Picture (above): Sunset over the ocean. Credit: Sascha Thiele (Pexels).

Given the global impact of El Niño-Southern Oscillation (ENSO) events it is essential to understand how different types of El Niño events may change in the future. Events are classified as eastern Pacific (EP) or central Pacific (CP) depending on where the greatest warming occurs. In recent decades, central Pacific El Niño events have occurred more frequently, while eastern Pacific El Niño events have increased in intensity.

CLEX researchers and colleagues investigated how these events change in the future using a large set of climate model simulations from the Coupled Model Intercomparison Project, phases 5 and 6 (CMIP5 & CMIP6). First, the models were evaluated in comparison with both extended instrumental and multi-century palaeoclimate records.

We then examined changes in future simulations. We found that future changes of El Niño are stronger for CP events than for EP events and differ between models. In particular, the warming pattern across the tropical Pacific influences the result: models which have more warming in the western Pacific (La Niña-like) tend to have more EP and fewer CP events in future, compared with models that have more future warming in the east (El Niño-like). Models that warm more in the east show changes which depend on the state of Pacific decadal variability in that model.

We conclude that future changes to El Niño may depend on both the pattern of warming and decadal scale natural variability.

  • Paper: Freund, M. B., J. R. Brown, B. J. Henley, D. J. Karoly, and J. N. Brown, Warming patterns affect El Niño diversity in CMIP5 and CMIP6 models. J. Climate, doi: https://doi.org/10.1175/JCLI-D-19-0890.1.