THE SILENT KILLER

Heat can have an impact o humans in a number of ways, including affecting the ability to sleep, work and study, but at extreme levels, it’s lethal. Heatstroke symptoms range from light-headedness and nausea to organ swelling, cell-signalling disruption, unconsciousness and death. Even healthy humans who are acclimatised to heat and have access to drinking water can be killed by a combination of extreme temperature and humidity as the body loses its ability to cool itself through sweating. The measurement of this combination of heat and humidity is known as the ‘wet bulb temperature’. A study published in 2020 found that two cities — Jacobabad in southern Pakistan and Ras Al-Khaimah in the United Arab Emirates — have already reached a wet bulb temperature of more than 35°C, judged to be the human body’s limit of survivability – on some days.

A cartoon commissioned by the Extreme Heat Alliance illustrates the idea of named heatwaves