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TALK about a left-right jab. One of the world鈥檚 biggest sources of climate variability is set to develop a devastating double hit.
The El Ni帽o Southern Oscillation is a natural fluctuation of ocean temperatures in the equatorial Pacific, whose extremes, El Ni帽o and La Ni帽a, drive droughts and floods from South-East Asia to the Americas. When they are strong, the impacts are devastating. The 1997 El Ni帽o, for example, is estimated to have killed 23,000 people and caused $45 billion in damage.
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Climate change is predicted to double the frequency of such El Ni帽os this century. Now it seems extreme La Ni帽as will also start happening once every 13 years instead of 23 years, says at the CSIRO in Melbourne, Australia, whose team ran 21 climate models with data for future carbon emissions (Nature, ).
The uneven warming of the Pacific Ocean is setting up a kind of see-saw, says Cai. 鈥淭hat means that the system swings between two extreme opposites.鈥� These can multiply the impacts of each event, with farmers being hit by droughts and then by floods.
This article appeared in print under the headline 鈥淐limate change鈥檚 double whammy鈥�
