A recent increase in stratospheric temperatures above Antarctica has the potential to influence weather patterns into summer, especially in south-east Australia, where similar events have previously led to hotter and drier conditions. This phenomenon, known as sudden stratospheric warming, is extremely rare in the southern hemisphere, having only occurred twice before in 2002 and 2019. The latter event worsened the conditions during the black summer bushfires.
In early September, air temperatures 30km above the Southern Ocean and Antarctica rose significantly, now approximately 30°C warmer than average. Dr. Martin Jucker, a senior lecturer in atmospheric science at the University of New South Wales, explains that while the temperatures are still quite cold, they have increased from the usual minus 50°C to minus 20°C.
The warming is associated with a decrease in the powerful polar winds, known as the polar vortex, slowing down from about 200km/h to 100km/h. This change is expected to lead to warmer and drier weather patterns at the surface, particularly in south-east Australia. However, Dr. Jucker points out that the effects of this event are still uncertain, as there is a balancing act between the very warm ocean temperatures, which would promote wet weather, and the influence of the stratosphere, which would contribute to dry conditions.
Past events of stratospheric warming have most significantly affected New South Wales and southern Queensland, with increased temperatures in spring and reduced rainfall. This sudden stratospheric warming may also influence a climate driver called the southern annular mode, increasing the chances of abnormally hot days in southern Australia and making conditions drier than average over eastern Australia.
While unusual in the southern hemisphere, sudden stratospheric warming events occur more frequently in the northern hemisphere, happening about six times per decade. Dr. Jucker highlights that there is a positive aspect to stratospheric warming: as temperatures increase above the threshold for ozone destruction, the extent of the ozone hole will decrease.
Source: https://www.theguardian.com/environment/2025/sep/26/fears-of-abnormally-hot-days-in-southern-australia-after-sudden-stratospheric-warming-over-antarctica
