Commonly used indices disagree on the role of humidity in heat-health impacts

Different indices for health impacts of heat stress (HSIs) use different relative importances of temperature and humidity, and may therefore support different adaptation measures to reduce adverse health effects.

In hot atmospheric conditions, humans sweat to maintain the body’s internal temperature. High air humidity can prevent sweating and, therefore, increase heat stress for the body. Urban greening is a popular adaptation measure to mitigate extreme temperatures and reduce adverse health impacts from heat.

However, a recent study published in Climate and Atmospheric Science, finds that depending on the HSI applied, measures like planting trees in cities, or irrigating land, could either temper or aggravate heat stress. The researchers urge to be critical when choosing or relying on HSIs for the evaluation of benefits from adaptation measures.