Fossil analyses have cast doubt on the prediction by some climate modellers that a warmer world will bring an enduring warming of the eastern Pacific as a result of the warm phase of the El Niño–Southern Oscillation becoming permanent.
El Niño, a quasiperiodic cycling of tropical Pacific water temperatures, causes extreme weather around the globe. Researchers looking at fossil evidence dating back to roughly 50 million years ago report that El Niño may still have been oscillating despite the higher temperature.
Linda Ivany at Syracuse University in New York and her team analysed Antarctic fossils from the Eocene warm period, 56 million to 34 million years ago, when the average global temperature exceeded today's by at least 10°C. They measured the width of growth bands in the fossils of wood and bivalves, a class of molluscs, as indicators of annual growth rate. They found growth rates that varied with a similar frequency to the El Niño cycle, suggesting that it was still occurring.
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El Niño in a warming world. Nature 477, 373 (2011). https://doi.org/10.1038/477373c
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DOI: https://doi.org/10.1038/477373c
