ABSTRACT
The climatic changes considered in this chapter were brought about by various internal and external mechanisms. The most notable aspect of climate during the past two million years has been the alternation between glacial and interglacial periods, between colder periods of major ice advance and warmer ones when the extent of ice was greatly reduced and temperatures were similar to those of today or even higher. The possibility that long-term variations in the Earth’s orbit might have been responsible for the glacial/interglacial sequence was first suggested in the 1860s by the Scottish natural historian James Croll. The abundance of foraminifera varies with ocean surface temperatures providing a link between the North Atlantic ocean circulation and the ice core evidence. The decline of the ice sheets may have been due as much to aridity as to rising temperatures, for the main phase of ice decay in Europe occurred before a marked rise in temperatures occurred.
