Studies of climate change in the Eocene are instructive regarding the kinds of changes driven by atmospheric CO2 levels. Those who take comfort in the fact that the climate has always changed — and it has — are clinging to false hope. One of the lessons of most climate shifts in the past — even big ones: picture palm trees on the eastern Antarctic coastline and alligators in the Canadian Arctic — is that they were slow and gradual giving animal and plant life time to migrate or to adapt. The obscenity of the current anthropogenic CO2 spike is that it is happening on a brief historical time scale as opposed to a protracted geologic time scale meaning that the flora and fauna have time to neither change latitudes nor adapt in place.
Eocene climate change study: