When we flew over the southern end of Greenland last year, it was still very white as far as I could see except for the normal seasonal melt on the southwest and southern coastlines. It is actually kind of a cool thing to see. Kind of other worldly.....basically just a whole lot of stone with zero signs of vegetation anywhere. Anyway, even there they use a lot of extrapolated data because the satellites are not exactly johnny on the spot measuring melt.