Contribution of El Nino amplitude change to tropical Pacific precipitation decline in the late 1990s

Equatorial central Pacific precipitation experienced a prominent decline in the late 1990s. This change was previously attributed to a La Nina-like mean sea surface temperature (SST) change in the Pacific Ocean associated with a phase switch of the Interdecadal Pacific Oscillation. Here, using a series of model experiments, the authors reveal that the El Nino-related interannual SST anomalies contributed largely to the precipitation decrease over the equatorial central Pacific. This El Nino SST effect was due to the change in the amplitude of El Nino events in the late 1990s. The 1980-98 decade had more large-amplitude El Nino events than the 1999-2014 decade. The nonlinear precipitation response to SST anomalies resulted in a larger decadal mean precipitation in the 1980-98 decade than in the 1999-2014 decade. The results highlight the importance of El Nino amplitude change in future climate change related to global warming.