Posted on 03/19/2008 2:36:03 PM PDT by blam
Ancient Global Dimming Linked to Volcanic Eruption
Ker Than
for National Geographic News
March 19, 2008
A "dry fog" that muted the sun's rays in A.D. 536 and plunged half the world into a famine-inducing chill was triggered by the eruption of a supervolcano, a new study says.
The cause of the sixth-century global dimming has long been a matter of debate, but a team of international researchers recently discovered acidic sulphate molecules, which are signs of an eruption, in Greenland ice.
This is the first physical evidence for the A.D. 536 event, which according to ancient texts from Mesoamerica, Europe, and Asia brought on a cold darkness that withered crops, sparked wars, and helped spread pestilence.
Scientists had suspected the dry fog was caused by a volcanic eruption or a comet strike, but searches had failed to uncover evidence for either catastrophe—until now.
"There is no need at the moment to invoke a large-scale extraterrestrial event as the cause, because the evidence is conclusive enough to say that it is certainly consistent with it being a large volcano," said study team member Keith Briffa of the University of East Anglia in the United Kingdom.
The discovery is detailed in a recent issue of the journal Geophysical Research Letters.
Global Ashfall
Tests show the Greenland sulphate molecules were deposited sometime between A.D. 533 and 536. This date correlates well with a sulphate peak found in an Antarctic ice core.
The team suspects the eruption occurred near the Equator, since its ash fell on both ends of the globe.
The Greenland evidence is also consistent with tree-ring data from around the Northern Hemisphere that show reduced growth rates lasting more than a decade starting in A.D. 536.
Curiously, the eruption's cooling effect did not extend to the southern hemisphere, the scientists say.
Together, the tree-ring and acid evidence suggest the sixth-century eruption was even bigger than Indonesia's Mount Tambora eruption of 1815, which also dimmed the sun.
Not Definitive
Ken Wohletz, a volcanologist at Los Alamos National Laboratory in New Mexico, said that while the new evidence strongly supports a large volcanic eruption, a space impact can't be ruled out yet.
"Over two-thirds of Earth's surface is covered with water, and because erosion so quickly wipes away evidence of impacts, the knowledge of when large-scale impacts have occurred in the past is still very incomplete," said Wohletz, who was not involved in the study.
To cement their case, volcano advocates will need to find ash layers deposited by the blast, Wohletz said.
William Ryan, an oceanographer at Columbia University's Lamont-Doherty Earth Observatory in New York, believes it is only a matter of time until ash layers are found.
"I suspect we haven't searched adequately, but this paper will start a hunt," Ryan said.
Indelible Mark
According to written records, the dry fog lingered for just over a year—leaving an indelible mark on human history.
Chinese historians recorded famine events and summer frosts for years after the event.
It was also around this time that a band of Mongolian nomads called the Avars migrated westward toward Europe, where they would eventually establish an empire.
The group may have left home when grasslands that their horses grazed on withered under the darkened skies, historians say.
More controversially, some historians claim that drought caused by the fog contributed to the decline of the Mesoamerican city of Teotihuacan.
The spread of bubonic plague throughout Europe and the Middle East, the rise of Islam, and even the fall of the Roman Empire have also been controversially tied to the event.
Still Vulnerable
If a similar volcanic eruption were to occur today, the effects could be just as devastating, experts say.
The reduced sunlight and ashfall would affect agriculture worldwide, and the thick veil of dust and ash could cripple transportation and communication systems.
"Most aircraft cannot fly in [volcanic] dust clouds," Los Alamos's Wohletz said.
"And these dust clouds have a large electrostatic potential that disrupts radio communication."
To make matters worse, there is practically nothing humans can do to prevent such a catastrophe from happening again—or to lessen its effects.
"In today's society, we're no less independent of nature than humankind has ever been," Wohletz said.
"In fact, we might even be more dependent on it."
Light Pollution Reduction Initiative !
Only a few letter off of what I think of Al Gore and his ilk.
Ping for after choir.
It’s quite intersting how many ways man or nature could conspire to knock 100 - 200 years of technology right out from under us. Or kill off 50% of the human race in a few years.
So where is the caldera? A crater larger than Tambora between 23N and 23S can’t be that hard to find.
Ring around the rosie, pocket full of posies, ashfall, ashfall, we all fall down....
susie
OK, smart guys, WHERE WAS THE VOLCANO?
Something of this magnitude could not have happened without leaving some serious clues as to its origin. Or perhaps it was an undersea eruption, maybe somewhere in the Bering Sea?
Interesting post - thanks!
Wait, I thought that driving around SUVs jacked up the temperature by many degrees. Now they say that there is nothing we can do to prevent the earth from cooling in case of a major volcanic eruption? I'm confused.
What is the expected rate of major volcanic eruptions per century? Is there any chance that we are below that rate which would account for any warming? I think Krakatoa in 1883 was the last one which had a major world wide effect on climate.
The book about this event is “Catastrophe”, written back aways. The author thinks the volcanoe that blew was in the area where Krakatau is now, and argued the eruption severed Java from Sumatra and created the Sunda Straits.
Carrier pigeons darkened the sky and buffalo darkened the prairie and ate all the corn.
Well, the abstract for the paper doesn’t say anything about candidate volcanoes. I’ll have to read the whole thing when I stop by the library.
Krakatau was proposed as a candidate and a PBS documentary made about “Catastrophe” but it’s not generally accepted.
I think there are some other 535 candidates, wikipedia mentions Rabaul caldera in the Solomons as a candidate.
China suffered for about 300 years. Byzentium was down for the count for at least 80 years.
Other areas, e.g. the realm of the Arabs who looked to Mecca for economic direction, didn't notice anything had gone wrong (relative to their earlier condition). They ended up conquering pretty much the rest of remaining civilization.
There were losses beyond imagining ~ for example, Michaelangelo was the first artist in a millenum who could produce sculpture the equal of the best produced by sculptors in Classical Times.
That's how much knowledge of that particular technology (sculpting) that had been lost.
A global catastrophe story that does NOT mention “global warming” ...
Oh. I see.
That's because it shows that climate changed naturally BEFORE us evil American capitalists spoiled the earth and killed all living things.
A global climate story that does NOT mention CO2 levels.
Oh. I see.
That's because it shows more evidence of (short-term) cooling in the Dark Ages, BEFORE the US emitted all those evil pollutants. (Of course, the LONG-TERM role of the varying solar output that actually CAUSED the Dark Ages, Medieval Warm Period, and Little Ice Age ARE NOT mentioned.
Bush’s great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-grandfather’s fault.
Thanks much for the post. As to where the supervolcano might have been ... the Gulf of Mexico, and in fact the whole of the Caribbean, seems to have a caldera shape. Any geologic studies been done on that, other than the possible meteor strike near the Yucatan peninsula?
I wish them luck, getting really crowded with volcanoes out there, the more we look the more we find.
“...the Bering Sea...”
That’s what I was thinking, somewhere in the northwest portion of North America. A sample of the ash is probably sitting in a storage drawer of some University in either Canada or the U.S.
Importantly, volcanoes are different in how they behave, depending on where they are in the world.
For example, volcanoes on the US side of the ring of fire tend to “belch”, like Mount St. Helens. However, on the far side of the ring of fire, volcanoes tend to be “brittle” and explode, blowing the volcano apart, like Krakatoa.
I doubt that it was a Krakatoa-like explosion, because such eruptions create noteworthy evidence around the world, that is sure not to be missed. For example, that explosion altered the level of the river Thames in London, on the other side of the planet, by almost a foot swell.
People all over the world knew about Krakatoa. It was hard to miss.
But compare that to Mount St. Helens or Mount Pinatubo in the Philippines. Both affected the world’s climate, but not in a very dramatic way, unless you were downwind of them.
Now, the *scale* of the cooling, as well as the “dry fog” would seem to indicate that perhaps *several* large volcanoes had “belching” eruptions at about the same time.
Say, if you had St. Helens, Mount Pinatubo, Popocatapetl in Mexico, or Mauna Loa in Hawaii and other such “new world” northern hemisphere volcanoes erupt at about the same time, all that the Europeans and Asians would notice is a “dry fog” and colder temperatures.
An example of climate change not caused by humans.
Maybe a meteor hit a volcano.
I've seen that mentioned at at cause of the Thera volcano in 1628BC. (Actually, it was a comet that was mentioned)
Mohammed was born some 35 years after this event. I am not sure how much of an impact it would have had on Islamic conquests 100+ years later. But you are correct that the impact would have certainly made it easier for Islam to get a foot hold in a much weakened Byzentium empire.
North of the equator - that is why all the sulphates are found north.
The equator forms a wind barrier, most of the time.
Much of the technology of the time before the Dark Ages was safeguarded by monks all over Europe.
Or a volcano that erupted continuously for a period of time instead of just one big eruption.
There are many volcanoes on the surface of our continents.
There are thousands of volcanoes on the ocean floor, that we know about.
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"In fact, we might even be more dependent on it."
Um, these statements are contradictory...gotta be careful when using those triple negatives...
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Thanks Blam.Tests show the Greenland sulphate molecules were deposited sometime between A.D. 533 and 536. This date correlates well with a sulphate peak found in an Antarctic ice core. The team suspects the eruption occurred near the Equator, since its ash fell on both ends of the globe... Curiously, the eruption's cooling effect did not extend to the southern hemisphere, the scientists say... Ken Wohletz, a volcanologist at Los Alamos National Laboratory in New Mexico, said that while the new evidence strongly supports a large volcanic eruption, a space impact can't be ruled out yet... To cement their case, volcano advocates will need to find ash layers deposited by the blast, Wohletz said.The volcano advocates will have to MATCH any evidence they are attempting to link with their hypothetical eruption to an actual volcanic eruption. 'Tis yet another dead end, IMHO. |
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The 536 AD Dust-Veil Event"There are two possibilities: a huge volcanic eruption or a collision between the Earth and a solid object: an asteroid or comet. Ice-cores drilled from Greenland show no evidence of large-scale volcanic activity at that time, so Professor Baillie and others now believe a cosmic impact is more likely. The result would have been to throw up a huge veil of dust and debris, cooling the Earth and producing widespread crop failures."
by William R. Corliss
Catastrophe:
A Quest for the Origins of the Modern World
by David KeysIt was a catastrophe without precedent in recorded history: for months on end, starting in A.D. 535, a strange, dusky haze robbed much of the earth of normal sunlight. Keys's narrative circles the globe as he identifies the eerie fallout from the months of darkness: unprecedented drought in Central America, a strange yellow dust drifting like snow over eastern Asia, prolonged famine, and the hideous pandemic of the bubonic plague. With a superb command of ancient literatures and historical records, Keys makes hitherto unrecognized connections between the "wasteland" that overspread the British countryside and the fall of the great pyramid-building Teotihuacan civilization in Mexico, between a little-known "Jewish empire" in Eastern Europe and the rise of the Japanese nation-state, between storms in France and pestilence in Ireland.
In this fascinating, groundbreaking, totally accessible book, archaeological journalist David Keys dramatically reconstructs the global chain of revolutions that began in the catastrophe of A.D. 535, then offers a definitive explanation of how and why this cataclysm occurred on that momentous day centuries ago. -- dead link
Vote for me for POTUS!
I promise, if I am elected, to make volcanoes and other icky catasstrophy things illegal!
I also promise to make lemons less tart and chocolate to be officially declared a health food!
And, last, but not least, I promise, if I am elected POTUS to teach the French to love catsup as a condiment!
So it wasn’t CO2 levels? Imagine that.
An eruption of Rabaul volcano is indicated in the discussion as a possible cause of this event.
An eruption of Rabaul volcano is indicated in the discussion as a possible cause of this event.
Increasing concentrations of atmospheric CO2 cause warming. Sulphate aerosols and ash from volcanic eruptions cause cooling. This article is about a cooling event.
A little off topic.
While cruising Google Earth I noticed a circular pattern in Alabama primarily.
Starts around Montgomery extends WNW into Mississippi and up into Tenn.
Almost looks like an ancient asteroid crater.
Can you enlighten me?
Sorry, no.
No hard evidence of that.
Besides, nowadays, man-made global warming caused by increasing CO2 levels are being blamed for taking us into the next ice age.
You did know, didn't you, that global warming causes temperatures to drop?
If you can make sense of that, let me know. The liberals have it figured out but no one else that I know of.
1816 was another “year without summer”
That's not how science works. Science is about data supporting an explanatory framework (colloquially called a "theory", but that gets confusing). Data and analyses of the data are interpreted in terms of how well they support alternate frameworks. A framework that gets considerable support from the observational data is considered a good explanation.
Thus, you get something like this:
Climate sensitivity constrained by CO2 concentrations over the past 420 million years (PDF)
Here's a readable summary:
Long-term geological record puts minimum value on climate sensitivity
Quote: "We were able to accomplish this tuning because one of the factors in the geochemical model is the relationship between carbon dioxide and temperature," said Royer. "We found that the deep-time geological records exclude the possibility of weak climate sensitivities: we conclude that the amount of warming for every doubling of carbon dioxide must be at least 1.5 °C."
Thus, the data and analyses of this study support the explanatory framework -- the relationship of atmospheric CO2 concentrations and global temperatures.
Nowadays, man-made global warming caused by increasing CO2 levels are being blamed for taking us into the next ice age. ... You did know, didn't you, that global warming causes temperatures to drop?
Yes. Read about the Younger Dryas
If you can make sense of that, let me know.
"The dense water masses that sink into the deep basins are formed in quite specific areas of the North Atlantic and the Southern Ocean. In these polar regions, seawater at the surface of the ocean is intensively cooled by the wind. Wind moving over the water also produces a great deal of evaporation, leading to a decrease in temperature, called evaporative cooling. Evaporation removes only molecules of pure water, resulting in an increase in the salinity of the seawater left behind, and thus an increase in the density of the water mass. In the Norwegian Sea evaporative cooling is predominant, and the sinking water mass, the North Atlantic Deep Water (NADW), fills the basin and spills southwards through crevasses in the submarine sills that connect Greenland, Iceland and Great Britain. It then flows very slowly into the deep abyssal plains of the Atlantic, always in a southerly direction. Flow from the Arctic Ocean Basin into the Pacific, however, is blocked by the narrow shallows of the Bering Strait."
If the cold water masses don't sink, extremely cold water stays at the ocean surface and thus the polar cold is not shunted into the deep ocean. So instead it would cool the atmosphere, particularly in the Northern Hemisphere and predominantly in North America and Europe.
There are far more variables to weather and climate than just CO2. There’s just no way it can all be attributed to one factor.
CO2 is only the third strongest greenhouse gas to begin with.
There’s no way the ocean’s circulation is going to stop.
Even if all that cold water got dammed up at the poles, doesn’t necessarily mean that it would cool the continents south of it. The Hadley cells don’t permit much interchange of atmosphere between the polar regions and the temperate regions so you’re not going to have much cooling through the atmosphere. And if the oceans circulation stops, unlikely as it seems, then there’s no cold water being drawn out to cool the continents.
The alleged drop in temperatures of the poles is not going to cool the whole planet. All it would do is increase the temperature gradient some between the equator and the poles.
Global warming is not going to cause global cooling. SOME parts, might temporarily get colder than others but that happens now anyway and that’s called weather.
Good, thanks.
"Climate science maverick James Lovelock believes catastrophe is inevitable, carbon offsetting is a joke and ethical living a scam. So what would he do? "
Eat, drink, and be merry for tomorrow we die?
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