New studies on Greenland have revealed that the the collapse of the Island's viking inhabitants did not occur because of climate only. For over 4 centuries the vikings settled the coasts of Greenland, experiencing the medieval warm period's end and the cooling period that followed. Trade with the island, notably in ivory, had declined by this time and traffic to and from the motherlands had all but ceased.
It seems that the islanders picked up and left, returning to their homelands as the prospects for a decent living dwindled. Had they only waited another 100 or so years they would have enjoyed the beginnings of the colonial period.
People are always so impatient.
More at Spiegel Online.