"Once we're over the
threshold...you're dealing with how the Earth works, and it goes on its own
ride."
The continuous accumulation of
carbon dioxide in the planet's oceans—which shows no sign of stopping due
to humanity's relentless consumption of fossil fuels—is likely to trigger
a chemical reaction in Earth's carbon cycle similar to those which happened just
before mass extinction events, according to a new study.
MIT geophysics professor
Daniel Rothman released new
data on Monday showing that carbon levels today could be fast approaching
a tipping point threshold that could trigger extreme ocean
acidification similar to the kind that contributed to
the Permian–Triassic mass extinction that occurred about 250 million years
ago.
Rothman's new research comes
two years after he predicted that a mass extinction event could take place at
the end of this century. Since 2017, he has been working to understand how life
on Earth might be wiped out due to increased carbon in the oceans.
Rothman created a model in
which he simulated adding carbon dioxide to oceans, finding that when the gas
was added to an already-stable marine environment, only temporary acidification
occurred.
When he continuously pumped
carbon into the oceans, however, as humans have been doing at greater and
greater levels since
the late 18th century, the ocean model eventually reached a threshold which
triggered what MIT called "a cascade of chemical feedbacks," or
"excitation," causing extreme acidification and worsening the warming
effects of the originally-added carbon.
Over the past 540 million
years, these chemical feedbacks have occurred at various times, Rothman noted.
But the most significant occurrences
took place around the time of four out of the five mass extinction events—and
today's oceans are absorbing carbon far more quickly than they did before the
Permian–Triassic extinction, in which 90 percent of life on Earth died out.
The planet may now be "at
the precipice of excitation," Rothman told MIT News.
On social media, one critic
called the study's implications about life on Earth "completely
terrifying."
The study, which was completed
with support from NASA and the National Science Foundation, also notes that
even though humans have only been pumping carbon into the oceans for hundreds
of years rather than the thousands of years it took for volcanic eruptions and
other events to bring about other extinctions, the result will likely be the
same.
"Once we're over the
threshold, how we got there may not matter," Rothman told MIT News.
"Once you get over it, you're dealing with how the Earth works, and it
goes on its own ride."
Other scientists said the
study, which will be published this week in the Proceedings of the
National Academy of Sciences, represents a clear call for immediate action to
drastically reduce the amount of carbon that is being pumped into the world's
oceans. Climate action groups and grassroots movements have long called on
governments to impose a moratorium on fossil fuel drilling, which pumps
about a
billion metric tons of carbon into the atmosphere every year.
"We already know that our
CO2-emitting actions will have consequences for many millennia," says
Timothy Lenton, a professor of climate change and earth systems science at the
University of Exeter. "This study suggests those consequences could be
much more dramatic than previously expected."
"If we push the Earth
system too far," Lenton added, "then it takes over and determines its
own response—past that point there will be little we can do about it."
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