The variability of quadratically detrended SST anomalies (°C) from 40, 20 and 30 large ensemble experiments using the CESM-LE, GFDL-CM3 and GFDL-ESM2M, respectively, all under historical forcing (up to 2005) and thereafter the representative concentration pathway 8.5 (RCP8.5) scenario (up to 2099). There is an anti-correlation between the initial and future 50-year SST s.d. values over the equatorial Pacific region where the E-index peaks, which is statistically significant above the 95% or 90% confidence level. These centres are: 2° S–2° N, 100° W–110 °W for CESM-LE; 2° S–2° N, 111° W–121° W for GFDL-CM3; and 2° S–2° N, 104° W–114° W for GFDL-ESM2M. The initial and future 50-year periods are 1920–1969 and 2050–2099 for CESM-LE and GFDL-CM3, and 1950–1999 and 2000–2049 for GFDL-ESM2M.