Western Australia's future climate

Western Australia’s climate in the decades ahead will be different from what it was in the past.

We can expect changes in:

You may need to modify your farming practices to manage the risks presented by the change in climate.

General threats for agriculture across southern Australia include:

  • decline in productivity due to increased drought and decreased soil moisture
  • crop yields benefiting from warmer conditions and higher carbon dioxide levels but vulnerable to reduced rainfall
  • greater exposure of stock and crops to heat-related stress and disease
  • earlier ripening and reduction in grape quality
  • less winter chilling for fruit and nuts
  • southern migration of some pests
  • potential increase in the distribution and abundance of some exotic weeds

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Temperature

Temperature projections for Western Australia indicate continued warming over the coming decades.

Projected temperature increases for 2030 and 2070 in Western Australia, relative to 1990 climate, are given in the table below.

YearMinimum increase in temperature
2030 1.0°C (southern and coastal parts of Western Australia)
1.5°C (inland South Australia)
2070 1.5°C (low greenhouse gas emission scenario)
3.0°C (high greenhouse gas emission scenario)

Less warming is expected along the coast and southern regions than in the rest of Western Australia.

Summer is expected to be warmer in line with the projected average increase.

Spring is likely to be warmer by slightly more than the average projected increase.

Autumn and winter are likely to be warmer by slightly less than the average projected increase.

Scientists have more confidence in the projections for mean temperature than in those for rainfall.

They have more confidence in the projections for 2030 than in those for 2070.

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Rainfall

Rainfall projections indicate a drying trend for the whole state, apart from the Kimberley region.

Rainfall projections for Western Australia are more mixed than for temperature.

We can expect a drying trend during winter and spring.

Summer and autumn rainfall changes are less certain.

Climate models consistently predict reduced winter and spring rainfall for south-west Western Australia. When a range of models predict the same result for a given region, it increases confidence in the prediction.

Projected annual rainfall decreases for 2030 and 2070 in South Australia, relative to 1990 climate, are given in the table below.

YearDecrease in annual rainfall
2030 2-5%
2070 5-10% (low greenhouse gas emission scenario)
10-20% (high greenhouse gas emission scenario)

Scientists have more confidence in the projections for temperature than in those for rainfall.

They have more confidence in the projections for 2030 than in those for 2070.

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Runoff and streamflow

The combination of projected warming and less rainfall has serious implications for runoff and water storage.

By 2030, streamflow into dams in the south-west is projected to decline by up to 40 per cent relative to historical average flows.

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Drought and extreme rainfall

Most models predict that potential evapotranspiration will increase over Western Australia. Evapotranspiration is the combination of evaporation from soil and water surfaces, and transpiration from vegetation.

When these changes are combined with the projected declines in rainfall, an increase in aridity and drought occurrence is likely.

Climate projections show an increase in daily precipitation intensity over much of the state, except the far south-west and central parts. The number of dry days is expected to increase significantly everywhere except for the Kimberley region.

Future rainfall patterns for many areas, including the northern part of the wheatbelt, will have longer dry spells interrupted by heavier precipitation events.

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