Abstract
AbstractThe latest generation of coupled models, the sixth Coupled Models Intercomparison Project (CMIP6), is used to study the changes in the El Niño–Southern Oscillation (ENSO) in a warming climate. For the four future scenarios studied, the sea surface temperature variability increases in most CMIP6 models, but to varying degrees. This increase is linked to a weakening of the east‐west temperature gradient in the tropical Pacific Ocean, which is evident across all models. Just as in previous generations of climate models, we find that many characteristics of future ENSO remain uncertain. This includes changes in dominant time scale, extratropical teleconnection patterns, and amplitude of El Niño and La Niña events. For models with the strongest increase in future variability, the majority of the increase happens in the Eastern Pacific, where the strongest El Niño events usually occur.
Highlights
El Niño–Southern Oscillation (ENSO) is characterized by irregular fluctuations between cold (La Niña) and warm (El Niño) conditions in the eastern and central equatorial Pacific on a time scale of 2–7 years
The power spectra of the Niño 3.4 index obtained from detrended scenarios show a wide range of variability with spectral peaks in the 2–7 year range (Figure 1 and Figure S1 in the supporting information), demonstrating the CMIP6 models' ability to produce a quasi‐oscillatory behavior that is reminiscent of ENSO in nature
CESM2‐WACCM and CESM2 show significant increases in power for most future scenarios with CESM2‐WACCM showing the largest increase around 3 years and CESM2 showing an increase at 1.5–3 year periodicities
Summary
El Niño–Southern Oscillation (ENSO) is characterized by irregular fluctuations between cold (La Niña) and warm (El Niño) conditions in the eastern and central equatorial Pacific on a time scale of 2–7 years. ENSO events display a broad spectrum of anomaly centers ranging from the dateline (CP events) to the far eastern equatorial Pacific (EP events, Capotondi et al, 2015, 2020), and the exact location of the warming centers may be model dependent (Cai et al, 2018) This diversity can have very important consequences for atmospheric teleconnections and worldwide impacts (Ashok et al, 2007; Larkin & Harrison, 2005; Patricola et al, 2018) and needs to be considered when examining ENSO response to global warming. We examine variance changes in the context of ENSO diversity, and at last, we investigate global sea‐level pressure teleconnection patterns during future El Niño and La Niña events
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