El Niño is overstated (oversimplified?) as a driver of global heating.  It is not a cause nor effect of climate change. 

Rather, El Niño along with La Niña are normal cyclical planetary oceanic (ENSO) phases, similar to the changing of seasons in the Northern and Southern hemispheres of Earth.  Could we equate climate change to either hemisphere going into the summer or winter seasons?  Not really, one hopes!

The causal link you're looking for to explain the "ratcheting function", likely has to do with greenhouse gas concentrations, constantly increasing, within a finite Earth atmosphere. 

Again, a finite atmosphere - something we have yet to appreciate on a mass scale it seems.  "Finitude" is difficult to grasp let alone deal with, when the prime social value across the globe is growth at all cost ("infinitude"). Oh mea culpa - I digress!

The "ratcheting function" is a question of how much solar energy is retained in Earth's finite atmosphere, vs how much energy can be reflected out. 

Any resulting disequilibrium is the source of "ratcheting".  ENSO and seasons are certainly not the culprit.