Climate stage· The columns of time
Last glacial
115 ka → 11.7 ka
A hundred thousand years of cold, and the stage during which our species leaves Africa for good, reaches Australia, enters Europe, and crosses into the Americas. Almost everything on this timeline happens inside it.
What the evidence shows
It is tempting to read the cold as an obstacle, and it was one; it was also a road. Lower seas laid bare the continental shelves, welded Australia to New Guinea, tied Britain to the continent, and opened Beringia between Siberia and Alaska. Each of those crossings existed only because water was locked up as ice somewhere else. The stage runs from MIS 5d to MIS 2, and its coldest point, the Last Glacial Maximum, has a band of its own below; the crossings were open long before that maximum, and people had used most of them before it arrived.
Bounds and conventions
A single colour for a stage that in fact oscillates violently. Three synchronised Greenland ice cores resolve a long series of abrupt climatic changes within it, each one numbered in the stratigraphic framework built from them, and several amounted to many degrees within a single lifetime. The band says cold, and cold is right on average, but nobody lived through an average.
MIS 5d to MIS 2: a hundred thousand years of mostly cold, unstable climate, with temperate interstadials that this rank does not detail.
Sources
- Lisiecki, L. E., Raymo, M. E. (2005). A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records. Paleoceanography 20, PA1003.
- Clark, P. U., Dyke, A. S., Shakun, J. D., et al. (2009). The Last Glacial Maximum. Science 325, 710–714.
- Rasmussen, S. O. et al. (2014). A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three synchronized Greenland ice-core records. Quaternary Science Reviews 106, 14-28.
- Lambeck, K., Rouby, H., Purcell, A., Sun, Y., Sambridge, M. (2014). Sea level and global ice volumes from the Last Glacial Maximum to the Holocene. PNAS 111(43), 15296-15303.