Climate Change Projections

Climate Change Projections

CSIRO and Bureau of Meteorology produced detailed climate change projections for the southwest of Western Australia.


Download the CSIRO Cluster Report


Assumptions on greenhouse gas, aerosol and land-use scenarios and socio-economic assumptions aid in developing simulations for the future. These simulations can predict how climate change may affect the region. However, these predications can change assuming different emission scenarios. Known as Representative Concentration Pathways (RCPs), there are four scenarios for the future.

High Emissions: RCP8.5 high radiative forcing

High-Intermediate Emissions: RCP6.0 intermediate radiative forcing

Low-Intermediate Emissions: RCP4.5 intermediate radiative forcing

Low Emissions: RCP 2.6 low radiative forcing

Basing the projections on the four emission scenarios the region could expect to experience:

Higher Temperature

The Swan Region could experience a 150% increase in the number of days above 35°C and 40°C in 75 years’ time.

Temperatures in the southwest have increased since national records began in 1910, especially since 1960. Mean surface air temperatures have increased by 1.1°C between 1910 and 2013 using a linear trend. The mean annual warming in the near future (2030) is around 0.5 to 1.1°C across the four scenarios.

However, there is an increase projection for the number and intensity for the hottest day. Under a lower-intermediate emissions scenario Perth may experience a 150% increase in the number of days above 35°C and 40°C in 75 years’ time.

Decrease Rainfall

Under all four scenarios, the region can expect a continual decline in rainfall with a particular decline in winter and spring.

The projected reduction in rainfall is not uniform across all seasons. The region could experience a drop in winter rainfall by 15% by 2030 and by 30% in 2090 given low-intermediate Emissions. However, autumn rainfall will change little.

While a reduction in rainfall is evident, stream flow within the region may reduce by as much as 90% in 2080.

Increased Drought

Under all four scenarios, region can expect to spend greater time in meteorological drought compared to the present climate.

The projected changes in rainfall will influence the regions surface and groundwater availability. While a reduction in rainfall is evident, stream flow within the region may reduce by as much as 90% in 2080.

Drier Soils

A decrease in rainfall and increase in potential evapotranspiration will influence and lessen soil moisture and runoff.

Decreases in rainfall and increases in potential evapotranspiration will lead to a decrease in soil moisture and runoff by 2090 under low-intermediate scenarios. The region needs more detailed hydrological modelling to assess changes to runoff, including the magnitude of the projected decreases.

Higher Sea Levels

There is very high confidence the sea level will continue to rise during the 21st century.

Relative sea level has risen around Australia at an average rate of 1.4 mm/year between 1966 and 2009. By 2030, the projected range of sea level rise at Fremantle is 0.07 to 0.17m above the 1986–2005 levels.