Lessons from a previous global warming event
The PETM took place at a point in Earth's development when the climate was very different than today. It's important to stress that none of the preceding discussion implies that direct and complete comparisons can be made between the Earth climate of today, and the Earth climate of 56 million years ago. Much has changed since then, such as the layout of the continents, and the development of major mountain chains such at the Himalayas and Andes, the growth of major ice sheets, major cooling of the deep ocean and the poles, slight warming of the Sun, and changing Earth-Sun orbital characteristics, all of which greatly alter global circulations and therefore climate.
But now that we humans have embarked on a global warming experiment, there are some useful lessons from the past:
- Ocean acidification (of the deep sea at least) can occur even under conditions of CO2 release much slower than today.
Whether the plants and animals upon which humans depend can survive the present rapidly changing environment remains to be seen.