Attribution of the 2023 extreme spring hot drought event in Southwest China: meteorological and agricultural perspectives

During March to May 2023, Southwestern China experienced a prolonged hot and dry spring. This study investigates the role of anthropogenic climate change (ACC) in this extreme event and its impact on crop yields, using a 525-member ensemble from the HadGEM3 atmospheric model and the WOFOST agricultural model, respectively. Observational results indicate that the area-averaged surface air temperature anomaly (TAS) was 1.4 °C higher than usual, and the percentage of anomalous precipitation was nearly 33% below normal, making both metrics the most extreme since 1960. The hot event was predominantly driven by ACC, contributing about 60% to the TAS strength and increasing its likelihood 7 fold. In contrast, internal climate variability appears to have been the primary trigger of the severe drought, although ACC significantly increased its likelihood by 9 fold. When these two extreme conditions are considered together as a concurrent hot-drought event, ACC increased its probability by about 3 fold. An attribution analysis of crop yields in the area was also conducted, revealing that ACC significantly shifts the probability distribution westward and reduces yields for both the winter wheat and rapeseed. Specifically, based on the simulated 2023 crop yield results driven by ERA5 as a proxy for observations, the likelihood of achieving the yield for winter wheat would have decreased by a factors of about 2 under ACC, while that for winter rapeseed is close to 1, despite its better simulation performance in the historical context. This underscores the challenge of accurately modeling and projecting crop yields under changing climate conditions. Additional analysis emphasizes the role of land–atmosphere interactions in amplifying the hot-drought event, as early-season soil moisture deficits reduced evapotranspiration and increased sensible heat flux, thereby intensifying local temperature extremes. Overall, global warming caused by anthropogenic activities has significantly increased the frequency of extreme hot drought events in Southwestern China, posing a severe threat to agricultural productivity.