Environment

A sixth mass extinction event could reach the tipping point by 2100

A sixth mass extinction event ...
An MIT professor has studied the worst mass extinction events in Earth's history, and calculated that we may be well on the way to triggering a sixth by the end of the century
An MIT professor has studied the worst mass extinction events in Earth's history, and calculated that we may be well on the way to triggering a sixth by the end of the century
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An MIT professor has studied the worst mass extinction events in Earth's history, and calculated that we may be well on the way to triggering a sixth by the end of the century
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An MIT professor has studied the worst mass extinction events in Earth's history, and calculated that we may be well on the way to triggering a sixth by the end of the century

In the history of life on Earth, there have been five mass extinction events, with the most extreme example, the Permian extinction, wiping out some 95 percent of all marine life. Now, an MIT professor has analyzed the changes that took place in the carbon cycle leading up to these five main events – as well as dozens of smaller ones – and found that the end of this century could mark the tipping point for a sixth mass extinction event.

Each of the five major extinction events can effectively be traced back to one little troublemaker: carbon. As respiring organisms inhale oxygen and exhale carbon dioxide, and photosynthesizing plants do the opposite, the Earth naturally cycles carbon through the atmosphere and ocean. But disruptions to that process can throw the whole planet's climate out of whack, either by adding too much carbon at once or by speeding up the rate at which it's being added.

While carbon is the common culprit, different initial triggers may have set the ball rolling each time. The Permian extinction is thought to have been caused by huge magma pulses that belched carbon dioxide into the atmosphere, while the dinosaur-killing K-T event was thanks to an asteroid impact triggering planet-wide wild fires and volcanic eruptions.

Daniel Rothman, a geophysics professor at MIT, wanted to investigate potential warning signs of disruptions to the carbon cycle, and find thresholds that could be used to predict whether we might be heading into a sixth mass extinction event. The trouble was, historical carbon anomalies can take thousands of years to play out, while the clear spike we're seeing today can only be traced back a hundred years or so.

"How can you really compare these great events in the geologic past, which occur over such vast timescales, to what's going on today, which is centuries at the longest?" says Rothman. "So I sat down one summer day and tried to think about how one might go about this systematically."

He developed a mathematical formula that takes into account the critical rate and magnitude of changes to the carbon cycle, and related that to the timescale that the change is playing out over. Rothman found that there are two different thresholds that, if crossed, would trigger a mass extinction event.

For long-term changes, the threshold is one of speed: if carbon is added too quickly, global ecosystems don't have time to adapt. Meanwhile, for changes over shorter timescales it's all about magnitude: adding too much carbon will upset the delicate balance.

Rothman then applied those thresholds to historical data, to see if his model accurately predicted mass extinctions. He identified 31 times there were major changes in the carbon cycle over the last 542 million years, including the five mass extinctions, and studied the rate and magnitude of the change for each of these events.

In doing so, he discovered a common threshold that reliably predicted a mass extinction. Although they still involved huge disruptions to the carbon cycle, most of the 31 events stayed below that line, avoiding global catastrophe. But that threshold was crossed four times, corresponding to four of the five worst mass extinctions.

By looking at that critical rate, as well as the 10,000-year timescale it takes for the marine carbon cycle to correct itself after a major disruption, Rothman calculated how much carbon it would take today to tip us over the threshold. According to his calculations, if an extra 310 gigatons of carbon is added – say, through human action – it would tip the carbon cycle into "unknown territory" that may lead to mass extinction.

"This is not saying that disaster occurs the next day," says Rothman. "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."

If 310 gigatons sounds like a lot, we have some bad news: humans are full steam ahead towards smashing that figure by the end of the century. According to the latest report from the Intergovernmental Panel on Climate Change, the best-case scenario for how much carbon humans will add to the oceans by the year 2100 is about 300 gigatons. In the worst case scenario, that number could surpass 500 gigatons.

Rothman isn't the only scientist to predict such a worldwide calamity in the next century. The World Wildlife Fund predicts that as many as two thirds of Earth's species could be wiped out in the next few years, while a Stanford study has found that currently, extinction rates of vertebrates are up to 114 times greater than the baseline.

The human impact on the Earth over the last few centuries is apparently so extreme that some groups are even calling for a new geological epoch, the Anthropocene, to be officially declared.

"There should be ways of pulling back," says Rothman. "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 research was published in the journal Science Advances.

Source: MIT

15 comments
aki009
My prediction is that 20 years from now these shills and their pronouncements of impending doom will be seen as just as self-serving and shortsighted as the promises of an impeding ice age and the end of oil were in the 1970's.
Bob
There are lots of key words in this article like carbon, major extinction, tipping point, mathematical model, and a few more. Nothing about pollution, over population, starvation, uncontrolled migration or war which are much more pressing to the current generation. Unfortunately for the con artists there isn't much money to be made or power to be grabbed by cleaning up pollution while over-population, immigration, and war are just chess pieces in the game of politics. That pretty much just leaves the carbon tax as the money maker and those controlling it as the power brokers. When I start reading about a new national rail system, more efficient mass transit or major upgrades in the power grid then I might start to believe our leaders are really serious about global warming.
c2cam
I have a problem when either events in past history or even knowledge of the universe is stated as fact. How do we know there have been only 5 mass extinctions. Perhaps there were more. Would it not be better to just say 5 known mass extinction events? Are we that full of ourselves that we think we know everything?
An article I read a short while ago was about the largest star in the universe. Really? We have no idea how big the universe is. If they had said the largest known star, or the largest start found to date in the known universe, that would be better.
It just really turns me off and most often, I don't even finish the article, since I wonder what else they are stating as fact, when really it isn't.
We need to state our facts based on what we know today, right now. There is much yet to still be discovered, and best not to imply that everything we know is carved in stone.
DavidRogerBrown
By the time the ignorant deniers get their heads out of the sand it will be too late for all. The baby boomers,especially the 1 %er's, have to be the most greedy,narcissistic generation ever. Not any concern about leaving a clean,healthy planet & resources for future generations. Our current disaster of a president & Congress is a perfect example. Mother Earth could care less,as it will spin on & continue to evolve. Time for us is indeed running out by our own short sighted stupidity. If not this,then other reasons mentioned below by Bob.
ADVENTUREMUFFINffin
Interesting assessment by MIT and the use of math to predict the future. To commentor Bob, after reading the book "Democracy in Chains", by Nancy MacLean, about the stealth takeover of all 3 branches governance, funded by Koch Brother David and Charles and academically supported by Libertarian such as Jame Buchanan, dont count on our government to do anything against the bidding of well funded industries, such as oil. Instead, expect anonymous operatives such as aki009 to keep the public skeptical of science based predictions.
WolfeSA
Actually Bob, you can merge the two. If we don't take care of the issues you raise, and more importantly, tackle the root cause which is an unsustainable economic model, the number if unstable countries and disaffected people will grow. This will then make cohesive efforts to rein in coal power, deforestation, pollution etc harder and harder. As the rich get more jumpy, the chances of global action will drop and so on and so on. We need a new system, something that regulates growth choices.
wildbill
Aaaah I love the deniers, blame it on everything other than the petros. We live in a freaking bubble floating in a void. The carbon we burn that was stored within the rocks as liquid doesn't magically go away. It is added to the system. Every car that passes by, every time you flip a switch, everytime your future burger bealches adds more carbon to the bubble. What he is saying is there is a time when the OCEANS become acid from all the carbon. That's the extinction level event, not a rock hitting us, not a volcano going nuts, the fricking OCEAN becomes uninhabitable.
That's when we all go bye, bye and sadly you are all happy it won't be you. Course it's your kids but who cares about them anyway?
ljaques
Hmm. It started as Global Warming, then the name was changed to Climate Change, and now it's Tipping Point. So now we're all gonna die because I drive a Toyota pickup instead of a Chebby Bolt, eh? Sorry, but I don't buy the Rothman line any more than I bought Algore's line (which has since been proven entirely wrong.) I'm a Baby Boomer and learned about the ecology in 1970. Since then, I've done more for the eco system than any millennial is liable to in his lifetime. It counted more back then because things were dirtier. But I'll be d*mned if I'm going to give up natural gas for my heater, gasoline for my truck (which I need, and only drive 3,000mi/yr, or I'd have a Tesla 3 by next month), and coal or nuclear power in addition to renewable energies for my lights. I'm already losing 15% in gas mileage to that darned corn ethanol that costs so much. Anyway, to MIT, I say NEXT, and go back to my small footprint life. My 1,125W of solar helps, too.
eric.verhulst@altreonic.com
Correlation is not causation. If the approach would have been scientifically correct, then one should know that making such a (model based) prediction must be backed up by an explanation of the mechanisms behind it. In all the major mass extinctions that we know of, earth was covered in a cloud of "dust" (like when a major vulcano erupts). Of course that went hand in hand with a major injection of CO2, dust and other gases (like SO2) in the atmosphere. This caused a major disruption in the amount of energy that we get daily from the sun. Why was that not analysed in the model? Today, we also have a kind of mass extinction going on. As far as I can see, this his not so much to do with CO2 but with overpopulation resulting in overfishing, overhunting and destroying vegetation (read: habitats for a lot of life forms) because in developing countries, people need the wood to cook and heat themselves. The analysis I present has nothing to do with being a "denier" or an "warmist", but simply with trying to analyse the facts and how a scientific approach can helps us in finding the facts. Clearly, being a professor at MIT is not a sufficient condition.
MartinVoelker
Bill McKibben and 350.org have offered a simpler yet convincing math using only 3 figures: We can emit 565 more gigatons of carbon dioxide to hopefully stay below 2°C of warming — but burning available fossil fuel reserves would emit 2,795 gigatons of carbon dioxide — five times the safe amount. Let’s face it: Fossil fuel companies are planning to burn it all with no regard for impending collapse.