this is true now but was NOT TRUE THEN ( yes, obviously the interior was still covered in ice ). when Erik the Red founded his settlements, the Vikings were quite successful at both farming crops AND rearing sheep and cattle. otherwise the Viking settlements would have been abandoned within a couple of years rather than lasting for centuries.

this fact is part of the data set which completely blows up all this idiotic bullshit that the AGW clowns are constantly trying to spread. the Viking settlements in Greenland were established early in the Medieval Warm Period, and died due to the onset of a Little Ice Age in the 1400s ( there was also a Little Ice Age in the 1800s ).

“The Norse settlements in Greenland disappeared during the 14th and early 15th centuries.[31] The decline of the Western Settlement coincided with a significant drop in both summer and winter temperatures. Research on North Atlantic temperature variability during the Little Ice Age indicates that maximum summer temperatures began to decrease around the early 14th century, dropping by as much as 6 to 8 °C (11 to 14 °F) below modern summer averages.[32] Additionally, the coldest winter temperatures in 2,000 years occurred during the late 14th and early 15th centuries.”

in much the same way, the proposed “runaway Greenhouse Effect” from methane release from plant material in thawing permafrost of the far north loses a lot of urgency when you realize that they also say that this plant matter which is now frozen was grown in the soil within the last 10,000 years. indicating quite clearly that the polar regions were significantly warmer almost into historical times. just as the Sahara was a lush Serengeti with the largest lakes on the planet almost within reach of historical records.