Climate Index – Spring a season of extremes

Date21st February 2021

Climate Risk Update

The latest Australian Actuaries Climate Index has reported a season of extremes with above average rainfall in spring, and Northern Queensland recording its second highest extreme temperature value. The Climate Index is published by the Actuaries Institute and calculated by Finity.

Australia experienced above average rainfall in the Spring of 2021, with the Bureau of Meteorology (BoM) flagging it as the wettest Spring since 2010. This was reflected in the extreme rainfall component of the Climate Index, which was above reference period averages for all regions nationally.

High volumes of rainfall marked November, which was the wettest November in 122 years nationally2, according to the BoM. Parts of NSW and QLD suffered flooding. Some residents were evacuated after areas experienced up to 40mm of rain in 30 minutes3 while Greater Sydney dams collected almost four times as much water as in November of 2020.

The high level of rain towards the end of the season was likely influenced by the El Niño-Southern Oscillation (ENSO) weather system entering a La Niña phase on November 10, this leads to wetter than usual weather for eastern, northern and central parts of Australia, according to Rade Musulin, Finity’s Climate Practice leader.

Despite these events, no records were set for the extreme rainfall index, partly because the index measures the frequency of extreme weather, from September to November, while many other metrics focus on averages.

During Spring, unusually high temperatures were recorded across northern Australia. The Wet Tropics region, which covers the most northern parts of Queensland, recorded the second highest index value ever. The BoM recorded the highest ever mean maximum temperature at Cape York Peninsula7.

La Niña will continue through the Summer of 2021/2022, increasing the possibility of above average cyclone activity. It may also decrease the severity of the upcoming bushfire season if it results in wetter and cooler weather.

The Climate Index is calculated at the end of each season by Finity following the release of data from the BoM.

Click here to read the Climate Index report.

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References

1 http://www.bom.gov.au/climate/current/season/aus/summary.shtml

2 http://www.bom.gov.au/clim_data/IDCKGC1AR0/202111.summary.shtml

3 https://www.theguardian.com/australia-news/2021/nov/11/warnings-of-life-threatening-flooding-in-queensland-and-nsw-after-deluges-trigger-emergency-rescues

4 https://www.waternsw.com.au/__data/assets/pdf_file/0019/217027/Greater-Sydney-Monthly-Operations-Report-November-2021.pdf

5 http://www.bom.gov.au/climate/enso/outlook/#tabs=ENSO-Outlook-history

6 http://www.bom.gov.au/climate/current/season/aus/summary.shtml

7 http://www.bom.gov.au/climate/current/season/aus/summary.shtml

 

 

Footnote: References are based on the data underlying the AACI, which tracks changes in the frequency of extreme high and low temperatures, heavy precipitation, dry days, strong wind, and changes in sea level, mainly concentrating on the 99th percentile of observations.