CLIMATE DRIVERS IN VICTORIA
All 6 Climatedogs have an effect on the rainfall in Victoria.
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.
Enso herds moisture from the Pacific Ocean towards Victoria, especially in winter and spring. When there’s an El Nino, he causes less rainfall. During La Ninas, he chases greater amounts of moist tropical air across Australia.
Indy herds moisture from the Indian Ocean, driving the spring rainfall. If Indy is positive, that means a drier spring, and if Indy is negative, that means a wetter spring.
Sam herds cold fronts from the southern ocean, bringing key rainfall triggers to Victoria in the cooler months. When Sam is in the positive phase, that bring more rain in spring and summer to southern and eastern Victoria, and less rain in winter, particularly in the south. When Sam is in the negative phase, he brings more rain during winter, particularly to the south.
Eastie scampers along the south-east coast of Australia, can go into action overnight, and his favourite seasons are autumn and winter. He can cause strong winds, heavy rains and lots of rough weather.
Mojo can sometimes influence rainfall in Victoria, especially if one of his moisture waves feeds into a timely weather event. He’s most active from October to April.
FUTURE CLIMATE IN VICTORIA
Victoria’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, runoff and streamflow, 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.
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
Projections for Victoria are for continued warming over the coming decades.
The projection is for a 0.6°C increase over 1990 climate by 2030. Under a low greenhouse gas emission scenario (best case), projection is for a 1.0°C increase over 1990 climate by 2070, and under a high greenhouse gas emission scenario (worst case), a 2.5°C increase is projected.
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 and spring we can expect more sunshine.
Small decreases in relative humidity are likely.
In winter small increases in wind speed are likely. In autumn decreases are likely.
Rainfall projections for Victoria are more mixed than the projections for temperature. Most projections indicate a drying trend, particularly during winter and spring. Changes in summer and autumn rainfall are less certain. The projection is for a 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.
The combination of projected warming and less rainfall has serious implications for runoff and water storage. By 2030, streamflow into Victorian dams is projected to decline by 7–35% relative to historical average flows.
Potential evapotranspiration is expected to increase over Victoria. 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. Projections show an increase in daily precipitation intensity and an increase in the number of dry days. This suggests that Victoria’s 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 Victoria include higher bushfire risk, fewer cool season tornadoes and increased hail risk in the far east of Victoria.
VICTORIAN CLIMATE EXPERTS
VICTORIAN CASE STUDIES