Scientific American: Roughly 1,000 years ago, Europe enjoyed several centuries of balmier average temperatures. Dubbed the “Medieval Warm Period,” it was the last time before the present that agriculture could flourish in Greenland. This era also shows yet again that changes to natural systems can drive local climate change–and provided fodder for countless misunderstandings about the nature of present day global warming. But new research shows that the MWP, as it is affectionately known in acronym-happy …