[cogitator]

If CO2 levels at the PETM were similar to today, then a human cause cannot be a logical assumption, since man was not present at the PETM event.

The "proof" of the causation of the current atmospheric CO2 levels as being primarily due to human activities is not reliant on the PETM. The main thing that the PETM does is show in the Earth system that greenhouse gases can force temperature changes (and apparently then cause some "downstream" effects).

[The_Victor]

The main thing that the PETM does is show in the Earth system that greenhouse gases can force temperature changes (and apparently then cause some "downstream" effects).

My point is not that the event won't happen as before, but that mankind may have absolutely nothing to do with it.

[The_Victor]

main thing that the PETM does is show in the Earth system that greenhouse gases can force temperature changes

Another point: The PETM does not establish the cause/effect relationship of CO2 to climate change. Just that the CO2 levels were elevated at the time of the "overturning". CO2 levels as a cause of that event, rather than an effect of it, or spuriously related to a different overriding cause, cannot be established.