and the result is a fertile winter ice ecosystem. …”

  34. 584
    Patrick 027 says:

    Re Rod – (as others contributed more about sea ice above and beyond what I could’ve, about your C math):

    1.) I calculate about 5.15 x 10^18 kg x 0.058% (by mass) = 3,000,000 Gt of CO2 in the atmosphere ”

    From p. 8 of “Global Physical Climatology” by Hartmann (1994) (Excellent book, by the way), the total mass of the atmosphere is 5.136 e18 kg, so your 5.15 e18 kg figure is close enough.

    (e18 = 10^18 = million trillion = million billion thousands)
    (e15 = thousand billion thousands)

    5.15 million billion thousand kg = 5.15 million billion metric tons = 5.15 million Gt.

    Molar mass of CO2 is about 44.01 g , molar mass of C is 12.011 g, average molar mass of air is about 28.97 g or 28.96 g (Hartmann lists 28.964 g for dry air and 28.97 g for all air, but the 17 e15 kg of water vapor has a smaller molar mass (18.015 g from Hartmann – I know offhand it is very close to 18 g) and so the average molar mass of all air should be LESS than that of dry air, so for the rest I’ll just use the dry air value).

    44.01/28.964 ~= 1.519
    12.011/28.964 ~= 0.4147
    12.011/44.01 ~= 0.2729 ~= 1 / 3.664

    mass fraction CO2 ~= molar fraction CO2 * 1.519
    mass C (in CO2) ~= molar fraction CO2 * 0.4147
    mass CO2 / mass C in CO2 ~= 3.664 ~= 1/0.2729

    0.058 mass % / (1.519 mass fraction/molar fraction) ~= 0.038 mole % = 380 ppm(v). So your percentage was correct for around the present time.

    But 0.058 % * 5.15 million Gt ~= 0.003 million Gt = 3000 Gt. So 380 ppm CO2 is about 3000 Gt of CO2 in the atmosphere. (Aside, if I hadn’t gone by ‘sig figs’, that final calculation gives, in Gt, 2987, which is also the constant from Wein’s displacement law :) .)

    I like to go by Gt C; 2987 Gt CO2 is about 815 Gt C. (by molecules or by mass, there is so much less methane than CO2 that the total atmospheric C content is approximately that in the form of CO2; back in the Archean eon this approximation wouldn’t work so well.)

  35. 585
    Patrick 027 says:

    Aside from changes in the amount of biological pumping and the organization of that relative to oceanic circulations, it occurs to me that an increase in bottom water CO2 from biological C sinking would then tend to dissolve CaCO3, etc, off the sea floor, so that upon upwelling, either less CO2 would be emitted or more CO2 would be taken up by the water; in that way it would be easier for the biological pump to sequester C below the upper ocean without so much of a compensating effect of increased CO2 release upon upwelling.

    Of course, depending on the residence time of the C, even if upwelling returned CO2 at the same rate biological pumping removed it when in equilibrium, there would be some lag time between changes in biological removal of CO2 and any return by upwelling.

    ———-

    PS of course, there is conservation of angular momentum; if an object x exerts a tidal torque on the Earth then the opposite torque must be exerted on the orbit of Earth and x.

    Since the angular momentum and energy of the Earth-moon system are quite small compared to their orbit about the sun, solar tidal torques on the Earth’s deviations from a perfect sphere and the solar tidal torque on the Earth-moon orbit would have little consequence on the eccentricity, orbital inclination, and semimajor axis of the Earth’s orbit about the sun. However, that does not preclude an effect on the orientation of the semimajor axis within the orbital plane (for the same distance from the sun to the Earth-moon barycenter (center of mass), the acceleration toward the sun will be greater when the Earth and moon are closer to alignment with the sun, and the effect would be greatest at perihelion, so there could be an accumulation of deviations over multiple orbits as the alignments shift without quite repeating…? – but I don’t know any specifics of this.)

    The sun’s tide on the Earth-moon orbit does cause the orbital plane of the Earth-moon system to wobble with a period a bit under 20 years (18.something), so to a first approximation, the long-term average effect of the moon’s torque on the Earth’s equatorial buldge should not cause a change in obliquity relative to the orbit about the sun.

    However, the Earth’s own equatorial bulge, other deviations, and the planets, and the tidal bulges, all also act to modify the moon’s orbit over time …
    —-
    (the most basic role of the tidal bulges is that the tidal torques of the moon and sun each act on the tides raised by the respective objects acts to slow the Earth’s rotation as the tides are pulled out of equilibrium by the Earth’s rotation (significant over geologic time), with some kinetic energy of rotation converted to heat and a remainder of that as well as some angular momentum of rotation being transfered to the energy and angular momentum of the orbits (each object also exerts a torque on the tide raised by the other, but at least to a first approximation the effect of that interaction averages to zero as sometimes this acts to speed up rotation and sometimes to slow it down) – however, the tilt of the Earth relative to the object causing the tide will cause the rotation to pull the tidal bulges out of the orbital plane, and the oceanic geometry and coriolis force will further affect it, and so there could be changes in obliquity, etc.))
    —–
    … and even without that, the orbits involved have nonzero eccentricies. The changes in obliquity caused by the moon may not cancel out after a single cycle in lunar orbit inclination, and may accumulate over mulitiple cycles, and unless all the ratios of all the cycles (ie precession/regression of perihelion, perigee, orbital inclination of Earth, etc.) form perfect rational numbers, there won’t be any perfect repitition, …. etc. It’s complicated and there’s a lot I don’t know about it, but it’s interesting.

    (PS the lunar orbit eccentricity also varies over time; I saw a paper that suggested changes in the tidal mixing of the oceans (significant along with winds and biological activity) could affect climate, but 1. on the longer timescales these are very small effects (or one would think?, even if there are a lot of nonlinearities), and 2. I never saw any mention of the changing eccentricity in that paper (it was on PNAS – don’t have time to find it just now, though).)

  36. 586
    Patrick 027 says:

    “It’s complicated and there’s a lot I don’t know about it, but it’s interesting.”

    ie Jupiter and Venus and the changing of the orientation of the orbital plane of the Earth itself might be more important than the moon in shaping the obliquity variation, for all I know – although counter to that, I have read that the presence of the moon shields the Earth from more wild obliquity variations such as those experienced by Mars (but this is not a generalizable effect – ie it is contingent on other things about the solar system – see disagreement on likelihood of habitable planets between James Kasting and … I want to say Peter Ward??, maybe somebody else too ???)

  37. 587
    Patrick 027 says:

    “between James Kasting and “…

    It may have been Kasting’s book review of “Rare Earth”

  38. 588
    Rod B says:

    Patrick 027, thanks. Those damn decimal points get me every time. Still the 3000Gt is greater then the 1170 Gt you said the ocean would release, though it does make your point. Interesting. Does none of the dissolved CO2 (Carbonic acid) stay within the ice?

  39. 589
    Ray Ladbury says:

    Rod B., I suggest using engineering or scientific notation–it makes it easier to check your math in some ways.

  40. 590
    Patrick 027 says:

    Re Rod B – just to clarify, I was going through a reasoning process when I wrote that the oceans would have to release 1170 Gt C (which is, after multiplying by 3.664 mass CO2/mass C, greater than the ~ 3000 Gt present at this point into the AGW experiment) IF the concentration were to remain constant. The point being the average concentration of the ocean has to increase even more to compensate. That isn’t necessarily a problem, but I thought it was an interesting point to bring up.

    Solid carbonate minerals and organic carbon material, as well as gases and brine, can be trapped within a body of ice (but mostly outside the individual crystal grains of ice; freezing tends to purify the H2O). But the volume of sea ice was not so great and even if it were it probably wouldn’t have been so contaminated/impure; the land ice was formed by falling snow and after compaction, the volume fraction of gas would have been small. I suppose maybe some gas enriched in CO2 could have been stored within snow due to riming (supercooled water droplets freezing onto snow as it falls) or freeze-thaw cycles, in particular if there was CaCO3 dissolved in the water from aerosols, which could react with CO2 dissolved in water and would release it upon coming out of solution during freezing – but this just wouldn’t make a significant impact on the C budgets. Although some aspect of that could be a concern for ice core records – Ruddiman’s book does state that CaCO3 aerosols can affect the CO2 record from Greenland ice cores, making Antarctic ice (farther downstream from any mineral dust sources) a better source for CO2 concentration – although I would think measurements of Ca, etc, along with other information and maybe some modeling could correct for this…

  41. 591
    Patrick 027 says:

    “but this just wouldn’t make a significant impact on the C budgets” And the effect on the ice core record would be limited by diffusion through porous riming and diffusion through snow before compaction …?????

  42. 592
    Patrick 027 says:

    In other words, I’ll assume it’s a minor effect until I find out otherwise from somebody who’s studied it.

  43. 593
    Mark says:

    RodB, someone else used the 3000Gt figures.

    It’s a long thread:

    http://www.bbc.co.uk/blogs/thereporters/richardblack/2009/04/sometimes_on_reading_comments.html#P78682921

    Which then went on to “It’s Wikipedia’s figures, not mine!”.

    Then when that didn’t work, “OK, the figures weren’t from there, but they are consistent with them”.

    Then when THAT didn’t work, silence.

  44. 594
    Rod B says:

    Thanks for the tip, Ray; but I did! It seems I not only have a problem with decimals but also with subtraction. :-)

  45. 595
    Patrick 027 says:

    Ruddiman, p.239: Greenland ice sheet: “Unfortunately, the windblown dust that helps define these annual ice layers is rich in fine CaCO3 particles eroded from northern hemisphere continents adn blown to the ice sheet by high-level winds. If even a small amount of the old carbon in this CaCO3 dust reacts chemically with the CO2 bubbles in the cores, it will contaminate the air bubbles and produce artificially high CO2 values.”

    (Now I would need to go back and learn how CO2 is actually measured in ice cores – I suppose isotopic analyses could be used to distinguish between atmospheric and mineral C given additional information or assumptions (about the C-13 from that time period in the atmosphere and the C-13 abundance from the source rocks, etc…; but without that I’m still not sure why the problem would occur unless the CaCO3 reacted with other mineral grains and CO2 to become indistinguishable from Ca-bearing silicates, but that doesn’t seem likely at cold temperatures so far as I know… anyway, the concern doesn’t seem to be with CaCO3 in CCN or IN (cloud condensation nuclei, ice nuclei), and I suspect the problem is not with a net CO2 uptake by the ice caused by some liquid water with CaCO3 … I’m guessing these are very small effects (what is the concentration of CO2 in rainwater, typically? If the riming occured at higher altitude (probably not a big factor except where the ice sheet surface was high enough), there would be less gas to escape from the water because of the lower pressure.) Also, in order for a rimed snow crystal to hold onto gas enriched in CO2 from the riming process, it would have to be encased inside the riming particles, which, unless my visualization is incorrect, implies CO2 escaping into a gas bubble inside an enclosed space with liquid water enveloped by ice, which might fracture when the inside expands upon freezing, breaking it open … etc. And CO2 could diffuse in between ice crystal grains (but how fast?). )

    Ruddiman p. 236

    “At depths of 50 meters or more below the surface of the ice sheet, air no longer circulates. Air that had been slowly diffusing down to these depths is sealed off as small bubbles and trapped in the ice, a process called sintering. Air sealed in ice forms a permanent record of the atmosphere at the time the sintering occured.” … “The difference in age between the air bubbles and the surrounding ice varies with the rate at which ice accumulates.”

    … for fast accumulation of 0.5 to 1 m/year, age difference of “only a few hundred years.”; slow accumulation of 0.05 to 0.1 m/year, age difference “can be as large as 1000 to 2000 years.”

    Lest I leave anyone feeling doubtful about the ice core data:

    “Before interpreting records of greenhouse gases trapped in ice cores, scientists first need to verify that the techniques they use to extract and measure the gas concentrations are reliable. To do so, they measure gas bubbles deposited in the upper layers of ice in cores taken from sheltered pockets on ice sheets where snow accumulates more rapidly than in other regions. Short ice cores taekn from these sites provide measurements of CO2 and methane values from recent centuries”…”accelerating trend in the ice core CO2 measurements merges smoothly with a record of atmospheric CO2 based on instrumental analyses of actual samples of air taken at the Mauna Loa Observatory in Hawaii by the atmospheric chemist David Keeling since 1958.” … [which, over time, also lines up well with other instrumental records from several other sites that start later.]

    —————

    Obliquity variation – actually, even if the orbits were perfect circles and the Sun, Earth, and Moon were the only objects involved, ignoring tides and other deviations from sphericity except for the equatorial bulge, ignoring relativistic effects, and setting aside the reaction of the Earth-moon orbital plane to the torque by the moon on the Earth’s equatorial bulge, it might still be possible for the moon to modify the Earth’s obliquity. Up to a point that is either 45 degrees …

    (I think that’s the angle at which an object exerts the greatest torque on a prolate or oblate spheroid, as defined by the princple axis of the spheroid and the direction to the object)

    … or larger …

    (the angle varies over the course of an orbit with extrema equal to the orbital inclination relative to the the spheroid – although only the component of the torque that is parallel to the intersection of the orbital plane and the symmetry (equatorial) plane of the spheroid will average to nonzero over a whole orbit assuming variations of the orbit and spheroid orientation are insignificant over only one orbit** … I haven’t really gone through the math)

    … the average torque will be stronger when the moon’s orbit is tilted farther from the Earth’s equatorial plane; thus, as the moon’s orbit wobbles due to the sun, the average torque could be skewed from what it would be if both orbits were coplanar; as a vector, the moon’s torque on the Earth could be outside the plane of the Earth-moon system’s orbit about the sun, thus changing the obliquity relative to the sun. But I haven’t yet factored in how the direction of torque changes as the moon’s orbit wobbles. Well, someone out there obviously already worked all this out so I’ll let the matter be.

    —-

    James Kasting’s work (an excellent reading list – not that I’ve gotten around to reading most of it!):

    http://www.geosc.psu.edu/~kasting/PersonalPage/Biblio.htm
    with links:
    http://www.geosc.psu.edu/~kasting/PersonalPage/PDFs.htm

    from that:

    Essay about Peter Ward and Donald Brownlee’s “Rare Earth: Why Complex Life Is Uncommon in the Universe”
    http://www.geosc.psu.edu/~kasting/PersonalPage/Pdf/Persp_Biol_Med_01.pdf

  46. 596
    Patrick 027 says:

    Other interesting tangents from the main discussion:

    “Possible forcing of global temperature by the oceanic tides”
    Charles D. Keeling, Timothy P. Whorf
    http://www.pnas.org/content/94/16/8321.full

    “Long Term Evolution of the Solar Insolation Variation over 4Ga” [evolution of Milankovitch cycles over 4 billion years] – Takashi Ito, Mineo Kumazawa, Yozo Hamano, Takafumi Matsui, Kooiti Masuda
    http://www.journalarchive.jst.go.jp/jnlpdf.php?cdjournal=pjab1977&cdvol=69&noissue=9&startpage=233&lang=en&from=jnlabstract

    “Numerical modelling of the paleotidal evolution of the Earth-Moon System”
    Eugene Poliakow
    http://journals.cambridge.org/download.php?file=%2FIAU%2FIAU2004_IAUC197%2FS174392130400897Xa.pdf&code=41ce103453270e61e5fb4dfe7e2a40f0

  47. 597
    Patrick 027 says:

    From Ruddiman – p. 218 – isostatic adjustment:

    A 3 km ice sheet would cause bedrock depression of about 1 km from isostatic adjustment, which is important in part because this tends to warm the ice sheet surface by about 6.5 K, give or take (typical atmospheric lapse rate is 6.5 K per km – it varies, though).

    About 30 % of isostatic adjustment is an immediate elastic response.

    About 70 % is a viscous response that approaches equilibrium with a ‘half life’ of about 3000 years.

    Also from Ruddiman; see also Hartmann, “Global Physical Climatology”:

    When deglaciation (which is not limited by the rate of snowfall) happens fast enough, the lowering ice surface adds to the tendency of deglaciation more than it would if isostatic adjustment kept up with the deglaciation.

    It’s possible that repeated scraping away of soil over multiple ice ages eventually (around 900,000 to 700,000 years ago) removed enough of the lubricating effect (under pressure, the base of an ice sheet may have liquid water, wet soil can slide, etc.) of the soil that would allow ice sheets to spread out more rapidly, so that ice sheets would instead build up greater thickness, thus surviving conditions that could otherwise cause deglaciation except when strong enough, so that the eccentricity cycle’s modulation of the precession cycle became more prominent in the glacial-interglacial variations; another possibal contribution to an increase in the eccentricity cycle’s prominence is longer term cooling having a similar effect on shifting the threshold for deglaciation.

    Note that the threshold for initiating a glaciation can be different than the threshold for initiating a deglaciation (hysteresis).

    There is also threshold behavior associated with precession cycle effects on monsoons – the Sahara won’t get wet every cycle, as I understand it.

  48. 598
    Patrick 027 says:

    “possibal”

    Well, I’ve gotta get some rest.

  49. 599
    Patrick 027 says:

    Rod, others – CO2 levels and unit conversions, nice graph found here:

    http://www.skepticalscience.com/Comparing-CO2-emissions-to-CO2-levels.html

  50. 600
    Patrick 027 says:

    A final point about Earth-moon-sun stuff:

    Consider the precession of the moon’s orbital plane caused by solar tidal torque – that torque will be strongest when:

    1. Earth-moon system is at perihelion (effect greater at greater eccentricity)
    2. Moon is at apogee (effect greater at greater eccentricity)
    3. The tilt of the moon’s orbit is ‘toward or away from’ the sun – analogous to the tilt of Earth at the solstices.
    4. As seen from above or below the Earth’s orbital plane about the sun, the Earth, moon, and sun are aligned.

    Which means that the moon’s orbit precession cycle can be lopsided, spending more time at one phase than another, etc, and that, as well as variations in the magnitude and direction of the torque the moon exerts on the Earth, can/might (haven’t done the math yet, only the qualitative ideas which would guide the math) result in some net effect over complete cycles. Etc.

    —-

    If it were only the Earth and the moon, the orbital plane and the Earth’s axis would precess at the same rate from the torque on the equatorial bulge and the equal and opposite torque on the orbit. The total angular momentum would remain fixed (as a vector), so the angular momentum vectors of the Earth’s spin and of the orbit would both revolve around their vector sum. Note however, that unless the two component vectors are equal in magnitude, the component of greater magnitude will make a smaller angle with the total. The orbital angular momentum of the Earth-moon system is a few times larger (but not by a whole order of magnitude) than the spin of the Earth, so the axis of the Earth shifts around more than the plane of the Earth-moon (in terms of angles, it makes a wider circle).


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