Ancient Mass Extinction Tied To Ozone Loss, Warming Climate (sciencemag.org) 34
A reader shares a report from Science Magazine: The end of the Devonian period, 359 million years ago, was an eventful time: Fish were inching out of the ocean, and fernlike forests were advancing on land. The world was recovering from a mass extinction 12 million years earlier, but the climate was still chaotic, swinging between hothouse conditions and freezes so deep that glaciers formed in the tropics. And then, just as the planet was warming from one of these ice ages, another extinction struck, seemingly without reason. Now, spores from fernlike plants, preserved in ancient lake sediments from eastern Greenland, suggest a culprit: The planet's protective ozone layer was suddenly stripped away, exposing surface life to a blast of mutation-causing ultraviolet (UV) radiation.
Just as the extinction set in, the spores became misshapen and dark, indicating DNA damage, John Marshall, a palynologist at the University of Southampton, and his co-authors say in a paper published in Science Advances. It's evidence, he says, that "all of the ozone protection is gone." Scientists have long believed -- at least before humanity became a force for extinction -- that there were just two ways to wipe out life on Earth: an asteroid strike or massive volcanic eruptions. But 2 years ago, researchers found evidence that in Earth's worst extinction -- the end-Permian, 252 million years ago -- volcanoes lofted Siberian salt deposits into the stratosphere, where they might have fed chemical reactions that obliterated the ozone layer and sterilized whole forests. Now, spores from the end-Devonian make a compelling case that, even without eruptions, a warming climate can deplete the ozone layer, says Lauren Sallan, a paleobiologist at the University of Pennsylvania. "Because the evidence is so strong, it will make people rethink other mass extinction events."
Just as the extinction set in, the spores became misshapen and dark, indicating DNA damage, John Marshall, a palynologist at the University of Southampton, and his co-authors say in a paper published in Science Advances. It's evidence, he says, that "all of the ozone protection is gone." Scientists have long believed -- at least before humanity became a force for extinction -- that there were just two ways to wipe out life on Earth: an asteroid strike or massive volcanic eruptions. But 2 years ago, researchers found evidence that in Earth's worst extinction -- the end-Permian, 252 million years ago -- volcanoes lofted Siberian salt deposits into the stratosphere, where they might have fed chemical reactions that obliterated the ozone layer and sterilized whole forests. Now, spores from the end-Devonian make a compelling case that, even without eruptions, a warming climate can deplete the ozone layer, says Lauren Sallan, a paleobiologist at the University of Pennsylvania. "Because the evidence is so strong, it will make people rethink other mass extinction events."
Well... (Score:3, Interesting)
Plausible, but keep going [Re:Well...] (Score:2)
"Because the evidence is so strong, it will make people rethink other mass extinction events."
Only if it matches their views.
For the public, probably.
For the actual scientists, rethinking your views when new evidence is strong comes is the way things are normally done.
I will note, however, that at the moment you should consider this an interesting hypothesis. Let's see what other scientists say before rewriting the textbooks. The comment from other scientists, so far, is "What they propose seems quite plausible", and "Carmichael, for her part, would like to see evidence beyond the pollen grains that UV drove the extinction."
It'
Re: Plausible, but keep going [Re:Well...] (Score:2)
Agreed, more data would be great to support this. I think if the same DNA destruction was seen at multiple places around the world from spores of the same period, it would strengthen this argument (since stratospheric O3 loss at this level would be a global issue). Figure 4 in the actual article is really convincing that whatever it was, something bad happened to those spores for a short period of time.
This will at least guide further research to prove or disprove the theory. I'm trying to think of other po
Re: (Score:2)
Ahemm, the evidence cited is of darkening of spores, not of DAN damage. Personally, I'm going to have to go and RTFP over that, because I'd like to see a stratigraphically localised anomalous change in vitrinite reflectivity (or some other established monotonic temperature indicator) that correlates with this clastic event. (Later : the paper compares the detailed types of deformation with lab studies.)
The oldest useful DNA sequence we have is from about 700,000
This is not about today's climate change (Score:2)
...I will also note that the part of the conclusions "It’s also a portent of what could happen in today’s warming world" is not really justified. The Earth has been considerably warmer than it is today for most of the history of land-dwelling life on Earth. Even if this is a mechanism, it clearly kicks in only when the Earth is much much warmer than it is now.
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Does that quote come from the news article? RTFP. They refer the ozone reduction to periods of warming, not to the absolute temperature achieved. To precÃs the mechanism they cite, warming leads to stronger evaporation, leading to more intense convection, leading to increased lofting of seawater spray and so sea salt in raindrops getting up to the stratosphere. There the chloride surfaces interact with UV to produce ClO, which does nasty things to ozone.
If you think about it, there has got to be a na
Temperature [Re:This is not about today's climate] (Score:2)
Does that quote come from the news article?
The word "portent" is from the press release [sciencemag.org]. The actual words in the article (from the abstract) are this work leads to "the unavoidable conclusion that we should be alert for such an eventuality in the future warming world."
I disagree.
RTFP. They refer the ozone reduction to periods of warming, not to the absolute temperature achieved.
I don't have the foggiest notion what your point is here. You do know that the warming rate is many orders of magnitude less than the time scales of convection. From the point of view of weather, the rate of change (on climate-change time scales )is so slow as to be compl
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Strong evidence wont stop the Climate Deniers, they are locked in in for the long haul. They can fall ill from an insect that has moved into their area because of climate change, and still say it is a hoax. Heck God can burn forest fires across America in English saying "Climate Change is Humans fault and it is real!" And they will still dismiss it.
Strong Evidence, will be helpful to make sure the people who don't have a stance on the topic, are faced with solid logical evidence, to make a better decision.
Not anthropogenic (Score:2)
Strong evidence of what?
TFA offers some more examples of climate changes, that were not anthropogenic — if only because they predated humans (indeed primates) by millions of years.
What makes you drag in "Climate Deniers"?
I'll take this one. (Score:1)
What makes you drag in "Climate Deniers"?
Past experience with crackpots on the Internet?
You take this one (Score:1)
Found a crackkettle... -1 Offtopic
Good to know (Score:2)
I'll use my ozone generator in the car and de pets' room more often then, to fill up.
1. Asteroids 2. Volcanoes 3. ... also volcanoes (Score:3)
Scientists have long believed -- at least before humanity became a force for extinction -- that there were just two ways to wipe out life on Earth: an asteroid strike or massive volcanic eruptions. But 2 years ago, researchers found evidence of a third way: volcanic eruptions changing the upper atmosphere.
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That's because volcanic dust and toxic gases in the LOWER atmosphere has a completely different effect from the new one proposed here. Take the time to think before posting.
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I remember reading a text book as a student in the 1980s with about 14 processes by which multi-environment extinctions had been recorded to happen.
Great Dying (Score:4, Interesting)
There was just a summary in Nature this week of research suggesting that the greatest mass extinction event in the history of the planet, The Great Dying, which led to the extinction of 90% or more of marine life and 70% of land species, was caused by Siberian volcanoes releasing tons of mercury for 300,000 years. This is based on mercury content of rocks from that era and computer simulations based on the mercury content of rocks of that age.
Just thought it was relevant so I'm sharing it.
See: https://pubs.geoscienceworld.o... [geoscienceworld.org]
Permian extinction [Re:Great Dying] (Score:3)
Fascinating-- I hadn't seen that one.
Do note that the last paragaph of the paper cited says
"It remains unlikely, though, that Hg contamination was the sole cause for the mass extinction, because decreases in dis- solved oxygen and pH known to have occurred during that time are additional critical stressors on marine life. These results suggest that mass-extinction processes that impacted the breadth of life during the late Permian are complex and likely involved multiple environmental stressors that
Re: (Score:2)
A grain of (say) feldspar with a few PPM of mercury, ejected from a deep-rooted volcano into the atmosphere and settling out a year later on the other side of the globe, will be corroded into an aluminosilicate gel, which recrystallises into indeterminate clay minerals which can't be distinguished from any other grain of clay. But the few parts-per-billion o
Gamma ray burst? (Score:5, Interesting)
I'm sure they've done more research than me, but a sudden disappearance of the ozone layer to me seems like a strong possibility of a gamma-ray burst.
Re: (Score:3)
I'm sure they've done more research than me, but a sudden disappearance of the ozone layer to me seems like a strong possibility of a gamma-ray burst.
Indeed, I'd say that the mechanism proposed is the most speculative part of this hypothesis. But, from the article, the particular mechanism seems to be only a minor part of their work, mostly they are talking about the malformed spores and attributing this to ozone depletion.
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No, it has to be the climate or else you don't get your research grants.
Bet it was tied to a SUN event (Score:1)
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You do know that there is no evidence whatsoever for your statement, right?
People have been looking for a connection between solar activity and global temperature for over a hundred years and not found one that is supported by the statistical record.
And, by the way, coronal mass ejections don't have any connection to temperature either. They do cause pretty aurorae, but the actual energy transported is trivial.
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other than volcano...but caused by a volcano? (Score:1)
The post says other than asteroid impact or volcano and then goes on to immediately describe the loss of ozone as being directly the result of a volcano.
So really, they meant either a blockout of the sun by asteroid impact or volcano ...or this new method of uv destruction by volcano.
Though, new is kind of relative for slashdot. since this is news from 1976 and didn't require a volcano to trigger since the loss of ozone and subsequent extinctions occurs whenever the magnetic field flips and varies depend
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Magnetic pole reversals happen all the time, if you're looking on a geological scale (about about every 200,000 to 300,000 years, in the recent record), and don't cause mass extinctions.
https://www.nasa.gov/topics/ea... [nasa.gov]
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