Noise-induced ENSO supercriticality due to greenhouse warming and implications for climate memory

How the El Niño-Southern Oscillation (ENSO) will respond to greenhouse warming remains uncertain. Here we present results from an ensemble of greenhouse warming simulations conducted with the AWI-CM3-resolution climate model at 30 km atmosphere and 4-25 km ocean resolution. The model simulates a rapid transition from a moderate-amplitude irregular ENSO regime, as observed in the current climate, to a highly regular oscillation with intensifying amplitude. Using low-order dynamical ENSO models, we demonstrate that this behaviour is mainly due to noise-induced supercriticality. As ENSO intensifies in the AWI-CM3 model, it also synchronizes with other prominent climate modes, such as the North Atlantic Oscillation and the Indian Ocean Dipole, thereby imprinting its regular, predictable variability on them. This process significantly alters the global patterns of climate memory.