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The magnitude of the floods that decimated Queensland’s east coast and New South Wales’ east coast in February and March were unprecedented. The sheer amount of rainfall that has fallen in such a short time is amazing. It caused flooding and death to whole communities. The estimated repair cost of roads and bridges alone will exceed $1 billion, not to mention homes, public facilities, farms and other infrastructure.
According to the Climate Council’s estimates, this flooding event will be one of the worst ever recorded. It concluded that weather patterns once thought to be extreme only occur once in a century are now more common.
Climate Council scientist Professor Will Steffan told the Australian Broadcasting Corporation (ABC): “The point is we’re having extreme events more often. ‘Ordinary’ extreme events are occurring now in rapid succession.”
The colossal rainfall totals at three weather stations ranged from 9 a.m., on February 24, to 9:59 a.m., on February 28. Mt. Glorious, an area in the rainforest located 84 km northwest of Brisbane, Queensland’s state capital, saw the greatest amount of 1,637mm. Pomona 135 km north of Brisbane had 1,180mm, and Bracken Ridge, an outer suburb of Brisbane, saw 1,094mm.
Brisbane recorded 677mm over three days—a three-day record. Northern New South Wales (NSW), has also experienced torrential rainfalls and flooding. The State Emergency Service in Lismore, a northern NSW city, was overwhelmed in minutes. It was unable and unwilling to respond to calls quickly, due to a shortage of personnel and only two boats to cover the city of 44,000. Over 14,000 houses were damaged.
In Sydney, the NSW state capital and Australia’s largest city, the worst affected areas were working-class suburbs in the city’s southwest, impacting more than 60,000 people.
The extreme weather event is a result of a number of climate phenomena. The immediate cause for the rainfall is a very slow-moving, low-pressure system. It dragged moist air out of the Coral Sea onto the Australian east coastline. This allowed it to evaporate its large water content within a narrow geographic area. The media has dubbed the phenomenon a “rain bomb.”
Nina Ridder is a research associate at Centre of Excellence for Climate Extremes. New Scientist that “because it’s so slow-moving (weather system)—it’s basically stationary—it’s dumping all the water that it has on the same area.”
Although it is difficult to determine the exact impact of climate change on specific extreme weather events, scientists are drawing some general conclusions.
According to the vice-chair of the Intergovernmental Panel on Climate Change (IPCC) and director of the ANU Institute for Climate, Energy and Disaster Solutions Mark Howden, the climate crisis was “embedded in this event.”
The IPCC’s latest report on climate changes was released 28 February. It predicts that an increase in atmospheric and sea temperature will lead to an increased intensity of storms.
“One of the clear projections is an increase in the intensity of heavy rainfall events,” said the coordinating lead author of an Australia-New Zealand chapter of the IPCC report Brendan Mackey.
Scientists predict that the atmospheric will hold 7 percent more moisture for every degree of rise in temperature. This could lead to heavier rain and more extreme flooding events. The global climate system is more humid due to increased surface ocean warming. The average atmospheric temperature in Australia has increased 1.4℃ since records began to be kept in 1910.
“Current ocean temperatures around eastern and northern Australia are about 1℃ warmer than the long-term average, and closer to 1.5℃ warmer than average off the NSW coast,” Joëlle Gergis, senior lecturer in Climate Science at Australian National University (ANU), stated in the Conversation.
The burning of fossil fuels like coal and petrol, which produces greenhouse gases such as carbon dioxide and methane, is the main cause of climate change. It is often difficult to pinpoint exactly how it affects the complex, interdependent factors that drive Australian weather patterns and extreme events.
Variations in the surface ocean temperatures in the Southern, Indian, and Pacific oceans are one of the key drivers of Australian weather systems. A significant factor is the El Niño–Southern Oscillation (ENSO), currently in the La Niña phase. ENSO is associated the variation in wind and ocean temperature in the eastern Pacific Ocean. La Niña is usually associated with low surface air pressure on the Australian continent and thus wetter weather patterns. The 2010–2012 La Niña was associated with the wettest two-year period on record up to that time, including flooding on the Australian east coast and Brisbane.
Oceanographers from the University of NSW who studied those floods found that it was likely that climate change had compounded the heavy rains during that La Niña event. Gergis explained that “their analysis highlighted how long‐term ocean warming can modify rain-producing systems, increasing the probability of extreme rainfall during La Niña events.”
Other important factors contributing to the current extreme rainfall include the negative Indian Ocean Dipoles (IOD) as well as a positive Southern Annular Modes (SAM). The IOD refers to a difference between the sea temperatures at two poles in South Asia’s Arabian Sea and the eastern Indian Ocean south. This is known to have an impact on rainfall patterns in Australia as well as neighbouring countries. It is associated with lower sea surface temperatures, and is known to cause more rain in northern and southern Australia.
The Southern Annular Mode (SAM), refers to strong westerly winds that blow almost constantly in the southern hemisphere’s mid- to high latitudes. These winds blow from west to east and have been known to bring rain to southern Australia. The winds contract towards South Pole in their positive phase, increasing the chances of rain in southwest Australia.
Since the 1980s, climate scientists have warned that global warming will lead to more extreme weather events. Over a long period, Australia has been repeatedly devastated by extreme weather conditions including a record drought and devastating bushfires. These events have happened in the past but have been magnified by climate change, which has led to an increase of catastrophic climate events.
The Millennium drought that lasted from mid-2006 to mid-2010 was part a long-term drying trend which has continued for more than forty years. It affected the Murray-Darling Basin and most of the country’s state capital cities. It led to greater monsoonal rainfall in northern subtropical Australia. This was driven by a very strong El Niño phase.
In 2009, 173 people were killed in bushfires that devastated Victoria. The Millennium drought was ended by the double La Niña of 2010-11 and 2011-12. In 2010-11, flooding occurred in Victoria, NSW, and Queensland. The Cyclone Oswald caused significant flooding in Queensland and NSW in 2013
Honorary professor in the University of Melbourne School of Geography, Earth and Atmospheric Sciences David Karoly told the Australian Broadcasting Corporation (ABC) that both climate change and the occurrence of La Niña are likely to have contributed to the increased risk of heavy rainfall in southeast Queensland in the current event.
“The difficult part is to precisely quantify the increase in risk or the contribution to the amount of rainfall, both of which are uncertain,” he said.
Researchers continue to study the links between climate change and extreme weather events in Australia.
Wenju Cai, director of Southern Hemisphere Oceans Research at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), and his team published a paper in August 2021 entitled “Changing El Niño–Southern Oscillation in a warming climate.” It examined ENSO events from the 1950s and compared them to the climate indicated by geological records. Their modelling implied “that ENSO would become more unstable and favour greater amplitude events under warming.”
A study by John Fasullo, project scientist at the Climate and Global Dynamics Laboratory, and his associates entitled “ENSO’s Changing Influence on Temperature, Precipitation, and Wildfire in a Warming Climate” also found that the effects of ENSO would be magnified under global warming. Examining the impact of El Niño, which is the opposite to La Niña, they predicted the worst impact would be felt in the US and Australia with increased impact of bush fires or wildfires and extreme temperatures.
Fasullo stated that the study revealed that the Guardian: “We can say that an El Niño of a given magnitude that forms in the future is likely to have more influence over our weather than if the same El Niño formed 50 years ago.”
Australian politicians tried to blame the flood crisis on processes that they had no control. NSW Liberal Premier Dominic Perrottet described the flooding as a “one-in-a-1000-year event,” while Queensland Labor Premier Annastacia Palaszczuk said “I can’t do anything about mother nature.”
While floods are caused by enormous natural forces, governments have done little, if any, to warn of floods, take flood prevention and mitigation steps, provide emergency services, or finance reconstruction.
As with many other countries, Australian governments have refused to implement policies that would halt and reverse climate change. Their cosmetic measures will only lead to more extreme weather events such as droughts and flooding in the future.
