Extreme heat likely to kill all mammals in 250 million years, study suggests

Extreme heat is likely to make all mammals extinct in 250 million years when the Earth’s continents merge to form one hot, dry, uninhabitable supercontinent, a study suggests.

Results from the first ever supercomputer climate models into the distant future show how the sun will become brighter with tectonic movements unleashing huge amounts of carbon dioxide (CO2) into the air through volcanic eruptions.

This is set to warm the planet to such an extent that many mammals will be unable to survive – and only 8% to 16% of this future continent will be habitable.

Mammals, including humans, are better adapted to living with cold, with many species growing fur or hibernating. They are less able to deal with extreme heat.

Lead author Dr Alexander Farnsworth of the University of Bristol said: “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.

“The result is a mostly hostile environment devoid of food and water sources for mammals.

“Widespread temperatures of between 40C to 50C, and even greater daily extremes, compounded by high levels of humidity would ultimately seal our fate.

“Humans – along with many other species – would expire due to their inability to shed this heat through sweat, cooling their bodies.”

The scientists believe that CO2 levels could rise from around 400 parts per million (ppm) today to more than 600 ppm by the time of the formation of the supercontinent – named Pangea Ultima.

This assumes however that humans stop burning fossil fuels – “otherwise we will see those numbers much, much sooner”, warned Professor Benjamin Mills, who calculated the future CO2 projections for the study.

Publishing their work in the journal Nature Geoscience, the researchers said these results should not mean any relaxation of human efforts to stop climate change as rising temperatures are already damaging people’s health.

Co-author Dr Eunice Lo of the University of Bristol said: “It is vitally important not to lose sight of our current climate crisis, which is a result of human emissions of greenhouse gases.

“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.”

The international team of scientists simulated temperature, wind, rain and humidity trends for Pangea Ultima and used models of tectonic plate movement, ocean chemistry and biology to estimate future CO2 levels.

They also said that when looking through space at other planets potentially suitable for humans, people should take into account how continents are spread as being in the habitable zone of a solar system may still mean a planet is uninhabitable.

Dr Farnsworth said: “The outlook in the distant future appears very bleak. Carbon dioxide levels could be double current levels.

“With the Sun also anticipated to emit about 2.5% more radiation and the supercontinent being located primarily in the hot, humid tropics, much of the planet could be facing temperatures of between 40C to 70C.

“This work also highlights that a world within the so-called habitable zone of a solar system may not be the most hospitable for humans depending on whether the continents are dispersed, as we have today, or in one large supercontinent.”