CLIMATE DRIVERS IN SOUTH AUSTRALIA
In South Australia, Ridgy is great at blocking rain-bearing fronts. He lets cold fronts through much more in winter, and brings fine and dry weather in summer.
Indy herds moisture from the Indian Ocean, bringing drier or wetter winter-springs depending on whether he’s feeling positive or negative.
Sam herds cold fronts and weather events from the Southern Ocean, mainly affecting southern areas during the cooler months of the year.
Enso herds moisture from the Pacific Ocean. During El Nino he tends to send less moisture during the cooler seasons. But in La Nina he can affect the state by chasing greater amounts of moist tropical air across Australia.
Mojo can sometimes influence rainfall in SA, especially if one of his moisture waves feeds into a timely weather event.
FUTURE CLIMATE IN SOUTH AUSTRALIA
South Australia’s climate in the decades ahead will be different from what it was in the past. We can expect changes in: temperature, extreme temperatures, sunshine, humidity, wind speed, rainfall, drought and extreme rainfall, and severe weather.
You may need to modify your farming practices to manage the risks presented by the change in climate.
The combination of projected warming and less rainfall has serious implications for farming across the state.
Farming of marginal land is likely to become even more challenging if rainfall declines substantially.
General threats to agriculture across southern Australia include:
- decline in productivity due to increased drought and bushfires
- 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 reduced 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
Temperature projections for South Australia are for continued warming over the coming decades.
The projection is for a 0.6°C increase over 1990 climate by 2030 in southern South Australia, and for a 1.0°C increase in northern South Australia. Under a low greenhouse gas emission scenario (best case), projection is for a 1.5°C increase over 1990 climate by 2070, and under a high greenhouse gas emission scenario (worst case), a 3.0°C increase is projected.
Less warming is expected along the coast than in the rest of South Australia.
Projected warming for spring and autumn is similar to the annual increase, but slightly greater for summer and slightly less for winter. 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.
We can expect more very hot days and nights. By 2070, under a high greenhouse gas emission scenario, the number of days per year above 35°C is likely to double. We can expect less frosts and less very cold days and nights.
In winter we can expect more sunshine.
Small decreases in relative humidity are likely.
In winter small increases in wind speed are likely. In all other seasons decreases are likely.
Rainfall projections for South Australia are more mixed than the projections for temperature. Most projections indicate a drying trend during winter and spring. Changes in summer and autumn rainfall are less certain.
The projection is for a 2-5% decrease in annual rainfall in 2030 relative to the 1990 climate. Under a low greenhouse gas emission scenario (best case), projection is for a 5-10% decrease in annual rainfall by 2070 when compared to 1990, and under a high greenhouse gas emission scenario (worst case), a 10-20% decrease is projected.
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.
Potential evapotranspiration is expected to increase over South 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 and an increase in the number of dry days. This suggests that future rainfall patterns will have longer dry spells interrupted by heavier rainfall events.
Vulnerability to changes in severe weather varies regionally. Potential changes that may impact agriculture in South Australia include higher bushfire risk, fewer cool-season tornadoes and more heatwaves.
SOUTH AUSTRALIAN CLIMATE EXPERTS
SOUTH AUSTRALIAN CASE STUDIES