"Scientists found frozen plant fossils, preserved under a mile of ice on Greenland. The discovery helps confirm a new and troubling understanding that the Greenland Ice Sheet has melted entirely during recent warm periods in Earth's history -- like the one we are now creating with human-caused climate change. The new study provides strong evidence that Greenland is more sensitive to climate change than previously understood -- and at risk of irreversibly melting." (Emphases mine.)