R.L. That makes sense; however, is that truely indicative of "global" tempatures or just "polar region" tempatures?
If for example a warm spell at the poles created greater evaporation...Or even a sub-surface volcano caused a warm current in the polar region...Then wouldn't that possibly cause greater evaporation of the heavier isotopes and thus alter the mix in the ice core sample?
As the ozone layer hole shows, the atmosphere of earth is anything but homogeneous and predicatable.