The disappearing quasi-biennial oscillation under sustained global warming

The stratospheric quasi-biennial oscillation (QBO) is a key modulator of interannual variability in global weather and climate. Over recent decades, the amplitude of the lower-stratospheric QBO has weakened, and in recent years the QBO has experienced unprecedented disruptions. However, the longer-term evolution of the QBO and its impact on tropospheric circulation remain uncertain. Here, based on CMIP6 models with extended projections beyond 2100 and targeted sensitivity experiments, we show that under ongoing global warming, the QBO exhibits a progressively weaker amplitude and shorter period, eventually risking complete disappearance. This is projected to reduce the predictability of 2-3-year climate forecasts in the troposphere. The weakening of the QBO amplitude arises from enhanced tropical upwelling, whereas the shortening of its period results from the combined influence of strengthened upwelling and intensified wave activity. The potential disappearance of the QBO poses new challenges for climate change under high emission.