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Drought makes heatwaves hotter but less deadly

Phys.org/news (JANUARY 10, 2022)

Titre : Drought makes heatwaves hotter but less deadly

During heatwaves, the land dries out. That drought further enhances the rising of heatwave temperatures. However, desiccated soils still make the heatwaves less rather than more deadly to humans, due to a reduction in air humidity.

Phys.org/news (JANUARY 10, 2022)

Présentation
Heatwaves and droughts are causing acute excess mortality and damage to society worldwide. For instance, the number of deaths related to the European heatwave of 2003 reached more than 70,000, but more recent heatwaves have resulted in substantial excess mortality, on top of the COVID-19 pandemic.

Until now, it was believed that dried out soils make heatwaves even more deadly as it pushes heatwave temperatures even higher. After all, drier land results in lower evaporation. Consequently, more energy is left at the Earth’s surface to heat up the outside air further. But the temperature effect of drought is deceiving : high air humidity also hampers cooling of the human body through transpiration, hence a higher chance for overheating. Lower evaporation concurrently leads to lower air humidity. That beneficial effect takes over, and makes heatwaves less deadly.

The results reveal which measures against periods of drought and deadly heat are most effective. Such periods are becoming longer, more frequent and more intense in a warming climate. Many measures are already taking place, such as (re)afforestation and irrigation of croplands, and these are necessary for nature conservation, biodiversity, agriculture and food production. However, the current study shows that these drought-resistant measures are ineffective against deadly heat and can even be detrimental, despite the fact that they smooth out the extremely high temperatures. The favorable effect due to a lower temperature is canceled out by the higher humidity, which makes the heat sultrier. The measures therefore remove the beneficial effect of drought during deadly heatwaves.

Source  : Ghent University

Annonce (Phys.org/news)

Page publiée le 16 janvier 2023