Fig. 2: El Niño-Southern Oscillation (ENSO) regularity and amplitude changes in observations, Alfred Wegener Institute Climate Model (AWI-CM3), and Coupled Model Intercomparison Project Phase 6 (CMIP6) models.
From: Global climate mode resonance due to rapidly intensifying El Niño-Southern Oscillation
Moving 21-year changes of sample entropy (SampEn) (a) and standard deviation (SD) (b) of the Niño3.4 SST anomaly index in observations (black), the 150-year AWI-CM3 1950 control simulation (CTL1950, blue), and the AWI-CM3 shared socio-economic pathway (SSP)5-8.5 scenario simulation (red). Solid lines and shading indicate the multi-product/multi-member mean and the 1 SD spread of 10,000 inter-realizations using a bootstrap method, respectively. The error bars indicate the mean and 1 SD of values across all overlapping 21-year windows for the observations (1950–2024), CTL1950 (150-yr), and SSP5-8.5 (2050–2100). Violin plots showing the probability density distribution of ENSO regularity change (c) and amplitude change (d) across 49 CMIP6 models. The change is calculated as the difference between 2050–2100 and 1900–2000. Dots represent individual model results, with E3SM-1-1, EC-Earth3, and EC-Earth3-Veg highlighted in distinct colors; the red star marks the AWI-CM3 result (2050–2100 minus CTL1950). In a and c, the y-axis is inverted to emphasize decreasing SampEn, indicating increasing regularity.
