As Australia faces more intense extreme weather events, cities and urban infrastructure become increasingly vulnerable. Laure Poncet from the Australian Research Council Centre of Excellence for Climate Extremes looks at what happened across the country in 2023, and what we need to design for in the future.

Laure Poncet is a Communications Officer at the ARC Centre of Excellence for Climate Extremes. With a background in climate science and journalism, Laure coordinates communication activities at the Centre, which includes promoting new research to the media and other key audiences. She is particularly interested in translating complex scientific research into accessible language and raising awareness about climate extremes.

Destructive cyclones, extreme heat, back-to-back fires and floods… Australia was hit by a cascade of particularly intense events in 2023. Halfway through 2024, we’ve already seen cyclones, successive heatwaves and severe thunderstorms. Will this year echo the last?

This is hard to predict, but as climate change makes our world hotter, Australia will likely face more intense extreme events impacting all aspects of society. Cities and urban infrastructure are on the front line of the risks associated with these extremes.

In Australia, more than 90 percent of the population lives in cities. To protect the lives and livelihoods of our residents, we must do two things urgently: reduce greenhouse gas emissions and adapt our cities to be more resilient to climate extremes.

Australia has a variable climate

Australia’s climate is highly variable from one year to the next. These changes are primarily driven by natural climate variability, including events such as El Niño and La Niña in the Pacific Ocean, and the Indian Ocean Dipole (IOD). These natural phenomena can lead to changes in rainfall, temperature and weather patterns that can cause droughts, heatwaves, fires, intense rainfall and floods.

For instance, during an El Niño year, we typically expect drier and warmer weather in spring and early summer, particularly in southern and eastern Australia. This dry, warm weather can exacerbate drought conditions and increase fire risk. In contrast, La Niña typically brings above-average rainfall to much of Australia in winter and spring. Through its positive and negative phases, the IOD has similar impacts to El Niño and La Niña. A strong positive IOD was a significant cause of the devastating Black Summer bushfires of 2019–20.

Climate change makes extreme events worse

Our world keeps getting hotter as we continue to emit heat-trapping greenhouse gases. In Australia, temperatures have increased by about 1.5 degrees Celsius since 1910. Superimposing climate change on top of our natural climate variability alters its effects, worsening some extreme events.

For example, climate change causes shifts in weather patterns that can result in more persistent conditions, such as prolonged heatwaves or droughts. Additionally, as the temperature increases, the atmosphere can hold more moisture, fuelling heavy rainfall events, tropical cyclones and severe thunderstorms.

If we look at long-term trends, the role of climate change in extreme events is clear. Since 1950, heatwaves have become more frequent and intense across much of the country, extreme fire weather has increased, and fire seasons have become longer. In some regions, short-duration extreme rainfall events have also intensified. For example, in Sydney, these events have increased by 40 percent over the past two decades.

2023: a year of extremes

In 2023, Australia was hit by a broad range of extreme events, with economy-wide impacts (Figure 1).1 Against the backdrop of the warmest year on record globally, temperatures in Australia were almost 1 degree Celsius above the long-term average. Winter was the warmest on record, while September was the driest since at least 1900.

The year started with above-average rainfall across the country, influenced by three consecutive La Niña events. In January, Cyclone Ellie brought heavy rain to the country’s northern parts, resulting in a rare 1-in-100-year flooding event of the Fitzroy River in the Kimberley region of Western Australia.

Heavy rainfall and flooding impacted transport routes in the Northern Territory and north-western Queensland from late February to early March, leading to widespread food shortages. Increasingly dry conditions developed in late autumn and winter, with New South Wales experiencing its warmest winter on record and its second-worst snow season.

El Niño and a positive IOD, declared in September, brought exceptionally dry conditions and gave rise to an unusually early fire season in Queensland and Victoria. In late October, Queensland’s Western Downs region experienced more than 1,000 bushfires, during which 300 people were evacuated. In the same month, Gippsland in Victoria experienced back-to-back fires and floods. This phenomenon, where two extreme events occur simultaneously, is called a compound event and can be particularly destructive.

The year ended with Queensland being badly hit by an intense thunderstorm over the Lockyer Valley in the south-east of the state, while Cyclone Jasper caused widespread damage to roads, buildings and crops in the north, leaving more than 43,000 homes and businesses without power.

What lies ahead?

Although it’s too early to attribute all these events to climate change (this usually requires several years of research), they indicate what we can expect. In the coming decades, Australia will get hotter. Heatwaves are expected to become more frequent and intense, and to occur earlier in the season. We will likely experience more hot and dry winters, increasing the risk of early-season fires. The trends in tropical cyclones are less certain. Although there will potentially be fewer cyclones, the intensity of cyclones could increase.

While it’s crucial to consider how the number and intensity of extreme events will change, we also need to understand how successive events will compound to cause more significant damage. For example, compound events where extreme wind combines with heavy rainfall are expected to become more common. Heatwaves combined with droughts could also happen more often.

Cities on the front line

Around the world, many cities are already experiencing the impacts of climate change, and these are likely to worsen in the future. The high concentration of buildings and roads, and the lack of trees, make our cities particularly good at absorbing and retaining heat – a phenomenon known as the urban heat island effect. In the future, more frequent and intense heatwaves could exacerbate this effect, putting the wellbeing of residents at risk. Additionally, intense rainfall events could cause flooding and damage infrastructure, while extreme drought conditions could lead to water shortages. Fewer but more intense tropical cyclones are likely to damage buildings, cause widespread power outages and disrupt transportation networks.

To protect the health and safety of urban populations, cities need to adapt to climate change and become resilient to the impacts of extreme events. Strategies such as increasing vegetation and adopting urban design principles that prioritise shade and ventilation can help mitigate the impact of heatwaves and reduce the urban heat island effect. We need to invest in resilient infrastructure that can withstand high winds, heavy rainfall and storm surges, as well as develop a clear understanding of where the risks are, where to build, and where not to.

To manage human-induced climate change, we must drastically cut greenhouse gas emissions. At the same time as dramatically cutting emissions, and as we continue to experience new extremes, we need to reimagine our cities to enable residents to live with these extremes and plan for future climate events.

Footnotes:

(1) Australian Research Council Centre of Excellence for Climate Extremes, The State of Weather and Climate Extremes 2023, climateextremes.org.au/the-state-of-weather-and-climate-extremes-2023; doi.org/10.26190/92kr-0w80.

This article was republished with permission from the author Laure Poncent.