Climate change: we haz that

One of the theories behind the Bronze age collapse (1200 BC) was climate change that cause migration and invasions.

I have linked in an earlier post to Eric Cline's audiobook about this, but internet Archive had the ebook LINK

And one of the theories behind why the Indus Valley civilization collapsed was a period of drought, which also caused the fall of the Old Kingdom of Egypt.

Wikipedia calls it the 4.2 kiloyear event. (2000 BC)

But right now I'm trying to finish reading the book The Horse the Wheel and Language and came to the part where they said the Indo European migration was spurred by drought conditions.

Wikipeda calls it the 5.9 kiloyear event. (4000 BC).

hmmm...

and this doesn't include the 8.2 kiloyear event or the younger Dryads (12000 BC).

and this doesn't include more recent warming and cooling times like the medieval warm period or the little ice age.

In other words, climate change cycles occur alas frequently, and alas often are associated with the fall of civilizations.