A link between global climate variability in the Pleistocene and variations in the Earth’s orbital parameters

The study demonstrates that the orbital climatic diagram (OCD) built on the basis of the simplified and general concepts of mechanisms for climatic response to orbital forcing can be a reasonable alternative to Milankovitch’s and his followers’ discrete insolation curves, which are widely used in paleoclimate interpretations. Comparison of the OCD and the oxygen isotope record LR04 indicates a fairly good match (considering the simplicity of the OCD construction and interpretation) in 0–1240 ka. The study discusses some discrepancies in the chronology and structure of the LR04 and OCD. It was shown that climate response may differ from that predicted by orbital insolation forcing on the basis of the generally accepted mechanisms causing transformation of orbital signals. It was shown that a shift from a dominant glacial periodicity of 41 to 100 k.y. (Middle Pleistocene transition) took place at ∼1240 ka. Since then, the 100-k.y. eccentricity cycle has not been interrupted. Therefore, strictly speaking, the revised numbering of marine isotope stages (MIS) should be adopted for the interval of 1240-900 ka to reflect realistic 100-k.y. cycles instead of 41-k.y. cycles, similar to the interval of 900–100 ka.