Human survivability in hot regions does not depend only on temperature, but also on humidity levels in ambient air. In fact, the body’s ability to shed heat is diminished when the air around it is saturated with humidity. The wet bulb temperature (also called heat stress) is the temperature of the air when it is saturated by humidity. If it approaches our core body temperature (of 37 degrees), there is a risk of hyperthermia and organs start to shut down.
Based on IASI observations and ERA5 reanalyses, Safieddine et al. (2022) recently showed that the wet bulb temperature changes with the time of day. In the Persian Gulf and around Oman it is higher in the early evening of summer because the air is saturated with humidity (see figure). Future climate projections over this region suggest that without strict climate mitigation plans, this region of the globe will become inhabitable by the end of the century.