African City Heat Is Set to Grow Intolerably

Up to a third of urban dwellers could soon face extreme African city heat and humidity.  Risks could at worst multiply 50-fold.

An entire continent faces lethal conditions for many of its people: by 2090, one person in three can expect African city heat in the great conurbations severe enough to expose them to potentially deadly temperatures.

That is:  the number of days in which the apparent temperature – a notional balance of thermometer-measured heat and maximum humidity – could reach or surpass 40.6°C will increase dramatically, and the days when individuals could be at risk could in some scenarios multiply 50-fold.

The scientists selected this “apparent” temperature of 40.6°C because it is significantly beyond the natural temperature of the human body, which must then be kept cool by perspiration.  This is possible in arid climates.

But as humidity goes up – and with each 1°C rise in temperature, the capacity of the air to hold moisture rises by 7% – cooling by perspiration becomes less efficient.

So at this notionally-defined apparent temperature, people who cannot retreat to air-conditioned or cooler, shadier places could die.  Heat kills:  researchers recently counted 27 ways in which extreme temperatures could claim lives.

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