Posted by This was first published in the Western Advocate (Bathurst, NSW, Australia) on March 23, 2024.
What happened to the long, hot El Niño summer? It has been hot, however, no where near what some were expecting. Instead, Bathurst has had a variable summer with quite a bit of rain and humidity. What is happening?
This summer there were actually three climate drivers in play.
By itself, El Niño, with its warm winds moving westerly across the Pacific Ocean, is meant to produce dry and hot conditions. This contributes to drought and bushfires in the eastern states.
However, along with El Niño, there was a positive SAM. SAM (the Southern Annular Mode, also known as the Antarctic Oscillation) is a driver that lies between the south of our continent and the Antarctic, circulating winds anti-clockwise and in an east-west direction. This summer it was in positive mode. This means that it moved further south. As it did this, it pulled Australia’s northern tropical weather down, impacting the eastern states. This is what happened to us.
Also, this summer, the ocean off eastern Australia was 3 degrees warmer than the average. This has contributed to the generation of (to date) four tropical cyclones. Three of these, Jasper, Kirrily, and Megan, varyingly influenced by SAM, have shaped our weather; Kirrily in particular. In a sense, this summer, the tropics have come to Bathurst with increased rain and humidity.
The third climate driver to have an impact this summer is the Indian Ocean Dipole (IOD). This driver was also in a positive mode and, as such, caused hotter and drier conditions in Australia’s north-west. Unfortunately, a positive SAM also causes hot and dry conditions in the west. These two positive drivers, SAM and IOD, have produced the extended heatwave conditions experienced there. SAM has also contributed to the recent bushfires in the south-east of Australia.
It us unusual to see these climate drivers, El Niño, SAM, and the IOD, happening concurrently. SAM, in particular, has been prolonged this year. The Bureau of Meteorology has said that this concurrence is “most likely” the result of climate change.
Our summer may not have been typically hot and dry. However, climate change continues to contribute to the increasing volatility and unusual coming together of Australia’s climate drivers. This will continue well into the future. And without sustained effort to significantly reduce green house gases, it will get worse.