Grant Piper's July 16 letter, "Misplaced excitement of the G8," about ice ages seems a little bit confused. The ice ages are cyclical; they never truly end. We are currently in an interglacial period — literally, "between glaciers." Our current interglacial period will end when the ice caps and glaciers thicken and expand. This is largely due to variations in Earth's orbital motion that cause the Northern Hemisphere to receive less sunlight. Since this is cyclical, there is no reason to state that global temperature rise is unstoppable. Temperatures will rise and fall with the advance and retreat of the ice.
Scientists at present think that our next period of glaciation could start either 130,000 or 620,000 years from now. It is a distant problem. Man-made greenhouse gases are an immediate problem and it's good that the Group of Eight nations are trying to do something about it.
The situation can be summed up with an analogy: Houses rarely last more than 100 years. Still, if you found a fire starting in your house you would try and put it out, as it is the immediate and most dangerous problem. Once your house is safe, then you can consider its permanence problem, if you care to.
We have at least 130,000 years to act on ice age glaciation. The problem of man-made greenhouse gases needs more immediate action.