Climate models struggle to accurately simulate the asymmetry between El Niño and La Niña phases of the El Niño-Southern Oscillation (ENSO). This study reveals that the simulated ENSO asymmetry is strongly correlated with subsurface nonlinear dynamical heating (NDH) along the equatorial Pacific thermocline. Models with realistic NDH demonstrate a linear relationship between El Niño-like equatorial Pacific warming patterns and ENSO amplitude changes in response to greenhouse warming. Improving the simulation of ENSO asymmetry dynamics is crucial for reducing uncertainties in future climate projections.

Michiya Hayashi, Fei-Fei Jin, Malte F. Stuecker