That's an old assumption. Modern modelling shows that the southern hemisphere gets it's share from the northern hemisphere relatively fast. Only the shortest li

That's an old assumption. Modern modelling shows that the southern hemisphere gets it's share from the northern hemisphere relatively fast. Only the shortest lived isotopes won't make it down there. Then there is the dust/smoke/black carbon to consider. If there is much, that will make it down there, too. Causing weather weirdness, misharvests, and so on.