The El Niño/Southern Oscillation (ENSO) has a profound influence on global climate and ecosystems. Determining how the ENSO responds to greenhouse warming is a crucial issue in climate science. Despite recent progress in understanding, the responses of important ENSO characteristics, such as air temperature and atmospheric circulation, are still unknown. Here, we use a suite of global climate model projections to show that greenhouse warming drives a robust intensification of ENSO-driven variability in boreal winter tropical upper tropospheric temperature and geopotential height, tropical humidity, subtropical jets and tropical Pacific rainfall. These robust changes are primarily due to the Clausius–Clapeyron relationship, whereby saturation vapour pressure increases nearly exponentially with increasing temperature. Therefore, the vapour response to temperature variability is larger under a warmer climate. As a result, under global warming, even if the ENSO’s sea surface temperature remains unchanged, the response of tropical lower tropospheric humidity to the ENSO amplifies, which in turn results in major reorganization of atmospheric temperature, circulation and rainfall. These findings provide a novel theoretical constraint for ENSO changes and reduce uncertainty in the ENSO response to greenhouse warming.

厄尔尼诺/南方涛动（ENSO）对全球气候和生态系统有着深远的影响。确定 ENSO 如何应对温室效应是气候科学中的一个关键问题。尽管最近在理解方面取得了进展，但重要的 ENSO 特征（如气温和大气环流）的响应仍然未知。在这里，我们使用一套全球气候模型预测来表明温室变暖推动了由 ENSO 驱动的北方冬季热带对流层上层温度和位势高度、热带湿度、副热带急流和热带太平洋降雨量的变异性的强烈增强。这些强劲的变化主要是由于克劳修斯-克拉佩龙关系，即饱和蒸汽压随温度升高几乎呈指数增加。所以，在温暖的气候下，蒸汽对温度变化的响应更大。因此，在全球变暖的情况下，即使ENSO的海面温度保持不变，热带对流层低层湿度对ENSO的响应也会放大，进而导致大气温度、环流和降雨的重大重组。这些发现为ENSO的变化提供了一个新的理论约束，并减少了ENSO对温室变暖反应的不确定性。