Evans et al. (2026) Fifteen years of regional climate downscaling in CORDEX-Australasia

Identification

• Journal: PLOS Climate
• Year: 2026
• Date: 2026-09-24
• Authors: Jason P. Evans, Marcus Thatcher, Daniel Argüeso, Alejandro Di Luca, Ralph Trancoso, Julia Andrys, Sarah Chapman, Giovanni Di Virgilio, Andrew Dowdy, Lluís Fita, Peter B. Gibson, Michael Grose, Emma Howard, Fei Ji, Jatin Kala, Jack Katzfey, Leena Khadke, Omer Mughal, Benjamin Ng, Neelesh Rampal, Christian Stassen, Stephen J. Stuart, Chun Hsu Su, Jozef Syktus, Son C. H. Truong, Harvey Ye
• DOI: 10.1371/journal.pclm.0001066

Research Groups

• Climate Change Research Centre, University of New South Wales, Sydney, Australia
• CSIRO Environment, Aspendale, Victoria, Australia
• Physics Department, University of the Balearic Islands, Palma, Spain
• Département des sciences de la Terre et de l’atmosphère, Centre pour l’étude et la simulation du climat à l’échelle régionale (ESCER), Université du Québec à Montréal, Montreal, Canada
• Queensland Future Climate Science Program, Queensland Government, Brisbane, Australia
• The University of Queensland, School of The Environment, Brisbane, Australia
• School of Environmental and Conservation Sciences and Centre for Terrestrial Ecosystem Science and Sustainability, Harry Butler Institute, Murdoch University, Murdoch, Western Australia, Australia
• Climate Research, Climate and Atmospheric Science Branch, NSW Department of Climate Change, Energy, the Environment and Water, Sydney, New South Wales, Australia
• The University of Melbourne, School of Geography, Earth and Atmospheric Sciences, Melbourne, Australia
• Bureau of Meteorology, Melbourne, Australia
• Centro de Investigaciones del Mar y la Atmósfera (CIMA), UBA-CONICET, Buenos Aires, Argentina
• CNRS–IRD–CONICET–UBA, Institut Franco-Argentin d’Études sur le Climat et ses Impacts (IRL IFAECI), Buenos Aires, Argentina
• Earth Sciences New Zealand, Wellington, New Zealand
• Department of Water and Environmental Regulation, Western Australian Government, Perth, Australia
• Earth Sciences New Zealand, Auckland, New Zealand

Short Summary

This paper synthesizes fifteen years of regional climate downscaling in CORDEX-Australasia, highlighting the evolution, achievements, and scientific advances in providing high-resolution climate projections for the region. It demonstrates clear added value over global models, particularly for temperature extremes and heavy precipitation, while outlining future priorities and challenges.

Objective

• To synthesize the evolution, achievements, scientific advances, applications, and future priorities of regional climate modelling in Australasia over the past fifteen years, particularly within the CORDEX-Australasia framework and complementary national and state-based initiatives.

Study Configuration

• Spatial Scale: Australasia (encompassing Australia, New Zealand, and neighboring Pacific and Southeast Asian areas), with resolutions ranging from approximately 60 kilometers down to 4 kilometers (convection-permitting) and kilometre-scale. Specific focus on southeastern Australia (4 kilometers), New Zealand (12 kilometers), and the wider South Pacific (approximately 12–30 kilometers).
• Temporal Scale: Fifteen years of regional climate downscaling (since 2009), with historical reference periods (1976–2005, 1985–2014) and future projections for the 21st century (e.g., late 21st century, 2080-2099).

Methodology and Data

• Models used:
  • Regional Climate Models (RCMs): NARCliM (1.0, 1.5, 2.0), CSIRO regional model, CCAM (Conformal Cubic Atmospheric Model), Unified Model, BARPA (BoM Atmospheric Regional Projections for Australia), WRF (Weather Research and Forecasting model).
  • Global Climate Models (GCMs): CMIP5, CMIP6.
  • Downscaling techniques: Dynamical downscaling, convection-permitting modelling, bias correction, generative-AI-based regional climate model emulator.
• Data sources:
  • Gridded observation datasets (e.g., ACORN-SATv2.6 for temperature, AGCD for rainfall).
  • Global reanalysis (e.g., ERA5).
  • CMIP datasets (CMIP5, CMIP6).
  • Earth System Grid Federation (ESGF) and Australia’s National Computational Infrastructure (NCI) for data access.

Main Results

• The CORDEX-CMIP5 ensemble (20 simulations from 11 GCMs using 6 RCMs) reproduced principal observed climate features but exhibited systematic biases, including underestimation of daily maximum temperature and overestimation of minimum temperature.
• Regional Climate Models (RCMs) consistently demonstrated clear added value over their driving Global Climate Models (GCMs), particularly in representing temperature extremes, heavy precipitation, coastal processes, and complex terrain.
• CMIP6-based projections show robust multi-model agreement on substantial 21st-century warming across Australasia, with temperatures projected to increase by approximately 2–5 K over Australia by the late 21st century under SSP3–7.0, with uncertainty dominated by emissions scenarios.
• Precipitation responses remain more regionally heterogeneous and uncertain, with widespread winter drying projected, while summer responses show substantial inter-model disagreement.
• Projections of rare extreme rainfall indicate greater consistency, with increases to 1-in-100 year events expected across Australia and its capital cities.
• The CORDEX-CMIP6 ensemble shows higher added value for maximum and minimum temperature extremes compared to CORDEX-CMIP5, but less spatial consistency of added value in precipitation extremes.
• Advances in convection-permitting modelling, benchmarking frameworks, and bias-correction methods have further improved process representation and evaluation.

Contributions

• Provides a comprehensive synthesis of fifteen years of regional climate downscaling efforts in Australasia, integrating both the CORDEX framework and complementary national/state-based initiatives.
• Documents the evolution, achievements, scientific advances, and diverse applications of regional climate modelling in a complex and vulnerable region.
• Quantifies and highlights the "added value" of RCMs over GCMs for providing enhanced regional climate information, particularly for extremes and finer-scale climate features.
• Identifies key persistent challenges (e.g., computational demands, model biases, precipitation uncertainty, ensemble design, science-policy gap) and outlines strategic future priorities for the next 15 years (e.g., kilometre-scale modelling, enhanced Earth system coupling, coordinated super-ensembles, responsible AI integration, strengthened observational constraints, expanded support for vulnerable Pacific Island nations).
• Emphasizes the critical role of shared infrastructure (National Computational Infrastructure) and coordination mechanisms (National Partnership for Climate Projections) in fostering a mature and dynamic regional modelling ecosystem that links research, operations, and applications.

Funding

• NARCliM2.0: New South Wales (NSW) Department of Climate Change, Energy; NSW Climate Change Adaptation Strategy; NSW Climate Change Fund (CCF).
• Western Australian Climate Science Initiative Project: Department of Water and Environmental Regulation (DWER) of Western Australia.
• HYDROMED grant (PID2023-146625OBI00 to DA): MICIU/AEI/ 10.13039/501100011033 by ERDF/EU.
• Natural Sciences and Engineering Research Council of Canada (NSERC) (RGPIN-2020-05631 to AD).
• Queensland Government (RT, JS, SC received salary).
• National Computational Infrastructure (NCI Australia).
• CSIRO HPC (Petrichor).
• Pawsey Supercomputing Research Centre.

Citation

@article{Evans2026Fifteen,
  author = {Evans, Jason P. and Thatcher, Marcus and Argüeso, Daniel and Luca, Alejandro Di and Trancoso, Ralph and Andrys, Julia and Chapman, Sarah and Virgilio, Giovanni Di and Dowdy, Andrew and Fita, Lluís and Gibson, Peter B. and Grose, Michael and Howard, Emma and Ji, Fei and Kala, Jatin and Katzfey, Jack and Khadke, Leena and Mughal, Omer and Ng, Benjamin and Rampal, Neelesh and Stassen, Christian and Stuart, Stephen J. and Su, Chun Hsu and Syktus, Jozef and Truong, Son C. H. and Ye, Harvey},
  title = {Fifteen years of regional climate downscaling in CORDEX-Australasia},
  journal = {PLOS Climate},
  year = {2026},
  doi = {10.1371/journal.pclm.0001066},
  url = {https://doi.org/10.1371/journal.pclm.0001066}
}