The question is, how long did it take them to play out? And how severe were the effects, how long did it take for conditions to reach a new equilibrium? The relevancy to today's AGW/climate change situation is if there had been a complex civilization on earth back then, would it have been able to respond and adapt to the change in conditions?

The climate denialists are always reminding us that "history tells us climate change is normal and inevitable", but they are always loathe to consider whether or not it will be so quick or severe that massive human dislocations will occur because the society will be overwhelmed by it. And our own role in provoking these long-term changes for the sole purpose of generating short term profits is conveniently swept under the rug.

The purpose, of course, is to justify their business as usual policy--there is no point in protecting the global environment since it is going to go to hell anyway. Drill, baby, drill!