The climate changes
Even though the Viking colony in North America was short-lived, largely because of the hostility of the natives there, the Viking colonies on Iceland and Greenland were generally successful. Iceland had been settled by the Vikings in about 874 AD and Greenland in about 980 AD. Tax records in Iceland in the year 1095 indicate that 72,000 Scandinavians were living there at that time. Archeologists estimate that about 5,000 Vikings lived in Greenland by about 1150.
Ruins of a Norse church at Hvalsey, Greenland
Studies of skeletal remains indicate that the people in both settlements were tall and healthy. Written descriptions speak of green pastures, ample livestock, and an abundance of fish in the seas as well as ample wild game such as seal, walruses and whales. Beginning around 1150 AD, however, conditions rapidly deteriorated.
The Vikings had no way of knowing that the relatively warm temperatures of the Middle Ages, now known as the “Medieval Warm Period” between the years 600 and 1150, would come to an end. They had no way to foresee the much colder temperatures that were to come from 1150 to 1460 eventually leading up to what is now called the “Little Ice Age” from 1560 to 1850.