Andrew, in regard to this quote:
My understanding is that it's a known scientific fact, not open to any reasonable doubt whatesoever, proven via many indepent tree ring studies and correlated with various other temperature records, that over recorded history, the climate used to be both substantially warmer and substantially colder than it is now. If as far as we know a warmer climate didn't cause disaster during the "medieval climate optimum" - and we know it didn't - then a similarly warmer climate now probably isn't going to cause disaster either.
the concern of biologists and ecologists (meaning the science of studying ecosystem, i.e. communities of organisms, not "PopEco") is not simply with the endpoints.
It is with the pace of climate change. The very records you cite make it clear that the pace we're seeing is abormally rapid.
And from a practical, management point of view we're far more locked into a pattern of land allocation and use than was true during, say, medieval times. This potentially has a huge impact on our ability to mitigate through management because in much of the world, conservation strategy has been based on the creation of conservation reserves (in our country National Parks and to some extent National Forests, wildlife refuges, and the like). Typically these are surrounded by private lands devoted to intense agricultural use or, in a surprisingly large number of cases, heavy urban or suburban use.
And, as mentioned above, from a practical, management point of view (if one is a conservation biologist) the whole debate over climate change is moot. We've been seeing the effects on the ground for a couple of decades now and conservation biologists aren't asking "what if", they're working on "what can we do to mitigate?".
