16 October 2019
This research and the associated synthesis brochures were undertaken by Hub researchers from Project 2.8 – Extreme weather projections.
Extreme events have always been part of Australia’s variable climate and can cause large impacts on communities, businesses and ecosystems. However, human-caused greenhouse gas emissions are causing many extreme weather events to become significantly different to what we have previously experienced.
The Earth Systems and Climate Change Hub has developed improved knowledge and resources on tropical cyclones, east coast lows, bushfires and thunderstorms and how they may change in the future to help us plan for and deal with climate change with greater confidence.
Four brochures are now available on these extreme weather events, including information on associated hazards such as lightning, hail, extreme wind, waves, rainfall, heat and flooding.
Tropical cyclones
Tropical cyclones impact many parts of northern Australia, where they can produce extreme winds, waves and rainfall and can cause coastal hazards such as storm surges, flooding and coastal erosion.
What we’ve seen already
On average, about 11 tropical cyclones form or move into the Australian region each year. The total number of tropical cyclones observed in the Australian region has decreased significantly in recent decades. This decrease is thought to be due to a combination of both climate change and natural variability.
What’s in store for the future
Climate models project a future decrease in the total number of tropical cyclones, but an increase in the proportion of severe tropical cyclones due to increasing greenhouse gas emissions. There is a high degree of confidence that extreme rainfall caused by tropical cyclones will increase in intensity, and rising sea levels will also act to increase coastal impacts.
Read more: Tropical cyclones and climate change in Australia
East coast lows
East coast lows are low-pressure systems near south-east Australia that can cause a range of hazards including damaging winds, prolonged heavy rainfall and very rough seas. The more intense events can lead to impacts such as injury, loss of life, infrastructure damage and large insurance losses, as well as benefits such as contributing to water availability for this densely populated region of Australia.
What we’ve seen already
East coast lows occur on average about 22 times per year. There is large variability from year to year in the number of east coast lows that occur in Australia, with no clear trend in the number of east coast lows observed over recent decades.
What’s in store for the future
Climate models project fewer east coast lows are likely to occur in the future due to increasing greenhouse gas emissions. The projections show larger reductions of east coast lows for higher greenhouse gas emission scenarios. Although fewer east coast lows are projected to occur into the future, other important changes in our climate will affect the impact of future east coast lows on eastern Australia. For example, rising sea levels are likely to increase the impact of large waves on coastal regions, and extreme rainfall is predicted to increase in intensity resulting in increased risk factors for flooding in some cases.
Read more: East coast lows and climate change in Australia
Bushfires
Bushfires have always been an important part of Australia’s environment. They have the potential to cause severe economic costs as well as damage to property, loss of life and harm to ecosystems.
What we’ve seen already
Human-caused climate change has already resulted in more dangerous weather conditions for bushfires in recent decades for many regions of Australia. There is a trend towards more dangerous conditions during summer and an earlier start to the fire season, particularly in parts of southern and eastern Australia.
What’s in store for the future
Climate models show an increase in future dangerous fire weather conditions throughout Australia due to increasing greenhouse gas emissions. Projections also indicate a future increase in dangerous pyroconvection conditions (storms within a bushfire) for many regions of southern Australia.
Read more: Bushfires and climate change in Australia
Thunderstorms
Thunderstorms are relatively small-scale weather systems which can cause hazards such as lightning, hail, extreme winds, tornadoes, extreme rainfall and flash flooding. The impacts of thunderstorms in Australia include disruption to power networks, damage to property and injury or loss of life. In addition, lightning during thunderstorms can also ignite bushfires, leading to a range of further impacts to our communities, businesses and ecosystems.
What we’ve seen already
Thunderstorms in Australia occur predominantly during the warmer months of the year, with more activity towards the north and east of the continent. Thunderstorms can combine with other weather events such as tropical cyclones, east coast lows and cold fronts, resulting in more extreme weather conditions. There is no clear trend in thunderstorm occurrence in Australia over the past decades, based on observational data.
What’s in store for the future
Climate models indicate a potential increase in future thunderstorm frequency for parts of eastern Australia, while changes for other regions of Australia are more uncertain. Extreme rainfall caused by thunderstorms is likely to increase in intensity resulting in increased flood risk factors in some cases.
Read more: Thunderstorms and climate change in Australia
Climate change science to inform policy and decisions
Climate change information is critical to help deal with the impacts of extreme weather hazards. Some management and policy decisions in response to extreme weather will require detailed climate change information, but others will only need more general information.
Research under the Earth Systems and Climate Change Hub is improving our confidence in climate change projections and is increasing our understanding of how the climate system works. The Hub is working to make climate change information more user-friendly, so it can more easily be applied to risk assessment and adaptation activities.
More research into extreme weather hazards is continuing under the Hub through Project 5.5 Changing extreme weather hazards.
For more information
Dr Andrew Dowdy, Bureau of Meteorology
Main image: Property damage resulting from the 2016 east coast low on Collaroy Beach, Sydney.
Image credit: C. Drummond, NSW Water Research Laboratory