Reconstructing the climate of medieval Europe

One of the uncertainties in climate science is figuring out how global climate trends translate into local predictions and reconstructions, and vice versa. A classic example of this is the medieval warm period, the time when Vikings roamed the North Sea and North Atlantic in shallow-draft open boats. They settled Greenland and made periodic visits to North America to get timber, placing some short-lived settlements there.

But there's a problem. We have the evidence from the adventures of the Norse, but the change to the European climate was so subtle that not many Europeans actually noted it at the time. Apart from exceptional—in both good and bad ways—years, it has been hard to gain a sense of what the typical climate in Europe was like.