The ENSO variations and their link with solar and volcanic activity

We investigate the Oceanic Niño Index (ONI), for simplicity called in this paper an El Nino Southern Oscillation (ENSO) index in 1950-2023  by applying  the wavelet spectral transform and the IBM SPSS correlations analysis.  ONI follows the three months current measurements of an average temperature of the sea surface  in the East-Central tropical part of the Pacific ocean nearby the international line of the date change over the average sea surface temperature over the past 30 years. The ENSO index is found to have a strong  ($>$0.87) correlation with the Global Land-Ocean Temperature (GLOT). The scatter plots  of the  ENSO-GLOT correlation with the linear and cubic fits have shown that the ENSO index is better fit by the cubic polynomial increasing proportionally to a cubic power of the GLOT variations.  The  wavelet analysis  allowed us to detect the two key periods in the ENSO (ONI) index: 4-5 year and 12 years.  The smaller period of 4.5 years can be linked to the motion of tectonic plates while the larger period of 12 years is shown to have a noticeable correlation of 0.25 with  frequencies of the under-water (submarine) volcanic eruptions in  the areas with ENSO occurrences.  Not withstanding any local terrestrial factors considered to contribute to the ENSO  occurrences, we investigated the possibility of these volcanic eruptions to be also induced by tidal forces of the Jupiter and Sun showing the correlation of  the under-water volcanic eruption frequency to be 0.12 with the Jupiter-Earth distances and 0.15 with the Sun-Earth distances in January, induced by the solar inertial motion, when the Earth is turned to the Sun with the southern hemisphere where the ENSO occurs.  Hence,  the underwater volcanic eruptions induced by tidal forces  of Jupiter and Sun can be the essential additional factors imposing this 12 year period of the ENSO (ONI) index variations.