ENSO diversity, transitions and projected changes 

<p>Diverse characteristics of ENSO events occurring either in the Eastern Pacific (EP) and Central Pacific (CP), have led to a shift in the traditional view of tropical coupled ocean- atmosphere systems and present a challenge in light of recent changes and possible future ENSO behaviour. The probability of a transition from one type of event to another is influenced by multiple factors of which many are projected to change with global warming. Here we assess the likelihood of transition from one ENSO state to another in long instrumental records and climate models. We find specific transitions are more likely than others. For example, strong EP El Ni&#241;o events are more likely to transition to La Ni&#241;a events than to El Ni&#241;o events. The strength of an El Ni&#241;o event is found to be an important factor. Consecutive CP El Ni&#241;o events, unlike consecutive EP El Ni&#241;o events, are more likely to occur after a strong CP event. Under a high emission scenario, we find significant changes of transitions.</p>