and how will future El Nino episodes evolve as the baseline SSTs keep trending up. And does El Nino itself affect SSTs on longer time scales. The reason for bringing it up is the apparent trimodal distribution of SST shown on this climate reanalyzer page

https://climatereanalyzer.org/clim/sst_daily/

The cluster of traces approximately between the -2sigma and 1982-2011 mean lines cover the years 1982 to 2001. 

The cluster of traces approximately between the mean and +2 sigma lines covers the years 2002-2014.

The years 2015 and later have all been above the +2 sigma line.

The transitions between these three regimes are not gradual as expected for a gradual trend. Instead there are jumps that leave gaps with few traces around the mean and +2 sigma lines themselves.

The 97/98 El Nino jumped up into the next regime but fell back until it became permanent in the 2001/2002 period.

The 2015 jump did stick with all subsequent years staying at an elevated level.

This year we are seeing what could be the next jump in the ratchet. Each jump has about a 2 sigma step size. Will it fall back after this El Nino episode is over or will it stick and become the new normal?

I wonder what causes these discrete regime changes leading to a multi-modal distribution. Have we seen enough of them to actually believe this is a pattern and, if so, are they triggered by large El Nino events?