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<p>Multi-year El Niño events are the key drivers of persistent extreme weather and climate anomalies worldwide. Understanding the factors influencing multi-year El Niño variations over the past millennium is crucial for predicting its future occurrences in warmer climates. This study reconstructs the frequency of multi-year El Niño events from 848 to 1992 CE using a global tree-ring network. The ratio of multi-year El Niño events to all El Niño events in recent decades (∼30%) is not the highest over the past millennium, and the peak occurrences are observed during 1500–1550 and 1620–1670 (∼60%). State-of-the-art model simulations suggest that multidecadal variations in the frequency of multi-year El Niño events over the past millennium are primarily driven by internal variability associated with the Interdecadal Pacific Oscillation (IPO), whereas external forcing plays a minimal role. During positive IPO phases, an enhanced inter-basin sea surface temperature (SST) gradient between the tropical Pacific and other oceans increases the occurrence of westerly wind anomalies in the equatorial western Pacific during the post-El Niño spring, fostering persistent SST warming and the development of multi-year El Niño events. Our results suggest that the incorporation of IPO phase shifts may improve projections of multidecadal variations in multi-year El Niño events.</p>

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Multidecadal modulation of multi-year El Niño events over the past millennium

  • 期刊论文

  • 发表日期：

    2025年8月15日

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  • Shuheng Lin,
  • Keyan Fang,
  • Hao Wu,
  • Hanjie Fan,
  • Feifei Zhou,
  • Jinbao Li,
  • Kaiqiang Deng,
  • Hans W. Linderholm,
  • Song Yang

摘要

Multi-year El Niño events are the key drivers of persistent extreme weather and climate anomalies worldwide. Understanding the factors influencing multi-year El Niño variations over the past millennium is crucial for predicting its future occurrences in warmer climates. This study reconstructs the frequency of multi-year El Niño events from 848 to 1992 CE using a global tree-ring network. The ratio of multi-year El Niño events to all El Niño events in recent decades (∼30%) is not the highest over the past millennium, and the peak occurrences are observed during 1500–1550 and 1620–1670 (∼60%). State-of-the-art model simulations suggest that multidecadal variations in the frequency of multi-year El Niño events over the past millennium are primarily driven by internal variability associated with the Interdecadal Pacific Oscillation (IPO), whereas external forcing plays a minimal role. During positive IPO phases, an enhanced inter-basin sea surface temperature (SST) gradient between the tropical Pacific and other oceans increases the occurrence of westerly wind anomalies in the equatorial western Pacific during the post-El Niño spring, fostering persistent SST warming and the development of multi-year El Niño events. Our results suggest that the incorporation of IPO phase shifts may improve projections of multidecadal variations in multi-year El Niño events.