Much of North China has endured widespread temperatures above 35°C this summer, with even typically cooler, high-latitude areas like Harbin—long a summer refuge from the heat—recording mercury levels soaring past 35°C in late June and July. Scientists warn that such extreme heat events will grow increasingly frequent as climate change accelerates.

The trend echoes a searing three-day heatwave in late June 2023, which struck weeks earlier than usual and shattered 60-year temperature records across North China. Daily highs surged past 40°C in some regions, triggering heat-related illnesses, straining the local power grid, and threatening crops during a critical growing period. For millions in this vital agricultural and industrial heartland, the scorching conditions served as a stark reminder of the mounting risks posed by climate extremes.

A new study led by Profs. GUI Kexin and ZHOU Tianjun from the Institute of Atmospheric Physics of the Chinese Academy of Sciences, has identified dual drivers behind such unprecedented heat: large-scale atmospheric circulation and unusually strong soil moisture feedback. Their findings were published in Earth's Future .

Using advanced climate analysis techniques, the researchers found that an anomalous high-pressure system accounted for nearly 70% of the 2023 heatwave's intensity, while early-season drought and dry soils added another 40%—amplifying the severity far beyond what would have occurred otherwise.

"Dry soils, caused by the lowest rainfall in over four decades, acted like a giant amplifier," explained the lead author Prof. GUI. "With little moisture left to evaporate, the land surface heated up rapidly, pushing temperatures to extremes rarely seen in North China's early summer."

The study warns that such conditions may become more common under climate change. Model projections suggest heatwaves as intense as the 2023 event could become the new normal by the end of the century, though the influence of soil moisture feedback on extreme heat may weaken in the long term due to projected increases in soil moisture.

"Heatwaves of this magnitude put enormous pressure on energy systems, agriculture, and public health," noted Prof. ZHOU. "Understanding how soil moisture and atmospheric processes interact is crucial for better predicting and mitigating future extreme weather events."

This study underscore the urgency of climate adaptation strategies in North China, where increasingly extreme heat poses a significant threat to livelihoods and ecosystems.

Beijing commuters endure scorching heat as they brave the sun-drenched streets. (Image by Prof. GUI Kexin)