‘Triple whammy’ of extreme heat could make Earth uninhabitable for humans, climate models reveal

‘Triple whammy’ of extreme heat could make Earth uninhabitable for humans, climate models reveal

Humans could be wiped out by the formation of a ‘supercontinent’ in the next 250 million years, according to a new study.

The research, published in the scientific journal Nature Geoscience, offers the first ever supercomputer climate models of the distant future.

It predicts that as continents converge to form one hot, dry and largely uninhabitable supercontinent, it will “probably lead to a climate tipping point” and the “mass extinction” of mammals.

A rise in planet-heating volcanic activity and increased warming from the sun will result in unprecedented heat that makes the Earth unliveable for humans, it predicts.

“The outlook in the distant future appears very bleak,” says the study’s lead author Dr Alexander Farnsworth, a senior research associate at the University of Bristol. Carbon dioxide levels could be double current levels in 250 million years’ time.

“With the sun also anticipated to emit about 2.5 per cent more radiation and the supercontinent being located primarily in the hot, humid tropics, much of the planet could be facing temperatures of between 40 to 70°C,” he adds.

Why would the new supercontinent make Earth uninhabitable?

Adaptations like hibernation and fur have helped mammals survive extreme cold in the past. However our tolerance to high temperatures has remained largely constant, the researchers note.

If the climate simulations modelled in the study played out, most mammals would be unlikely to survive the prolonged excessive heat.

Although the Earth will still be within the habitable zone in 250 million years’ time, the formation of a supercontinent with elevated CO2 will make most of the world uninhabitable for humans and other mammals. The findings show that only somewhere between 8 and 16 per cent of land would be habitable.

Tectonic processes that cause the Earth’s continents to merge would lead to more frequent volcanic eruptions, which release huge amounts of carbon dioxide. This would contribute to the extreme heat.

“The newly-emerged supercontinent would effectively create a triple whammy, comprising the continentality effect, hotter sun and more CO2 in the atmosphere, of increasing heat for much of the planet,” says Dr Farnsworth. “The result is a mostly hostile environment devoid of food and water sources for mammals.”

Facing temperatures of between 40 and 50°C and high humidity, humans would be unable to cool their bodies through sweat, ultimately “sealing our fate”.

Will fossil fuels make Earth uninhabitable before the supercontinent forms?

When we’re urgently pushing to drive down emissions, 250 million years seems a long way off.

But the fact that parts of the planet will still be inhabitable in the distant future doesn’t make our efforts futile.

Human-induced global warming is already a major source of heat stress and death in some regions - and the problem is getting worse.

“It is vitally important not to lose sight of our current climate crisis, which is a result of human emissions of greenhouse gases,” says the study’s co-author Dr Eunice Lo, a research fellow in climate change and health at the University of Bristol.

“While we are predicting an uninhabitable planet in 250 million years, today we are already experiencing extreme heat that is detrimental to human health. This is why it is crucial to reach net-zero emissions as soon as possible,” she urges.

The researchers worked on the assumption that humans will stop burning fossil fuels. Failing to do so could see CO2 levels rise “much, much sooner”, they warned.

How was the research carried out?

UK Met Office climate models and a University of Bristol supercomputer were used to simulate temperature, wind, rain and humidity trends for the supercontinent - known as Pangea Ultima - that is expected to form in the next 250 million years.

The international team of scientists also used models of tectonic plate movement, ocean chemistry and biology to estimate future CO2 levels.

The research was part of a funded project, backed by the UK Research and Innovation Natural Environment Research Council (UKRI NERC) looking at the climates of supercontinents and mass extinctions.