Hemispheric warming asymmetry and its contribution to El Niño and Southern Oscillation

Traditional theory treats El Niño event and the subsequent sea temperature oscillation as a self-sustaining process, which is thermodynamically unrealistic, as it overlooks the need for an external energy source. Moreover, current models do not capture key features of the observed Oceanic Niño Index (ONI), making long-term prediction of El Niño events a persistent challenge. This study proposes that hemispheric asymmetry in sea surface warming gives rise to El Niño events. During these events, tropical winds are significantly weakened, allowing wind thrust and momentum flux to generate potential energy cycles in the tropical atmosphere. Fluctuations in this potential energy produce the sea warm and cold phases, characteristic of El Niño Southern Oscillation (ENSO). A theoretical equation for ONI is derived from this framework and demonstrates consistency with observational data. As the hemispheric imbalance in surface warming continues to intensify, the frequency of El Niño events and associated climate extremes is expected to rise over time. This emerging trend may potentially be attributed to anthropogenic influences, which warrant further investigation.