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Post by sentient on Jan 21, 2010 14:25:06 GMT
nautonnier,
From all that I have read, the stochastic climate response to what appear to be a host of intertwined variables is sort of a chaotic mix of lower and higher frequency cyclicities overprinted by orbital dynamics, overprinted again by solar/magnetic/cosmic effects. The ends of the interglacials appears, again, from all that I have read, to be primarily paced by orbital dynamics.
Which brings us back to our nearly circular orbit at this eccentricity minimum. With the distance to the sun remaining fairly static for the next few tens of thousands of years, some say 50-65kyrs, other estimates range either side, obliquity and precession are consequently muted as well.
This brings in the other variables, the predominant one, at least in my mind, is solar. Which acceding to Svensmark's research necessarily entails careful consideration of the cosmic ray hypothesis at the end of this relatively weak precessional cycle. At a time when orbital dynamics are muted, call it low orbital noise, the other variables can be considered as secondary signals within this noise.
A perfect storm at the end of the half-precessional old Holocene might be something like what we are seeing right now, negative flips to PDO and AMDO coupled with a dramatically shrunken and still shrinking solar magnetic field strength loom large as a strengthened trigger.
Which brings us to Sole et al's analysis of the D-O oscillations and the ameliorating effect of CO2 on the 1500 year cycle. I continue to muse on how our inadvertent spewing of CO2 and other trace GHGs just might be the only prescription anthropogenetically available for such a condition. It may very well prove to be the only geoengineering we can actually accomplish, and quickly, in response to what may be the perfect storm of cosmic and oceanic forcings which might very well tip the Holocene into the next ice age.
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Post by spaceman on Jan 22, 2010 5:09:58 GMT
I agree and understand what you are saying Sentient. It is worth noting and saying that there is more than one variable. It is a complex system. Depending on where the vectors are at any given time, determine the climate we are having.
I think that there is a component to the weather that is unaccounted for. It could be magnetism or gravity waves, solar wind pressure or something we haven't observed. (that's a lot of ice to melt to raise the sea level 20m. Somehow I don't see atmospheric warming doing that. It could be, I have not done the math. If it's that hard to raise the temp in the air 1 or 2 C, imagine raising the temps on that amount of ice.) Providing of course we still have a 1/4 to go in the current cycle. If we are standing at the edge of another ice age, it would be useful to know what that energy is. Perhaps we could use it.
I suppose you read on global cooling where I microwaved ice. I expected it to melt. It didn't. It also did something I didn't expect, it fused. Instead of seperate ice cubes they became one big glob.
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Post by graywolf on Jan 22, 2010 18:59:53 GMT
I think we've got to look to the oceans and their slow warming over the initial phase. We do not need rocketing temps to destabilise section of EAIS and WAIS thermal expansion of the oceans and a little sea level increase would be enough to start to lift the likes of Ross off it's grounding line and lead to a mechanical collapse of it and sections of the buttressed ice behind. We are currently seeing the Pine island region of WAIS suffer the fate that awaits Ross with the final demise of that which holds back the cliffs of grounded ice behind. Gravity alone will bring a lot of changes to 2 mile thick ice without resorting to blowtorches. The same goes for Ross. MIS 11 also didn't have mans ozone whammy insulating the Antarctic continent so thing would have been markedly different with a south not in splendid isolation.
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Post by sentient on Jan 23, 2010 2:14:53 GMT
The greatest contribution to MIS 11 sea-level was probably made from the marine-based West Antarctic ice sheet (WAIS) and adjacent ice drainages, as we have published elsewhere (e.g., Hearty et al., 1999) and there is evidence supporting the collapse of the WAIS during the middle Pleistocene as inferred from diatom assemblages and cosmogenic isotopes (Scherer et al., 1998). Melting of the WAIS would contribute another 8.0 m to global sea-level (Williams and Ferrigno, 2008), which would mean that the East Antarctic ice sheet would have to have contributed about 5.5 m in MIS 11 in order to raise sea-level to þ20 m. Isotopic composition of the ice and air suggests no significant changes in surface elevation at Vostok or Dome C in the central part of East Antarctica (EPICA, 2004), which has been raised as an objection to the our contention of a 20 m rise, but this evidence comes from a distant part of East Antarctica which may have been less sensitive physically to ice drawdown on the opposite side of the continent.
A sustained +21 m sea-level highstand during MIS 11 (400 ka): direct fossil and sedimentary evidence from Bermuda Storrs L. Olson and Paul J. Hearty Quaternary Science Reviews 28 (2009) 271–285
"Marine Isotope Stage MIS.11 is easily recognized in Southern Ocean sediment cores by virtue of its white, high-carbonate layers in otherwise highly diatomaceous sequences (Shipboard Scientific Party, 1999). This observation seemingly fits with the general notion of MIS11 as a time when the ocean was warmer and sea level was higher than today (Howard, 1997). The distinctiveness of MIS11 in deep sea sediment cores has even prompted speculation that the West Antarctic Ice Sheet may have collapsed at this time (Scherer, 1991; Scherer et al., 1998). These issues are of concern because the Earth’s orbital configuration at ~400 kyr was similar to present; therefore, MIS11, in some respects, can be taken as an analog for future climate change (Berger, 1999)."
D.A. Hodell et al./Global and Planetary Change 24(2000)7–26
"Moreover, MIS 11 is characterized by the highest amplitude deglacial warming in the past 5 My. MIS 11 most likely witnessed sea levels 13 to 20 meters above current sea levels, which would imply that, at minimum, the Greenland and West Antarctic ice sheets had melted."
Unique and Exceptionally Long Interglacial Marine Isotope Stage 11: Window into Earth Warm Future Climate André W. Droxler, Richard B. Alley, William R. Howard, Richard Z. Poore, and Lloyd H. Burckle
To mention just a few.......
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Post by spaceman on Jan 23, 2010 20:46:39 GMT
Greywolf,
I took the time to read the papers that sentient has presented here. I think they are right in there assessment. From the evidence that has been presented from core drillings, high water stands, and the similar position the earth is in as in MIS 11, I think that this will become the accepted view and AGW will not. For one thing it supports MWP and LIA, where AGW does not. AGW depends on a static climate prior to the introduction of man made co2. AGW has no explaination for any of the past warming cooling and does not have an explaination for the recent cooling.
In light of this information, which I am sure the IPCC had access to, makes me think that they made this AGW up in order to profit by it, and second to destroy the west. The current scandal looks like an attempt to discredit anyone having a different point of view. They are still using terms like denialists and skeptics, as if some of us don't have a clue as to what we are talking about. They are still trying imply that if I disagree with the CAUSE of global warming, I am denying that there is global warming.
If in the event we are having a protracted interglacial, then warming will certainly continue.... along with periods of colder weather.... the WAIS will almost certainly collapse, as it has done before.
it will take an enormous amount of heat to melt those ice sheets. Whether gravity pulls them into the ocean or not, what's going to melt them? While it may be a trying time for us when ice sheets melt, it may be good for the planet. Ice can not keep building up in the same spot forever.
Sentient, the information you have presented ties together the astro history of the earth with the recorded history in the core samples. And they didn't have to fix the data to do it. While we don't have all the answers, the questions raised need to be answered as quickly as possible. It will tell us whether we are on the verge or a new ice age or watching the sea rise 20m (without any help from AGW, as I said before)
As an aside, one of the papers supporting AGW said that 'when water vapour condenses, the heat is returned'. I would have said the heat is released. The implication is that with returned the heat does not escape into space, with released it escapes and is no longer a part of the heat content on earth.
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Post by poitsplace on Jan 27, 2010 7:43:36 GMT
If we're in a potentially extended interglacial then indeed "little ice age" is far more descriptive of the state than anyone could imagine. The infamous "year without a summer" probably would have been THE event that drove us into the deep freeze.
I'm not sure if I've mentioned this but I've come to realize that the milankovitch cycles are entirely misunderstood by AGW fanatics. When they talk about their high feedbacks they mention cars parked on top of a hill requiring very little energy to get moving (and continue moving). While in some small sense the milankovitch cycles could be considered a "forcing" that's really not the best description.
The milankovitch cycles don't so much push the car...as they change the grade of the whole hill. The conditions that drive us into the glacial period are conditions that make the water cycle feedbacks particularly responsive to colder temperatures. The conditions that drive us out again are conditions that make the water cycle feedbacks favor warming.
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Post by sentient on Mar 21, 2010 22:47:08 GMT
Told ya a b s t r a c t Article history: Received 11 September 2009 Received in revised form 15 December 2009 Accepted 30 December 2009 Available online 25 January 2010 Editor: P. DeMenocal Keywords: sea level interglacials climate forcing The exceptionally long interglacial warm period known as Marine Isotope Stage 11 (MIS-11; 428–397 ky ago vs. ky vs. kyr) is often considered as a potential analogue for future climate development in the absence of human influence. We use a new high-resolution sea-level record—a globally integrated ice-volume signal—to compare MIS-11 and the current interglacial (Holocene). It is found that sea-level rise into both interglacials started over similar timescales relative to the respective insolation increases, and progressed up to −50 m at similar rates of 1.0–1.2 m per century. Subsequent weak insolation changes anomalously prolonged the MIS-11 deglaciation over more than 20 ky. The main sea-level highstand was achieved at the second MIS-11 insolation maximum, with a timing closely equivalent to that of the Holocene highstand compared to its single insolation maximum. Consequently, while MIS-11 was an exceptionally long period of interglacial warmth, its ice-volume minimum/sea-level highstand lasted less than 10 ky, which is similar to the duration of other major interglacials. Comparison of the ends of MIS-11 and the Holocene based on timings relative to their respective maxima in mean 21 June insolation at 65°N suggests that the end of Holocene conditions might have been expected 2.0–2.5 ky ago. Instead, interglacial conditions have continued, with CO2, temperature, and sea level remaining high or increasing. This apparent discrepancy highlights the need to consider that: (a) comparisons may need to focus on other orbital control indices, in which case the discrepancy can vanish; and/or (b) the feedback mechanisms that dominate the planetary energy balance may have become decoupled from insolation during the past 2millennia. © 2010 Elsevier B.V. All rights reserved www.soes.soton.ac.uk/staff/ejr/Rohling-papers/2010-Rohling%20et%20al%20MIS11%20EPSL.pdf
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Post by socold on Mar 22, 2010 1:51:24 GMT
"AGW depends on a static climate prior to the introduction of man made co2"
No it doesn't. Your conclusions don't seem to follow from sentients posts, which are very interesting.
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