How likely is an El Niño to break global mean surface temperature record during the 21st Century?


Chia-Wei Hsu
Jianjun Yin


The likelihood of an El Niño to break the global mean surface temperature (GMST) record during the 21st century is derived from 38 climate models in the Fifth Coupled Model Intercomparison Project (CMIP5). We find that, under a low emission scenario, one out of three El Niño events breaks the GMST record. The probability significantly increases to four out of five in a high emission scenario. About half of strong El Niños, but only one-fifth of weak El Niños, can set new GMST records in a low emission scenario. By contrast, even weak El Niños can break the GMST record more regularly (68%±8% chance) in high emission scenario. Both stronger El Niño and higher emission scenario induce a higher record-breaking GMST with magnitude range from 0.03°C to 0.21°C above the previous record. El Niño 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 complexity.

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Fig. 2: Identification of El Nino events and record-breaking GMSTs in two CMIP5 models - CCSM4 (left panel) and GFDL-ESM2G (right panel). Corresponding RCP scenarios are shown on the top left corner of each plot. Each plot shows annual GMST values in orange line (notice the GMST scales are different and on the right of each plot) and ONI values in blue line with the blue shaded regions indicating the identified El Ni˜no periods. The red dots are the record-breaking GMSTs associated with an El Ni˜no event and the gray dots are the one not associated with any El Ni˜no event. The red dotted line shows the record-breaking GMST value before 2006.

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