The El Niño/Southern Oscillation (ENSO) is the dominant climate phenomenon affecting extreme weather conditions worldwide. Its response to greenhouse warming has challenged scientists for decades, despite model agreement on projected changes in mean state. Recent studies have provided new insights into the elusive links between changes in ENSO and in the mean state of the Pacific climate. The projected slow-down in Walker circulation is expected to weaken equatorial Pacific Ocean currents, boosting the occurrences of eastward-propagating warm surface anomalies that characterize observed extreme El Niño events. Accelerated equatorial Pacific warming, particularly in the east, is expected to induce extreme rainfall in the eastern equatorial Pacific and extreme equatorward swings of the Pacific convergence zones, both of which are features of extreme El Niño. The frequency of extreme La Niña is also expected to increase in response to more extreme El Niños, an accelerated maritime continent warming and surface-intensified ocean warming. ENSO-related catastrophic weather events are thus likely to occur more frequently with unabated greenhouse-gas emissions. But model biases and recent observed strengthening of the Walker circulation highlight the need for further testing as new models, observations and insights become available.
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W.C. and G.W. are supported by the Australian Climate Change Science Program and a CSIRO Office of Chief Executive Science Leader award. A.S. is supported by the Australian Research Council. M.C. was supported by NERC NE/I022841/1. S.W.Y. is supported by the National Research Fund of Korea grant funded by the Korean Government (MEST) (NRF-2009-C1AAA001-2009-0093042). S.I.A. was supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Science, ICT and Future Planning (No. 2014R1A2A1A11049497). This is PMEL contribution number 4038.
The authors declare no competing financial interests.
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Cai, W., Santoso, A., Wang, G. et al. ENSO and greenhouse warming. Nature Clim Change 5, 849–859 (2015). https://doi.org/10.1038/nclimate2743
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