The El Niño/Southern Oscillation (ENSO) system during the Pliocene warm period (PWP; 3–5 million years ago) may have existed in a permanent El Niño state with a sharply reduced zonal sea surface temperature (SST) gradient in the equatorial Pacific Ocean1. This suggests that during the PWP, when global mean temperatures and atmospheric carbon dioxide concentrations were similar to those projected for near-term climate change2, ENSO variability—and related global climate teleconnections—could have been radically different from that today. Yet, owing to a lack of observational evidence on seasonal and interannual SST variability from crucial low-latitude sites, this fundamental climate characteristic of the PWP remains controversial1,3,4,5,6,7,8,9,10. Here we show that permanent El Niño conditions did not exist during the PWP. Our spectral analysis of the δ18O SST and salinity proxy, extracted from two 35-year, monthly resolved PWP Porites corals in the Philippines, reveals variability that is similar to present ENSO variation. Although our fossil corals cannot be directly compared with modern ENSO records, two lines of evidence suggest that Philippine corals are appropriate ENSO proxies. First, δ18O anomalies from a nearby live Porites coral are correlated with modern records of ENSO variability. Second, negative-δ18O events in the fossil corals closely resemble the decreases in δ18O seen in the live coral during El Niño events. Prior research advocating a permanent El Niño state may have been limited by the coarse resolution of many SST proxies, whereas our coral-based analysis identifies climate variability at the temporal scale required to resolve ENSO structure firmly.
This is a preview of subscription content
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Get time limited or full article access on ReadCube.
All prices are NET prices.
Wara, M. W., Ravelo, A. C. & Delaney, M. L. Permanent El Niño-like conditions during the Pliocene warm period. Science 309, 758–761 (2005)
Mix, A. C. et al. Benthic foraminiferal stable isotope record from Site 849, 0–5 Ma: local and global climate changes. Proc. ODP Sci. Res. 138, 371–412 (1995)
Molnar, P. & Cane, M. A. El Niño’s tropical climate and teleconnections as a blueprint for pre-Ice Age climates. Paleoceanography 17, 1021 (2002)
Ravelo, A. C., Andreasen, D. H., Lyle, M., Lyle, A. O. & Wara, M. W. Regional climate shifts caused by gradual global cooling in the Pliocene epoch. Nature 429, 263–267 (2004)
Rickaby, R. E. M. & Halloran, A. P. Cool La Niña during the warmth of the Pliocene? Science 307, 1948–1952 (2005)
Fedorov, A. V. et al. The Pliocene paradox (mechanisms for a permanent El Niño). Science 312, 1485–1489 (2006)
Haywood, A. M., Valdes, P. J. & Peck, V. L. A permanent El Niño-like state during the Pliocene? Paleoceanography 22, PA1213 (2007)
Molnar, P. & Cane, M. A. Early Pliocene (pre-Ice Age) El Niño-like global climate: which El Niño? Geosphere 3, 337–365 (2007)
Lawrence, K. T., Liu, Z. & Herbert, T. D. Evolution of the eastern tropical Pacific through Plio-Pleistocene glaciation. Science 312, 79–83 (2006)
Dowsett, H. J. & Robinson, M. M. Mid-Pliocene equatorial Pacific sea surface temperature reconstruction: a multi-proxy perspective. Phil. Trans. R. Soc. A 367, 109–125 (2009)
Philander, S. G. H. El Niño, La Niña and the Southern Oscillation 9–57 (Academic, 1990)
Cole, J. E., Fairbanks, R. G. & Shen, G. T. Recent variability in the southern oscillation: isotopic results from Tarawa Atoll coral. Science 260, 1790–1793 (1993)
Corrège, T. et al. Interdecadal variation in the extent of South Pacific tropical waters during the Younger Dryas event. Nature 428, 927–929 (2004)
Tudhope, A. W. et al. Variation in the El Niño-Southern Oscillation through a glacial-interglacial cycle. Science 291, 1511–1517 (2001)
Watanabe, T. et al. Oxygen isotope systematics in Diploastrea heliopora: new coral archive of tropical paleoclimate. Geochim. Cosmochim. Acta 67, 1349–1358 (2003)
Rasmusson, E. M. &. Carpenter, T. H. Variations in tropical sea surface temperature and surface wind fields associated with the Southern Oscillation/El Niño. Mon. Weath. Rev. 110, 354–384 (1982)
Ropelewski, C. F. & Halpert, M. S. Global and regional scale precipitation patterns associated with the El Niño/Southern Oscillation. Mon. Weath. Rev. 115, 1606–1626 (1987)
Dai, A. & Wigley, T. M. L. Global patterns of ENSO-induced precipitation. Geophys. Res. Lett. 27, 1283–1286 (2000)
Raffi, I. et al. A review of calcareous nannofossil astrobiochronology encompassing the past 25 million years. Quat. Sci. Rev. 25, 3113–3137 (2006)
Cobb, K. M. Charles, C. D. Cheng, H. & Edwards, R. L. El Niño/Southern oscillation and tropical Pacific climate during the last millennium. Nature 424, 271–276 (2003)
Urban, F. E., Cole, J. E. & Overpeck, J. T. Influence of mean climate change on climate variability from a 155-year tropical Pacific coral record. Nature 407, 989–993 (2000)
Fedorov, A. V., Brierley, C. M. & Emanuel, K. Tropical cyclones and permanent El Niño in the early Pliocene epoch. Nature 463, 1066–1070 (2010)
Reynolds, R. et al. Daily high-resolution blended analyses for sea surface temperature. J. Clim. 20, 5473–5496 (2007)
We would like to thank H. H. Ramos for a research permit and W. Mago and E. Azurin for their help with fieldwork. Special thanks go to F. P. Siringan for the study of modern coral; H. Nomura and K. Nakamura for preparing thin sections; R. Miyawaki for assistance with X-ray diffraction; S. Motai, Y. Seto and K. Omori for their assistance with synchrotron X-ray diffraction; C. Shimada, M. Ikeda and K. Hagino-Tomioka for their scanning electron microscopy observations; Y. Yoshinaga for microsampling; and A. Yamazaki for preparing the figures.
The authors declare no competing financial interests.
About this article
Cite this article
Watanabe, T., Suzuki, A., Minobe, S. et al. Permanent El Niño during the Pliocene warm period not supported by coral evidence. Nature 471, 209–211 (2011). https://doi.org/10.1038/nature09777
Nature Reviews Earth & Environment (2021)
Climatic Change (2020)
The changes in ENSO-induced tropical Pacific precipitation variability in the past warm and cold climates from the EC-Earth simulations
Climate Dynamics (2020)
Climatic, physical, and biogeochemical changes drive rapid oxygen loss and recovery in a marine ecosystem
Scientific Reports (2019)
Thermoluminescence of coral skeletons: a high-sensitivity proxy of diagenetic alteration of aragonite
Scientific Reports (2017)