Aspecten en bevindingen der palaeoklimatologie

Paleaoclimatology studies world climates of the geological past. Climatic changes are manifest from geological, biological and historical evidence, e.g. from slowly deposited deep-see sediments or from vegetation remnants. Long-periodical climatic changes are of global magnitude, and show generally the same circulation characteristics. The extremes are fully de-glaciated conditions with almost ice-free poles on the one hand, and full glacial conditions on the other, with 25-30% of the earth's surface ice-covered. Theories on the causes of climatic change are brought under two headings: those that assume extra-terrestrial causes and those that assume terrestrial causes. The former include changes in earth orbit and changes of solar radiation either emitted or received by the earth. The latter comprise explanations such as continental drifting, polar migration, thermal isolation, blocking of the jet stream, and variations in the CO2 content of the atmosphere.