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Climate change poses significant challenges for communities in Western Australia (WA) who are experiencing more extreme weather events such as tropical storms, floods and bushfires. The State ºÚÁÏÕýÄÜÁ¿ is supporting businesses, communities and local governments to understand the future climate and adapt to the impacts of climate change.

The CSI is developing climate projections for WA at 20-km and 4-km resolution in partnership with the NSW ºÚÁÏÕýÄÜÁ¿â€™s Department of Climate Change, Energy, Environment and Water, Murdoch University and WA’s Pawsey Supercomputing Research Centre.

The climate projections will represent our best understanding of WA’s future climate to 2100. The projections will support government agencies, businesses and individuals to prepare for events such as storms, floods, bushfires, and heatwaves, and protect WA’s unique biodiversity.

A global climate model (GCM) is a computer simulation of the Earth’s climate system based on real data. GCMs represent processes and interactions that drive the Earth’s climate and help us to understand changes resulting from activities such as burning of fossil fuels. The coarse resolution of GCMs (from 100 to 250 km) limits their ability to examine the impacts of climate change on local regions or towns.

The CSI will give us a better understanding of climate change at a local level by producing climate projections at smaller scales (20 km and 4 km resolution). At these scales, regional influences like topography, land use and coastlines can be better understood, as well as extreme events like storms. The figures below illustrate the improved resolution with a 4 km grid cell size.

Figure 1 Example of land use in a global climate model demonstrating the resolution difference with grid cell size

Figure 2 Example of topography in a global climate model, which also shows the need for downscaled regional models

Modelling at this scale has never been carried out for WA. It will represent our best understanding of how the climate will change over the next 75 years, using a range of important climate variables, including rainfall, temperature, humidity, and air/wind speed.

Climate projections will help government and industry manage the risks associated with climate change by providing robust future climate scenarios.

The projections will provide an overview of how conditions will change on average in a region over the coming decades (for example, the likely change in daily maximum summer temperatures in Joondalup by 2050). The projections will also provide vital information on climate extremes including the number of very hot days, severe fire danger days, drought duration and intensity of rainfall events.

The CSI will help answer questions like:

• What risks does climate change pose to specific regions?
• What impact can we expect on rainfall and regional water supplies?
• How will cyclones and tropical storm patterns change?
• What will be the change in fire risk in the southwest?

It is important to note that climate projections involve uncertainties due to the complexity of the Earth’s climate system and future greenhouse gas levels. CSI will synthesise and present the best available scientific information to support decision making.

CSI’s projections are being developed by scientists in the Department of Water and Environmental Regulation (the department) and Murdoch University’s Centre for Atmospheric Science. The projections are being produced in WA on one of the world’s most powerful supercomputers, the Pawsey Supercomputing Research Centre.

Global climate model information is processed in partnership with the NSW Department of Climate Change, Energy, the Environment and Water, via the NSW and Australian Regional Climate Modelling (NARCliM) program. This partnership provides the 20 km source data for further processing by the department and Murdoch University scientists to create the 4 km projections for WA.

The CSI follows the  (CORDEX) design for downscaling to 4 km resolution. This is international best practice. For WA, the model is validated using historical datasets from weather stations across the state, as well as reputable weather forecasting models (i.e.  and ), to ensure outputs are as accurate as possible.

The  (CMIP) provides a framework to analyse and validate GCM outputs. Its latest version,  is used in the CSI and provides:

• an improved representation of climate processes
• higher resolution, enhanced simulation of extreme events
• better uncertainty quantification
• incorporation of Earth system components
• integration of cutting-edge scientific advancements.

CMIP6 models represent a new generation of climate models and are highlighted in the  (released in sections from 2021 to 2023).

For more information on:

• The latest in climate modelling see: Everything you need to know about the latest in climate modelling
• The department and NARCliM partnership see: New partnerships boost climate science capability
• The NARCLiM project:

Climate change projections for the whole of WA at a grid resolution of 20 km will be available to technical users in early 2025. An online climate viewer map is currently in development to enhance the accessibility of projections for non-technical users and is expected to be available in the second half of 2025.

Projections at a grid scale of 4 km are anticipated to be available for the South West in mid-2025 and for the North West, covering the Pilbara and Kimberly regions, in 2026 (Figure 3).

Producing local climate projections is complex, highly technical work and is being undertaken for the first time in WA. The cutting-edge nature of this work involves solving tens of thousands of equations at every single grid point and timestep which represent the regional climate of WA.

The department will provide regular updates on delivery timeframes for local climate projections as the project progresses.

Figure 3 Map of WA showing the CSI’s southwest and northwest regions for the delivery of 4 km climate change projections 

Global temperatures are currently predicted to warm by between 1.8°C by 2100 for a low greenhouse gas emissions scenario, and 3.6°C by 2100 for a high greenhouse gas emissions scenario. The CSI will help us to understand what these global trends will mean for WA.

Initially, the CSI will produce projections using:

• a low emissions scenario where temperatures increase by about 1.8°C by 2100 (SSP1-2.6). This scenario envisions a future with stringent environmental policies and sustainable practices, leading to lower global greenhouse gas emissions
• a high emissions scenario where temperatures increase by about 3.6°C by 2100 (SSP3-7.0). This scenario is marked by high population growth, limited regulations, and a reliance on fossil fuels, resulting in elevated greenhouse gas emissions and a more severe impact on the climate.

An additional scenario will be incorporated progressively, providing projections based on an intermediate greenhouse gas emissions scenario with warming of 2.7°C by 2100 (SSP2-4.5).

Table 1 Shared socioeconomic pathways used in CSI

These scenarios are consistent in all GCMs and represent scientific consensus. They are based on scientific evidence from climate projections, advice from leading climate scientists and are used by prominent institutions such as the Australian Climate Service, CSIRO, BoM, as well as other jurisdictions.

There is a wide variety of climate projections data currently available. Climate projection data selection depends on the user's needs.

Please visit our guide to climate science resources for Western Australia for a list of resources currently available, including consideration of other sources of climate projection data.

Until CMIP6 projections are available, users are encouraged to use CMIP5 projections and prepare to transition to, or supplement with, CMIP6 data as it becomes available.

It’s important to note that there are only incremental differences between these generations, and broad trends remain largely the same. In CMIP6 generations, there are small improvements in the simulation of key earth processes, and greater details captured through advancements in big data analytics. Previous or current analysis based on CMIP5 models remains robust.

CMIP6 models represent a new generation of climate models. For more information see our explainer on the latest in climate modelling: Everything you need to know about the latest in climate modelling factsheet.

For further information about CMIP6 and climate modelling in general:

• Fact sheets and reports on CMIP6 models from the National Environmental Science Program’s Climate Systems Hub: 
• Climate explainers from NSW: 
• Australian Climate Service information on climate modelling: 
• Climate Explainers from QLD: 
• Climate Change in Australia information and projections: