[glenstein]

Right, and said slightly differently: this is the context against which we have to judge whether there was any natural experiment we can refer to. There's no reason to think that the history of life on earth thus far has presented a sufficiently comparable case, to reassure us that what's happening is a re-run of a familiar event we've already seen, where everything works out well.

[IdSayThatllDoIt]

Yes that is nicely concise, but in addition I was trying to say that the line of reasoning that life has persisted through cataclysmic environmental changes and therefore worrying about them is fearmongering is a facile argument as the persistence of lichens and prototaxites etc has no bearing on the survival of humans. The nature of a cataclysm is very relative, as the oxygenation of the atmosphere and oceans would be meaningless to geochemical anaerobic bacteria that live miles below us.

We only have coal because trees grew and fell on each other for like 60 million years before anything figured out how to decompose lignin.