The issue too is that most of the glacial ice on Greenland is 1000s of years old and covers 80 percent of the island. What's left is rock areas and well, pretty non-green. So the logical question would be: was Greenland that radically different back then? Of course not.

nce again: you can't draw conclusions about global climate from an anecdote about a single region, or even a few regions. You need detailed analysis of proxy climate indicators from around the world. These proxy reconstructions have shown that the Medieval Warm Period (around the time the Vikings are said to have discovered North America) was not as pronounced or as warm as today's warmth. From NOAA's paleoclimate website comes these quotes:

What records that do exist show that there was no multi-century periods when global or hemispheric temperatures were the same or warmer than in the 20th century ....

... In summary, it appears that the 20th century, and in particular the late 20th century, is likely the warmest the Earth has seen in at least 1200 years.