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. Plain Language Summary: The 2019 summer‐autumn drought (SAD) in the middle and lower reaches of the Yangtze River (MLRYR) caused a substantial loss of agriculture and economy. This SAD was accompanied by dry‐hot conditions, that is, high near‐surface temperature (T) and low precipitation (P). The impact of anthropogenic climate change (ACC) on these dry‐hot conditions and the past and future responses of SADs to them is unclear. To understand this, the present study investigates the historical and projected likelihood of dry‐hot conditions and droughts like those of the 2019 SAD under ACC in MLRYR. We found that ACC‐induce increases in T raises the likelihood of dry‐hot conditions from August–November 1901–2020 in MLRYR, as observed in both observations and simulations. The likelihood of SAD occurrence increased from 33.3% in 1901–2000 to 85.7% in 2001–2020 in MLRYR. Under the high‐emission scenario, the frequency of exceptional dry‐hot conditions is projected to increase by +10% per century. ACC‐increased dry‐hot conditions are expected to substantially elevate the likelihood of such SAD events as the 2019 event from 1.59% (1961–2020) to 17.82% (2041–2100). These findings help us understand how ACC influences the past and future likelihood of dry‐hot conditions and SAD occurrences in MLRYR. Key Points: ACC has increased the likelihood of dry‐hot conditions during August–November 1901–2020, leading to more SADs in MLRYRUnder a business‐as‐usual scenario, dry‐hot is projected to strengthen, with exceptional dry‐hot conditions grown by +10% per centuryUnder ACC‐increased dry‐hot conditions, the likelihood of SADs like the 2019 event increased from 1.59% (1961–2020) to 17.82% (2041–2100) [ABSTRACT FROM AUTHOR]