[henkster]

Ever since the notion got around that climate is not constant, but variable, some historians have been looking at climate data for their effects on civilization. The results so far point exactly to what you have described. Warming leads to a blossoming of civilization, cold times lead to a collapse.

The depredations of the “Sea Peoples” that destroyed several ancient middle eastern civilizations, appear to have been triggered by a forced migration of northern peoples who were driven south by the cold. The height of the Roman Empire coincided with the “Roman Warm Period,’ while the “Dark Ages” that followed the fall of the Western Empire in 476 seem to have been at the beginning of a colder period.

The “Medieval Warm Period” was the height of Medieval culture, and saw the building of the great cathedrals of Europe where a time of high population and prosperity allowed such great projects to take place.

And so on...

Warm = good. Cold = bad.

[Vigilanteman]

Exactly. Don't forget that what is now most of Northern Africa had a savanna type climate which supported elephants and similar large wildlife. As recently as the 13th century, the Sahara Desert was not much larger than the Mojave and Timbuktu was the center of civilization for northwest Africa.

See this map.