Whither ENSO and the Warming Hole

Since the end of 1998, global warming has slowed, largely due to cool SSTs in the eastern Pacific. In this talk, we use observations, ocean and atmosphere reanalyses, and coupled atmosphere-ocean global climate models to explore the connection between the hiatus, western Pacific long term warming trends, and Pacific Decadal Variability (PDV). Building on recent literature, we suggest that 1999-2014 Pacific SST may be understood as an interaction between a) the long term western Pacific warming trends identified in ENSO-residual SST and b) a slowing in long term warming trends in the eastern Pacific. While natural decadal variability has almost certainly contributed to cool east Pacific SSTs, the north Pacific ‘Warming Hole' (180°E, 0°N-110°W, 60°N) exhibits little similarity to the ensemble mean warming tendencies of global climate change ensembles. To explore this matter, we use ocean and atmosphere reanalyses to compare and contrast Pacific energy budgets during three eras: the 1948-1976 and 1999-2014 cool east pacific PDV periods and the 1977-1998 warm east Pacific period. Both the total amounts and temporal variability of radiative and advective energy fluxes are examined. Special attention is directed at understanding differences between the equatorial western, central. and eastern Pacific. The onset, intensity, and duration of El Niño events in these epochs are also evaluated.