Interhemispheric effect of global geography on Earth's climate response to orbital forcing

The climate response of the Earth to orbital forcing shows a distinct hemispheric asymmetry due to the unequal distribution of land in the Northern Hemisphere versus Southern Hemisphere. This asymmetry is examined using a global climate model (GCM) for different climate responses such as mean summer temperatures and positive degree days. A land asymmetry effect (LAE) is quantified for each hemisphere and the results show how changes in obliquity and precession translate into variations in the calculated LAE. We find that the global climate response to specific past orbits is likely unique and modified by complex climate-ocean-cryosphere interactions that remain poorly known. Nonetheless, these results provide a baseline for interpreting contemporaneous proxy climate data spanning a broad range of latitudes, which may be useful in paleoclimate data-model comparisons, and individual time-continuous records exhibiting orbital cyclicity.