Unprecedented high temperatures are likely to cause the next mass extinction since the dinosaurs, wiping out nearly all mammals in about 250 million years, according to a new study. The research, led by the University of Bristol and published in the journal Nature Geoscience on September 25, presents the first supercomputer climate model of the far future and shows how climate extremes will dramatically intensify when the world's continents eventually merge into a hot, dry and largely uninhabitable supercontinent.
Factors causing extreme temperatures
The findings predict that as the sun becomes brighter, releasing more energy and warming the planet, the heat will intensify further. Tectonic processes in the crust that led to the formation of supercontinents also led to more frequent volcanic eruptions, which produced large amounts of carbon dioxide and released them into the atmosphere, further warming the Earth.
Historically, mammals, including humans, have survived thanks to their ability to adapt to extreme weather, particularly through their fur and adaptations such as hibernating in the cold and briefly in warm weather.
While mammals have lowered their survival limits at low temperatures over the course of evolution, their tolerance of upper temperature limits has remained largely unchanged. This makes it harder for them to overcome exposure to long-term overheating, which would ultimately prove unviable if climate simulations were implemented.
Effects on mammals
Lead author Dr Alexander Farnsworth, senior research associate at the University of Bristol, said: "The emerging supercontinent would effectively create a triple whammy, including a continental effect, a hotter sun and more carbon dioxide in the atmosphere, increasing the heat over much of the planet. The result would be that large parts of the planet would The harsh environment in some areas with no food and water sources for mammals. Temperatures ranging from 40 to 50 degrees Celsius, with daily extremes of even higher, combined with high humidity, will ultimately determine our fate. Humans and many other species will die due to their inability to sweat to dissipate heat and cool their bodies."
While human-induced climate change and global warming are likely to be responsible for increasing heat stress and mortality in some areas, research suggests that Earth should remain largely habitable until seismic landmass changes occur deep in the future. But when the supercontinent formed, research suggests that only 8 to 16 percent of the landmass was habitable for mammals.
Co-author Dr Eunice Lo, a climate change and health researcher at the University of Bristol, said: "It is vital that we do not ignore the current climate crisis, which is caused by human emissions of greenhouse gases. While we predict that the Earth will be uninhabitable for humans in 250 million years, today we are already experiencing extremely hot weather that is harmful to human health. This is why reaching net zero emissions as soon as possible is crucial."
Methodology and future forecasts
An international team of scientists used climate models to simulate trends in temperature, wind, rain and humidity in the next supercontinent called Pangea Ultima, which is expected to form within the next 250 million years. To estimate future carbon dioxide levels, the team used tectonic plate movement, ocean chemistry and biological models to map carbon dioxide inputs and outputs.
Professor Benjamin Mills of the University of Leeds, who led the calculations for future carbon dioxide, said: "We think that in the next few million years, carbon dioxide could rise from around 400 parts per million (ppm) now to more than 600 parts per million. This, of course, assumes that humans will stop burning fossil fuels, otherwise we would see these figures much sooner."
Dr. Farthworth, Visiting Professor of Tibetan Plateau Earth Systems, Environment and Resources (TPESER) at the Institute of Tibetan Plateau Research, Chinese Academy of Sciences, said: "The outlook for the distant future seems very bleak. Carbon dioxide levels may be double current levels. Solar radiation is expected to increase by about 2.5%, and the supercontinent is mainly located in the Pacific. In the hot, humid tropics, temperatures across much of the planet would reach 40 to 70 degrees Celsius. The work also highlights that worlds within the solar system's so-called 'habitable zone' may not be the most habitable for humans, depending on whether the continents are spread out like ours today or concentrated in one large supercontinent."
Relevance to exoplanet research
Additionally, this study illustrates the importance of tectonics and continental layout when studying planets outside our solar system, known as exoplanets. While Earth will still be in the habitable zone 250 million years from now, for mammals, the formation of supercontinents with elevated carbon dioxide levels will make much of the world uninhabitable. The findings suggest that the layout of a distant world may be a key factor in determining whether it is habitable.