Deser et al. (2025) Northern Hemisphere Wintertime Teleconnections from the 2023–24 El Niño Offset by Background SST Trends

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Identification

• Journal: Journal of Climate
• Year: 2025
• Date: 2025-11-14
• Authors: Clara Deser, Stephen Yeager, Adam S. Phillips, Nan Rosenbloom, Xueying Zhao
• DOI: 10.1175/jcli-d-25-0227.1

Research Groups

This study investigated why the strong 2023-24 El Niño exhibited unexpectedly weak wintertime atmospheric teleconnections to the extratropical Northern Hemisphere, finding that long-term tropical sea surface temperature trends since 1980 largely counteracted the expected El Niño atmospheric response.

Objective

• To test the hypothesis that the observed pattern of background sea surface temperature (SST) trends since 1980 was responsible for counteracting the anticipated wintertime atmospheric teleconnection response of the 2023-24 El Niño to the extratropical Northern Hemisphere.

Study Configuration

• Spatial Scale: Global tropics (Indian, Atlantic, and Pacific Oceans) to the extratropical Northern Hemisphere, with specific focus on North America and Europe.
• Temporal Scale: Analysis of the 2023-24 El Niño event, considering background SST trends since 1980, and implications for the coming decades.

Methodology and Data

• Models used: Atmospheric modeling experiments.
• Data sources: Prescribed observed sea surface temperatures (SSTs) and radiative forcings.

Main Results

• A "SST pattern effect," characterized by enhanced warming in the tropical Indian and Atlantic Oceans and relative cooling in the eastern tropical Pacific, drives a teleconnection of the opposite sign to El Niño.
• This opposite teleconnection occurs via a Rossby wave response to anomalous precipitation over the western tropical Pacific, remotely driven from the Indian Ocean.
• The atmospheric circulation response expected from the 2023-24 El Niño, in the absence of background SST changes, was almost entirely cancelled by the teleconnection produced by these long-term SST trends.
• This cancellation had significant consequences for precipitation impacts over North America and Europe.
• Similar behavior was observed in actual circulation anomalies, although internal atmospheric variability may also have contributed.

Contributions

• Provides a mechanistic explanation for the unexpectedly weak atmospheric teleconnections of the strong 2023-24 El Niño event to the Northern Hemisphere.
• Highlights the critical importance of considering the modulating influence of background SST trends (both natural and anthropogenic) on El Niño teleconnections.
• Underscores the implications of these modulating effects for future climate impacts in the coming decades.

Funding

Citation

@article{Deser2025Northern,
  author = {Deser, Clara and Yeager, Stephen and Phillips, Adam S. and Rosenbloom, Nan and Zhao, Xueying},
  title = {Northern Hemisphere Wintertime Teleconnections from the 2023–24 El Niño Offset by Background SST Trends},
  journal = {Journal of Climate},
  year = {2025},
  doi = {10.1175/jcli-d-25-0227.1},
  url = {https://doi.org/10.1175/jcli-d-25-0227.1}
}