When the Vikings ( or their ancestors ) found Greenland, it was green. The world was warmer back then.
The oldest skeletons found on Greenland are big, newer ones are smaller. The reason is that as the earth cooled, less and less food could be harvested.
Side note: My old boss was a Norwegian. He said that people in Iceland spoke a language that the Norwegians refer to as "the old language." He said that it is likely very similar to what the Vikings spoke