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Post by sentient on Jan 4, 2010 0:20:32 GMT
For about the last 2 years now, I have been working my way back through the Pleistocene glacial/interglacial cycles using many Boolean search strings on scholar.google.com, a remarkable resource we should all be using more frequently. Recently I have been focusing on MIS-11, or Marine Isotope Stage 11, reputedly and frequently offered up as an analog for the Holocene. I thought I would share some text and links to some of the juicier bits: web.pdx.edu/~chulbe/COURSES/QCLIM/reprints/LisieckiRaymo_preprint.pdfIn this landmark paper (landmark herein defined as oft-quoted in the scientific literature, and frequently referred to as a landmark paper....) data from 57 global sites is used to extend the SPECMAP of Imbrie, et al, 1984 further back into the Pliocene-Pleistocene boundary, one of the memorable quotations is: “Recent research has focused on MIS 11 as a possible analog for the present interglacial [e.g., Loutre and Berger, 2003; EPICA community members, 2004] because both occur during times of low eccentricity. The LR04 age model establishes that MIS 11 spans two precession cycles, with 18O values below 3.6 o/oo for 20 kyr, from 398{418 ka. In comparison, stages 9 and 5 remained below 3.6 o/oo for 13 and 12 kyr, respectively, and the Holocene interglacial has lasted 11 kyr so far. In the LR04 age model, the average LSR of 29 sites is the same from 398{418 ka as from 250{650 ka; consequently, stage 11 is unlikely to be artificially stretched. However, the June 21 insolation minimum at 65N during MIS 11 is only 489 W/m2, much less pronounced than the present minimum of 474 W/m2. In addition, current insolation values are not predicted to return to the high values of late MIS 11 for another 65 kyr. We propose that this effectively precludes a "double precession-cycle" interglacial [e.g., Raymo, 1997] in the Holocene without human infuence.”To a seminal discussion of a 21.3 meter above present sea-level Bermuda highstand in MIS-11: si-pddr.si.edu/dspace/bitstream/10088/7516/1/vz_Olson_and_hearty_a_sustained_21m_sea-level_highstand_during_mis_1.pdfNot so different in the Red Sea: www.noc.soton.ac.uk/soes/staff/ejr/Rohling-papers/2007-Rohling%20et%20al%20MIS5e%20sea%20level%20rates%20NatGeosc.pdfThen on EPICA: www.climate.unibe.ch/~stocker/papers/mcmanus04nat.pdfAnd more recently: www.geologie.uni-frankfurt.de/Staff/Homepages/Pross/PDF/Mueller_Pross_QSR_2007.pdfWith more perspective provided in: www.clim-past-discuss.net/5/1553/2009/cpd-5-1553-2009.pdfWhat do you think? (Yet) More fixed links
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Post by nautonnier on Jan 17, 2010 22:09:29 GMT
Other than getting colder, has anyone identified the symptoms of an incipient ice age? It appears that the Milankovitch cycles cannot account for all ice ages - something else must assist the flip to the glacial stable state.
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mpaul
New Member
Posts: 30
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Post by mpaul on Jan 18, 2010 15:57:21 GMT
nautonnier: "It appears that the Milankovitch cycles cannot account for all ice ages - something else must assist the flip to the glacial stable state." ------ ------- Any better suspect than the sun? With cycles of various durations / lengths of time?
I (a.k.a. "Mere Layman") googled "solar geo magnetic cycles". The only things that came up are relationships of the geomagnetic index to sunspots and the like.
Point being: is there any record of geomagnetic cycles? If not, that would seem peculiar in light of the off the cliff index reading of late.
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Post by nautonnier on Jan 18, 2010 16:06:11 GMT
I was thinking more of what happens to the climate here rather than the instigating solar effects which we can only guess at or use Be10 or O18 proxies for and even they may be no better than a guess.
I have read conflicting views one that the Earth can flip into a glacial state in a decade another that it can take centuries to become glacial but that the exits are 'rapid'.
Whatever the case - are there markers for this in paleo records?
The LIA and other more recent cold periods appear to be relatively sudden in onset twenty years at most. Even then there are arguments over whether these changes are global.
Unfortunately, much of this is now colored by people trying to avoid making or breaking the case for CO2 warming rather than just reporting what appears to have happened.
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Post by stranger on Jan 18, 2010 20:48:47 GMT
The magnetic record is very difficult to read, much less interpret. Imagine a natural source of tape recorder tape that creates tape at a steady rate of an inch a year. And that the resultant tape is capable of recording the earth's magnetic field and direction at the instant it was created. Something much like that is what you want. But no one has found anything that fills that bill.
The best we have are magnetic rocks that cooled below the critical temperature at some time and still retain traces of induced magnetism. The result is much confusion and uncertainty about the record.
And we have enough of that with the AGW foolishness.
STranger
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Post by sentient on Jan 19, 2010 1:46:31 GMT
Although most of what I am about to post is essentially off-topic of MIS-11, it is germane to the issue of terminations in general. First, as just a single answer to mpaul, I suggest the following article from Rial, one of the more careful workers in this area: www.geolab.unc.edu/faculty/rial/FMpaper2.pdfBy no means is this the end-all in the discussion, as I could fill many posts with an enormous numver of papers and references to sites (such as above) for papers larger than I can attach. And if you are really interested in the to's and fro's of the orbital/climate dynamics, we can create such a thread and have a go at this unresolved topic in paleoclimate science. But the Rial paper is a good place to start. Many may also wish to use the advanced page of scholar.google.com to search out more of Rial's works. Those of you who may be familiar with the works of Richard B. Alley of the U.Penn. will also know that he has been on the National Academy of Sciences for well over a decade. In 2002, the NAS published "Abrupt Climate Change: Inevitable surprises. The book will set you back (as it did me) $58US and it is well worth the price. From the opening paragraph in the executive summary: "Recent scientific evidence shows that major and widespread climate changes have occurred with startling speed. For example, roughly half the north Atlantic warming since the last ice age was achieved in only a decade, and it was accompanied by significant climatic changes across most of the globe. Similar events, including local warmings as large as 16°C, occurred repeatedly during the slide into and climb out of the last ice age."Another excellent read targeted at the lay audience, also published through the National Academies Press, is "Climate Crash" (2005), by John D. Cox. Although in general, the sawtooth shape of both the ice age/interglacial transitions is preserved in the D-O oscillations as well, Dansgaard and Oeschger also saw the end of the Eemian thusly: The Dansgaard team noted that an event they estimated to have taken place 89,500 years in the past had plunged the climate “from warmer than today into full glacial severity” within just a century or even less. In fact, the drop in the oxygen isotope ratio, and thus in temperatures, might have occurred “almost instantaneously.” The curve in the climate profile, they wrote, “suggests that it took 1000 [years] to recover from this catastrophic event.”All up, it will cost you about $80US to pick up both these remarkable and credible books. You may never spend less than $100 for a more valuable perspective on abrupt climate change and how we came to understand it up to 2005. Well worth the investment. Suffice it to say, absent any credible effects of CO2, this natural noise just plain happens. It happens regularly. And when it happens again it will be devastating to our society. Regardless of CO2. In terms of the present interglacial, both sides of the issue on the mathematics of where we are relative to the end of the Holocene, I will post the following two papers, one in this post and one in the next: Attachments:
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Post by sentient on Jan 19, 2010 1:47:33 GMT
and on the other side of this issue we have the considered response of Lisiecki and Raymo: Attachments:
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Post by sentient on Jan 19, 2010 2:15:18 GMT
Now I am not entirely sure if nautonnier and stranger are talking about the same thing in terms of magnetics, so I will risk a stab at geomagnetic reversal as solar magnetics have been discussed to some extent elsewhere on this site. The geomagnetic reversal best studies with respect to climate is the Brunhes-Matuyama reversal at roughly 780kyrs ago, or close to the time many cite as the Mid Pleistocene Transition (though there is some controversy as to just how sudden this transition was). A search of my climate collection found 78 papers that reference the B/M reversal, so identifying a cogent one will take me some time. I suggest, again, going to scholar.google.com (the advanced page is more appropriate for Boolean searches) and search out the publicly available papers (on the cheap). The are relatively easy to identify by looking on the right-hand side of the list screens for pdf's. From a cursory review of the first 20 or so netted this little gem (oops, could not attach it so I searched it out once again and here is the link: bprc.osu.edu/Icecore/Marteel%20et%20al%20EPSL%202008.pdf
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Post by sentient on Jan 20, 2010 2:00:11 GMT
Another one worth reading: Attachments:
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Post by sentient on Jan 20, 2010 2:27:56 GMT
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Post by spaceman on Jan 20, 2010 4:48:49 GMT
sentient.. that article really throws a new light.. we could end up drowning. (before we freeze) That was a good discussion. Since it was 1999, I wonder what has taken place since?
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Post by sentient on Jan 20, 2010 12:56:43 GMT
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Post by spaceman on Jan 21, 2010 3:57:27 GMT
That was good sentient. I think the info there is good. It is pretty straight foward. We need to find a core sample that tells us about magnetism. I have that sinking feeling that the west Antartic ice sheet will melt raising sea levels 20m . It may get cooler in the short run because of the solar cycle, but I think the bigger cycle will be in charge and we have a ways to go. Really good evidence for either event.
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Post by sentient on Jan 21, 2010 4:54:22 GMT
spaceman, I understand your concern. In light of more recent research suggesting that MIS-11 had a sea level highstand of 21.3 meters, and this during an eccentricity minimum like in this interglacial, the range of natural noise could allow for this eventuality. Regardless of anthropogenic influence.
This is what I have been trying to communicate. It happens anyway. Engineering for a predicted anthropogenic signal of say +20 meters may have no influence whatsoever on the potentially similar most recent natural signal.
In other words, it may go up regardless of any perceived influence we may think we might have.
Doing something about climate change is not necessarily a bad thing. Doing the right thing might prove to be quite another. The ice ages and associated interglacials are well known to be paced by the eccentricity, obliquity and precession cycles in earth’s rickety orbit. These we will do nothing about. D-O oscillations show strong evidence of being tied to the 1,500 year cycle of solar output, something we cannot change. Higher frequency shifts from ocean drilling program littoral profiles show syncopation to oceanic circulations.
I accept CO2 as a variable we have undoubtedly influenced. Whether or not this constitutes anything other than a minor forcing requires a major re-thinking of the plethora of temperature and commensurate GHG excursions available in the ever meticulously subdivided wealth of proxy data. In comparison to the relentlessly expanding inventory of new variables, paleo-documented variables, this becomes what it should be.
A multivariate equation, pertinent variables, of which, remain undefined, and perhaps undiscovered.
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Post by nautonnier on Jan 21, 2010 12:37:30 GMT
Now I am not entirely sure if nautonnier and stranger are talking about the same thing in terms of magnetics, so I will risk a stab at geomagnetic reversal as solar magnetics have been discussed to some extent elsewhere on this site. The geomagnetic reversal best studies with respect to climate is the Brunhes-Matuyama reversal at roughly 780kyrs ago, or close to the time many cite as the Mid Pleistocene Transition (though there is some controversy as to just how sudden this transition was). A search of my climate collection found 78 papers that reference the B/M reversal, so identifying a cogent one will take me some time. I suggest, again, going to scholar.google.com (the advanced page is more appropriate for Boolean searches) and search out the publicly available papers (on the cheap). The are relatively easy to identify by looking on the right-hand side of the list screens for pdf's. From a cursory review of the first 20 or so netted this little gem (oops, could not attach it so I searched it out once again and here is the link: bprc.osu.edu/Icecore/Marteel%20et%20al%20EPSL%202008.pdf "I am not entirely sure if nautonnier and stranger are talking about the same thing"No I don't think we are. Although your answer #7 addresses some of my thoughts. If we take the end of the Eemian which from your post is said to have finished rapidly: "In fact, the drop in the oxygen isotope ratio, and thus in temperatures, might have occurred “almost instantaneously."So given that is the effect - what was the cause or the symptoms of an approaching crash in temperatures? From a scientific viewpoint the rise out of glaciation is interesting - but from a human race perspective - a potential precipitous drop from the Holocene is probably of more concern One would assume that the sudden drop in Be 10 and O 18 implies something dramatic happening to solar activity or perhaps the heliosphere, rather than something in the internal climate cycles. So has there been any research into the circumstances preceding/initiating the sudden drop into glacial temperatures?
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