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A large polar stratospheric warming is under way in the Southern Hemisphere. It is expected to be on a par with the last large event, in 2002, according to the Australia Bureau of Meteorology, the US National Oceanic and Atmospheric Administration and NASA, the UK Met Office and the European Centre for Medium-Range Weather Forecasts, and the Japan Meteorological Agency. The ability to forecast these rare occurrences has improved hugely in the past decade owing to dramatic advances in the fusion of weather and climate prediction.