The El Niño–Southern Oscillation (ENSO) in a warming climate has been studied extensively, but the response beyond 2100 has received little attention. Here, using long-term model simulations, we find that while ENSO variability exhibits diverse changes in the short term, there is a robust reduction in ENSO variability by 2300. Continued warming beyond 2100 pushes sea surface temperature above the convective threshold over the eastern Pacific, causing collapsed mean equatorial upwelling with intensified deep convection. We show that the weakened thermocline feedback due to the collapsed upwelling and increased thermal expansion coefficient, along with enhanced thermodynamic damping, are crucial to reducing ENSO amplitude under sustained warming. Our results suggest a threshold behaviour in the tropical Pacific, where a convective atmosphere over the eastern equatorial Pacific causes dramatic shifts in ENSO variability. This threshold is not crossed under low-emission scenarios.

气候变暖时的厄尔尼诺-南方涛动（ENSO）已被广泛研究，但 2100 年以后的响应却很少受到关注。在这里，使用长期模型模拟，我们发现虽然 ENSO 变率在短期内表现出不同的变化，但到 2300 年，ENSO 变率将大幅下降。2100 年之后的持续变暖使东太平洋海面温度高于对流阈值，导致赤道平均上升流塌陷，深层对流增强。我们表明，由于上升流塌陷和热膨胀系数增加而减弱的温跃层反馈，以及热力学阻尼的增强，对于在持续变暖的情况下降低 ENSO 振幅至关重要。我们的结果表明热带太平洋存在阈值行为，赤道东太平洋上空的对流大气导致 ENSO 变化发生巨大变化。在低排放情况下不会超过该阈值。