The GISP2 data (R Alley data at the WDC paleoclimatology site) says that the Greenland temperature peaked in 8000BC and in 7000BC and in 1400BC (with a sub peak half a degree lower in 100BC), at about 2 degrees C warmer than today.
The World Data Center (WDC) for Paleoclimatology maintains archives of ice core data from polar and low - latitude mountain glaciers and ice caps throughout the world.