The late Oligocene warming
The ice pulls back for a couple of million years and the world briefly reverses course.
- When
- —
- Duration
- 2.5 million years
- Known to
- ± 500 thousand years
- Era
- Oligocene, Cenozoic
From roughly 26.5 to 24 million years ago, deep-sea temperatures rise and Antarctic ice volume falls substantially — one of the few sustained warm reversals in the long Cenozoic cooling. Carbon dioxide appears to rise with it. The interval matters because it demonstrates that the Antarctic ice sheet, once formed, was not irreversible: it could and did lose a large fraction of its mass under only moderately higher greenhouse forcing, which is precisely the question being asked of it today.