The earth is now on the brink of entering another Ice Age, according to a large and compelling body of evidence from within the field of climate science. Many sources of data which provide our knowledge base of long-term climate change indicate that the warm, twelve thousand year-long Holocene period will rather soon be coming to an end, and then the earth will return to Ice Age conditions for the next 100,000 years.
Ice cores, ocean sediment cores, the geologic record, and studies of ancient plant and animal populations all demonstrate a regular cyclic pattern of Ice Age glacial maximums which each last about 100,000 years, separated by intervening warm interglacials, each lasting about 12,000 years.
Most of the long-term climate data collected from various sources also shows a strong correlation with the three astronomical cycles which are together known as the Milankovich cycles. The three Milankovich cycles include the tilt of the earth, which varies over a 41,000 year period; the shape of the earth’s orbit, which changes over a period of 100,000 years; and the Precession of the Equinoxes, also known as the earth’s ‘wobble’, which gradually rotates the direction of the earth’s axis over a period of 26,000 years. According to the Milankovich theory of Ice Age causation, these three astronomical cycles, each of which effects the amount of solar radiation which reaches the earth, act together to produce the cycle of cold Ice Age maximums and warm interglacials.
Elements of the astronomical theory of Ice Age causation were first presented by the French mathematician Joseph Adhemar in 1842, it was developed further by the English prodigy Joseph Croll in 1875, and the theory was established in its present form by the Serbian mathematician Milutin Milankovich in the 1920s and 30s. In 1976 the prestigious journal “Science” published a landmark paper by John Imbrie, James Hays, and Nicholas Shackleton entitled “Variations in the Earth's orbit: Pacemaker of the Ice Ages,” which described the correlation which the trio of scientist/authors had found between the climate data obtained from ocean sediment cores and the patterns of the astronomical Milankovich cycles. Since the late 1970s, the Milankovich theory has remained the predominant theory to account for Ice Age causation among climate scientists, and hence the Milankovich theory is always described in textbooks of climatology and in encyclopaedia articles about the Ice Ages.