Global Multiproxy ENSO Reconstruction Over the Past Millennium

El Niño‐Southern Oscillation (ENSO) is the leading mode of interannual climate variability that affects climate and society across the world. However, our understanding of ENSO variability is currently lacking due to short instrumental observations, which limit our confidence in predicting its future occurrence and impact. In this study, we use the nested principal component regression method to reconstruct the ENSO index based on a global‐scale proxy network of stable oxygen isotopes (δ18O). We account for the teleconnection changes that influence proxy records corresponding to different ENSO phases by using the isotope‐enabled Community Earth System Model. According to the precipitation δ18O–ENSO relationship, we reconstruct the ENSO index over the last eight hundred years based on the first two leading modes of the selected proxy records. The skill of ENSO reconstruction improves with an increased number of δ18O series distributed over the ENSO‐affected regions. Our new reconstruction shows high consistency with existing ENSO reconstructions during periods of strong ENSO variability, indicating that the global proxy records capture enhanced teleconnection signals during the phase of strong ENSO amplitude. There is a weak El Niño response 1 year after the large volcanic eruptions in our reconstruction, and the amplitude of ENSO is significantly correlated with volcanic intensity. The strengthened energetic interactions between the ocean and atmosphere following large volcanic eruptions result in enhanced sea surface temperature variability. Plain Language Summary El Niño‐Southern Oscillation (ENSO) is a mode of interannual climate variability originating in the tropical Pacific region. Our understanding of the range of natural variability in ENSO and the long‐term relationships between ENSO and climate change is still limited due to short instrumental observations. Global proxy records preserved in tree rings and caves are a common data source for ENSO variability over the preindustrial period. We use a climate model to interpret the patterns of proxy records associated with different ENSO phases. According to the proxy–ENSO relationship, we reconstruct the ENSO index over the last eight hundred years based on global proxy records. They could reasonably represent ENSO variability when distributed around the ENSO‐affected regions, including the Asian–Australian monsoon region, the tropical Pacific, northern South America, and Africa. Our reconstruction sh