Scientific Reports from the journal Nature – see https://doi.org/10.1038/s41598-022-14684-y … tells us the Holocene, beginning around 11,700 years ago, has been punctuated by large scale rapid changes in the climate system. These were abrupt events – as witnessed in ice cores. Numerous abrupt events are recognised but the source of them is unclear. Two of the events have been studied much more than the others. These are the 4.2 and 8.2 ky events. The 4.2 event lasted around 300 years we are told, although it would be more accurate to say that there were two events separated by around 200 years, with after effects, such as cooling, in their aftermath. Tree ring data defines these at 2345BC and roughly 2150BC. The Akkadian empire arose in the aftermath of the first event, representing a movement of people from North Syria into what is now Iraq. They established control of the area of their new settlement in Babylonia but decided to go on and expand into the region from which they had originated from. They disappeared in the aftermath of the second event. Whatever was the cause led to widespread migration in diverse parts of the globe. Including Europe. The largest and most significant abrupt event in ice core records is the 8.2 ky event, at 6200-6000BC. There was a drop in temperature in the North Atlantic, for example. Greenland ice cores show a 2 degrees fall in temperature – on average [celsius], across a period of 163 years. A global compilation of recontructed temperatures, including marine, lake varves, ice cores and peat accumulations as well as speleotherm chronologies show widespread cooling. Discontinuities associated with the cooling in more tropical zones – and wetter conditions in southern hemisphere tropical regions, appear to indicate abrupt changes in the monsoon track and the inter tropical zone [a sort of tropical jet stream] as one would expect if severe cooling had kicked in. The process is clearly outlined in HH Lamb’s books on climate over the last thousand years in Europe – which also includes global data. Cool periods coincided with an expansion of the polar zone at the expense of the temperate zone, which in turn put pressure on the tropical zone. One can see the process quite clearly when looking at past sea levels in the Caspian. When the jet stream moved south with the expansion of the polar zone the Caspian and Aral seas expanded and when the polar zone contracted and the temperature zone expanded northwards, in warmer weather, the Caspian shrank. All this is well known science. The novelty is that the 4.2 and the 8.2 ky periods lasted for such a long time. Volcanic eruptions usually result in cool weather for two or three years and then it reverts back to the norm. Something peculiar was going on. The number one question for all concerned is what caused these cooling events – and could they happen in the modern world. The mainstream answer is an influx of fresh water into the Labrador Sea from retreating ice sheets. Why ice sheets should have still brrn around after the end of the Late Glacial Maximum, which occurred 10,000 to 7000 years earlier than the 8.2 ky event, is a mystery. The mainstream response is that melted ice survived as a huge fresh water lake somewhere in what is now Ontario. Some scientists say there is no evidence of a huge pulse of water running down through the St Lawrence at this time. Never the less, this is the consensus explanation – mostly because a better explanation can’t be dreamt up.
Evidence for the event comes from marine oxygen isotope data as well as speleotherm records. These changes are observed across Asia and Europe, the Mediterranean basin, South America and southern Africa, even in Malagasy. It was therefore global in extent and may have an extraterrestrial explanation. The earth passing through a dense stream of meteoric material with an origin in a comet, or centaur object, in the process of breaking up over thousands of years, is one explanation. It is unlikely such a cooling event will happen in the near feature basically because the streams of material have dissipated and any large pieces have long since splintered into small pieces, and even smaller pieces. In order to create an abrupt cooling event of the kind noted at 6.2 ky ago it would take a succession of Tunguska like objects exploding in the lower atmosphere as the orbit of the earth passed through the stream. It is also worth bearing in mind that Comet Halley was much bigger when it first entered the inner solar system and has over the centuries, and probably for thousands of years, been in the process of shedding material each time it rounded the Sun. It would have been considerably bigger. It too would have created streams of meteoric like material.