Robust decrease in El Niño/Southern Oscillation amplitude under long-term warming

Callahan, C. W., Chen, C., Rugenstein, M., Bloch-Johnson, J. ORCID: https://orcid.org/0000-0002-8465-5383, Yang, S. and Moyer, E. J. (2021) Robust decrease in El Niño/Southern Oscillation amplitude under long-term warming. Nature Climate Change, 11 (9). pp. 752-757. ISSN 1758-678X doi: 10.1038/s41558-021-01099-2

Abstract/Summary

El Niño/Southern Oscillation (ENSO) is the primary mode of interannual climate variability, and understanding its response to climate change is critical, but research remains divided on the direction and magnitude of that response. Some twenty-first-century simulations suggest that increased CO2 strengthens ENSO, but studies suggest that on palaeoclimate timescales higher temperatures are associated with a reduced ENSO amplitude and a weaker Pacific zonal temperature gradient, sometimes termed a ‘permanent El Niño’. Internal variability complicates this debate by masking the response of ENSO to forcing in centennial-length projections. Here we exploit millennial-length climate model simulations to disentangle forced changes to ENSO under transient and equilibrated conditions. On transient timescales, models show a wide spread in ENSO responses but, on millennial timescales, nearly all of them show decreased ENSO amplitude and a weakened Pacific zonal temperature gradient. Our results reconcile differences among twenty-first-century simulations and suggest that CO2 forcing dampens ENSO over the long term.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/107473
Item Type	Article
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	Nature Publishing Group
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