Mass Extinction Event Looms As Oceans Poised To Breach Carbon Dioxide Threshold

Continued accumulation of carbon dioxide in the world’s oceans could trigger a chemical reaction in the planet’s carbon cycle that could potentially lead to a mass extinction event.

MIT geophysics professor Daniel Rothman explained that once the rate at which the ocean stores carbon dioxide surpasses a certain threshold, the planet could respond with an unstoppable cascade of chemical feedbacks. This phenomenon could cause extreme acidification of the ocean and could release more carbon dioxide.

In a study published in the Proceedings of the National Academy of Sciences on July 8, Rothman showed that the current carbon dioxide levels in the ocean could be fast approaching a tipping point threshold.

He warned this could lead to extreme acidification of the ocean, similar to the kind that contributed to the Permian–Triassic mass extinction that happened about 250 million years ago.

Rothman looked through geologic records and found that over the past 540 million years, the storage of carbon in the ocean changed abruptly but recovered several times.

He also observed that the “excitation” of the carbon cycle tends to be most dramatic near the time of four of the five great mass extinction events in the planet’s history, suggesting that the patterns observed today have correlation with catastrophic events.

Unlike the previous spikes in carbon dioxide levels in the ocean, however, current levels are rising faster due to human activities. Humans have been releasing carbon dioxide at an unprecedented level just as volcanic eruptions and other natural causes that occurred in the past disturbed the carbon cycle.

“The relatively slow rate of CO2 injection commensurate with massive volcanism at geologic timescales turns out to be roughly equivalent, in terms of its potential to reach the threshold, to the much stronger but briefer perturbation of the modern carbon cycle,” Rothman wrote in the study.

Using a mathematical model, Rothman found that when carbon is continuously pumped into the oceans as humans have been doing increasingly since the late 18th century, the world’s oceans could eventually reach the carbon dioxide threshold.

“It’s difficult to know how things will end up given what’s happening today,” Rothman said. “But we’re probably close to a critical threshold. Any spike would reach its maximum after about 10,000 years. Hopefully that would give us time to find a solution.”