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Nightprowler,
You could argue that that happens on much shorter time scales than 500-700million years. We have had 5 major extinctions in the last 440mil yr. The causes range from bollide impacts (like what killed the dinosaurs) to flood volcanism that caused rapid warming, to rapid fall and rise of sea level in response to an ice-age...
Wheresmy50
Do I believe that we as a species have an impact on the planet; yes. As a geologist do I know that the earth has been warmer in the past you betcha. Look at the Cretaceous (~65Mil years ago) sea level was MUCH higher than today, most of North America between the Appalachians and Rocky mtns were flooded with a huge sea.. Whats the point of all this rambling...
On a geologic time scale we have seen more rapid and larger changes in climate; in our recorded history we have not. So if we are having an impact you're right NP, on the geologic time scale we're a flea on a dogs back and would/could be wiped out as a species, but since we deal with shorter timescales than that when talking about human lives I do agree we have something we need to worry about, but I still think the timescale you're talking about is a bit rapid (children's children's lifetime; I think nuclear war is a threat in that time scale not global warming) Probably the biggest threat of global warming would be slow change, as climate shifts, food production would decrease and shift North (think Canada growing oranges) which would slowly suffocate the species, not cause a catastrophic wipe-out for the species.
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