How Unexpected Was the 2022 Summertime Heat Extremes in the Middle Reaches of the Yangtze River?

The 2022 heatwave in China featured record‐shattering high temperatures, raising questions about its origin and possible link to global warming. Here we show that the maximum temperature anomalies over Central China reached 13.1°C in the summer of 2022, which is ∼4.2σ above the 1981–2010 mean with a return period of tens of thousands of years. Our results suggested that the persistent high‐pressure anomaly and associated extreme heatwave likely resulted mainly from internal variability, although anthropogenic warming has increased the probability of such extreme heatwaves. We also estimate that the 2022‐like heatwave becomes six to seven times more likely under persistent high‐pressure conditions when compared to stochastic circulation states. Due to a shift toward warmer mean temperatures and a flattening of the probability distribution function, such rare extreme heatwaves are projected to become much more common at a global warming level of 4°C, occurring once about every 8.5 years. Plain Language Summary China experienced an extensive and long‐lasting heatwave in the summer of 2022, especially in the middle reaches of the Yangtze River. Using state‐of‐the‐art reanalysis and models, here we show that the 2022 heatwave is among the most severe events ever recorded in China with a return period of tens of thousands of years. The atmospheric circulation patterns associated with the 2022 heatwave are not caused by external forcing, but due to internal atmospheric variability characterized by extremely warm anomalies and positive high‐pressure anomalies around central China, which increase the chance of such events by more than six times. A shift of the temperature distribution toward higher mean values and enlarged variability under global warming would increase the chances of new record‐breaking temperatures in the future. Such rare heatwaves in the natural and present climate could become much more common in the middle reaches of the Yangtze River under anthropogenic warming, occurring at least once every eight years at a global warming level of 4°C. Thus, efforts to build social resilience to extreme heatwaves are therefore urgently needed. Key Points Atmospheric circulation patterns associated with the 2022 heatwave likely resulted from internal variability, enhanced by external forcing The 2022‐like heatwave becomes six to seven times more likely under persistent high‐pressure conditions compared to stochastic circulation states Such rare heatwaves in