On the variability of ENSO over the past six centuries

The instrumental record is too brief for evaluation of the El Nino-Southern Oscillation (ENSO) system and its long-term response to climate forcing. To supplement these data, we use a new reconstruction of December-February Nino-3 sea surface temperatures based on subtropical North American tree-ring records to investigate aspects of ENSO variability over the past six centuries (AD 1408-1978). Spectral analyses reveal that the reconstruction best resolves variability within the "classical'' ENSO band of 2 - 8 years. A low amplitude ENSO epoch in the 17th to 18th centuries broadly coincides with "Little Ice Age'' conditions over much of the globe. The detailed behavior shows good agreement with shorter tree-ring reconstructions of ENSO over the past few centuries, but differs at times from other longer coral ENSO records and recent model simulations of past ENSO behavior. We discuss possible reasons for these discrepancies.