Milankovitch developed a mathematical theory of climate change based on the seasonal and latitudinal variations in the solar radiation received by the Earth from our Sun - it was the first truly plausible theory for how minor shifts of sunlight could ...
I couldn't get a quote of the above article to load right. So, the word button above is the best I can do. However, what I got from this article is:
1. we are due for an ice age almost any time now and
2. localized droughts can be devastating to local economies
In the past, whole civilizations were lost to droughts that lasted over 25 years or so like the Mayans and the Akkadians. The Akkadians of Mesopotamia appeared to have had an over 300 year drought locally and this basically ended their successful civilization.
Developed nations can afford to buy the food of other nations now and have it shipped by plane, truck, or ship or a combination of all these. But, the 50% who are the poorest nations often can't do that. So, a localized drought in a poor nation could almost lead to extinction except for organizations that bring in food to avoid starvation of the masses there.
But, if an actual ICE Age arrives (like it might have arrived on other technologically developed cultures before in the past, might end or severely change such a culture if it is in the band of the world that stays completely covered in ice more than one year or so at a time. If that snow or ice is deeper than 5 to 10 feet deep continuously.