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a Milankovitch glitch

22 March 2015

This story was also in the latest issue of the journal Geology and is interesting as it raises questions about the Milankovitch theory of climate associated with the Ice Ages – see http://phys.org/print346065297.html … which supposes the expansion and contraction of a northern ice sheet is influenced by cyclic fluctuations in solar radiation, inter-acting due to wobbles in the Earth's orbit that restricted sunlight in one hemisphere while the opposite hemisphere brightened. In other words, fluctuations in the northern hemisphere should be compensated by the opposite in the southern hemisphere. Whereas in the north the glaciers grew, in the south they should have shrunk – or that is what is claimed by the authors of the article. Scientists in New Zealand have identified seven episodes of expansion of mountain glaciers during the last Ice Age and the remains of four moraines. The conclusion was that New Zealand glaciers were large at the same time as ice sheets expanded in the northern hemisphere, especially during the Late Glacial Maximum 20,000 plus years ago. This only makes sense if the whole world was cold at the same time – which contradicts the Milankovitch theory it would seem (at face value). It should have been warmer in the northern hemisphere when it was colder in the northern hemisphere. However, that does not take into account the cosmic induced cold spell we saw associated with an event at 40,000 years ago (previous post). Such cold spells, with an origin in a cosmic event, would have had global effects, thereby undermining some of the thinking from the research in New Zealand.

Four dates were provided from the geology of the four moraines (ridges of sedimentary material pushed forth by glaciers) using the beryllium 10 methodology (dating material that had been buried and which is said to preserve measureable beryllium 10 from the date of burial) and these panned out at 35,500, 27,170, 20,270 and 18,290 years ago. They are said to align with sea surface temperatures off the coast of New Zealand. These are presumably based on the oxygen isotopes in the shells of foraminifera plankton so it might be worth having a look at a post on foraminifera I did last week – where it was said that such plankton could be moved on ocean currents long distances before settling on the sea floor (and becoming part of the sediment).

The authors do not imagine ditching Milankovitch as they say the timing of the northern hemisphere Ice Ages and ice sheets is still 'paced by how Earth orbits the Sun' – and they clearly expect somebody to come up with an explanation, pointing the proverbial finger at ocean currents (the catch all clothes peg of palaeo-climate changes). However, this is to be expected as they did not want to upset the applecart. Milankovitch will live another day and probably thrive in spite of this evidence which appears to completely contradict it. Further, EM Smith has a nice take on Milankovitch at his blog, http://chiefio.wordpress.com/2015/03/20/ice-ages-and-the-book-about-mila… … which is thought provoking and controversial from a catastrophist point of view – but does show Milankovitch was a very unusual and clever man, and is worth reading. He completely unseats the idea that it should be warmer in New Zealand when it is colder in the northern hemisphere – or that is the idea.

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