Anthropogenic Exacerbation in Dry-Hot Probability and Consequential Record-Shattering Droughts in the Middle and Lower Reaches of the Yangtze River

In the year 2019, the middle and lower reaches of the Yangtze River (MLRYR) experienced an unprecedented summer-autumn drought (SAD) driven by dry-hot conditions [high near-surface air temperatures (T) and low precipitation (P)], causing substantial agricultural and economic losses. However, the influence of anthropogenic climate change (ACC) on these dry-hot conditions and their impacts on SAD occurrences remains uncertain. Here, both observations and simulations show that an ACC-driven T increase led to the greater likelihood of dry-hot conditions from August to November 1901–2020 in MLRYR. Using the self-calibrating Palmer drought index (scPDSI) to assess SAD severity, we find an increasing likelihood of SAD occurrence (from 33.3% in 1901–2000 to 85.7% in 2001–2020) in MLRYR associated with more frequent dry-hot conditions. Under a business-as-usual scenario, future dry-hot association is projected to be stronger, with exceptional dry-hot conditions to increase by +10% per century. ACC-induced increase in dry-hot conditions would elevate the likelihood of SAD events like the 2019 event from 1.59% (1961–2020) to 17.82% (2041–2100). Therefore, effective measures are needed in MLRYR to adapt to increasing dry-hot conditions and associated SAD occurrences under anthropogenic warming.