Large parts of northern and eastern Australia have been experiencing significant weather events over the past few weeks and now they can be partly attributed to the developing La NiÃ±a.
The Australian Bureau of Meteorology (BOM) declared a La NiÃ±a on Tuesday (23 November) which will see above average rainfall across much of northern and eastern Australia as we head into summer.
CQUniversity Adjunct Professor of Environmental Geography' Steve Turton' said the declaration by BOM meant that those living in northern and eastern Australia could expect to see an increased chance of widespread rainfall and flooding this season.
"We need to keep in mind' that several other climatic drivers affect our weather from year-to-year'" Professor Turton explained.
"These include the El NiÃ±o-Southern Oscillation (ENSO)' the Indian Ocean Dipole (IOD) and the Southern Annular Mode (SAM). ENSO and IOD are most important for tropical and sub-tropical areas of Australia' while SAM largely influences southern parts of the country."
Professor Turton' who will soon release a book titled Climate-resilient development pathways and opportunities in the Anthropocene: Australian perspectives and solutions said El NiÃ±o and La NiÃ±a were opposite phases of a natural – but powerful – climate phenomenon across the tropical Pacific Ocean that swing back and forth with an average periodicity of three to seven years.
"The last La NiÃ±a was 2020-21' so not long ago' however the last significant La NiÃ±a was 2010-12 and that saw the Brisbane and Rockhampton floods and Cyclone Yasi in far North Queensland'" Professor Turton said.
"The strongest La NiÃ±a in history was the 1973-74 event that is still Australia's wettest year on record. The devastating Brisbane floods of February 1893' January 1974 and January 2011 were all associated with strong La NiÃ±a events."
Professor Turton said this week's La NiÃ±a declaration also meant an increased risk in cyclone activity for the season.
"This La NiÃ±a is shaping up to be weaker than the moderate 2020-21 event and much weaker than the strong 2010-12 event'" Professor Turton assured.
"This event is likely to only last until early February. Meanwhile' a developing positive phase in the IOD will counteract the La NiÃ±a to some extent ahead of the monsoon wet season kicking in around Christmas time."
Professor Turton said the La NiÃ±a and its opposite El NiÃ±o could be affected by climate change as the world continues to warm.
"The latest global assessments (IPCC 2021) show that it is very likely that the amplitude of ENSO rainfall variability will intensify in response to global warming this century'" he said.
"This means extreme weather events will be more pronounced if El NiÃ±os and La NiÃ±as increase in frequency and strength' meaning increased risk for droughts' intense heatwaves' bushfires and floods for most of eastern and southern Australia. So not good news."