Unprecedented heat in North China: how soil moisture amplified 2023's record heatwave

This summer, much of North China has endured widespread temperatures above 35°C. Even typically cooler, high-latitude summer retreats like Harbin in Northeast China—usually a refuge from the heat—saw temperatures soar past 35°C in late June and July. As climate change accelerates, extreme heat events will become increasingly frequent.

Just two years earlier, in late June 2023, North China sweltered under a searing three-day heatwave that arrived weeks earlier than usual and broke six decades temperature records. Daily highs soared past 40°C in some areas, triggering heat-related illnesses, straining the region’s power grid, and threatening crops at the growing season. For millions living in this vital agricultural and industrial heartland, the scorching conditions were a stark reminder of the mounting risks posed by climate extremes.

A new study published in Earth’s Future by researchers Kexin Gui and Tianjun Zhou of the Institute of Atmospheric Physics, Chinese Academy of Sciences, has pointed the dual drivers behind this unprecedented heat: large-scale atmospheric circulation and an unusually strong soil moisture feedback. Using advanced climate analysis techniques, the team found that while an anomalous high-pressure system accounted for nearly 70% of the heatwave’s intensity, the early-season drought and dry soils added another 40%—amplifying the heatwave’s 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 lead author Kexin 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 that heatwaves with the same intensity as the 2023 event could become the new normal by the end of the century. While 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,” said Dr. Zhou. “Understanding how soil moisture and atmospheric processes interact is crucial for better predicting and mitigating future extreme weather events.”

The findings underscore the urgency of climate adaptation strategies in North China, where the increasing heat extremes poses a significant threat to livelihoods and ecosystems.