Müller et al. (2025) The ICON-based Earth System Model for climate predictions and projections (ICON XPP v1.0)

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Identification

• Journal: Repository for Publications and Research Data (ETH Zurich)
• Year: 2025
• Date: 2025-12-03
• Authors: Wolfgang A. Müller, Stephan Lorenz, Trang V. Pham, Andrea Schneidereit, Renate Brokopf, Victor Brovkin, Nils Brüggemann, Fatemeh Chegini, Dietmar Dommenget, Kristina J. H. Fröhlich, Barbara Früh, Veronika Gayler, Helmuth Haak, Stefan Hagemann, Moritz Hanke, Tatiana Ilyina, Johann Jungclaus, Martin Köhler, Peter Korn, Luis Kornblueh, Clarissa Kroll, et. al.
• DOI: 10.3929/ethz-c-000789896

Research Groups

Not specified in the provided text.

Short Summary

This paper introduces and evaluates ICON XPP, a new Earth System model configuration designed for next-generation climate predictions and projections. The model generally reproduces basic coupled climate properties and performs comparably to CMIP6 models, despite exhibiting some regional biases.

Objective

• To develop and provide a first evaluation of ICON XPP, a new Earth System model configuration framed within the ICON architecture, intended as a baseline for next-generation climate predictions, projections, climate research, and operational climate forecasting.

Study Configuration

• Spatial Scale:
  • Atmospheric horizontal resolution: 160 km and 80 km.
  • Oceanic horizontal resolution: 40 km and 20 km.
• Temporal Scale:
  • Simulations of pre-industrial climate.
  • Simulations covering the current climate, including trends since the 1850s.
  • Evaluation of various climate phenomena and oscillations over their respective timescales (e.g., El Niño/Southern Oscillation, Madden-Julian Oscillation, quasi-biennial oscillation).

Methodology and Data

• Models used: ICON XPP, comprising the ICON atmospheric component (from numerical weather prediction), ICON ocean, ICON land surface components, and an ensemble-variational data assimilation system.
• Data sources: Evaluation performed using a CMIP DECK (Diagnostic, Evaluation and Characterization of Klima) experimentation framework, comparison with reference datasets, and observations (implied for biases and circulation strengths).

Main Results

• ICON XPP successfully depicts the basic properties of the coupled climate system.
• The pre-industrial climate simulation shows a balanced top-of-atmosphere radiation budget and a global mean near-surface temperature of 13.8-14.0 °C.
• Ocean circulation strengths, such as the Atlantic Meridional Overturning Circulation (AMOC) at 16-18 Sv, are within the range of observed values.
• The current climate simulation reproduces a global mean temperature trend of approximately 1.2 °C since the 1850s, consistent with reference datasets.
• Dynamical processes, including El Niño/Southern Oscillation (ENSO), tropical waves, and the Madden-Julian Oscillation, perform similarly to CMIP6-like coupled models.
• The 40 km atmospheric configuration spontaneously generates a weak quasi-biennial oscillation.
• Atmospheric dynamics in the northern extra-tropics accurately represent the position of the jet stream and the influences of transient momentum transports.
• Regional biases are noted, including a double-peak inter-tropical convergence zone (ITCZ) with a wet southern subtropical branch across the oceans, and a strong positive mean bias (up to 5 °C) in Southern Ocean sea surface temperature compared to observations.

Contributions

• Development and initial comprehensive evaluation of ICON XPP, a new, high-resolution Earth System model configuration based on the ICON architecture, establishing a baseline for next-generation climate predictions, projections, and operational climate forecasting.
• Demonstration of ICON XPP's capability to reproduce key coupled climate features and major dynamical processes at a performance level comparable to state-of-the-art CMIP6 models.
• Identification of specific regional model biases, providing clear targets for future model development and improvement efforts.

Funding

Not specified in the provided text.

Citation

@article{Müller2025ICONbased,
  author = {Müller, Wolfgang A. and Lorenz, Stephan and Pham, Trang V. and Schneidereit, Andrea and Brokopf, Renate and Brovkin, Victor and Brüggemann, Nils and Chegini, Fatemeh and Dommenget, Dietmar and Fröhlich, Kristina J. H. and Früh, Barbara and Gayler, Veronika and Haak, Helmuth and Hagemann, Stefan and Hanke, Moritz and Ilyina, Tatiana and Jungclaus, Johann and Köhler, Martin and Korn, Peter and Kornblueh, Luis and Kroll, Clarissa and al., et.},
  title = {The ICON-based Earth System Model for climate predictions and projections (ICON XPP v1.0)},
  journal = {Repository for Publications and Research Data (ETH Zurich)},
  year = {2025},
  doi = {10.3929/ethz-c-000789896},
  url = {https://doi.org/10.3929/ethz-c-000789896}
}