Vegetation dynamics amplifies precessional forcing

The astronomical theory of climate variations predicts that the climatic precession which changes the seasonal distance between Earth and Sun does not affect the annual mean irradiation at any given latitude. However, previous modeling studies suggest that during interglacials, the interaction between atmosphere, vegetation and ocean can transform the seasonal forcing by precession into an annual mean global signal. Here, we show that this result can be generalized. A distinct precessional signal emerges in a climate system model over many precessional cycles. While neither the atmosphere-ocean nor the atmosphere-vegetation model are able to produce a large amplitude of global temperature in the precessional band, only the mutual amplification of biogeophysical feedback and sea ice-albedo feedback allows a strong amplification of the precessional signal.