Any assessment of future climate change requires knowledge of the full range of natural variability in the El Niño/Southern Oscillation (ENSO) phenomenon. Here we splice together fossil-coral oxygen isotopic records from Palmyra Island in the tropical Pacific Ocean to provide 30-150-year windows of tropical Pacific climate variability within the last 1,100 years. The records indicate mean climate conditions in the central tropical Pacific ranging from relatively cool and dry during the tenth century to increasingly warmer and wetter climate in the twentieth century. But the corals also document a broad range of ENSO behaviour that correlates poorly with these estimates of mean climate. The most intense ENSO activity within the reconstruction occurred during the mid-seventeenth century. Taken together, the coral data imply that the majority of ENSO variability over the last millennium may have arisen from dynamics internal to the ENSO system itself.
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Acknowledgements We thank M. Moore and J. Ardai for field assistance, T. Guilderson for preliminary radiocarbon dates, and A. Timmermann for comments on an early draft of the manuscript. We also thank the Khaled bin Sultan Living Ocean Foundation and The Nature Conservancy for financial and logistical support during two field excursions to Palmyra. K.M.C. was supported by a NSF graduate fellowship, and the work was supported by NOAA (C.D.C.) and NSF (R.L.E.).
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