How did anthropogenic forcing influence the exceptional heatwave in the summer of 2022 over the Yangtze River Basin through subtropical high?

The attribution study of extreme weather events has attracted the interests of climate change science communities in recent years. From July–August 2022, an extraordinary heatwave with record-breaking high temperatures occurred in Central and Eastern China, especially over the Yangtze River Basin, for what period the China Meteorological Administration gave the first “red heat warning” in history. Meanwhile, the western Pacific subtropical high leaped over the Tibetan Plateau, which was rarely seen in the past. Understanding the causes of such extreme events and distinguishing the role of human played are both helpful for mitigation and adaptation of climate change, although it is full of challenges. This study used a risk ratio approach (PR) to investigate whether and to what extent atmospheric circulation and other factors (such as anthropogenic climate change, greenhouse gases, and aerosols) contributed to this event, 42 members out of 12 CMIP6 models. According to the CMIP6 simulations, the contribution results show that the existence of anomalous anticyclones would have increased the probability of this extreme heatwave by 4.5 times, making it the main driver for this extreme event in the past 60 years, while the anthropogenic climate change contributed the most (PR = 3.9) for the past 30 years. Additionally, we found that anthropogenic aerosols had no significant impact on the likelihood of this event (PR = 0.82 (0.74) in the past 30 (60) years). This study provides a strong warning that global warming caused by anthropogenic activities in recent decades may result in more frequent extreme heatwaves of summers similar to the summer of 2022. Therefore, measures for mitigating and adapting to global warming are urgently needed.