I'm not an old earth guy and it was named Greenland around 1000 AD so I would say it was green within at least 1000 years ago. And plate tectonics is still involved in climate change since God divided the land in Genesis 10.When was Greenland green? Sure 359 million years ago, but that was because Greenland was in the temperate region of the Earth, that is plate tectonics, not climate change.