Answer: involve rapid, nonlinear, reactions of ice volume, CO2, and temperature to external astronomical forcing. The precise timing of events may be modulated by millennial‐scale climate change that can lead to a contrasting timing of maximum interglacial intensity in each hemisphere. A variety of temporal trends is observed, such that maxima in the main records are observed either early or late in different interglacials. The end of an interglacial (glacial inception) is a slower process involving a global sequence of changes. Interglacials have been typically 10–30 ka long. The combination of minimal reduction in northern summer insolation over the next few orbital cycles, owing to low eccentricity, and high atmospheric greenhouse gas concentrations implies that the next glacial inception is many tens of millennia in the future.
1 Introduction—Interglacials of the Last 800 ka
Earth's climate of the last 800 ka (1 ka = 1000 years) is the latest stage in a slow cooling that has been in progress for the last ~50 Ma (1 Ma = 1 million years) [Zachos et al., 2008]. During this cooling, ice sheets formed on the Antarctic continent ~40 Ma ago, while the first signs of Northern Hemisphere (NH) glaciation appeared much more recently. Only at the start of the Quaternary Period and the Pleistocene Epoch, ~2.6 Ma ago, did alternations between cold glacial periods with ice on the NH continents, and warmer intervals with little or no NH continental ice, first appear, reflected in the appearance of ice‐rafted debris
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