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My oh Miocene!

Guest commentary by Sarah Feakins

Our recent study in Nature Geoscience reconstructed conditions at the Antarctic coast during a warm period of Earth’s history. Today the Ross Sea has an ice shelf and the continent is ice covered; but we found the Antarctic coast was covered with tundra vegetation for some periods between 20 million and 15.5 million years ago. These findings are based on the isotopic composition of plant leaf waxes in marine sediments.

That temperatures were warm at that time was not a huge surprise; surprising, was how much warmer things were – up to 11ºC (20ºF) warmer at the Antarctic coast! We expected to see polar amplification, i.e. greater changes towards the poles as the planet warms. This study found those coastal temperatures to be as warm as 7ºC or 45ºF during the summer months. This is a surprise because conventional wisdom has tended to think of Antarctica being getting progressively colder since ice sheets first appeared on Antarctica 34 million years ago (but see Ruddiman (2010) for a good discussion of some of the puzzles).

Where did this record come from?

The ANDRILL program is a multinational collaboration involving scientists from Germany, Italy, New Zealand and the United States to drill through ocean sediments around Antarctica. The drilling effort in the austral summer of 2007 involved a rig perched upon the Ross Ice Shelf, drilling down through the ice, 400m of water below that and then grinding down 1km into the sediments. The sediments are bagged and then transported back to the storage facility in Florida from where they are parcelled out to analysis laboratories across the world.

It can take years to process all this sediment and perform all the compositional, elemental and isotopic analyses that need to be done. Numerous scientists work on getting the most information possible out of the core. One of the early findings was the unexpected discovery of abundant pollen in the Miocene part of the core by Sophie Warny (Warny et al, 2009). The pollen came from types of tundra vegetation and indicated summer temperatures above freezing, which was also inferred from the presence of freshwater algae.

After Sophie found the pollen, I began to search for molecular fossils of those same plants. The waxy coating of plant leaves is remarkable for its resilience in sediments. In addition those leaf wax molecules capture an isotopic record of past rainfall. It is these isotopic signatures that allow quantitative insights into temperature and rainfall.

To extract the leaf waxes we don’t look for visual fossils, instead we use organic solvents to dissolve and extract the leaf waxes out from the sediments. Those organic molecules are then purified by passing through a series of filtering steps in the lab. Ultimately we wind up with a pure concentration of the leaf waxes which can be analyzed by mass spectrometry (see photo).

How are the results interpreted?

The leaf wax hydrogen isotope evidence was interpreted in comparison to model experiments. Jung-Eun Lee (JPL) conducted experiments, after adding water isotopes into a model dubbed GRAM (Frierson et al, 2006) because it requires a gram of computational effort rather than a ton in a full general circulation model. With the aid of the isotope-enabled model version, iGRAM, we can simulate the movement of water around the planet and track the water isotopic signatures. The goal was to see if modern relationships between different points in space that have different isotopes in precipitation and temperature are valid when we instead consider changes at the same point over time. Model experiments suggested a small upwards tweak in the temperature reconstructions for the Miocene from 2ºC to 7ºC. These experiments also reveal the dynamics behind the isotopic values: more evaporation from the warmer high latitude oceans and increased rainfall at high latitudes. (Ed. In similar experiments for Greenland (Werner et al, 2000), the changes in the seasonal cycle were important in understanding the isotope paleo-thermometer).

The iGRAM model is however an idealised aquaplanet, (i.e. no continents at all) so it isn’t useful for the interior of Antarctica, but deep sea records suggest that glacial ice volume was about 50% of modern volume at that time. It is however difficult to do full general circulation model experiments for this period because of the difficulty of constraining boundary conditions in the Miocene – what the land surface looked like, what greenhouse gas levels were, etc. An aquaplanet is perhaps good enough for these tests as conditions at the coast are really set by the oceans.

In terms of figuring out how the climate system operates, temperature is one of the simpler variables to reconstruct (not that any of this is really simple). Figuring out how precipitation changes is harder, largely because models can’t capture the scale of clouds let alone raindrops. What the leaf waxes provide is an archive of the isotopic composition of precipitation – much as the ice cores do for the past million years. Of course an ice core is not as simple as a rain gauge, and a plant has biology that an ice core doesn’t, but crucially if plants are growing, leaf waxes are probably preserved in sediments allowing us to push these isotopic records back beyond the ice core records to address questions about what climate was like further back in time.

How robust are these results?

What is reassuring here is that all the lines of evidence presented, from various microfossils, molecular fossils, isotopes and model experiments, all point to temperatures at the coast of Antarctica reaching above freezing point in summer months, probably around 7ºC (45ºF).

Downcore results through the Miocene section show at least two periods of exceptional warmth.

It is in those warm, periods further back in time, that might help us understand a little more about how warmer climate systems operate, and that information might just be important as we contemplate our future.


  1. S.J. Feakins, S. Warny, and J. Lee, "Hydrologic cycling over Antarctica during the middle Miocene warming", Nature Geosci, vol. 5, pp. 557-560, 2012.
  2. W.F. Ruddiman, "A Paleoclimatic Enigma?", Science, vol. 328, pp. 838-839, 2010.
  3. S. Warny, R.A. Askin, M.J. Hannah, B.A. Mohr, J.I. Raine, D.M. Harwood, and F. Florindo, "Palynomorphs from a sediment core reveal a sudden remarkably warm Antarctica during the middle Miocene", Geology, vol. 37, pp. 955-958, 2009.
  4. D.M.W. Frierson, I.M. Held, and P. Zurita-Gotor, "A Gray-Radiation Aquaplanet Moist GCM. Part I: Static Stability and Eddy Scale", Journal of the Atmospheric Sciences, vol. 63, pp. 2548-2566, 2006.
  5. M. Werner, U. Mikolajewicz, M. Heimann, and G. Hoffmann, "Borehole versus isotope temperatures on Greenland: Seasonality does matter", Geophysical Research Letters, vol. 27, pp. 723-726, 2000.

193 Responses to “My oh Miocene!”

  1. 151

    re 149 Susan Anderson,

    You refer to, ” — our conviction we can engineeer earth to feed our exploitive needs forever.” I am not sure what you mean, but it sounds like you would like to return to days of yore, sometime or other. As an artist, that must work for you.

    As an engineer, I would work to arrange our resources to avoid floods and droughts as much as possible, whether or not these were caused by CO2, however it got into the air. Also as an engineer, the whole problem must be understood, so arranging our resources must be done to also face the CO2 crisis. Also a part of the problem is the fact that there is a lot of starvation in the world, and it seems we have no problem making it worse by doing such idiotic things as using feed grain for fueling energy guzzling vehicles; done as I recall by environmentalists and politicians in the name of reducing CO2, along with the farm lobby of course.

    I see it as unconscionable that we have not done simple things that we knnow how to do, to irrigate and drain land, thereby reducing misery in the world. True, population seems to ever insist on expanding to keep a certain level of misery in being. I don’t have an answer for that.

    One relatively simple area of improvement seems possible based on a farm vehicle recently demonstrated by Miastrada Company. Perhaps realclimate folks will see how solving farm labor problems connects with water and land problems which connect with climate problems. Look at to see a way we might engineer our resources.

  2. 152

    That’s classic DanH. Thanks RealClimate!

  3. 153
    Susan Anderson says:

    Jim Bullis, change the subject much? I was referring to some striking similarities between the dust bowl era and the present, having to do with heedless overexploitation and failure to regard consequences as having any significance.

    I have no issue with engineers if they can make smart changes that improve our lot, which is deteriorating rapidly, but I do take issue with the idea that infinite expansion leads to a positive endgame. A the moment, we appear not to be doing the simple things we could be doing due to political stalemate, and the circular firing squad does not help.

    I was struck today by a new AP item about fish deaths in the heat. Consequences are multiplying. Claiming that we are all powerful does not meet the case in real reality.
    However, I disregard my own advice, which would indicate I should maintain a stately inattention to these distractive items.

  4. 154

    re 153 Susan Anderson,

    I guess you do not see how all these things are connected, yes, through their consequences.

    The “simple things” we might do I am imagining to be the kind of things that impact energy supplies and give industry pause in planning investments. If so, the consequences could be serious to the developed world.

    I don’t see anything I said to be ‘claiming to be all powerful’ so you might ask yourself about changing the subject.

  5. 155
    Hank Roberts says:

    Change the subject? Heaven forbid. It’s so rare that authors of papers stick around to take questions and expand on what they’re interested in doing.

    Let’s focus on the subject. And how to fund more research.

    “My oh Miocene!
    Arctic and Antarctic
    Guest commentary by Sarah Feakins

    Our recent study in Nature Geoscience reconstructed conditions at the Antarctic coast during a warm period of Earth’s history…..”

    I have a question at least tangentially relevant.

    Are there any borehole temperature series from that area of the Antarctic? How far back do they go in time?

  6. 156
    Ron R. says:

    Perhaps a dumb question: the time period under question in this topic, the middle Miocene, is famous for its flood basalts which lack the large atmospheric ejections of the more normal stratovolcanos. Does that mean that, though these eruptions released both CO2 and sulfur dioxide, the latter did not make it into the stratosphere where it could have offset the CO2 and cooled temps? Could that help explain the anomalous warming of the period? All positive and no negative?

  7. 157
    Dan H. says:

    Thanks for at least trying to understand the consistency – yours appears to be the most coherent response. My statement does not say that the Dust Bowl was entirely natural – that is just a misconception posted by those who contend that it must be one or the other, and cannot be both. My statement is that natural variability is definitely a cause (I never said the only cause) of the American Dust Bowl. I also said that the effects of CO2 on the Dust Bowl could not be ascertained (not that it had no affect). This is mostly due to the calculated effects of the addition CO2 in the atmosphere (only ~6% above the pre-industrial average), is very small compared to the natural variation at the time. Evidence has been presented that other human influences had a greater influence in making the Dust Bowl worse than would have occurred naturally.

    This is not a case of either/or, as both natural and manmade cause can affect the environment today and yesterday alike. Not only is there ample evidence for this, but it is the more logical response. Reading through many of the previous posts, I see many people repeat illogical statements that it cannot be one cause or the other, as if only one cause can occur at a time.

  8. 158
    Jim Larsen says:

    148 Unsettled, read my 130 on quakes. I noted the ~3-6 orders of magnitude involved means the results would be so small as to be moot, even if true. I disavowed finding much scientific knowledge. I think that “conclusion” post was reasonable, yet you subsequently and still seem to be asking for more. I don’t see how I can comply.

    On Dan’s Dust Bowl, it seems you’re mostly agreeing with me in a way that appears to disagree. Perhaps my saying “land use” once but “CO2″ thrice was confusing since land use was “THE” cause. (No dust bowl this year!) Also, IMO Dan’s not being argumentative. He’s his usual helpful, forthright, and unteachable self. Perhaps if you’d visualize Dunning-Kruger as a handicap? (Interesting that I’m defending Dan by saying he’s “consistently wrong”, and receiving flak for it!)

    Also, 1930s US temperatures were influenced by the Dust Bowl itself, so comparing current US temperatures to the 30s (as skeptics do) is tenuous, perhaps needing a sort of Regional Heat Island adjustment. Any experts have an estimate of the effect? It would be a good counter to a common talking point.

    On topic, this bothers me: “An aquaplanet is perhaps good enough for these tests as conditions at the coast are really set by the oceans.” I figured that Antarctica’s coastal conditions are often set by katabatic winds. Is that wrong, or was the 50% reduction in ice enough to change the game?

  9. 159
    Hank Roberts says:

    For Jim, you’re asking if, during the Miocene, katabatic wind from the much smaller icecap would still reach –and set the weather at — the coast, dominating the effect of the ocean on the coast?

    I’ve been trying to come up with any case where katabatic wind falling off the edge of an ice field extends that far across vegetated land; I haven’t found anything by looking for contemporary examples. Can you?

    (Wondering if you have an actual example in mind of the conditions you’re describing as possible, or if you’re ‘asking to provoke’ without a basis for it)

    Seems the alternative to the model they used is no model (as they say alternative models don’t have enough information to be used).

  10. 160
    Patrick 027 says:

    Re 157 Dan H. – um,… well that (generally) makes more sense, but I don’t get where you got what others were saying (perhaps I just assumed they weren’t meaning to say what isn’t correct? … or maybe it wasn’t me …)

    It can be consistent to say that the CO2 effects cannot be ascertained while still putting a limit on what it may have been (not 100 % of the cause) – and it is generally consistent to say that you can ascertain the extent to which something cannot be ascertained; however, it sounds weird to go on to ascertain (via “the calculated effects of the addition CO2“) just why it cannot be ascertained in such a way that seems to imply that it can be ascertained to some extent.

  11. 161
    Unsettled Scientist says:

    Jim, when I replied that 130 wasn’t visible to me, only the 131 was there I believe. Regardless, I was mostly replying to your claim that I didn’t provide a citation. Since we now agree there is no science to back up the idea that fracking reduces the frequency of HUGE earthquakes and pumping water into the ground in California to cause smalls ones is a bad idea, we can move past that and let it go.

    As for Dan H, the only way I’ve ever found him helpful is in the replies he generates from Gavin, Tamino, Hank and others. I certainly do learn more about the science because of their responses, and I learn how to better deal with people who spread confusion because people like Gavin are ridiculously good at it. By now I’d have pulled all my hair, even my eyebrows, out of my head if I was in his position.

    It’s a repeating cycle, Dan H claims the NC legislation is based on more science than the assessment report, it gets pointed out that he’s wrong. He disappears for a couple months, comes back and we’re discussing him again instead of science. I’m partly to fault for getting baited into it. So like the earthquakes, I’m letting this go now as well. Parsing Dan H’s language is not going to lead us towards any kind of enlightenment.

  12. 162
    SecularAnimist says:

    Jim Bullis wrote: “… we have no problem making it worse by doing such idiotic things as using feed grain for fueling energy guzzling vehicles …”

    I’m not sure that’s any more “idiotic” than feeding most of the corn and soybeans grown in the USA to factory-farmed animals raised for meat, with a resulting LOSS of up to 90 percent of the protein available for human consumption — not to mention the resulting epidemics of entirely preventable degenerative diseases.

  13. 163
    David B. Benson says:

    Ron R. @154 — The SO2 washes out fast enough that it should have little long-term effect.

  14. 164
    Susan Anderson says:

    What Hank Roberts said:

    It’s so rare that authors of papers stick around to take questions and expand on what they’re interested in doing.

    Let’s focus on the subject. And how to fund more research.

    “My oh Miocene!
    Arctic and Antarctic
    Guest commentary by Sarah Feakins

    Our recent study in Nature Geoscience reconstructed conditions at the Antarctic coast during a warm period of Earth’s history…..”

    Thanks for the reminder. Guilty as charged.

  15. 165
    Ron R. says:

    David B. Benson at 6:23 PM.

    The SO2 washes out fast enough that it should have little long-term effect.

    Right, thanks David. Decades. On the other hand we are talking about continual eruptions and large amounts of gasses over a long period of time.

    See comments here under Columbia River Basalts: Climate

    I was thinking that perhaps the low altitude that SO2 from flood provinces are ejected to prevented it from making a difference, but the CO2 from the same volcanos apparently made it high enough to heat the earth. So maybe it’s as you say, simply the longevity of CO2 over SO2.

  16. 166
    Jim Larsen says:

    159 Hank,

    It was just an honest question. I didn’t assume that a 50% reduction in global ice makes a significant difference in ice area for the EAIS, nor that there were vast areas of vegetation, so there are no conditions in mind, which is pretty much the basis for the question! I don’t see where the OP is inconsistent with an East Antarctica with essentially no change except a lower ice sheet, no ice shelves, and a TINY fringe of life along PART of the coast. Since Andrill is next to the dry valleys, it could be a special case.

    Anybody have a map of Antarctica during the Miocene?

  17. 167
    Ron R. says:

    Jim Larsen @ 2:54 PM: Anybody have a map of Antarctica during the Miocene

    Please see comment #74, it’s similar to Sarah Feakins estimate in comment #65.

  18. 168
    Hank Roberts says:

    > a map of Antarctica

    The main post refers to “the difficulty of constraining boundary conditions in the Miocene – what the land surface looked like …..”

    There’s the problem.

    I turned up references to the roughly 50 percent ice cover, but only in chart and table form.

    Google image search found some maps, sketchy and old, but the recent papers citing ANDRILL work that might have newer maps are paywalled, no imagery visible with abstracts that I came across.

    Did you look at the ANDRILL website? It’s linked up near the top.

    This is where we try chanting “Author! Author!” hoping Dr. Feakins looks in.

  19. 169

    162 Secular,

    Ok, there is a reasonable argument for vegetarian diets as opposed to meat, fish, poultry intensive diets, though the people European and American continents have been eating meat etc. for thousands of years. And I only assert idiocy when it comes to tinkering with this way of life, which I tend to like.

    As to the factory farmed meat, that is disturbing and I am open to being convinced that this is problematic. Certainly we need to be very careful about factory like operations. But if it means that some will come up short of food to eat, our efforts to make the situation better need to be very well supported by evidence.

    What we might do to improve productivity in growing of organic crops is something we are looking into in regard to the farm vehicle that we at Miastrada Co. are now testing. By making it more attractive to tend crops with hand work instead of machines we are thinking we can improve things here. Look at, to see the concept.

  20. 170
    flxible says:

    “Certainly we need to be very careful about factory like operations. But if it means that some will come up short of food to eat, our efforts to make the situation better need to be very well supported by evidence.”
    The evidence has been in for some time, many come up short of food now because of industrial farming methods, particularly animal agriculture – read the details here . . . look at the graphs here. Your assertions are unfounded and irrelevent, please don’t return to pitches for your products here, even in Unforced Variations.

  21. 171
    Dan H. says:

    Most of the people who are short of food is directly related to lack of money, rather than food production.

    From the report, “Nor are science and technology by themselves a panacea for world hunger. Poverty, not lack of food production, is the root cause. The world currently has more than enough food, but some 1 billion people still go hungry because they cannot afford to pay for it.”

  22. 172
    Hank Roberts says:

    > ice volume
    Ah, when I looked up the Miocene I found the _Antarctic_ ice described as around 50 percent what it is today. The main post refers to “glacial ice” from deep sea records. I didn’t read that as meaning “global” — but perhaps it’s ambiguous.
    Iceland is mentioned as a contemporary example in one of the press reports, for what Antarctica may have been like in the Miocene. Here’s one paper on how the catabatic wind behaves on one particular icecap in Iceland, for whatever it’s worth (PDF)

    Glacier winds on Vatnajökull ice cap, Iceland and their relation to temperatures of its environs.

    Perhaps a more direct answer comes from the ANDRILL papers; the pollen and plant-derived waxes described from the drill cores fit a coastal ground cover, seems to me. But I’m just some guy on a blog. Plants haven’t changed that much since the Miocene, anyhow.

  23. 173
    Hank Roberts says:

    Quoting from Dan’s source,

    “… today’s brand of resource-intensive, environmentally destructive agriculture is a poor option. Therein lies the real challenge in the coming decades: how to expand agricultural output massively without increasing by much the amount of land used.

    What is needed is a second green revolution …. Such a revolution will require a wholesale realignment of priorities in agricultural research.”

    Always, always, check the cite and context; suspect spin. But you knew that.

  24. 174
    flxible says:

    Yes Hank, always the spin from that quarter, and the limited understanding – as Wanda said “Of course apes read philosophy Otto, they just don’t understand it.”
    About the ‘Green Revolution’: “… the global increase in crop yields per ha from 1961 – 1999 was accompanied by a 97% increase in irrigated acreage, 638% increase in use of nitrogen fertilizer, 203% increase in use of phosphorus fertilizer, and 854% increased production of pesticides …”
    It’s hardly any wonder when so much of that is invested in animal agriculture that poor folks go hungry.

  25. 175
    Ray Ladbury says:

    Dan H.,
    Much of the world’s population are still subsistence farmers…or in many caseds sub-subsistance farmers.

    The town I lived in when I was in Africa had a thriving market where you could pick up fruit, meat, vegetables, staples (rice, flour, corn) and even bread. Things got lean in the hot season, but you could usually find at least bananas.

    Fifteen km up a dirt road, the situation was entirely different. The kids there considered carrots a rare delicacy, and during the hot season, dogs started to disappear.

    Hunger is not a simple problem. It doesn’t reduce to one or even a few causes. And an agricultural system that produces monocultures of corn and soy is not a solution to it.

  26. 176
    Jim Larsen says:

    172 Hank, yes, I wasn’t sure whether global or local volume or area was “50%”, but 74′s map sure looks like local area is even less than 50% in that rendition.

  27. 177
    Dan H. says:

    During the same 40 year period, the real price of food fell over 50%. There has been a significant increase since, but is a result of rising energy prices, not farming practices.

    Yet, during this period of globally affordable food, still a billion people go hungry. Some people just do not get it. To truly solve the hunger problem, we must first attack poverty. Maybe apes can understand that.

  28. 178
    Ray Ladbury says:

    Dan it is not just “poverty”. Poverty and hunger are two sides of the same coin. Yes, poverty matters, but transport matters, distribution of wealth matters, sustainability matters, population matters, culture matters, education matters, land tenure matters, corruption matters. It ALL matters. We solve nothing if all we do is provide calories devoid of nutrition or grown in land rendered toxic or if we increase yield of terrestrial crops while rendering our estuaries fetid cesspools. As an ape, I do understand this. How ’bout you?

  29. 179
    flxible says:

    Yes Dan, the “real price” of food fell in the developed world during the period that cheap fossil fuels allowed industrial agriculture to develop it’s meat market, your without-context graph does not represent “global affordability” nor extent and quantity of distribution. Please stop your disinformational games.

  30. 180
    Steve Fish says:

    Re- Comment by flxible — 9 Aug 2012 @ 11:03 AM:

    Although this should be in Unforced Variations I can’t resist. There were 3.1 gig people in the world in 1961, while in 1968, at 3.5 gig people, Paul and Ann Ehrlich explained what was happening and we now, having ignored their caution, have 7 gig people plus global warming, peak oil, fresh water shortages, ocean degradation, habitat degradation (including for food crops), desertification, all of the additional things listed in the recent past by Hank Roberts and Ray Ladbury, and you are concerned about dietary habits? All we need is resource allocation to solve the problem? What do you think would happen if we can produce much more food, even without producing more CO2? We may be Homo but our response so far is not very sapient.


  31. 181
    Ron R. says:

    Jim Larsen @ 12:40 PM. I wasn’t sure whether global or local volume or area was “50%”, but 74′s map sure looks like local area is even less than 50% in that rendition.

    Not sure what the question is. Is there doubt about the middle Miocene Antarctic ice cap was less than today? The fact that sea levels were so much higher then would show that. 75 – 120 ft higher is the figure I remember. California had a large inland sea, formerly called the San Joachin, now the Temblor. ‘Course The coast was lower then too, but the sea levels were high all over. Look at Florida for example. Evidence of much higher temps.

    The map I provided is rough. Like I said, I can’t account for the absolute accuracy.

    Anyway, Sarah Feakins in comment 65 above says: Yes, despite the warming around the edges and the presence of vegetation during the mid-Miocene there was still a substantial ice sheet on Antarctica. The ice sheet was probably about 50% of the current size, likely mostly on East Antarctica.

  32. 182
    Ray Ladbury says:

    The real reason food prices dropped during the “green revolution” was that we learned to eat petroleum–by first adding lots of fossil water and turning it into corn and soy.

  33. 183
    Ron R. says:

    Steve Fish — @ 5:21 PM All we need is resource allocation to solve the problem? What do you think would happen if we can produce much more food, even without producing more CO2? We may be Homo but our response so far is not very sapient.

    You nailed it.

    IMO, environmentalists have been gagged by the rightwing think tank spin machine from saying what we really mean, from arguing the real issue, so we end up arguing around the edges, arguing the spinners argument. I mean, we surely don’t want to appear anti-human right? And that is how the spinners spin any discussion about population control. So instead we defensively talk small fixes, hoping that people will see the forest for the trees.

    The truth of the matter is though that it is the spinmeisters that are anti-human, for what kind of world would their policies leave future generations? None worth living in. It is the policies of environmentalists which, if followed, will lead to there even being a future for the human race.

  34. 184
    flxible says:

    Steve, see 169 and following, it’s JimBullis and DanH who believe “modern” animal agriculture is no problem and simple ‘resource re-allocation’ will take care of the impoverished starving millions, not I – you could find comments from me here over the long term that specifically show I believe overpopulation is the root of nearly every problem we now face, including climate change, I’m of an age to be quite familiar with the Erlichs. Yes, sorry about the OT posts, but I did apparently dissuade JimBullis – I should know there’s no dissuading DanH.

  35. 185
    David B. Benson says:

    Ron R. @165 — Thanks for the link; I have yet to visit some of those locations.

    Carbon dioxide is a well-mixed gas in the atmosphere with a mixing time of close to 2 years. It is the CO2 at all altitudes that produces the so-called greenhouse feect, not just the CO2 at any one particular altitude.

  36. 186
    David B. Benson says:

    The warmest part of the Miocene is the
    age (or stage) during which the majority of the Columbia Flood Basalts were extruded:
    (thanks to Ron R. for this link). These extensive flood basalts (or traps) probably expressed considerable CO2, raising temperatures.

    [Of particulr interest to me since I live on top of these basalts.]

  37. 187
    Patrick 027 says:

    Re 149 Susan Anderson – thanks – I’m going to post those comments on celestial mechanics and related stuff, but I’ll put it over at unforced variations. Maybe in a few days.

  38. 188
    Ron R. says:

    David B. Benson — @ 11:15 PM, Yes, someone can correct me if wrong but I read somewhere that peak warming was between 16.25 and 16.75 ma. So if you’re planning on a visit bring your AC.

    Another interesting side note from the CRFB volcanism was the creation of beautiful opals. Again from my notes:

    Virgin Valley, Humboldt County Nevada. “Some 16 million years ago the Virgin Valley was formed during a series of rhyolite volcanic flows, resulting in a large basin enclosed by low hills. This basin contained a succession of lakes and forests of spruce, hemlock, birch, chestnut and even sequoia which were periodically buried by volcanic ash hundreds of feet thick. A large lake formed within the basin which deposited large amounts of diatomite, a biogenic form of silica. Seepage of super-heated water percolated through the ash layers, carrying silica to the long-buried trees.” This resulted in the slow creation over time of world famous opals, The Virgin Valley opals being one of just a few places in the world for famous opals, the others being Australia and Ethiopia.

    Unfortunately, unlike the Aussie ones, most of those found in the Virgin Valley must be be kept submerged in water or they will “craze” or crack. Also some of these opals, possibly more than a third, are radioactive, esp. the pale green ones.

  39. 189
    Steve Fish says:

    Re- Comment by flxible — 9 Aug 2012 @ 8:17 PM

    No I haven’t misunderstood you. I am posting the rest of this response in Unforced Variations.


  40. 190

    re 183 flxible

    You did not dissuade Jim Bullis about anything. He just does other things so is not immediately here to deal with argumentative statements that seem to rely on deliberate misreading.

    Your assertion that people come up short on food due to industrial farming methods leaves a lot undefined. I intended a make a more specific statement referring to the use of corn to make ethanol as a motor fuel as being a harmful diversion of feed grains from the food chain. You certainly can not challenge that.

    I certainly am trying to introduce a new way to do farm labor with a machine I am developing. If you took a moment to watch the youtube video I linked to, you would realize the machine is oriented to increasing the role of hand labor in farm operations, which is certainly not an industrializing trend. The machine here is designed to make the work less injurious to workers, and would thus tend to enable significant expansion of agricultural operations. Type Miastrada Dragon on the youtube search line to see it.

  41. 191
    Sarah Feakins says:

    Hank, Jim (168, 172,176,181)
    This was a great question. It turns out that we have estimates of the global ice volume – using the oxygen isotope ratios of the foraminfera that lived in the deep sea. The oxygen isotope ratios record how much water is locked up in ice on land globally. Sea level reconstructions are also useful as you mention. Spatial reconstructions of where the ice was, are another question and the answers are more elusive. People are working on these questions though, as although hard problems, they are important ones to solve.

  42. 192
    David B. Benson says:

    I broke the link in #185. It should be

  43. 193
    Jim Larsen says:

    I was originally basing my ice coments on OP’s, “but deep sea records suggest that glacial ice volume was about 50% of modern volume at that time.”

    and then got into volume VS area, and a map of one educated guess of conditions at the time…

    But too late. Hank’s point remains the best of the thread. Lots of discussion lost by chasing off topic fluff.

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