Surface Warming Patterns, Cloud Feedbacks, and Inter-basin Energy Redistribution During ENSO

Internal variability, particularly ENSO, plays a critical role in modulating global warming on interannual to decadal timescales. Its canonical surface temperature signature is well characterized, but the complex and non-linear relation between surface temperature and top-of-atmosphere (TOA) radiative response requires attention. Here, we use coupled atmosphere-ocean simulations to diagnose the energy redistribution and radiative feedbacks across ENSO phases. During the growth phase of El Niño, boundary-layer destabilization enhances ocean-atmosphere heat exchange in the tropical Pacific, while a positive net TOA flux anomaly amplifies surface warming, contrary to the canonical feedback perspective. This excess energy is transported poleward and zonally, with remote ocean basins exhibiting shallow heat uptake. At the El Niño peak, rapid atmospheric stabilization increases low-level cloudiness and shortwave reflection, while the subsequent decay phase is marked by net radiative cooling to space. In parallel, we find that high cloud fraction and upper-tropospheric humidity evolve in an anticorrelated manner across the tropics and extratropics. These changes are not directly tied to boundary-layer stability, and their opposing regional signatures largely cancel in the global mean. Notably, tropical drying and cloud loss co-occur with increased precipitation. Our findings clarify the role of ENSO in Earth's radiative variability and highlight key differences from CO2-forced warming.