A good article:
http://wattsupwiththat.com/2016/01/17/once-again-el-nino-didnt-do-what-was-forecast-why/
Once again we are in the middle of an El Nino event that is reportedly modifying temperatures beyond the claimed human effect. The predictions about its strength and impact were wrong again. Why? As Erl Happ noted,
If we wish to understand the ENSO phenomenon we must look beyond the tropics for causal factors. ENSO in the Pacific is just one facet of change in the tropics. Change is driven by air pressure variations at mid and especially high latitudes...
Most of the public incorrectly thinks El Nino is a new phenomenon resulting from global warming. The only thing relatively new is scientific awareness and its influence on global climate. Inca, who sailed the Pacific coast of South America for millennia, knew its effects well. Their priests observed the Pleiades star formation in the spring from high in the Andes to study the optical conditions. They knew empirically that the difference between a clear or shimmering cluster of stars determined the precipitation pattern. It was a useful rainfall predictor and guided when to plant their main crop, potatoes. The atmospheric conditions vary between unstable and stable conditions as the Pacific Ocean switches between El Nino and La Nina, which determines the precipitation pattern...
“There are also apparent decadal variations in ENSO forecast skill (Balmaseda et al., 1995; Ji et al., 1996; Kirtman and Schopf, 1998), and the sources of these variations are the subject of some debate. Finally, it remains unclear how changes in the mean climate will ultimately affect ENSO predictability (Collins et al., 2002).”
They are just as unsure in the 2013 IPCC Report. As an unusual NOAA analysis says,
"The IPCC has LOW confidence in exactly what will happen to ENSO in the future even while they have HIGH confidence that ENSO itself will continue."
They are all ignoring the obvious. They assume that the cause and effect are within the ocean/atmosphere system. It is not. There is no explanation for the mechanism that causes the reversal of pressure between the different sides of the Pacific. Surface pressure differences are caused by temperature difference, but there is no evidence or plausible explanation for that temperature difference. It appears that the primary forcing is in the mechanism that causes a reversal of the Equatorial easterlies.