The Northern Hemisphere temperature history as modeled using Milankovitch variations in solar radiation modulated by volcanic aerosols, using oceans and carbon dioxide only as minor dependent variables. BP means before 1955 CE.
This figure captures very well, the “little ice age”, the Medieval Warm Period, and other known variations of late BCE and early CE times. The drivers of this model are Milankovitch calculations (average for the entire Hemisphere) and the observed volcanic record described above. Carbon dioxide is treated as a very minor dependent variable. It is unlikely that a general circulation model which assumes a major role of carbon dioxide can duplicate this known climatic sequence.
