The current generation of climate models does not properly resolve oceanic mesoscale processes in tropical oceans, such as tropical instability waves. The associated deficit in explicit vertical and lateral heat exchange can further contribute to large-scale equatorial temperature biases, which in turn impact the representation of the El Niño/Southern Oscillation (ENSO) and its sensitivity to greenhouse warming. Here, using a mesoscale-resolving global climate model with an improved representation of tropical climate, we show that a quadrupling of atmospheric CO₂ causes a robust weakening of future simulated ENSO sea surface temperature variability. This sensitivity is caused mainly by stronger latent heat flux damping and weaker advective feedbacks. Stratification-induced weakening of tropical instability wave activity and the corresponding growth of ENSO instability partly offset the effect of other negative dynamical feedbacks. Our results demonstrate that previous lower-resolution greenhouse warming projections did not adequately simulate important ENSO-relevant ocean mesoscale processes.

当前一代的气候模型不能正确解决热带海洋中的海洋中尺度过程，例如热带不稳定波。显式垂直和横向热交换的相关缺陷可能进一步导致大尺度赤道温度偏差，进而影响厄尔尼诺/南方涛动 (ENSO) 的代表性及其对温室变暖的敏感性。在这里，使用具有改进的热带气候表示的中尺度分辨全球气候模型，我们表明大气 CO _{2增加了四倍}导致未来模拟 ENSO 海面温度变化的强烈减弱。这种敏感性主要是由较强的潜热通量阻尼和较弱的平流反馈引起的。分层引起的热带不稳定波活动减弱和ENSO不稳定性的相应增长部分抵消了其他负动力反馈的影响。我们的结果表明，以前的低分辨率温室变暖预测并不能充分模拟重要的与 ENSO 相关的海洋中尺度过程。