Climate change is increasingly creating conditions that are fatal to humans across vast swathes of the planet – Scotsman comment

46 days to Cop26: Human beings have evolved over millennia to be able to live in almost every corner of the planet.

As temperatures reach 40 degrees Celsius, people cool off in a canal in Lahore, Pakistan, in May last year (Picture: Arif Ali/AFP via Getty Images)

We are, for example, much better at getting rid of excess heat than dogs, as demonstrated by the fatal risks they face in hot cars but we do not.

When we sweat, the moisture evaporates and this cools us down, meaning humans can survive in many places that are much hotter than our body temperature, providing we have access to water.

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But this highly efficient system is being tested to its limits by climate change.

A new analysis by the BBC has found that the number of days a year when the temperature goes above 50 degrees Celsius has doubled since the 1980s. On average between 1980 to 2009, this happened on 14 days a year, but between 2010 and 2019 there were 26 days of at least 50-degree heat a year.

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However, the temperature at which humans can be at risk is actually much lower than this because of the effect of humidity.

To maintain a normal body temperature, the skin needs to be about 35C, so if temperatures rise above this in 100 per cent humidity, people will start to die because our main cooling process, sweating, stops working.

Also, when we move around, this generates heat which once again reduces the air temperature necessary for heat-related deaths. For example, in the deadly heatwaves in Europe in 2003 and Russian in 2010, wet-bulb thermometer readings, which record temperature as if humidity was 100 per cent, were no greater than 28C.

A study published in the journal Environmental Research Letters last year concluded the 1C rise in average global temperatures had increased the number of people experiencing at least one day a year of wet-bulb temperatures of 33C or more from 97 million to 275 million. They projected this would rise to 508 million at 1.5C of global warming and 1.22 billion at 3C.

These figures are a reminder of why the world needs delegates at the UN’s Cop26 summit in Glasgow in November to reach a meaningful agreement. For, just as dogs did not evolve to survive the unnatural conditions of a car, humans have not evolved to survive the new climate we are creating in many parts of the world.

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