I saw a program (also produced by the BBC) a few years back where they said that in the late 1200s to early 1300s, the climate in the British Isles changed enough that grapes could no longer be grown. Thus wine disappeared from the Britain's diet and was replaced by ale (made from grain of course). After that it was Southern Europe that became known for wine making.

I would think that a climatic shift significant enough to cause both an ecological and cultural change of that significance would be enough to conclude that the 'little ice age' had begun in earnest.