3 - Orbital-forcing of climatic oscillations

Summary

All processes, geological and biological, taking place at the surface of the Earth are controlled and influenced by local, regional, and global climate. In this chapter, the way in which climates change with time is described, together with the reasons for thinking that the patterns observed for the last few million years are likely to be a reasonable representation of the way in which climates have changed throughout Earth history.

Solar insolation is the main source of heat for the surface of the Earth and a crucial element in global climate systems today and in the past. Diurnal and annual periodicities in temperature and other climatic parameters are familiar consequences of life on a planet that spins about an axis that is inclined to the plane of its orbit around its heat source. The Earth's location and velocity in space are critical for determining the amount of solar insolation received at its surface, and the latitudinal distribution of that insolation. However, the Earth's orbital characteristics arise from gravitational attractions, dominated by the Sun, but also including gravitational attractions between the Earth, the Moon, and the other planets. The Solar System is a dynamic system: the location and velocity of any of its elements at any point in time is influenced by the locations and velocities of all the others, to at least some extent. This system is, in general, deterministic, but it is currently not possible to obtain a general relationship that enables the determination of the location and velocity of all the planets for all times, past, present and future. Approximations need to be made for all cases of this type, involving three or more elements.