Earth's equator is sometimes viewed as a bit of a virtual wall that separates the climates of the northern and southern hemispheres. Ocean currents, the main driver of climate, tend to confine themselves to one side or the other. When waters from North and South meet at the equator, they combine lazily and create an utter lack of wind known as the doldrums. But a new study finds the climates in each half of the planet are linked by the oceans over the long run. Ocean circulation in the Southern Hemisphere has in the past adapted to sudden changes in...