Heavy rain in Cyclone Alfred locally intensified by human-driven climate change

Contact Authors

• Davide Faranda, IPSL-CNRS, France  📨davide.faranda@lsce.ipsl.fr    🗣️French, Italian, English

• Tommaso Alberti, INGV, Italy  📨tommaso.Alberti@ingv.it    🗣️Italian, English

• Stavros Dafis, NOA/METEO, Greece 📨sdafis@noa.gr  🗣️Greek, English

Citation

• Faranda, D., Alberti, T., & Dafis, S. (2025). Heavy rain in Cyclone Alfred locally intensified by human-driven climate change. ClimaMeter, Institut Pierre Simon Laplace, CNRS. https://doi.org/10.5281/zenodo.14982634

Press Summary (First Published 2025/02/14)

• Cyclones similar to Alfred are up to 1 hPa shallower, locally wetter by up to 7 mm/day (10%), and have wind speeds reduced by up to 5 km/h (-10%) in the present compared to the past. They also contribute to locally colder conditions over the Australian continent, with temperatures dropping by up to 1°C.

• This event is associated with very exceptional meteorological conditions. 

• We mostly ascribe heavier precipitation in Cyclone Alfred to human-driven climate change, with natural climate variability likely playing a modest role.​

Event Description

Tropical Cyclone Alfred, a Category 2 storm, is currently approaching the southeast coast of Queensland, Australia, expecting to make landfall near Brisbane by Saturday 8 March in the morning. As of March 6, 2025, Alfred is moving westward at 12 km/h, with sustained winds near the center of 100 km/h and wind gusts up to 130 km/h. The cyclone has already brought destructive winds and heavy rainfall in many parts of eastern Australia. Authorities have issued severe weather warnings for New South Wales and Queensland, including Northern Rivers, Mid North Coast, and Northern Tablelands. Major cities and towns at risk include Tweed Heads, Byron Bay, and Coffs Harbour, where officials are bracing for coastal flooding, riverine inundation, and potential landslides in elevated terrain. Authorities in northern New South Wales have issued evacuation orders for residents in 11 locations, including Uki, Fingal Heads, and Lismore, due to potential flooding. Approximately 660 schools in southern Queensland and 280 in northern New South Wales have been closed. Public transport services in Brisbane have been suspended. Strong winds have already caused power outages, affecting thousands of properties.

Prime Minister Anthony Albanese described the situation as "very serious," and updates are being provided by meteorologists. Forecasts predict heavy rainfall, with some areas expecting up to 180 mm overnight, leading to potential flash flooding. Destructive winds up to 155 km/h and storm surges are anticipated, particularly along coastal regions from Cape Moreton to Yamba. Residents are securing properties and utilizing sandbag depots to protect against flooding. Emergency services are on high alert, with shelters established for evacuees.

The surface pressure anomalies show a large negative anomaly, up to -20 hPa, over the southeast coast of Queensland. Temperature anomalies display  a complex structure with land areas of positive (+2°C) and negative (-2°C) anomalies, with a warm core of the cyclone. Precipitation data indicate extremely high daily amounts exceeding 150 mm/day over the cyclone core and along the mountainous coastline. Wind speed data indicate strong sustained winds (up to 100 km/h) directed from the ocean towards the coast, with stronger gusts near the eyewall. These winds enhance precipitation over the mountainous areas, contributing to the flooding. Our analysis is based on ERA5 data, which integrates some station observations, especially for rain data. The values reported here can differ from those observed at individual weather stations.​

Climate and Data Background for the Analysis

The Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6) highlights significant concerns regarding climate change and its impact on flooding in Australia. The report indicates that climate change is expected to increase the frequency and severity of heavy rainfall events, leading to more frequent and intense river floods across the country. Since 1982, there has been a decrease in the number of tropical cyclones occurring in the Australian region. However, the proportion of severe cyclones has increased, indicating that while fewer cyclones are forming, those that do are more intense. Projections suggest a continued decrease in the number of tropical cyclones in the Australian region. At the same time, there is an expected increase in the proportion of severe cyclones, with a greater percentage anticipated to reach higher categories. Additionally, an increase in heavy rainfall intensity is projected, leading to more severe flooding events. ​

Our analysis approach rests on looking for weather situations similar to those of the event of interest having been observed in the past. For this event, we have low confidence in the robustness of our approach given the available climate data, as the event is very exceptional in the data record.

ClimaMeter Analysis 

We analyze here (see Methodology for more details) how events similar to the meteorological conditions leading to the Queensland Floods have changed in the present (1987–2023) compared to what they would have looked like if they had occurred in the past (1950–1986) in the region [150°E 150°E 22°S 32°S].  The Surface Pressure Changes show that cyclones similar to Alfred are up to 1 hPa shallower in the present climate than they would have been in the past on the southeast coast of Queensland.​ Temperature Changes show that similar events produce temperatures in the present climate that are locally 1°C colder than they would have been in the past inland.​ Precipitation Changes show  that there are up to 7 mm/day (up to 10%) wetter conditions over localised coastal areas of Australia.​ Wind speed changes have shown reduced windier conditions, with decreases of up to 5 km/h (up to -10%) offshore Australia.

We also note that similar past events occur with similar seasonality in the past and present periods. Changes in urban areas reveal that Brisbane, Bundaberg and the Gold Coast experience heavier rain in the present than in the past. Brisbane also experiences a small reduction in wind (up to 3 km/h). The city of Sunshine Coast does not experience significant changes.​

Finally, we find that sources of natural climate variability, notably the Atlantic Multidecadal Oscillation, may have only partly influenced the event. This means that the changes we see in the event compared to the past may be mostly due to human driven climate change. 

Conclusion

Based on the above, we conclude that cyclones similar to Alfred are up to 1 hPa shallower, locally wetter by up to 7 mm/day (10%), and have wind speeds reduced by up to 5 km/h (-10%) in the present compared to the past. They also contribute to locally colder conditions over the Australian continent, with temperatures dropping by up to 1°C. We interpret Cyclone Alfred as an event driven by very exceptional meteorological conditions whose characteristics can mostly be ascribed to human driven climate change.