I am reading about the evolution of humans from ~2mya to today, and am running into some stuff on Geology like the 8.2-kiloyear event, and other "cooling" events and warming events. I briefly saw something about axial precession, but wasn't sure that was the main cause. I would imagine if it was the main cause, like a spinning top sometimes the earth axis changes direction rapidly and that would mean different areas are further from or closer to the sun/moon, etc.. which would change their temperature and thus climate.

So my layman question is, without having studied deeply all the various geological theory/background, what generally are the causes for the abrupt changes in climate/temperature for the past 10 million years? Is it solely the axial precession, or some other factors? If it is only mainly the axial precession, I'd be curious to know what "states" it can be in, how it occasionally abruptly transitions from hot to cold to hot to cold, etc..

Basically I would just like to have a slightly better intuition for these things, not having a geology background.


1 Answer 1


The mentioned "8.2ky event" was probably caused by a meltwater inflow surge or a change of meltwater inflow. Meltwater from parts of the thawing Laurentide ice shield or a lake that formed or had oveflown, as written in the Wikipedia link. There is no link to earth's axial precession, which has a period of 26,000 years.

This inflow suppressed the oceanic circulation in the North Atlantic. This thermohaline circulation is driven by density differences, a sudden inflow of lesss dense fresh water at the spot of a main driver of that circulation would disturb that circulation, push it farther south or slow its overturning effect down, and thus influence the global heat distrubution, resulting in a cooling effect in the north.

This cooling effect through temporarily suppressed heat distribution by density changes caused by the freshwater inflow was the probable cause of the 8.2ky cooling event.

On a broader picture, during the 10 million years the isthmus at Panama closes, thus changing global circulation and heat distribution, creating the golf stream and the AMOC and transporting moisture to the north, ice cap buildup in the north. Towards today, the Pleistocene, Milankovic cycles (of which axial precession is an element) take over control of the climate, as reflected in for example ice cores and sediment cores.

So there is a lot going on the 10 million years.

  • $\begingroup$ I was mainly looking for a broad overview of how the earth changes temperature, not specifically just this one event. $\endgroup$
    – Lance
    Oct 1, 2023 at 23:00
  • $\begingroup$ Added a paragraph, but is is really getting broad ... $\endgroup$
    – user29219
    Oct 2, 2023 at 8:57
  • 1
    $\begingroup$ You might want to check out "Milankovitch Cycles". Precession ist just a third of the ingredients you need to explain a vast majority of how earths tempeature evolved. $\endgroup$ Oct 2, 2023 at 11:48
  • $\begingroup$ @JoschaFregin: You might want to read the answer. It is in the second link, but they play a major role only towards the second half of the Pleistocene, while the question asked for 10 My. $\endgroup$
    – user29219
    Oct 3, 2023 at 15:42

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