El Niño dampens hurricane activity. During El Niño periods, increased wind shear across the Gulf makes it difficult for hurricanes to survive much less intensify.

El Niño results from interaction between the surface layers of the ocean and the overlying atmosphere in tropical Pacific. It is the internal dynamics of the coupled ocean-atmosphere system that determine the onset and termination of El Niño events. The physical processes are complicated, but they involve unstable air-sea interaction and planetary scale oceanic waves. The system oscillates between warm (El Niño) to neutral (or cold) conditions with a natural periodicity of roughly 3-4 years. External forcing from volcanic eruptions (submarine or terrestial) have no connnection with El Niño. Nor do sunspots as far as we know.

In addition to El Nino which is correllated to Equitorial and South Pacific Currents, there is another oscillation called the Pacific Decadal Oscillation (PDO) which is primarily active in the North Pacific ocean.

Combining  AMD (20-40 years) and ENSO (3-4 years) perodicity and PDO (with two cycles 20 years, 50 years) might be a better predictor of ACE than AMD alone.