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Ice Ages

13 January 2014
Climate change

At http://astroclimateconnection.blogspot.com.au/2013/06/are-dansgaard-oesc… … we have the idea that abrupt increases in temperature that occurred in a series of events interrupting the last Ice Age, the so called Dansgaard-Oeschger events (DO for convenience),  can be explained by cycles affecting the Earth system. These sudden warm-ups were quickly followed by glacial activity, and the theory is that these have a 1470 year frequency and an internal oscillation. Orbital cycles are highly regular, it is assumed, and do not fluctuate as in the DO events.

An 1832 year lunar tidal cycle must also be taken into account – but how does this interact with the 1470 year DO cycle. As in all these things the blog author is convinced he can reconcile what are two separate clear-cut cycles, one orbital and the other, within the Earth system. He uses seasonalities to satisfy his curiosity. In contrast, EM Smith at http://chiefio.wordpress.com/2013/01/04/lunar-cycles-more-than-one/ … has a different view of the cycles and turns up to comment at 3.06pm, pointing out that 1470 years is just an average and actual DO/ or Bond events (these are similar if not the same thing but generally seen as possibly Holocene versions of DOs), have spacings off-set to either end and work out at anything between 1200 and 1800 year periodicities. Both blog authors also acknowledge that some researchers have defined 'half Bond events' – at 739 year cycles.

At http://clivebest.com/blog/?p=2775 … we have 'The Phenomenology of Ice Ages' which proves to be an illuminating read. It is all about the mystery of why the Earth's climate is considered to change every 100,000 years, a periodicity that goes unchallenged by Clive Best and his commenters. This is an essential read if you want to understand how mainstream views the Ice Ages – and their frequency. It seems the consensus paradigm that Milankovitch orbital cycles control the Ice Ages is somewhat suspect in that the effect is not nearly powerful enough on its own. Hence, the search is on by some scientists to find additional effects to drive the 100,000 year periodicities – which will provide a boost to the small orbital changes in the orbit of the Earth around the Sun. Milankovitch, in other words, is not powerful enough on its own to account for the 100,000 year cycle. Such small radiative effects have been asked to do a very big job – switch the Earth system from very cool conditions towards temperatures as warm as today – on a regular clockwork basis. The 100,000 year cycle is a uniformitarian driven hypothesis that is thought to have been proven beyond reasonable doubt by oxygen isotope changes in foraminifera shells found in sediments on the ocean bed – in combination with the magnetic stripes on the ocean floor (and some other factors). In addition to this, uniformitarian geology claims long term global temperatures have been falling over 20 million years. The Earth did not suddenly sink into an Ice Age switchback system – it took place over time and co2 has been fingered as a culprit – and various changes in the postions of the continents (moving pieces of Plate around a computer screen). One of these involves the opening of the Drake Passage, which affected the ocean current that circles the Antarctic continent (and other geological changes in different parts of the world). In other words, the assumption is that the Earth grew an ice cap at the South Pole only recently and prior to that global temperatures were much higher (especially during the Dinosaur Age). This implies the consensus is probably not as stable as 'confidently' espoused by various scientists, text books, commentators, tutors and teachers, as well as the plethora of web pages. There are a lot of imponderables. For instance, why did S America break apart from Antarctica. It was clearly joined to what is now the West Antarctic peninsular and the tips of both seem to bend around as if wrenched apart. Some people claim they can see an impact site hiding in the curve – others claim it is associated with stress (a fossil bit of continent showing its agony as it is buffered this way and then that way). Such ideas are not considered in mainstream thinking but the change in ocean currents is a major plank in thinking – as it obviously is an important part of the Earth system. The Drake Passage allows cold water to run up on the Pacific side of S America, contributing to the La Nina/ El Nino sequence, which has gloabl repercussions in the movement of ocean water, and weather, around the world.

A part of the Ice Age theory (where it comes to 100,000 year cycles) revolves around O18 and O16 content in foraminifera plankton shells found in ocean sediments. No mention is made of the recent study on these creatures that concluded the science of O18 to O16 change is not as clear cut as previously thought. It might even be described as suspect. The use of O18 to O16 changes was a boon to uniformitarian science – but they may have embraced the idea (or what they thought the isotopes were telling them) just a bit too quickly and without checking it out sufficiently. None of this is mentioned by Clive Best – no uncertainties in the methodology at all. The 100,000 year periodicities are accepted as facts. However, see In the News, 27 November 2013, 'Foraminifera' and the state of play.

Of course, Clive Best may be right to have faith in those periodicities. Out of them he is able to tell his readers that all he needs to do is find the extra bit of effect that boosts the Milankovitch orbital changes. These appear in a series of other posts. At http://clivebest.com/blog/?p=2840 … he looks at the interglacial episodes and at http://clivebest.com/blog/?p=2862 … he blames 'resonant dust clouds' for the Ice Ages, or the regular switches from interglacial to glacial etc. Meanwhile, at http://clivebest.com/blog/?p=5464 … he suggests the trigger for interglacial periods is not galactic dust but the Moon – a large resonant interplanetary body. The trigger for interglacials is not changes in insolation (Milankovitch) but changes in tidal forces acting on the ocean and cryosphere. Every 100,000 years, he goes on to say, super tides must occur whenever the decreasing perihelion distance of the Earth from the Sun and the Moon coincides and are synchronised with maximum eccentricity (Milankovitch). Tidal forces in combination with increases in insolation may be the trigger that initiates a rapid break-up and melting of the northern glaciers. We shall have to see what his next post says – and what else might be considered a trigger mechanism. Give it a while and he might read up on the solar cycle around its barycentre – and yipee.

For another kind of view on the Ice Ages go to www.thunderbolts.info/forum/phpBB3/viewtopic.php?f=4&t=6372

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