Volcanic activity behind Little Ice Age - Randy Boswell

http://www.vancouversun.com/life/Volcanic+activity+behind+Little/6077087/story.html

It is important to note the important caveat "research suggests", but this would make sense. It would be my first guess.

Melting icefields on Baffin Island, one of the clearest signs of climate change on Earth, have yielded the strongest evidence yet for the timing and cause of another major climate event from the planet's past: the so-called Little Ice Age, a sudden and mysterious cooling of the globe that began about 700 years ago.
Recently exposed remains of plants that had been buried under Baffin Island ice for centuries provided the crucial clue that has led an international team of researchers to conclude the Little Ice Age was triggered by volcanic eruptions between 1275 and 1300 and was sustained by changes in Arctic sea-ice cover that lasted several centuries.