Because ENSO events differ in their strength, coverage, and seasonality, there isn't unanimous agreement
on what constitutes and ENSO event. But, there are broad agreements and you can find some of the lists
researchers have used along with how they chose those years. The list in the right column represents ENSO
years based on PSD's Extended Multivariate ENSO Index (MEI.ext).
Years are determined from Dec-Jan-Feb (DJF) values of the PSD MEI.ext index. ENSO events are most clearly defined in northern winter (DJF), both in terms of impacts and robustness with regard to the ENSO index used. Other seasons have impacts, too, but do not necessarily match the winter seasons.