In Brief
Professor of geophysics Daniel Rothman has concluded that if 310 gigatons of carbon are added to the world's oceans by 2100, they'll be capable of triggering a sixth mass extinction event. This would potentially propel the world into what he calls "unknown territory."

“Thresholds of Catastrophe”

Daniel Rothman, a professor of geophysics in MIT’s Department of Earth, Atmospheric, and Planetary Sciences, recently published a study in Science Advances that could change how we think about the future of our environment.

For his study, Rothman analyzed changes in the carbon cycle over the past 540 million years, including all five mass extinction events, and used mathematics to demarcate “thresholds of catastrophe” in the carbon cycle. Moving beyond those thresholds can catapult the Earth into an unstable environment, causing a mass extinction event.

Based on his research, Rothman asserts that, if we don’t change course, the world may enter what he calls “unknown territory” by 2100, causing an ecological disaster that would take 10,000 years to fully play out.

Those are scare quotes.

Rothman suggests that these mass extinction events are triggered after one of two critical thresholds are passed. The first takes place over a longer timeline. If changes in the carbon cycle, no matter how small, progress faster than global ecosystems can adapt, we have a mass extinction event. On a shorter timescale, the size and magnitude of the changes are important. If significant enough, the changes will increase the probability of a mass extinction event.

Five mass extinction events have occurred on the Earth in the last 540 million years. Each one caused massive disturbances in the normal cycling of carbon through the oceans and atmosphere. For thousands to millions of years, these events coincided with the extermination of marine species worldwide.

According to Rothman, the recent rapid spike in carbon dioxide emissions could lead to a sixth mass extinction. The deciding factor will be whether a critical quantity of carbon makes its way into our oceans. He calculates this amount to be about 310 gigatons — roughly the same amount of carbon that human civilization will have added to the oceans by the year 2100, based on Rothman’s estimates.

“This is not saying that disaster occurs the next day,” Rothman explained in a press release. “It’s saying that, if left unchecked, the carbon cycle would move into a realm which would no longer be 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.”

Parameters of Doom

Today, many scientists speculate about how the climate change we’re currently experiencing will potentially affect the planet’s carbon cycle. Could it push the world into a sixth mass extinction?

The World’s Worst Mass Extinctions
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We’ve already seen a steady rise in carbon dioxide emissions since the 19th century, but interpolating the recent spike of carbon into a diagnosis of imminent mass extinction is no easy task. The difficulty lies in the dissimilar timespans — comparing changes that took place over thousands or millions of years to the century-long spike in which we’re currently living.

We like to think nobody wants to trigger mass extinctions on the Earth, above or below water. Sadly, preserving the ecosphere we need to survive is not a priority for many of those in power, on both sides of the American political spectrum. It’s up to us to spread the word that this “threshold of catastrophe” is a bullet we should most definitely be trying dodge.