A period of warmer climate in much of northern Europe, the North Atlantic, southern Greenland, and Iceland from about the tenth to thirteenth centuries A. D. , coinciding roughly with Europe's Middle Ages. As the number of well-understood proxy records of climate covering this time period in many parts of the world has increased in recent years, it has become clear that it would be an oversimplification to view this period as uniformly warmer in all seasons, even within the relatively limited North Atlantic/northern Europe region, let alone on a global scale (Hughes and Diaz 1994).