Planet Earth has been around for about 4.5 billion years, and it has changed a lot in that time. What started as a ball of molten, bubbling magma eventually cooled and a few small tectonic plates formed; about a couple of billion years later, the planet was covered with various formations of supercontinents and teeming with life.
But cosmologically speaking, the Earth is still young. We are barely more than a third of their likely lifespan behind us and there are still many changes ahead.
Unfortunately, it seems unlikely that we will survive it. According to a study published last year that used supercomputers to model the climate over the next 250 million years, the world of the future will again be dominated by a single supercontinent – and will be virtually uninhabitable for any mammal.
“The outlook for the distant future appears very bleak,” confirmed Alexander Farnsworth, senior research associate at the Cabot Institute for the Environment at the University of Bristol and lead author of the study, in a statement.
“Carbon dioxide levels could be twice as high as they are today,” he explained. “Because the Sun is also expected to emit about 2.5 percent more radiation and the supercontinent lies primarily in the hot, humid tropics, large parts of the planet could be exposed to temperatures between 40 and 70 °C. [104 to 158 °F].”
The new supercontinent – known as Pangea Ultima, in reference to the ancient supercontinent Pangaea – would represent a “triple blow”, says Farnsworth: Not only would the world have to cope with around 50 percent more CO2 in the atmosphere than the current values; Not only would the Sun be hotter than it is now – that’s what happens to all stars as they age, due to the evolving push-and-pull between gravity and fusion in the core – but the size of the supercontinent itself would make it so almost completely uninhabitable. This is due to the continentality effect—the fact that coastal areas are cooler and wetter than inland areas, and the reason why summer and winter temperatures in Lawrence, Kansas, for example, are so much more extreme than in Baltimore.
“The result is a predominantly hostile environment with no food or water sources for mammals,” Farnsworth said. “General temperatures between 40 and 50 degrees Celsius and even greater daytime extremes, coupled with high humidity, would ultimately seal our fate. Humans – like many other living beings – would die because they cannot give off this heat through sweat and thus cool their bodies.”
And here’s the kicker: This is a best-case scenario, so to speak. “We think CO2 could rise from around 400 parts per million (ppm) today to over 600 ppm in many millions of years,” said Benjamin Mills, professor of Earth system development at the University of Leeds, who led the calculations for the study. “This assumes, of course, that people stop burning fossil fuels, otherwise we will see these numbers much, much sooner.”
So while the study paints a dire picture of what Earth will look like many millions of years from now, the authors warn us not to forget the problems ahead. “It is vital not to lose sight of our current climate crisis, which is due to human emissions of greenhouse gases,” warned Eunice Lo, research fellow in climate change and health at the University of Bristol and co-author of the paper.
“We are already experiencing extreme heat that is detrimental to human health,” she emphasized. “That’s why it’s important to achieve net zero emissions as quickly as possible.”
The study was published in the journal Nature Geoscience.