Increasing Temperatures of ENSO Seasons by Type

Awhile ago I posted about the temperatures of different types of ENSO seasons -- La Ninas, El Ninos, and neutral seasons -- and said I would put up a graph that showed these in a better context. Here it is:

There are the average NOAA surface temperatures for each ENSO season, which runs from July to the following June. (So 2007.0 is for the ENSO season July 2006 - June 2007). This differs from plotting ENSO temperatures versus year, which never made sense to me, especially when an ENSO goes from late in one year to early in another (like the La Nina of 2017-2018, or the El Nino of 1997-1998.)

I started in the climate business about 2018 (when, for about a year, I actually thought AGW was overblown -- until I actually learned something about it, starting with Ross Gelbspan's book), and I remember the talk then was about the "monster" El Nino of 1997-98. In just 20 years that record has been beaten three times. The most recent monster El Nino, 2015-2016, was about 0.4°C higher than the previous monster 1997-98, which itself was about 0.4°C higher than the 1982-83 monster El Nino season. Something is going on here.