BOSTON — Researchers from the Massachusetts Institute of Technology (MIT) predict that by 2100, the earth’s oceans will contain so much carbon that a sixth mass extinction will begin.
“This is not saying that disaster occurs the next day,” explains Daniel Rothman, a professor of geophysics in the MIT Department of Earth, Atmospheric and Planetary Sciences, about his recent study in a media release. “It’s saying that, if left unchecked, the carbon cycle would move into a realm which would be no longer stable, and would behave in a way that would be difficult to predict. In the geologic past, this type of behavior is associated with mass extinction.”
Over the past 540 million years, Earth has been through five mass extinctions. Each event, according to scientists, was precipitated by events that disrupted or upended the natural cycling of carbon through the oceans and atmosphere. These global carbon cycle disruptions each took thousands or millions of years, and coincided with each massive die-off of many of the planet’s species.
Climatologists and other scientists have long speculated that the carbon cycle of our modern age is being fatally disrupted. The main difference between carbon cycle disruptions of the past and now, of course, is time. Carbon levels have only been rising precipitously for the past 100 to 150 years, hardly comparable to disruptions of ancient times.
Rothman and his team studied the significant alterations in the carbon cycle in the past, including those that caused each of the five major extinctions in Earth’s history. The researchers identified what Rothman calls “thresholds of catastrophe” in the carbon cycle, which, if exceeded, would lead to the kind of unstable environment that has caused mass extinctions in the past. If the carbon scales are upset faster than the natural environment can adapt, the environmental cataclysms that follow could play out and kill off huge amounts of life over millennia.
Rothman estimates that our oceans would have to accumulate 310 gigaton of carbon in order for a sixth extinction to takes place. He predicts humans are on pace to contribute that level of carbon across the globe by the year 2100. That said, he notes it would likely still take yet another 10,000 years for an actual catastrophic event to occur as a result. But once we’ve entered this “unknown territory,” it’s anyone’s guess as to exactly how and when the planet will react.
In the meantime, this dire warning should serve as good reason for humans to continue to look for ways to be more environmentally conscious.
“There should be ways of pulling back [emissions of carbon dioxide],” Rothman says. “But this work points out reasons why we need to be careful, and it gives more reasons for studying the past to inform the present.”
The study, which was supported in part by NASA and the National Science Foundation, was published September 20, 2017 in the journal Science Advances.