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Southern Hemisphere Drying Due to Major Climate Zone Shift October 12, 2012
Graphic of Earth's basic atmospheric circulation model.
A decline in April-May rainfall over southeastern Australia is associated with a southward expansion of the Southern Hemisphere Hadley cell.
The southward shift of an atmospheric belt in the Southern Hemisphere since the 1970s is why parts of Australia and southern Africa are drying out, according to new research.

Scientists at the Commonwealth Scientific and Industrial Research Organization write in the journal Scientific Reports that the southward expansion of a meteorological feature known as the Hadley cell is most pronounced in autumn.

The shift of between 125 and 250 miles has resulted in less rainfall during April and May over southeastern Australia, and to a lesser extent in southern Africa.

Rain that previously would fall 125 to 250 miles farther north is now being directed that distance to the south due to climate change’s effect on the Hadley cell.

However, no such change has been detected during autumn in southern South America, the researchers say.

The researchers don’t know specifically what is causing the shift, and climate models have not accurately represented it.

“The Hadley cell is comprised of a number of individual branches, so the impact of a southward shift of the subtropical dry zone on rainfall is not the same across the different semi-arid regions of the Southern Hemisphere,” said CSIRO's Wenju Cai.

Graphic: Earthweek