Australia’s floods, spurred by climate change, make Sydney history

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A powerful weather system near the east coast of Australia dumped huge rainfall in the state of New South Wales for days, putting Sydney on track for its wettest year on record.

The torrents caused widespread flooding in eastern New South Wales for the fourth time in less than 18 months. The flood triggered more than 100 evacuation orders.

Hundreds rescued as Sydney suffers fourth flood in less than 18 months

Since Friday, Sydney has seen 8.6 inches (220mm) of rain, while surrounding areas have seen significantly more – some approaching 28 inches (700mm) – roughly matching the amount London is seeing in a whole year.

Sydney accumulated the same amount of rain over four days that it typically sees in a month and a half, according to WeatherZone, an Australian weather information company.

The city recorded about 70 inches (1,769 mm) of rain this year, jumping 7.5 inches past 1890, its next wettest year through July 4. And, with almost five months of the year still to go, it has already notched up at least its 11th wettest year on record.

Many parts of Sydney have seen around 8 inches (200mm) of rain over the past week.

Scientists attributed the excessive rainfall to a combination of factors:

  • The presence of several natural climatic factors: La Niña conditions, a periodic cooling of the tropical Pacific Ocean, are linked to increased rainfall in eastern Australia. Periodic La Niña-related western Indian Ocean cooling is associated with increased rainfall in southern Australia. A positive southerly annular mode causes easterly winds to bring moist air from the Tasman Sea to eastern Australia, which falls as rain.
  • Human-caused climate change, which warms the atmosphere and oceans and intensifies precipitation globally.

The Australian Bureau of Meteorology also noted that warm ocean waters are helping to intensify rainfall.

“During this recent rain event, very warm waters off the Australian coast (21-23°C) provided additional energy and moisture contributing to the deep trough and east coast depression. , leading to the relative concentration of heavy rainfall over a 24-hour period,” he writes.

New South Wales’ heaviest rain up to Tuesday morning had fallen in Brogers Creek, about 65 miles south of Sydney, which recorded 36.7 inches (933 mm). WeatherZone wrote that such precipitation only has a 1-2% chance of occurring in any given year. Brogers Creek has seen more than Melbourne, Canberra, Hobart, Adelaide or Perth in a month.

Darkes Forest, about 40 miles south of Sydney, recorded 27.4 inches (697 mm) of rain.

Researchers say climate change is making the situation worse. Australia has warmed by about 2.6 degrees (1.5 Celsius) since 1910. A warming atmosphere retains more moisture and can increase the intensity of extreme rainfall events.

“Australia has long been a continent of droughts and torrential rains; That said, projections indicate that climate change will amplify this variability,” said Chiara Holgate, a researcher at the Australian National University and the ARC Center of Excellence for Climate Extremes, in an email. “Observations show that there has been an increase in the intensity of heavy rainfall in Australia, including short-lived events, which may be associated with flash flooding.”

Holgate said Australia needed to prepare for more intense flooding as flooding is one of the costliest disasters the country faces. Flooding in southeast Queensland and New South Wales in February and March cost an estimated $3.35 billion in insured losses, according to the Insurance Council of Australia, making it the worst flood costly in the country’s history.

“Major flooding poses a threat to water supplies and drinking water, straining the operation of water treatment plants due to increased sediment load and potential contaminants,” he said. said environmental scientist Klaus Joehnk in a press release.

Researchers have found that climate change has exacerbated several recent floods around the world. The World Weather Attribution group found that record flooding in Brazil in May, which displaced at least 25,000 people and killed more than 130, was exacerbated by climate change. The group also found that global warming caused torrential rains in South Africa in April, which killed more than 400 people, twice as likely to occur and 4-8% more intense.

On Tuesday, the Australian Bureau of Meteorology tweeted that major flooding continued in parts of New South Wales, even as it subsided in Sydney. More than 20 warnings were active.

Until Wednesday, the heaviest additional rainfall is projected mainly north of Sydney, where the European forecast model is simulating up to 1 to 3 inches (30 to 80 mm) of additional rainfall.


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