term "Holocene Climatic Optimum" to describe the earlier southern warm period as well. Comparison of ice cores A comparison of the delta profiles at Byrd Station, West Antarctica (2164 m ice core recovered, 1968), and Camp Century, Northwest Greenland, shows the post-glacial climatic optimum. Points of correlation indicate that in both locations, the Holocene climatic optimum (post-glacial climatic optimum) probably occurred at the same time. A similar comparison is evident between the Dye 3 1979 and the Camp Century 1963 cores regarding this period. The Hans Tausen Ice Cap, in Peary Land (northern Greenland), was drilled in 1977, with a new deep drill to 325 m. The ice core contained distinct melt layers all the way to the bedrock. That indicates that Hans Tausen Iskappe contains no ice from the last glaciation and so the world's northernmost ice cap melted away during the post-glacial climatic optimum and was rebuilt when the climate cooled some 4000 years ago. From the delta-profile, the Renland ice cap in the Scoresby Sound has always been separated from the inland ice, but all of the delta-leaps revealed in the Camp Century 1963 core recurred in the Renland 1985 ice core. The Renland ice core from East Greenland apparently covers a full glacial cycle from the Holocene into the previous Eemian interglacial. The Renland ice core is 325 m long. Although the depths are different, the GRIP and NGRIP cores also contain the climatic optimum at very similar times. Milankovitch cycles The climatic event was probably a result of predictable changes in the Earth's orbit (Milankovitch cycles) and a continuation of changes that caused the end of the last glacial period. The effect would have had the maximum heating of the Northern Hemisphere 9,000 years ago, when the axial tilt was 24° and the nearest approach to the Sun (perihelion) was during the Northern Hemisphere's summer. The calculated Milankovitch Forcing would have provided 0.2% more solar radiation (+40 W/m2) to the Northern Hemisphere in summer, which tended to cause more heating. There seems to have been the predicted southward shift in the global band of thunderstorms, the Intertropical Convergence Zone. However, orbital forcing would predict maximum climate response several thousand years earlier than those observed in the Northern Hemisphere. The delay may be a result of the continuing changes in climate, as the Earth emerged from the last glacial period and related to ice–albedo feedback. Different