Human Thermal Limits — and when we exceed them
The human body relies primarily upon sweat to cool itself. But if the air is hot enough and humid enough, your sweat no longer evaporates, and sweating for cooling no longer works.
The critical point is a wet-bulb temperature of 35°C. Beyond that, fans don't help. Drinking doesn't help. Shade doesn't help. Rest doesn't help. When the wet-bulb temperature exceeds 35°C, unprotected humans die.
Some areas of the Earth are getting alarmingly close to this limit.
Wetbulb temperatures of 35°C have not yet been widely reported, but there is some evidence that they are starting to occur in Southwest Asia. Climate change then offers the prospect that some of the most densely populated regions on Earth could pass this threshold by the end of the century, with the Persian Gulf, South Asia, and most recently the North China Plain on the front line. These regions are, together, home to billions of people.
When regions cross the 35°C wetbulb limit, they will quite simply become uninhabitable by humans outside of air-conditioned environments. And we simply do not have sufficient power to air-condition that much of the world ... and trying to generate it will only make the problem worse unless we can do so using non-carbon-emitting means.
By 2050, cooling systems are expected to increase electricity demand by an amount equivalent to the present capacity of the US, EU, and Japan combined.
Even then, that heat doesn't just go nowhere; remember, we cool buildings by moving the unwanted heat outside. The more we cool the inside, the hotter the outside gets. Which means we need to turn up the air conditioning to keep the building cool, dumping even more heat outside...
You can see where that's going.
The short version is that if we keep on our current path, in as little as another few decades large areas of our planet are on track to become uninhabitable. And the people who live there now are going to have to either find a new place to live, or die.
Finding new places is going to be very hard. Look at all the resistance to the relatively tiny refugee movements happening today. If we pass 35°C wet-bulb, entire nations
may need to relocate. And a LOT
of them are going to die.https://www.sciencealert.com/think-it-s-hot-in-europe-in-these-places-the-human-body-is-close-to-its-thermal-limitHat tip
I am a scientist who researches climate hazards. This week I have published research on the potential for a catastrophic cyclone-heatwave combo in the global south.www.sciencealert.com