CLIMATE
The Hottest the World Has Been
~94 to 83 million years ago
Phanerozoic · Mesozoic · Cretaceous
For more than ten million years there was no permanent ice anywhere, the sea stood at its highest level of the last half billion years, and the temperature gap between the tropics and the higher latitudes was under fourteen degrees, against about twenty today. Relatives of crocodiles lived within reach of the Arctic.
Why it matters
Nothing since has been this warm, and this stretch of the Cretaceous has become the reference case for any model of a high-carbon future. The awkward part is that the measurements run hotter than the models will go, so the best-measured hot world we have is also the one the models cannot yet match.
Dating & uncertaintyDisputed
Peak warmth is placed in the Cenomanian and Turonian by both organic and oxygen-isotope thermometers. The absolute values are contested: sub-Antarctic surface waters above 27 degrees, and tropical shells suggesting 41 to 45 degrees, are warmer than climate models will produce, and can be brought into line only by assuming very heavy rainfall at high latitudes.
Sources
- O'Brien et al. (2017), Earth-Science Reviews · Cretaceous sea-surface temperature evolution: constraints from TEX86 and planktonic foraminiferal oxygen isotopes
- Huber et al. (2018), Global and Planetary Change · The rise and fall of the Cretaceous hot greenhouse climate
- Křížová et al. (2024), Palaeogeography, Palaeoclimatology, Palaeoecology · Late Cretaceous (Cenomanian-Turonian) temperature evolution and biotic response in the Adriatic Carbonate Platform region of Friuli, northeast Italy
Earth history as one day
23:30:1129 min 49 s before midnight
if Earth’s 4.54 billion years were compressed into a single day
See it on the timeline