Tab. 1

Basic information of the 23 CMIP6 global climate models"

Tab. 2

Basic information of the 32 CMIP5 global climate models"

Fig. 1

Boreal winter mean SST anomalies (K; shading) in the tropical Pacific during EP El Niño (left column) and CP El Niño (right column) events. (a, b) Observation; (c, d) CMIP5; (e, f) CMIP6. The numbers in the upper right brackets of Figs. 1c ~ 1f represent the spatial correlation coefficients between the MME results and the observations"

Fig. 2

Taylor diagram displaying the spatial patterns of the SST anomalies in (a) CMIP5 and (b) CMIP6 models relative to the observation. MME indicates the multi-model ensemble, and green and purple dots represent the EP El Niño and CP El Niño, respectively"

Fig. 3

Time-longitude cross-section of the SST anomalies (K; shading) at the equator (averaged from 5°S to 5°N) for EP El Niño (left column) and CP El Niño (right column) events, where (0) indicates the El Niño year and (1) represents the following year. (a, b) Observation; (c, d) CMIP5; (e, f) CMIP6. Green contours indicate the regions with the SST anomalies greater than +0.5 K, and the regions surrounded by two white dotted lines represent the core area of the SST anomalies associated with EP and CP El Niño"

Fig. 4

Time evolution of the SST anomalies (K) associated with the (a) EP El Niño and (b) CP El Niño events in the observation (black curve), the multi-model ensemble (MME) from CMIP5 models (blue curve) and the MME from CMIP6 models (red curve). The core area of the SST anomalies associated with EP and CP El Niño is the region of (5°S—5°N, 150°—90°W) and (5°S—5°N, 180°—130°W), respectively. Blue and red shaded regions represent the spread of the CMIP5 and CMIP6 models, respectively. The green dashed line indicates the location with the SST anomalies equal to +0.5 K"

Fig. 5

Boxplots of the frequency ratio for the CP-to-EP Niño events in the observation and various scenarios of CMIP5 and CMIP6 models. The black boxplot is based on the observation, the green, light blue and blue boxplots represent the historical simulation (CMIP5-Hist), the RCP45 and RCP85 scenarios in CMIP5 models, and the orange, red and purple boxplots indicate the historical simulation (CMIP6-Hist), the SSP245, SSP585 scenarios in CMIP6 models, respectively. Markers with the red plus denote the extreme outliers simulated by the models"

Fig. 6

Differences between the MME mean SST (units: K) composites for the CMIP5 and CMIP6 projection and those for the corresponding historical runs for EP (left column) and CP El Niño (right column) events. (a, b) RCP45 scenario in CMIP5; (c, d) RCP85 scenario in CMIP5; (e, f) SSP245 scenario in CMIP6; (g, h) SSP585 scenario in CMIP6. Black counters indicate the El Niño-related SST anomalies simulated by the historical runs of CMIP5 and CMIP6 models, and color shadings represent the projected changes in El Niño SST anomalies. Gray crosses indicate locations over which more than 70% of CMIP5/6 models agree on the sign of SST difference between historical and future runs"