The 100,000-year world
Glacial cycles settle into long, deep, sawtooth swings — slow to build, fast to collapse.
- When
- —
- Duration
- 571 thousand years
- Known to
- ± 30 thousand years
- Era
- Middle Pleistocene, Quaternary
After the Mid-Pleistocene Transition completes, the ice ages take their final form: roughly 100,000-year cycles in which ice builds gradually over some 90,000 years and then collapses within a few thousand. Sea level swings by up to 120 metres, and carbon dioxide oscillates between about 180 parts per million at glacial maxima and 280 in interglacials. The 100,000-year period matches orbital eccentricity, but eccentricity is the weakest of the orbital forcings — the mismatch between a feeble cause and an enormous effect is the central unsolved problem of ice age theory.