Historical change of El Niño properties sheds light on future changes of extreme El Niño

Bin Wang; Xiao Luo; Young Min Yang; Weiyi Sun; Mark A. Cane; Wenju Cai; Sang Wook Yeh; Jian Liu

doi:10.1073/pnas.1911130116

Historical change of El Niño properties sheds light on future changes of extreme El Niño

Bin Wang
, Xiao Luo
, Young Min Yang
, Weiyi Sun
, Mark A. Cane
, Wenju Cai
, Sang Wook Yeh
, Jian Liu

Research output: Contribution to journal › Article › peer-review

296 Scopus citations

Abstract

El Niño’s intensity change under anthropogenic warming is of great importance to society, yet current climate models’ projections remain largely uncertain. The current classification of El Niño does not distinguish the strong from the moderate El Niño events, making it difficult to project future change of El Niño’s intensity. Here we classify 33 El Niño events from 1901 to 2017 by cluster analysis of the onset and amplification processes, and the resultant 4 types of El Niño distinguish the strong from the moderate events and the onset from successive events. The 3 categories of El Niño onset exhibit distinct development mechanisms. We find El Niño onset regime has changed from eastern Pacific origin to western Pacific origin with more frequent occurrence of extreme events since the 1970s. This regime change is hypothesized to arise from a background warming in the western Pacific and the associated increased zonal and vertical sea-surface temperature (SST) gradients in the equatorial central Pacific, which reveals a controlling factor that could lead to increased extreme El Niño events in the future. The Coupled Model Intercomparison Project phase 5 (CMIP5) models’ projections demonstrate that both the frequency and intensity of the strong El Niño events will increase significantly if the projected central Pacific zonal SST gradients become enhanced. If the currently observed background changes continue under future anthropogenic forcing, more frequent strong El Niño events are anticipated. The models’ uncertainty in the projected equatorial zonal SST gradients, however, remains a major roadblock for faithful prediction of El Niño’s future changes.

Original language	English
Pages (from-to)	22512-22517
Number of pages	6
Journal	Proceedings of the National Academy of Sciences of the United States of America
Volume	116
Issue number	45
DOIs	https://doi.org/10.1073/pnas.1911130116
State	Published - Nov 5 2019
Externally published	Yes

Funding

ACKNOWLEDGMENTS. B.W., Y.-M.Y., and X.L. are supported by Nanjing University of Information Science and Technology through the establishment of the China-US Joint Atmosphere-Ocean Research Center at the University of Hawaii, and by NSF/Climate Dynamics Award AGS-1540783. J.L. and B.W. are supported by the National Natural Science Foundation of China (Grant 41420104002) and the National Key Research and Development Program of China (Grant 2016YFA0600401). W.C. is supported by Centre for Southern Hemisphere Oceans Research (CSHOR) and the Earth System and Climate Change Hub of the Australian Government’s National Environment Science Program. CSHOR is a joint research center between Qingdao National Laboratory for Marine Science and Technology (QNLM) and Commonwealth Scientific and Industrial Research Organisation (CSIRO). S.-W.Y. is supported by National Research Foundation Grant NRF-2018R1A5A1024958. M.A.C. was supported by NSF Award OCE 1657209. This is the International Pacific Research Center (IPRC) publication no. 1404, the School of Ocean and Earth Science and Technology (SOEST) publication no. 10794, and Earth System Modeling Center (ESMC) publication no. 279. B.W., Y.-M.Y., and X.L. are supported by Nanjing University of Information Science and Technology through the establishment of the China-US Joint Atmosphere-Ocean Research Center at the University of Hawaii, and by NSF/Climate Dynamics Award AGS-1540783. J.L. and B.W. are supported by the National Natural Science Foundation of China (Grant 41420104002) and the National Key Research and Development Program of China (Grant 2016YFA0600401). W.C. is supported by Centre for Southern Hemisphere Oceans Research (CSHOR) and the Earth System and Climate Change Hub of the Australian Government?s National Environment Science Program. CSHOR is a joint research center between Qingdao National Laboratory for Marine Science and Technology (QNLM) and Commonwealth Scientific and Industrial Research Organisation (CSIRO). S.-W.Y. is supported by National Research Foundation Grant NRF-2018R1A5A1024958. M.A.C. was supported by NSF Award OCE 1657209. This is the International Pacific Research Center (IPRC) publication no. 1404, the School of Ocean and Earth Science and Technology (SOEST) publication no. 10794, and Earth System Modeling Center (ESMC) publication no. 279.

Keywords

El Niño diversity
El Niño onset
El Niño onset regime shift
Future projection of extreme El Niño

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10.1073/pnas.1911130116

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title = "Historical change of El Ni{\~n}o properties sheds light on future changes of extreme El Ni{\~n}o",

abstract = "El Ni{\~n}o{\textquoteright}s intensity change under anthropogenic warming is of great importance to society, yet current climate models{\textquoteright} projections remain largely uncertain. The current classification of El Ni{\~n}o does not distinguish the strong from the moderate El Ni{\~n}o events, making it difficult to project future change of El Ni{\~n}o{\textquoteright}s intensity. Here we classify 33 El Ni{\~n}o events from 1901 to 2017 by cluster analysis of the onset and amplification processes, and the resultant 4 types of El Ni{\~n}o distinguish the strong from the moderate events and the onset from successive events. The 3 categories of El Ni{\~n}o onset exhibit distinct development mechanisms. We find El Ni{\~n}o onset regime has changed from eastern Pacific origin to western Pacific origin with more frequent occurrence of extreme events since the 1970s. This regime change is hypothesized to arise from a background warming in the western Pacific and the associated increased zonal and vertical sea-surface temperature (SST) gradients in the equatorial central Pacific, which reveals a controlling factor that could lead to increased extreme El Ni{\~n}o events in the future. The Coupled Model Intercomparison Project phase 5 (CMIP5) models{\textquoteright} projections demonstrate that both the frequency and intensity of the strong El Ni{\~n}o events will increase significantly if the projected central Pacific zonal SST gradients become enhanced. If the currently observed background changes continue under future anthropogenic forcing, more frequent strong El Ni{\~n}o events are anticipated. The models{\textquoteright} uncertainty in the projected equatorial zonal SST gradients, however, remains a major roadblock for faithful prediction of El Ni{\~n}o{\textquoteright}s future changes.",

keywords = "El Ni{\~n}o diversity, El Ni{\~n}o onset, El Ni{\~n}o onset regime shift, Future projection of extreme El Ni{\~n}o",

author = "Bin Wang and Xiao Luo and Yang, \{Young Min\} and Weiyi Sun and Cane, \{Mark A.\} and Wenju Cai and Yeh, \{Sang Wook\} and Jian Liu",

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AU - Cai, Wenju

AU - Yeh, Sang Wook

AU - Liu, Jian

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KW - Future projection of extreme El Niño

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ER -

Historical change of El Niño properties sheds light on future changes of extreme El Niño

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