ENSO is the strongest interannual signal in the global climate system with worldwide climatic, ecological and societal impacts. Over the past decades, the research about ENSO prediction and predictability has attracted broad attention. With the development of coupled models, the improvement in initialization schemes and the progress in theoretical studies, ENSO has become the most predictable climate mode at the time scales from months to seasons. This paper reviews in detail the progress in ENSO predictions and predictability studies achieved in recent years. An emphasis is placed on two fundamental issues: the improvement in practical prediction skills and progress in the theoretical study of the intrinsic predictability limit. The former includes progress in the couple models, data assimilations, ensemble predictions and so on, and the latter focuses on efforts in the study of the optimal error growth and in the estimate of the intrinsic predictability limit.

The Roman Warm Period (RWP) and Late Antique Little Ice Age (LALIA) are two periods of remarkably strong climate anomalies during the first millennium of the Common Era (CE). Previous researches have suggested that the RWP was even warmer than the Medieval Climate Anomaly (MCA) and the Current Warm Period (CWP) (Bianchi & McCave, 1999;Keigwin, 1996). The RWP has been defined as the interval 1-300 CE from the