I didn't mention desertification, but habitability - I meant to imply "inhabitable by unprotected humans." The Eocene saw a thermal maximum in which global mea

I didn't mention desertification, but habitability - I meant to imply "inhabitable by unprotected humans." The Eocene saw a thermal maximum in which global mean temperature increased by about 6 ºC, and a much wetter climate: https://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Thermal_Maximum#Evidence_for_global_warming https://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Therm... https://en.wikipedia.org/wiki/Wet-bulb_temperature https://en.wikipedia.org/wiki/Wet-bulb_temperature: > The theoretical limit to human survival for more than a few hours in the shade, even with unlimited water, is a wet-bulb temperature of 35 °C (95 °F) https://www.nature.com/articles/s41561-021-00695-3 https://www.nature.com/articles/s41561-021-00695-3: > Limiting global warming to 1.5 °C will prevent most of the tropics from reaching a TW of 35 °C, the limit of human adaptation.