28 Mar 2022
28 Mar 2022
Status: this preprint is open for discussion.

Insignificant but robust decrease of ENSO predictability in an equilibrium warmer climate

Yiyu Zheng1, Maria Rugenstein2, Patrick Pieper1, Goratz Beobide-Arsuaga1, and Johanna Baehr1 Yiyu Zheng et al.
  • 1Institute of Oceanography, The Center for Earth System Research and Sustainability, Universität Hamburg, Hamburg, Germany
  • 2Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA

Abstract. Responses of El Niño-Southern Oscillation (ENSO) to global warming remain uncertain, which challenges ENSO forecasts in a warming climate. We investigate changes in ENSO characteristics and predictability in idealized simulations with quadrupled CO2 forcing from seven general circulation models. Comparing the warmer climate to control simulations, ENSO variability weakens, with the neutral state lasts longer, while active ENSO states last shorter and skew to favor the La Niña state. Six-month persistence-assessed ENSO predictability slightly reduces in five models and increases in two models under the warming condition. While the overall changes in ENSO predictability are insignificant, we find significant relationships between changes in predictability and intensity, duration and skewness of the three individual ENSO states. The maximal contribution to changes in the predictability of El Niño, La Niña and neutral states stems from changes in skewness and events' duration. Our findings show that a robust and significant decrease in ENSO characteristics does not imply a similar change in ENSO predictability in a warmer climate. This could be due to model deficiencies in ENSO dynamics and limitations in persistence model when predicting ENSO.

Yiyu Zheng et al.

Status: open (until 06 Jun 2022)

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Yiyu Zheng et al.

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Yiyu Zheng et al.


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Short summary
ENSO is one of the dominant climatic phenomena in the equatorial Pacific. Understanding and predicting how ENSO might change in a warmer climate is both societally and scientifically important. We use thousand-year-long simulations from seven climate models to analyze ENSO in an idealized stable climate. We show that ENSO will be weaker and last shorter under the warming, while the skill of ENSO prediction will unlikely to change.