Deadly heatwaves are likely to increase on the North China Plain under a business-as-usual scenario of greenhouse gas emissions, reports a study published in Nature Communications this week. The study uses high-resolution model simulations to show that over well-irrigated agricultural areas, the wet-bulb temperature (an integrated measure of temperature and humidity) increasingly exceeds the daily maximum threshold for human survival.

Low rainfall levels on the North China Plain make irrigation of agricultural areas necessary. However, irrigation increases surface humidity and can contribute to the enhancement of heatwaves. Although an increase in deadly heatwaves (defined as a wet-bulb temperature of 35°C for more than 6 hours) is expected in this region, the impact of irrigation on such heatwaves has not been examined.

Elfatih Eltahir and Suchul Kang use a high resolution model to show that under a business-as-usual scenario, irrigation further intensifies deadly heatwaves in the North China Plain. The compounding effects of irrigation and climate change result in a larger increase in the wet-bulb temperature (3.9°C) than that of each effect alone (0.5°C for irrigation, 2.9°C for climate change). The study confirms the important role of humidity in heatwaves.