Insolation signatures of Quaternary climatic changes

From a set of simple trigonometrical formulae allowing the computation of long-term variations of the Earth's orbital elements, mid month daily insolations have been computed for each 10-deg latitude and, by steps of 1000 y, for one million years before present (YBP) and one hundred thousand years after present. The deviations from present values and especially from mean values computed over the past 10/sup 6/ y are graphically reproduced for 60 degrees N latitude which is thought to be one of the most sensitive latitudes as far as glacial-intergalactic sequences of the Quaternary period are concerned. From these data, some specific features, called insolation signatures, of the insolation pattern are found to be significantly related to well-established climatic changes, like the 125000 YBP interglacial, the 70000 YBP persistent-cooling tend and the 20000 YBP glacial maximum. Mathematical techniques of data analysis, like harmonic analysis and principal-component analysis, have been used to statistically improve the validity of the relationship that has been found between glaciation extent, mainly their triggering, and April to October insolations.