I've done a series of great earthquakes, and now I'll do great climate scares of the past. This is the 'Great Drought' of about 2000 BC.
I'm doing this because I just read that they are calling this era of the Holocene, the Meghan Markle era, or some such thing.
If you read the reference, you will find that there was a tremendous drought in the Northern Hemisphere about 4000 years ago. Not a speck of water anywhere. All the ice sheets ignored it and even advanced a bit.
If you believe in those other guys, then you will 'know', absolutely know, that it was caused by the damned Egyptians raising cattle, and all the carbon dioxide and methane. The Southern Hemisphere was unaffected, but they didn't have much in the way of civilization, or caves, or whatever.
If you read the Ancient Greek newspapers of the time, this would have been a big thing. Whole civilizations moved to the water. Huge groundwater cisterns were constructed. The desert tribes of the US south-west were wiped out.
My thoughts are, that this was one of the many attempted ice advance times, but it failed. The major reason it failed was because the highlands were still too low, but it was a good college try. Our wonderful ocean currents that keep the N Hemisphere alive all failed. Cold and dry. Sort of like now. I have postulated that a mini ice age is caused by both the Atlantic and Pacific currents dying, but there must be 'wet and dry' versions of this. There must be some cycle more severe than just a mini ice age. I can't think of it now, but we must consider it. Perhaps, if I had access to some super-duper computer, then we could play, but those things are used for bitcoin now. :)
Okay, thought about it. This was the Atlantic, Pacific and Indian Ocean currents failing. Neat.