For example that glaciers have all disappeared from the state of Illinois, does not mean they are gone forever. In the geologic view this is our state of variation right now. Absence.
The problem with this thinking is, this is a global event, not the glaciers that were covering Illinois, leading to global extinctions of a vast number of animals. Extinct animals don't come back. Extinct is forever. Natural variation would not be as extreme as current models are showing this current swing of global conditions to be. Global changes of 2 degrees over a millenia is fairly extreme under natural conditions, 2 degrees in less than a century is concerning.
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