In a hotter world, periods of extreme heat are on the increase. And that presents a massive threat to life and health.

LONDON, 27 August, 2021 − In 2019, extreme heat claimed almost a thousand lives a day worldwide. And that number will grow. If the world cannot limit planetary temperature increase by just 1.5°C by 2100 − a target agreed by 195 countries − then deaths in heat waves will become substantial.

That’s the verdict of a careful study in one of the world’s oldest and most distinguished medical journals, The Lancet, which warns that almost half the world’s population and more than one billion workers are already exposed to episodes of extreme heat: more than a third of those workers already have what the scientists called “negative health effects.”

Helpfully, the researchers list these effects. They include “an increased risk of hyperthermia and cardiovascular failure or collapse, and increased risk of acute kidney disease.”

The researchers also looked at almost 65 million records of causes of death in nine nations to identify at least 17 conditions linked to heat-related death: ischaemic heart disease, stroke, cardiomyopathy and myocarditis, hypertensive heart disease, diabetes, chronic kidney disease, lower respiratory infection and chronic obstructive pulmonary disease.

Homicide, suicide, drowning and unintentional injury also increased with temperature. Yes, in 2019, more people died from extreme cold − an estimated 1.3 million − and 356,000 from extreme heat. But since 1990, cold-related deaths have increased by 31%. Deaths attributable to extreme heat have gone up by 74%.

“Urgent investment in research and measures to combat the risks of extreme heat is critical if society is not only to survive but thrive”

So besides taking global and concerted action to limit global heating to the 1.5°C target set in Paris in 2015, nations will need to start thinking of sustainable ways to keep populations cool in dangerous temperatures.

“Extremely hot days or heat waves that were experienced approximately every 20 years are now being seen more frequently and could even occur every year by the end of the century if current greenhouse gas emissions continue unabated,” said Kristie Ebi, of the University of Washington in the US, who led the study. “These rising temperatures combined with a larger and older population mean that even more people will be at risk for heat-related health effects.”

Extreme heat is on the way. One recent study in Nature Climate Change calculated that, as humans go on putting more and more carbon dioxide into the atmosphere, the number of week-long record-breaking extremes of heat will become between two and seven times more probable by 2050. By 2080, the probability increases by between three and 21 times.

The Lancet study says that steps to limit global heating and to mitigate the impact of heat extremes could save lives: at the same time global numbers are growing, so ever more people are likely to be at risk, especially in crowded cities.

In 1950, the number of urban dwellers was around 751 million. By 2018, this had grown to 4.2 billion. By 2030, six out of every 10 humans will be living in cities and the number of megacities − metropolitan areas with more than 10 million people − will have grown, from 31 in 2016 to 43.

Olympics ruled out

And air conditioning is unlikely to help. Between 1990 and 2016, the volume of carbon dioxide emitted by air conditioning units actually doubled, to make global heating even more intense. In 2019, space cooling systems added up to one billion tonnes of carbon dioxide to the atmosphere: this is 3% of the entire sum of global emissions that year.

Although more frequent, more prolonged and more intense extremes of heat are likely to hit hardest at the poorest, and at outdoor workers in many countries, such extremes will damage national economies and will diminish life for everybody.

By 2085, the researchers warn, very few of the world’s great cities will be able to host the summer Olympic Games because of the risk to athletes. One study in West Australia calculated that by 2070 the number of days on which it might not be safe to undertake even mild physical activity could increase by a factor of eight, or even 50-fold.

“As a result of human activity, it is inevitable that much of the planet’s population will be at greater risk of exposure to extreme heat than they are today,” said Ollie Jay of the University of Sydney in Australia, another of the authors.

“Amid stark projections about the increasing effects of climate change, urgent investment in research and measures to combat the risks of extreme heat is critical if society is not only to survive, but thrive, in a hotter, future world.” − Climate News Network