Million year old plant fossils were found.

The real "so what": It shows that even without human-induced climate change with lower atmospheric C02, Greenland was completely without ice "just" a million years ago (not enough time for the position of Greenland to significantly shift).

Greenland is 100% definitely going to lose it's ice, given that it's more prone to not having ice than we thought, and unprecedented atmospheric C02. "UVM's Paul Bierman, 'it can quickly melt, pouring enough into the oceans that New York, Miami, Dhaka—pick your city—will go underwater.'"