This yellow rock is where magma burned through a coal bed 250 million years ago, releasing CO2. (Courtesy of Ben Black)
Today’s unsettling comparison to ‘the great dying’
250 million years ago, rising greenhouse-gas levels set off catastrophic changes.
By Moises Velasquez-Manoff | Staff writer of The Christian Science Monitor/ November 19, 2008 edition
New York
In 1980, scientists Luis Alvarez and his son, Walter, proposed a new explanation for the dinosaurs’ disappearance 65 million years ago: a meteor strike. Initially, the idea was met with resistance. But the evidence was convincing: a sediment layer high in iridium, an element common in asteroids, was found the world over, along with a 110-mile-wide impact crater in the Yucatán of the same age. What started as a fringe idea has gone mainstream.
Now scientists are rethinking another of earth’s great die-offs. The end-Permian extinction 251 million years ago was the worst of earth’s five mass extinctions. Ninety percent of all marine life and 70 percent of terrestrial life disappeared. It took five million years, perhaps more, for the biosphere to recover.
But while the die-off was uniquely devastating, evidence of a single cataclysmic event, like an asteroid strike, hasn’t been found in the geological record. Scientists now suspect that “the mother of all mass extinctions” was of Earth’s own making. And the more they learn about it, the more parallels they see to today’s world: A bout of greenhouse-gas-induced global warming, much like today’s, set off a chain of events that culminated in oxygen-depleted oceans exhaling poison gas.
And as in today’s human-dominated earthscape, life was already stressed.
“Something came along and kicked it over the edge,” says Linda Elkins-Tanton, an assistant professor of geology at the Massachusetts Institute of Technology in Cambridge, Mass. She heads a recently launched multidisciplinary effort to study the extinction. “Should there be a great kick [now], we are in a position for a great die-off,”
she says.
Two hundred and fifty million years ago, Earth was emerging from a period of glaciation. The transition from icehouse to greenhouse was already stressing life, scientists think. Then magma began bursting through the crust of what is now Siberia. The eruption was tremendous, says Professor Elkins-Tanton. Over the course of maybe 1 million years, enough lava flowed to cover the continental United States half a mile deep.
The crust through which it bubbled contained vast coal and limestone deposits from an earlier time. As it burned through this fossilized organic material, it released huge amounts of carbon.
Today, by burning fossil fuels, humans are again releasing carbon sequestered long ago, and at a similarly rapid rate.
“There may be some pretty direct parallels between the end-Permian extinction and today,” says Jonathan Payne, professor of geological and environmental sciences at Stanford University in Palo Alto, Calif.
The eruption and release of greenhouse gas was just the beginning. The warmer atmosphere heated the ocean surface, effectively capping the seas with a warmer layer. The result: The overturning of the ocean’s water, which keeps deep waters oxygenated, likely stopped. Deeper waters became oxygen-depleted.
Meanwhile, erosion accelerated on land, says Lee Kump, professor of geosciences at Penn State University, University Park, dumping more fertilizers, like phosphorus, into the seas. High nutrient influx led to plankton blooms. As the organic matter decomposed, it sucked up what oxygen remained – the same process now observed in the world’s dead zones. Widespread ocean anoxia (oxygen depletion) suffocated much oxygen-dependent marine life.
Then came the final blow. In waterways that are anoxic beyond a certain depth, like today’s Black Sea, oxygen-dependent organisms live near the surface and oxygen-avoiding microbes live deeper. Scientists call the boundary between them the “chemocline.” Organisms below the chemocline “breathe” sulfates, not oxygen. Just as oxygen-dependent organisms exhale CO2, these bacteria give off hydrogen sulfide, a gas toxic in high concentrations to many life forms, including plants and animals. The gas neatly explains one of the mysteries of the Permian die-off: how an extinction event that began at sea could have decimated life on land.
Scientists find molecular “signatures” of anaerobic organisms at what was the water’s surface in end-Permian times. Lack of oxygen let sulfate-breathers rise from the ocean deep and spew hydrogen sulfide directly into Earth’s atmosphere.
Hydrogen sulfide would have also eaten holes in the earth’s protective ozone layer. Plants and animals either suffocated directly – atmospheric oxygen levels plummeted to 15 percent (it’s about 21 percent today) – or succumbed to the combination of long-term stresses.
And the lessons for today? At the Permian boundary, “you’re in a state of gradual warming, then as you approach that boundary, the warming increases dramatically,” says Jeff Kiehl, a senior scientist at the National Center for Atmospheric Research in Boulder, Colo. “It wasn’t a linear warming.” Says Professor Kump: “This shows us what could happen if we push the system too hard…. We don’t know where the intermediate thresholds are.”
We’re still some way from the atmospheric CO2 levels hypothesized at the end-Permian extinction – which were perhaps 10 times preindustrial levels, or 2,800 ppm. Yet, according the Intergovernmental Panel on Climate Change, if trends continue we’re still approaching 1,000 ppm of CO2 by 2100. That’s not Permian-extinction levels, but it would be the highest CO2 concentration in 80 million years, and a level at which both ocean anoxia and lesser extinctions have occurred.
“Do we want to put ourselves on a very risky path of possibly repeating earth’s history, or do we want to be more cautious?” says Dr. Kiehl. “I would hope as a conscious species that we would choose the latter.”
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Comments
2. Bill | 11.20.08
Relax people! Like my favorite Surgen General of all time (Joslyn Elders)used to say “…we al have to die of something sometime…”
4. Doug | 11.20.08
While what Bill says is true, I would prefer it not be the result of blatant stupidity.
5. Judynz | 11.20.08
For crying out loud you are being bombarded with all kinds of theories most untrue.
I see mathmatically you could give everyone in the world a 1/4 acre section in Australia & still have Queensland bare.
As for the argument about whether or not man is responsible for CLIMATE CHANGES you must first define what is being said & what camp its coming from. NOTE well that few speak of the deliberate BOILING of the Ionisphere & the many disaserous effects involed. (via American & Russian technologies. Who speaks of the MASSIVE pollutions of war & how many thousands of years this pollution remains?….& how around 80% of pollution comes from vehicles & how it has NEVER been necessary to run vehicles on (oil)petrols.
The list goes on & on.
6. Mike Moxcey | 11.21.08
Whether global warming is ‘true’ or not is as irrelevant as whether it is manmade or not. If you take a long view, the problem is overpopulation. (Argument: if there were less people, we’d just move our farms and cities to where the food would grow just like in the past.) Looking 250 years into the future, or 10 generations,
Mankind has 4 options:
1)go extinct,
2)maintain dynamic population equilibrium with excess population culled thru wars and famines,
3)maintain stable population (and hope climate never changes or decrease our popn so large amounts of land area are off-limits (either is unlikely)), or
4)move into space.
We still need to address the current things causing climate change to give us time, but any longterm ‘fix’ requires a movement into outer space if we wish to avoid war or other forms of population control.
7. John Berbatis | 11.21.08
Many citizens of earth do not realize the seriousness of the parlous state of the global environment, but will just prior to their obliteration by ‘a raging mother nature’. Judging by the current extremes of global weather conditions and the recent increase in worldwide seismic activity, I believe humanity will face extinction before the end of 2008. In the past ten years there has been an exponential melting of the ice sheets and a noticeable disintegration of the ice shelves, owing to ‘global warming’. The loss of mass from the underlying Tectonics Plates causes them to ascend (iso-static rebound), and this results in an increase in the intensification and frequency of global seismological activity. The seismic data of the past ten years confirm this conjecture. Furthermore, the ice shelves impede the flow of glaciers and ice sheets into to the oceans; and when the ‘polar regions’ are subjected to unprecedented seismic upheavals, these events will then cause the ice sheets and glaciers to be dislodged en masse into the oceans. This occurrence will then instantly destabilize the earth’s surface weight distribution (isostasy), and so precipitate a ‘crust displacement’ (Mag. 12). i.e., axis change. The previous subterranean extraction of fossil fuels will greatly exacerbate this impending Apocalypse. Currently, the excessive amount of carbon and methane gasses in the atmosphere is causing catastrophic weather conditions, globally - and this situation will rapidly deteriorate… ‘a climate runaway’. The global environmental and geo-political situations are now coalescing into a ‘critical mass’; so I believe humanity can expect a catastrophe of worldwide proportions within this year. In 1998, I submitted my dissertation on the above matter to various eminent institutions and individuals, to which I received positive responses from PM’s Tony Blair, Helen Clark (NZ) & Lee Kwain Yew (Singapore) as well as the UN’s - Dr Mary Robinson, Hon. Justice Michael Kirby AC CMG of the High Court of Australia, Premier P. Beattie (Queensland, Au) and Chief Justices of Canada, Norway, Taiwan, Mexico and Netherlands etc,. Reality rules this universe! … not unproductive discussion & debate? John Berbatis [Editor’s note: The commenter left his phone number and address, which have been removed.]
8. Judy | 11.21.08
Dear John! If you prognosticate the end of the world by 12/31/08, then I think I will just go ahead and shop. If nothing else, the economy will rebound just in time for all to go black — pun intended!
9. Luise of the Phoenix | 11.22.08
Don’t know about you, but seems to me the announcing the death of the human race by the end of 2008 is highly presumptive. Alternate and renewable sources of energy must be developed.
There’s no doubt that the global climate crisis grows worse with every passing day, but as long as international mega-corporations think there’s one more dollar to be squeezed out of fossil fuels, the pollution of air, land and sea will continue.
It’s the old Golden Rule distorteded: “Those who have the gold make the Rules.”
10. agueybana | 11.22.08
If there are more doomday Johns out there, please feel free to donate your worldly goods to my favorite charity. I need more cash flow to help me by in the present recession. I promise to toast to you on New Year’s day!!!!
11. Kerry Joels | 11.24.08
John Young, former Apollo and Shuttle Astronaut, and former Director of the Astronaut Program said: “Single planet species don’t survive”. Maybe going back to the moon and on to Mars isn’t so far fetched.
12. Amber Scott | 11.24.08
We may be in for a ‘great dying’ but I think that there is a better corollary between our warming climate now and what happened during the PETM mass extinction 55 million years ago (Paleocene-Eocene Thermal Maximum).
In that instance, the world warmed up due to release of methane. The methane we could potentially release today is from glacial melt. There are trillions of bacterium trapped under the northern permafrost. A thawing of the permafrost could result in these long-dormant creatures coming back in a massive bloom, consuming the thawed rotted material under the ice, and releasing large amounts of methane.
Unlike carbon dioxide which captures 2 molecules of oxygen when it’s burned, methane captures 4. So if we see an increase in global warming, we may be on the way to asphyxiation - which was exactly what happened during the PETM extinction.
13. George Emery | 11.28.08
Every one wakeup stop wasting energy pretending you know something about the passed (dreaming) and fearing the future make the changes that you think you need to make as an indavidual in the now!stop talking about it, and injoy the moment becouse that is all there really is, create a relationship with the earth and start living
14. Michael | 12.04.08
“Unlike carbon dioxide which captures 2 molecules of oxygen when it’s burned, methane captures 4″
How are you getting C02 to burn? The science I was taught suggested that C02 was the result of something carbon based (like… let’s say methane for example) burning… Am i missing something here?
“humanity will face extinction before the end of 2008″
So I should just go put a supercharger on my Hummer, eat whale steaks and small children since the planet is going down the tube in a few weeks?
That’s the sort of stuff that makes the mainstream look rather askance at the eco movement.
This is perhaps what we get for teaching “self esteem” and liberal arts in place of logic and science in school :(
Michael
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1. Michael | 11.19.08
What concerns me is the possibility that human activity, even if successfully curtailed, could still pace the way for a geological event one or even several orders of magnitude smaller to “tip the scales” in this equation for disaster wee trying so desperately to avert. What happens when minor vulcanism combines with our own greenhouse gases? Our estimates for “safe zones” and margins of error could be undone in an instant.