Orbital Mechanics

Orbital Mechanics

Orbital Mechanics

It is clear from the fossil and geological record that the earth has periodically gone through times of much colder temperatures than today---and much hotter. Abrupt warming occurs at regular intervals, with more moderate cooling over a longer period of time to follow. The time scale of the most prominent of these events has varied from 41,000 to 100,000 years, and there are discernible cycles of other periodicities.

What causes an ice age?

The earth's atmosphere is in a precarious equilibrium, as radiation heats the equator and cools the poles. The oceans and atmosphere transfer heat poleward to keep the temperature in balance. The exact temperature of this balance can change with the process that leads to heating---the absorption of solar radiation. And the process that cools---the earth's radiation to space. These radiative regimes operate on different wavelengths. The incoming radiation is primarily in the visible band of the spectrum, while the outgoing radiation is in the microwave region. The whole system is sensitive to very minor changes in the composition of the earth's surface, it's cloud cover, and the composition of the gases in the atmosphere, as well as the variation of radiation from one place to another over the entire globe.