Removing ENSO’s Influence from Global SST Variability, with Insights into the Record-Setting Marine Heat Waves of 2023–24

El Niño–Southern Oscillation (ENSO) is a dominant driver of seasonal–interannual climate variability and has been linked to record-setting extremes such as marine heat waves (MHWs). However, quantifying the effects of ENSO on MHW characteristics remains a challenge due to data limitations. Here, we used an ensemble of tropical Pacific “pacemaker” simulations with a fully coupled Earth system model as a testbed for assessing the skill of four empirical methods aimed at isolating ENSO’s contribution to monthly SST anomalies including MHW extremes. We then applied the most skillful method to the observational record to determine ENSO’s impact on the spatial coverage, intensity, and duration of MHWs since 1960 (after removing the background warming trend). We found that El Niño of 2023–24 contributed to about half of the global coverage of record-setting MHWs, with the tropical Indian and tropical Atlantic Oceans being most clearly impacted. Our results shed light on the critical role ENSO plays in driving the most severe MHW conditions in the historical record.