[Graybeard58]

it and the plague which it had a hand in causing

Never heard that before. Got any links?

[swilhelm73]

It is a commonly held supposition. Global cooling caused massive crop yield reductions, leading to a hungry and weak population ripe for an epidemic.

I've seen more specific theories dealing with the specifics of plague transmission and temperature, but they haven't really convinced me.

Certainly the fact that the earlier major outbreak of plague in Europe seems to have coincided with an earlier period of global cooling (Krakatoa's 535 eruption) strongly suggests there is a link.

[swilhelm73]

Here is a link on the specifics;

http://dml.cmnh.org/2001Feb/msg00388.html

Though I still don't understand then why 25 degrees celcius would be such a bottleneck as even in the Mediterrian world (where most of Europe's urban population was in 540 and 1347) still gets below that temperature on a regular basis.