A possible bias of simulating the post-2000 changing ENSO

Since the late 1990s, a climate shift has occurred over the tropical Pacific that is characterized with a La Niña-like mean state. Coincident with this climate shift, climate models' skills in predicting the El Niño Southern Oscillation (ENSO) events in the 2000s are significantly lower than in the 1980s-1990s. A common bias is likely to exist in contemporary ENSO models that got amplified after the climate shift. In this study, we identify this model bias to be the wind-sea surface temperature coupling processes over the tropical Pacific. Evidence is presented to show that this coupling process experienced an obvious shift around year 2000 in its coupling strength and coupling center. A simple ENSO coupled model is used to demonstrate that the changing properties of the post-2000 ENSO events can be more realistically simulated if this model bias is alleviated.