Stuecker et al. (2025) Global climate mode resonance due to rapidly intensifying El Niño-Southern Oscillation

Identification

• Journal: Nature Communications
• Year: 2025
• Date: 2025-10-16
• Authors: Malte F. Stuecker, Sen Zhao, Axel Timmermann, Rohit Ghosh, Tido Semmler, Sun‐Seon Lee, Ja-Yeon Moon, Fei‐Fei Jin, Thomas Jung
• DOI: 10.1038/s41467-025-64619-0

Research Groups

• Department of Oceanography, University of Hawaiʻi at Mānoa, Honolulu, USA
• International Pacific Research Center, University of Hawaiʻi at Mānoa, Honolulu, USA
• Department of Atmospheric Sciences, University of Hawaiʻi at Mānoa, Honolulu, USA
• Center for Climate Physics, Institute for Basic Science, Busan, Republic of Korea
• Pusan National University, Busan, Republic of Korea
• Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
• Met Éireann, Dublin, Ireland
• Department of Physics and Electrical Engineering, University of Bremen, Bremen, Germany

Short Summary

A high-resolution climate model projects that greenhouse warming will cause the El Niño-Southern Oscillation (ENSO) to rapidly transition to a highly regular, intensifying oscillation, leading to global climate mode resonance where ENSO synchronizes with other major climate modes. This synchronization would imprint ENSO's predictable variability onto these modes, potentially causing widespread "whiplash impacts" on regional hydroclimates.

Objective

• To investigate the anthropogenically forced rapid emergence of ENSO supercriticality and its potential repercussions on global climate using a state-of-the-art high-resolution climate model.
• To demonstrate that this model simulates a rapid intensification of ENSO by mid-twenty-first century, a transition to a regular, strongly seasonally-locked oscillation, and an unprecedented resonance with other important modes of climate variability.

Study Configuration

• Spatial Scale: Global. The AWI-CM3 model has an atmospheric horizontal resolution of approximately 31 km (TCo319) with 137 vertical layers, and an oceanic horizontal resolution ranging from 4 km to 25 km with 80 vertical layers. Specific regions of interest include the eastern equatorial Pacific (180°W–90°W, 6°S–6°N) for ENSO and the North Atlantic sector (90°W–40°E, 20°N–80°N) for the North Atlantic Oscillation (NAO).
• Temporal Scale:
  • Model Simulations: A full transient simulation from 1950 to 2100 (historical forcing 1950–2014, SSP5-8.5 scenario thereafter). Three additional ensemble simulations from 2055 to 2100. A 150-year control simulation with fixed 1950 forcing (CTL1950).
  • Analysis Periods: Period 1 (P1): 2015–2035; Period 2 (P2): 2080–2100.
  • Observational Data: 1871–2024 for SST (HadISST, ERSSTv5, COBE2); 1940–2024 for SST, precipitation, and sea level pressure (ERA5).
  • CMIP6 Data: 1850–2100 (historical and SSP5-8.5 scenarios).

Methodology and Data

• Models used:
  • Alfred Wegener Institute Climate Model (AWI-CM3): Coupled OpenIFS (atmosphere) and FESOM2 (ocean).
  • Recharge Oscillator (RO) model: A conceptual model for ENSO dynamics.
  • Extended Recharge Oscillator (XRO) model: A modified conceptual model for ENSO coupled to other climate modes.
• Data sources:
  • AWI-CM3 transient, ensemble, and control simulations.
  • Observational SST reconstructions/reanalysis: Hadley Centre Sea Ice and Sea Surface Temperature dataset v.1.1 (HadISST), Extended Reconstructed Sea Surface Temperature v.5 (ERSSTv5), Centennial in situ Observation-Based Estimates of Sea Surface Temperature v.2 (COBE2).
  • Reanalysis data: European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis 5 (ERA5) for monthly precipitation and sea level pressure.
  • Coupled Model Intercomparison Project Phase 6 (CMIP6) model archive (49 models).
  • Methods: Wavelet analysis, Multi-Taper Method (MTM) for power spectral density (PSD), Sample Entropy (SampEn) for ENSO regularity, Floquet eigen analysis for growth rates and frequencies, Bjerknes stability analysis for ENSO feedbacks, multivariate linear regression, Hilbert transforms for phase synchronization.

Main Results

• The AWI-CM3 model simulates a rapid transition of ENSO from an irregular, moderate-amplitude regime (observed in the current climate) to a highly regular oscillation with intensifying amplitude by the mid-21st century under the SSP5-8.5 scenario.
• This regime shift is driven by increasing air-sea feedbacks, which approach criticality, and growing atmospheric noise, particularly in boreal spring to summer. The increased ENSO growth rate is primarily due to reduced damping from thermocline adjustment and a modest enhancement of the Bjerknes feedback.
• As ENSO intensifies, it synchronizes with other prominent climate modes, including the North Atlantic Oscillation (NAO), Indian Ocean Dipole (IOD), Tropical North Atlantic (TNA) mode, Indian Ocean Basin (IOB) mode, and North Pacific Meridional Mode (NPMM).
• The amplitudes of these other climate modes are projected to intensify by 40% to 75%, and their phase synchronization with ENSO strengthens significantly, especially after 2060.
• The ENSO-NAO teleconnection strengthens, leading to enhanced precipitation responses over western Europe (e.g., Iberian Peninsula) during El Niño events. This is attributed to both increased ENSO amplitude and a higher sensitivity of the extratropical atmospheric circulation to ENSO forcing.
• Analysis of 49 CMIP6 models shows that 55% project an increase in ENSO regularity and 82% project an increase in ENSO SST anomaly amplitude by the second half of this century under SSP5-8.5, with a few models showing qualitatively similar behavior to AWI-CM3.

Contributions

• Provides the first clear evidence from a state-of-the-art high-resolution coupled climate model (AWI-CM3) of a rapid transition of ENSO to a highly regular, intensifying oscillation and an unprecedented global climate mode resonance under greenhouse warming.
• Elucidates the physical mechanisms underlying this projected ENSO regime shift, highlighting the critical roles of increasing air-sea feedbacks (reduced thermocline damping, enhanced Bjerknes feedback) and growing atmospheric noise.
• Demonstrates that the strengthening of ENSO teleconnections, such as with the NAO, is a result of both increased ENSO amplitude and an enhanced sensitivity of the extratropical atmospheric circulation to ENSO forcing.
• Suggests that while increased ENSO regularity could enhance predictability, the amplified amplitude and global synchronization of climate modes could lead to more severe and widespread "whiplash impacts" on regional hydroclimates, necessitating additional planning and management strategies.
• Confirms and extends previous findings on anthropogenically forced rapid emergence of ENSO supercriticality, providing a detailed dynamical scenario from a high-resolution model.

Funding

• U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research (Award Number DE-SC0025595)
• Institute for Basic Science (IBS) (IBS-R028-D1)
• EERIE project (Grant Agreement No. 101081383) funded by the European Union
• NOAA Climate Program Office’s Modeling, Analysis, Predictions, and Projections (MAPP) Program (Grant NA23OAR4310602)
• U.S. National Science Foundation (Grant AGS-2219257)
• KREONET

Citation

@article{Stuecker2025Global,
  author = {Stuecker, Malte F. and Zhao, Sen and Timmermann, Axel and Ghosh, Rohit and Semmler, Tido and Lee, Sun‐Seon and Moon, Ja-Yeon and Jin, Fei‐Fei and Jung, Thomas},
  title = {Global climate mode resonance due to rapidly intensifying El Niño-Southern Oscillation},
  journal = {Nature Communications},
  year = {2025},
  doi = {10.1038/s41467-025-64619-0},
  url = {https://doi.org/10.1038/s41467-025-64619-0}
}