The El Niño–Southern Oscillation (ENSO) is the dominant natural climate pattern that influences the global climate on subdecadal timescales. Thus, a better understanding of the impacts of global warming on the characteristics of ENSO events offers large socioeconomic benefits. Changes in the frequency of the eastern Pacific (EP), central Pacific (CP) and total El Niño events are analysed in the future period (2051–2100) under the two shared socioeconomic pathways (SSPs) scenarios (i.e., SSP2-4.5 and SSP5-8.5) compared to the historical period (1951–2000) using outputs of eight models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6). Types of El Niño events are diagnosed based on pattern correlation coefficients (PCCs) between monthly sea surface temperature (SST) anomalies and the first two leading empirical orthogonal function (EOF) modes of SST anomalies in the tropical Pacific. Based on the ensemble of models, the number of total El Niño events decreases by 26 and 16% under the SSP2-4.5 and SSP5-8.5 scenarios, respectively, in the future compared to the historical period. A smaller decrease in the number of total El Niño events under the faster warming rate of the SSP5-8.5 scenario suggests that the response of ENSO dynamics to global warming is not linear. Analysis of the Extended Reconstructed Sea Surface Temperature, version 5 (ERSSTv5) dataset during the period 1951–2020 indicates that the ratio of the number of CP El Niño to EP El Niño has substantially increased over the past two decades. Nevertheless, under both the SSP2-4.5 and SSP5-8.5 scenarios in the future period, the ratio of the number of CP El Niño to EP El Niño does not change considerably compared to that in the historical period. This suggests that the recent increase in the frequency of CP El Niño could be a result of multidecadal variations rather than anthropogenic global warming.

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全球变暖下不同类型厄尔尼诺事件的发生频率

厄尔尼诺-南方涛动 (ENSO) 是影响亚年代际时间尺度全球气候的主要自然气候模式。因此，更好地了解全球变暖对 ENSO 事件特征的影响具有巨大的社会经济效益。在两种共享社会经济路径 (SSP) 情景（即 SSP2-4.5 和SSP5-8.5）与历史时期（1951-2000）相比，使用参与耦合模型比较项目第 6 阶段（CMIP6）的八个模型的输出。厄尔尼诺事件的类型是根据月海面温度 (SST) 异常与热带太平洋海温异常的前两个主要经验正交函数 (EOF) 模式之间的模式相关系数 (PCC) 诊断的。基于模型集合，与历史时期相比，未来厄尔尼诺事件总数在 SSP2-4.5 和 SSP5-8.5 情景下分别减少 26% 和 16%。在 SSP5-8.5 情景变暖速度加快的情况下，厄尔尼诺事件总数的减少幅度较小，这表明 ENSO 动力学对全球变暖的响应不是线性的。扩展重建海面温度分析，version 5 (ERSSTv5) 1951-2020 年数据集表明，中部型厄尔尼诺与东部型厄尔尼诺的数量之比在过去二十年中大幅增加。尽管如此，无论是SSP2-4.5情景还是SSP5-8.5情景下，未来时期中部型厄尔尼诺与东部型厄尔尼诺的数量比值与历史时期相比均无明显变化。这表明最近中部厄尔尼诺频率的增加可能是多年代际变化的结果，而不是人为全球变暖的结果。