Rothman issued a dreaded warning in 2017 that the oceans, if they absorbed much more carbon from human carbon dioxide emissions, could start a massive extinction by 2100. Its article in the journal Science Advances was titled: "Disaster thresholds in the Earth system."
In his new article titled "Characteristics of an Excitable Carbon Cycle," published Monday in the Proceedings of the National Academy of Sciences, he described the development of a simple mathematical model to represent the carbon cycle in the upper part of the ocean and its possible behavior.
The carbon cycle is the process by which carbon circulates in various forms through nature. In one part of the cycle, carbon is exchanged between ocean surface waters and the atmosphere, or stored for long periods in the depths of the ocean.
Using the model, Rothman stated in the study that carbon cycle disturbances are "caused by the disruption of a steady state permanently beyond a threshold".
"This article suggests (…) that the magnitude of many disturbances is determined not by the strength of external stressors, but by the intrinsic dynamics of the carbon cycle," he wrote.
In the university statement, Rothman said: "When you go over a threshold, the system responds freely".
He also warned in the study that the effect of the unprecedented carbon injection into the ocean currently caused by the emission of carbon dioxide into the atmosphere could be similar to that of injecting at a rate lower over a much longer period caused by massive volcanic activity there are millions of years.
"The unusually strong but geologically brief duration of modern anthropogenic oceanic CO2 absorption is roughly equivalent, with respect to its potential for major excitation, to relatively small but longer disturbances associated with volcanism." massive in the geological past, "wrote Rothman.
Changes in the amount of carbon stored by the ocean have occurred periodically during the Earth's history. Most of the disturbances were relatively benign, but all past mass extinction events were accompanied by such disturbances, the study said.
The increasing levels of carbon dioxide in the atmosphere since the industrial revolution are at the origin of climate change, with impacts such as global warming, bad weather and rising sea levels. But rising carbon emissions are also impacting the oceans, which absorb about 30 percent of the carbon dioxide released into the atmosphere, according to the National Ocean and Atmospheric Administration.
Excess carbon dioxide makes the oceans more acidic, which affects the ability of marine organisms to build their shells and skeletons.
The Rothman model has incorporated a feedback mechanism that researchers say occurs when these organisms decline – leading to even more extreme ocean acidification.
The study, which he described as "exploratory theory" and "first attempt," suggests that once the threshold is reached, "the effects could be greater and more lasting than people think," he said. Rothman by phone. interview.
"Our emission trajectory seems to bring us to a level compatible with past thresholds. What happens after that is not clear, "he said.
"We should limit carbon dioxide emissions," said Rothman. "The carbon cycle is a non-linear system, and if you disturb it, surprising things can happen."
Globe Jeremiah Manion staff contributed to this report.