Giani et al. (2025) Origin and Limits of Invariant Warming Patterns in Climate Models

⚠️ Warning: This summary was generated from the abstract only, as the full text was not available.

Identification

• Journal: Journal of Climate
• Year: 2025
• Date: 2025-12-11
• Authors: Paolo Giani, Arlene M. Fiore, Glenn R. Flierl, Raffaele Ferrari, Noelle E. Selin
• DOI: 10.1175/jcli-d-24-0683.1

Research Groups

Not available in the provided abstract.

Short Summary

This paper presents a simple theory based on local energy balance to reconcile the apparent contradiction between approximately invariant surface warming patterns in typical end-of-century climate projections and evolving patterns in idealized CO2 increase experiments. It shows that pattern invariance arises under specific conditions met in future projections, while idealized experiments exhibit evolution due to spatially inhomogeneous ocean heat uptake.

Objective

• To reconcile the apparent contradiction between the approximately invariant surface warming pattern in typical end-of-century climate projections (amenable to pattern scaling) and the time-varying warming patterns observed in idealized experiments (related to the pattern effect).

Study Configuration

• Spatial Scale: Global, with specific considerations for local temperature anomalies, the Arctic, and regions affected by aerosol projections.
• Temporal Scale: End-of-century projections, time evolution of warming patterns, and transient responses in idealized abrupt carbon dioxide (CO2) increase experiments.

Methodology and Data

• Models used: Coupled Model Intercomparison Project phase 6 (CMIP6) shared socioeconomic pathways (SSPs), idealized experiments involving abrupt increases in CO2 concentrations.
• Data sources: Model outputs from CMIP6 SSPs and idealized CO2 increase experiments. Theoretical framework based on local energy balance arguments.

Main Results

• Pattern invariance in typical end-of-century projections arises from the combination of exponential forcing, linear feedbacks, a constant forcing pattern, and linear changes in heat transport.
• These conditions are approximately met in typical CMIP6 SSPs, except in the Arctic where nonlinear feedbacks are important and in regions where different aerosol projections alter the forcing pattern.
• In idealized experiments with abruptly increased CO2, the warming pattern evolves considerably over time due to spatially inhomogeneous ocean heat uptake, even in the absence of nonlinear feedbacks.
• The findings illustrate why typical future projections are amenable to pattern scaling and provide a plausible explanation for why more complicated approaches, such as nonlinear emulators, have shown only marginal improvements in accuracy over simple linear calculations.

Contributions

• Provides a simple theory based on local energy balance to reconcile the apparent contradiction between pattern scaling effectiveness in future projections and the pattern effect observed in idealized experiments.
• Clarifies the specific conditions under which surface warming patterns remain approximately invariant, explaining the utility of pattern scaling for most future climate projections.
• Offers a theoretical basis for understanding why complex nonlinear emulators have yielded only marginal improvements over simpler linear pattern scaling methods.

Funding

Not available in the provided abstract.

Citation

@article{Giani2025Origin,
  author = {Giani, Paolo and Fiore, Arlene M. and Flierl, Glenn R. and Ferrari, Raffaele and Selin, Noelle E.},
  title = {Origin and Limits of Invariant Warming Patterns in Climate Models},
  journal = {Journal of Climate},
  year = {2025},
  doi = {10.1175/jcli-d-24-0683.1},
  url = {https://doi.org/10.1175/jcli-d-24-0683.1}
}