The rapid succession of El Niños beginning in the early 1990's was unusual.
El Niño, where the water is warmer than normal, is indicated by the red/yellow colors, and can be seen in  1986-1987, 1991-1992, 1993, 1994, 1997-1998 and 2015-2016. The rapid succession of El Niños beginning in the early 1990's was unusual.