How likely is an El Ni&no to break the global mean surface temperature record during the 21st century?

The likelihood of an El Ni&no breaking the annual global mean surface temperature (GMST) record during the 21st century is derived from 38 climate models from the Fifth Coupled Model Intercomparison Project (CMIP5). We find that, under a low emission scenario, one out of three El Ni&no events break the GMST record. The probability significantly increases to four out of five in a high emission scenario. About half of strong El Ni&nos, but only one-fifth of weak El Ni&nos, can set new GMST records in a low emission scenario. By contrast, even weak El Ni&nos break the GMST record more regularly (68 8% chance) in a high emission scenario. Both a stronger El Ni&no and a higher emission scenario induce a higher record-breaking GMST with a magnitude range from 0.03 C to 0.21 C above the previous record. El Ni&no accounts for more than half of record-breaking GMST occurrences in all emission scenarios. A comparison between CMIP3, CMIP5, and CMIP6 suggests that the analyses are not affected by model generations.