See https://www.pnas.org/doi/10.1073/pnas.2302283120 … or https://doi.org/10.1073/pnas.2302283120 … these are abrupt climate transitions between stadial and interstadial conditions during glacial periods. In this instance the glacial period is the last 100,000 years and the stadials are warming and cooling episodes during that period of time. The key point to bear in mind is that although these events can be determined from ice cores and speleotherm data exactly why they happen is a bit of a mystery. The stadials, in some ways, upset the idea that the last Ice Age lasted a full 100,000 years, as it is now interspersed with these stadials [coolings] and interstadials [warmings]. However, the significance of them is that they are now said to represent atmospheric reorganisation = climate transitions. This rather mild description of them is somewhat bogus as Dansgaard-Oeschger events can raise temperatures by 15 degrees – very quickly. What was going on?
They are supported by globally distributed speleotherm proxy data. C14 methodology cannot go back much further, if at all, than 40,000 years ago. This date marks the Laschamp electromagnetic event that temporarily reversed earth’s magnetic field and coincided with the disappearance of the Neanderthals and a mass die-off of mammals. Speleotherm proxy data can go back by hundreds of thousands of years. This explains why the researchers made use of it, in spite of its uncertainties. Dansgaard-Oeschger events, named after the Danish discoverers of them, seem to have altered atmospheric circulation patterns. Ice core records from Greenland provide evidence for multiple abrupt cold and warming events recurring at millennial time scales during the last 00,000 years.
See also https://phys.org/news/2023-08-abrupt-north-atlantic-overturning-impacted.html … where we are told the Dansgaard-Oeschger events were rapid temperature jumps of up to 15 degrees celsius. Currently, we have a fearful mainstream at an approaching 1.5 degrees increase in temperature. A rise of 15 degrees is more than enough to send them batty – if not already. They repeatedly occurred within, or lasted, a few decades at a time. What caused them and why were they of such short duration? The impact of these events were felt globally and most severely in the sub tropical monsoon regimes. Changes in rainfall patterns, it would seem. Some one hundred cave formations were used to construct a speleotherm data bank, mostly using flowstone [dripstone] formations. These events are now being used to investigate how modern climate change will respond. In other words, their research is carefully targeted to climate change in order to elicit funding. By researching past warming they will, it is suggested, be able to pinpoint tipping points. This, in spite of the fact that in the past there was no human input for the warming. Never the less, it is a valuable research paper and provides us with evidence that even in dark days some good information may emerge. In this case, on these enigmatic events.
Catastrophism is ignored of course as it is assumed it is all to do with ocean currents and atmospheric changes. The actual vector that caused these changes is not mentioned – as often in such studies. It would no doubt hamper publication. Even in the Little Ice Age there were differences between then and now as far as ocean currents and monsoons were concerned. The polar zone expanded and squeezed the temperature zone, as HH Lamb might have said. Conversely, we have to assume that during an abrupt warming event the polar zone shrank and the temperate zone expanded – bringing with it a preponderance of Azores highs rather than Icelandic low weather systems – in the North Atlantic. In other words, the change in temperature is the cause of these changes in weather – but why did it suddenly warm up? That is a different question. How many times did it happen, and what was happening at the axis of rotation? Does the time span in any way correspond to Chandler wobbles?