THE El Ni帽o Southern Oscillation (ENSO) 鈥� a climate mechanism that brings extreme weather 鈥� is likely to continue in a warmer world. That could be good news, though.
At the moment the Pacific Ocean oscillates between two extreme states, El Ni帽o and La Ni帽a, every few years. Floods and droughts follow both; the recent floods in Australia were a result of La Ni帽a. There have been fears that as global temperatures rise, the ENSO may shut down and send the Pacific into a permanent El Ni帽o. Without La Ni帽a鈥檚 upwelling of cold water, warm water would cover most of the Pacific, heating the atmosphere even more.
But of the University of Oxford thinks this scenario is unlikely. She studied plankton fossils from the Pliocene (4.5 to 3 million years ago), during which global temperature was 3 掳C higher than now.
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The plankton鈥檚 tiny calcium carbonate shells record the temperature they grew in. Rickaby found that the fossils had experienced a wider range of temperatures than seasonal change alone would explain. There must have been an extra source of variation, which she thinks was the ENSO (Paleoceanography, ).
of the National Oceanic and Atmospheric Administration in Miami, Florida, has produced models that also suggest the ENSO will continue in future, but warns that the Pliocene may have little to tell us about the present, because the climate is now changing much faster than it did then.