From the University of Cambridge, it makes you wonder how climate could just go and change abruptly on its own back then, with CO2 levels being in the “safe zone” and all that:
===========================================================
Decline of Bronze Age ‘megacities’ linked to climate change
Climate change may have contributed to the decline of a city-dwelling civilization in Pakistan and India 4,100 years ago, according to new research
Scientists from the University of Cambridge have demonstrated that an abrupt weakening of the summer monsoon affected northwest India 4,100 years ago. The resulting drought coincided with the beginning of the decline of the metropolis-building Indus Civilisation, which spanned present-day Pakistan and India, suggesting that climate change could be why many of the major cities of the civilisation were abandoned.
The research, reported online on 25 February, 2014, in the journal Geology, involved the collection of snail shells preserved in the sediments of an ancient lake bed. By analysing the oxygen isotopes in the shells, the scientists were able to tell how much rain fell in the lake where the snails lived thousands of years ago.
The results shed light on a mystery surrounding why the major cities of the Indus Civilisation (also known as the Harappan Civilisation, after Harappa, one of the five cities) were abandoned. Climate change had been suggested as a possible reason for this transformation before but, until now, there has been no direct evidence for climate change in the region where Indus settlements were located.
Moreover, the finding now links the decline of the Indus cities to a documented global scale climate event and its impact on the Old Kingdom in Egypt, the Early Bronze Age civilisations of Greece and Crete, and the Akkadian Empire in Mesopotamia, whose decline has previously been linked to abrupt climate change.
“We think that we now have a really strong indication that a major climate event occurred in the area where a large number of Indus settlements were situated,” said Professor David Hodell, from Cambridge’s Department of Earth Sciences. “Taken together with other evidence from Meghalaya in northeast India, Oman and the Arabian Sea, our results provide strong evidence for a widespread weakening of the Indian summer monsoon across large parts of India 4,100 years ago.”
Hodell together with University of Cambridge archaeologist Dr Cameron Petrie and Gates scholar Dr Yama Dixit collected Melanoides tuberculata snail shells from the sediments of the ancient lake Kotla Dahar in Haryana, India. “As today, the major source of water into the lake throughout the Holocene is likely to have been the summer monsoon,” said Dixit. “But we have observed that there was an abrupt change, when the amount of evaporation from the lake exceeded the rainfall – indicative of a drought.”
At this time large parts of modern Pakistan and much of western India was home to South Asia’s great Bronze Age urban society. As Petrie explained: “The major cities of the Indus civilisation flourished in the mid-late 3rd and early 2nd millennium BC. Large proportions of the population lived in villages, but many people also lived in ‘megacities’ that were 80 hectares or more in size – roughly the size of 100 football pitches. They engaged in elaborate crafts, extensive local trade and long-ranging trade with regions as far away as the modern-day Middle East. But, by the mid 2nd millennium BC, all of the great urban centres had dramatically reduced in size or been abandoned.”
Many possible causes have been suggested, including the claim that major glacier-fed rivers changed their course, dramatically affecting the water supply and the reliant agriculture. It has also been suggested that an increasing population level caused problems, there was invasion and conflict, or that climate change caused a drought that large cities could not withstand long-term.
“We know that there was a clear shift away from large populations living in megacities,” said Petrie. “But precisely what happened to the Indus Civilisation has remained a mystery. It is unlikely that there was a single cause, but a climate change event would have induced a whole host of knock-on effects.
“We have lacked well-dated local climate data, as well as dates for when perennial water flowed and stopped in a number of now abandoned river channels, and an understanding of the spatial and temporal relationships between settlements and their environmental contexts. A lot of the archaeological debate has really been well-argued speculation.”
The new data, collected with funding from the Natural Environment Research Council, show a decreased summer monsoon rainfall at the same time that archaeological records and radiocarbon dates suggest the beginning of the Indus de-urbanisation. From 6,500 to 5,800 years ago, a deep fresh-water lake existed at Kotla Dahar. The deep lake transformed to a shallow lake after 5,800 years ago, indicating a weakening of the Indian summer monsoon. But an abrupt monsoon weakening occurred 4,100 years ago for 200 years and the lake became ephemeral after this time.
Until now, the suggestion that climate change might have had an impact on the Indus Civilisation was based on data showing a lessening of the monsoon in Oman and the Arabian Sea, which are both located at a considerable distance from Indus Civilisation settlements and at least partly affected by different weather systems.
Hodell and Dixit used isotope geochemical analysis of shells as a proxy for tracing the climate history of the region. Oxygen exists in two forms – the lighter 16O and a heavier 18O variant. When water evaporates from a closed lake (one that is fed by rainfall and rivers but has no outflow), molecules containing the lighter isotope evaporate at a faster rate than those containing the heavier isotopes; at times of drought, when the evaporation exceeds rainfall, there is a net increase in the ratio of 18O to 16O of the water. Organisms living in the lake record this ratio when they incorporate oxygen into the calcium carbonate (CaCO3) of their shells, and can therefore be used, in conjunction with radiocarbon dating, to reconstruct the climate of the region thousands of years ago.
Speculating on the effect lessening rainfall would have had on the Indus Civilisation, Petrie said: “Archaeological records suggest they were masters of many trades. They used elaborate techniques to produce a range of extremely impressive craft products using materials like steatite, carnelian and gold, and this material was widely distributed within South Asia, but also internationally. Each city had substantial fortification walls, civic amenities, craft workshops and possibly also palaces. Houses were arranged on wide main streets and narrow alleyways, and many had their own wells and drainage systems. Water was clearly an integral part of urban planning, and was also essential for supporting the agricultural base.
At around the time we see the evidence for climatic change, archaeologists have found evidence of previously maintained streets start to fill with rubbish, over time there is a reduced sophistication in the crafts they used, the script that had been used for several centuries disappears and there were changes in the location of settlements, suggesting some degree of demographic shift.”
“We estimate that the climate event lasted about 200 years before recovering to the previous conditions, which we still see today, and we believe that the civilisation somehow had to cope with this prolonged period of drought,” said Hodell.
The new research is part of a wider joint project led by the University of Cambridge and Banaras Hindu University in India, which has been funded by the British Council UK-India Education and Research Initiative to investigate the archaeology, river systems and climate of north-west India using a combination of archaeology and geoscience. The multidisciplinary project hopes to provide new understanding of the relationships between humans and their environment, and also involves researchers at Imperial College London, the University of Oxford, the Indian Institute of Technology Kanpur and the Uttar Pradesh State Archaeology Department.
“It is essential to understand the link between human settlement, water resources and landscape in antiquity, and this research is an important step in that direction,” explained Petrie. “We hope that this will hold lessons for us as we seek to find means of dealing with climate change in our own and future generations.”
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Not having anything better to do, I counted the number of occurrences of several phrases in the report above:
climate change 11
climate 8
warm 0
warming 0
cool 0
cold 0
There’s no mention of whether the collapse was caused by warming, cooling or neither.
A quick glance at the GRIP2 ice core record shows a sharp cooling that corresponds exactly with the date of demise. This cooling may also have caused the collapse of the Egyptian Old Kingdom. Droughts are normally associated with cooling, and not warming.
Of course, the fact that many civilisations failed due to cooling is just too inconvenient, if you want to demonise a warmer world. History is clear: when the world gets warmer mankind prospers, as in the Roman, Medieval and modern 20th century periods. It’s when the world gets colder that people suffer and civilisations fail.
“We hope that this will hold lessons for us as we seek to find means of dealing with climate change in our own and future generations.”
Yes, the lesson is very clear. Warm is good. Cold is bad.
The other lesson is that it’s not just climate scientists who suffer from an integrity deficit.
Chris
Nothing new here. Happened to the Anasazi.
Climate changes…..
“By 1300 Mesa Verde was deserted. Here is another mystery. We know that the last quarter of the century was a time of drought and crop failures.”
http://www.gorp.com/parks-guide/travel-ta-mesa-verde-national-park-archaeology-colorado-sidwcmdev_067311.html
Chris Wright 6:12 a.m. – “Yes, the lesson is very clear. Warm is good. Cold is bad”
Yes, but at the same time, we humans today can adapt to almost anything if we put our minds and resources to the task. That means taking away from the declension-elites — who want to end current civilization’s marvelous successes — all that they greedily desire for only themselves — solar and wind power, indeed. Boondoggles, and many more. Their mantra is “equality” for all, but they mean poverty and death for most.
We need to learn from the “regular” demise of civilizations (city states, major societies) over at least the Holocene.
Do not forget water aka RAIN eould cause civilizations to collapse:
Shifts in Monsoons is documented:
The Holocene Asian Monsoon: Links to Solar Changes and North Atlantic Climate (Links to more articles)
Paleotemperature variability in central China during the last 13 ka recorded by a novel microbial lipid proxy in the Dajiuhu peat deposit
hol(DOT)sagepub.com/content/23/8/1123.abstract
Atlantic Forcing of Persistent Drought in West Africa
(wwwDOT)sciencemag.org/content/324/5925/377.abstract
Multidecadal to multicentury scale collapses of Northern Hemisphere monsoons over the past millennium
(wwwDOT)pnas.org/content/110/24/9651.abstract
A 2,300-year-long annually resolved record of the South American summer monsoon from the Peruvian Andes
(wwwDOT)pnas.org/content/108/21/8583.abstract
ezra abrams says: @ur momisugly February 26, 2014 at 3:08 pm
I am undecided on climate change, and think this is a silly post
Your logic is, drastic climate change occurs naturally, therefore *adding* manmade change is not worse ???
>>>>>>>>>>>>>>>>>>>>>>>>
I suggest you stick around and read. Many many different scientific papers are read and discussed here.
Pay close attention to when Dr Brown of Duke Univ (rgbatduke) is kind enough to drop by and comment.
Why is it that there is more certainty of climate change from 4,000 years ago due to the analysis of isotope changes in snails versus the actual documented climate change from written records of contemporary historians reported during the Midieval Warm Period? I love how we’d rather put stock in a couple of fossils rather than historical records that had no bias for or against regarding climate change.
Wonder what kind of climate change it is. Acoording to IPCC language climate change means anthrogenic changes, so to be explicit with their language they should have mentioned that it was a kind of natural or nonanthropogenic change. Just so that nobody gets confused and ask how they managed to burn all that fuel.
rgbatduke says:February 26, 2014 at 2:51 pm
I read about that city when it was discovered, I assume in Archeology Magazine but can find nothing in their archives. There are claims they saw geometric shapes in sonar and found human remains. From digs I’ve read about, sea level is down a couple of meters in the last 4-6K years, the shoreline of the Gulf of Mexico was some 50 miles inland then.
I don’t know why the Egyptian, Greek, and Cretan disruptions were brought into the discussion, since there’s a bit of evidence that the eruption of Thera/Santorini was responsible. There’s even a hint that the Exodus occurred during the eruption, based only on the Bible mentioning a “pillar of cloud by day, and pillar of fire by night.” It might be far fetched to include that event with the Harappan decline at the same time, unless the eruption was truly gigantic or had special properties, like large quantities of copper in the ejecta causing crop failure.
I believe this likely was Anthropogenic. Agriculture began 13KYA near the Turkish town of E-din. The irrigation methods, deforestation and other practices cause hydrological changes such as those described. It took a while for agriculture to spread and for this civilization to fall.
Our own civilization is threatened by the same thing–droughts caused by monocropping, deforestation, wasteful irrigation and other practices. It is called Desertification.
It can be reversed. Google “Permaculture” and go to http://www.originalsonicbloom.com for the agricultural breakthroughs that will restore abundance to this world.
More CO2 from burning fossil fuels will also promote abundance.
The following snippets of the comments above are significant and show a red line, which is explained below. Also notice that the timings/dating of all these similar events are not equivocal, but differ wildly. There is no “consensus.”
The SNAIL Research however concluded: “But an abrupt monsoon weakening occurred 4,100 years ago for 200 years and the lake became ephemeral after this time.” Read the comments carefully.
“Not only there, “The Akkadian empire flourished for about 100 years until, at 4170 +/- 150 years BP, it suddenly collapsed”
“There is nothing interesting happening near 4000 BP” [??]
“Even if the graph is “ridiculously scaled” it is pretty clear that CO2 wasn’t driving anything dramatic. However, to then claim that there couldn’t have been a big shift in climate is to ignore shifts in climate due to other causes.”
“I remembered reading that climate change brought down the Egyptian empire of old and quickly googled it. Looks like there may be a “consensus” that climate change did them in about 4kyr ago or so”
“Are they sure? Maybe it was not Climate Change what done it.
What if it was Water Wet?”
“This particular link goes on to mention other civilization-killing droughts 3,000 and 5,000 years ago and links to another discussion of Khmer and Mayans experiencing climate change”
“The dating of the destruction or abandonment of these Indian cities coincides with the time when the Hindu calendar changed from 360 days per annum to the present 365.25 days per annum. Whatever the event was which caused this calendar change, it was a global rather than a local event as all the calendars around the world (Mayan, Chinese, Hindu, Greek, Hebrew & Egyptian) all changed from a 360 day year to 365.25.”
“The early Indus city-state civilizations such as Moheno Darro may have well died due to climate change, but not global warming. The warmistas are trying to throw dust into the eyes of the incogniscentii.
We know over the past few thousand years, sea levels have risen – don’t forget all that ice melting from the deep freeze of the ice-age.
There was a land bridge between the following in barely pre-historic times: Ceylon – India :British Isles – France (phew that was a close one! 😉 Australia – rest of the world”
“In Saudi many neolithic remains of long dried out villages remain where petroglyphs show the animals of the time etc.”
“Egypt in the 3rd millennium BC (4000-5000 years ago) also recorded a warm period, which coincides, at least as to its end, with the collapse of the Indus civilisation.”
“The change lingered for 200 years!”
“Minimum of about 260 ppm at roughly 6000 to 5500 BC – about the time of the flooding of the Black Sea.”
“I wish all societies – the “wacky one” in California first and foremost – would end the focus on CO2 and turn to drought as a problem to be solved. No humans ever should suffer from drought again.”
“The reference is about Sahara turning green 12.000 years ago and dried up 3500 years agp.”
“Sahara had turned into a savanna-like ecosystem with trees and grass and grazing animals.”
“He speculates that there could be an insolation tipping point “whereby subtropical African climate flips abruptly between humid and arid””
“Not sure if anyone has mentioned it, but Indians were Australia’s first boat people.”
“Two years is the weather and not the climate. Four years out of phase would not have been sufficient to destroy those civilizations. ”
“I counted the number of occurrences of several phrases in the report above:
climate change 11 – climate 8 warm 0 warming 0 cool 0 cold 0″
“By 1300 Mesa Verde was deserted. Here is another mystery. We know that the last quarter of the century was a time of drought and crop failures.”
” Gail Combs says: ‘Do not forget water aka RAIN could cause civilizations to collapse:’”
“Why is it that there is more certainty of climate change from 4,000 years ago due to the analysis of isotope changes in snails”
“I don’t know why the Egyptian, Greek, and Cretan disruptions were brought into the discussion, since there’s a bit of evidence that the eruption of Thera/Santorini was responsible. There’s even a hint that the Exodus occurred during the eruption,”
“In 2002 a 10 sq. mile city was found off the coast of west India in 120 feet of water. Climate has probably changed since when it thrived as well.”
The Red Line in the comments goes like this:
Some big change happened 4000 BP, that was not CO2 driven, yet dried out most ancient civilisations, a change that was most likley a “Climate Change”, yet not caused by Solar activitynor Global Warming. Then some propose that perhaps the change had to do with wetness, monsoons, water, rainfall, or rather the LACK of it, yet this great change (which lasted about 200 years) resulted in a rise of sea levels inundating cities in around “120 ft. of water!”
Here the scientific empirical instinct of the commenters, which instinct lies behind the success and reason WATTSUP became the best skeptical scientific blog I know of. But yet all these sharp minds seem to be unable to come to the ONLY conclusion and rainy reason for the wet season!
Could it be all have been caused by a lack of RAINFALL, perhaps? I will show you that this reason is under-supported by politically correct Wikipedia & mainstream historians who danced around the obvious for over a century, but first allow me to point out the also under-reported tremendous research of Australia’s government astronomer George Dodwell who proved that indeed around 2345 BC an enormous event must have taken place which caused the axis to tilt first to 26.5 degrees which since then wobbled back to 23.5 degrees and stabilised in 1880 AD. He figured something big must have set that change off.
Now 101 climatology: When the earth warms by conventional solar means, the resulting evaporation turning into more clouds and rain would cool the Earth back down, keeping it in blessed equilibrium, the reason why we have survived this long.
Thus the only possible mechanism that could lead to more rainfall, as witnessed by the erosion of the Sphynx and her quarry which lay in utter dryness buried in sand for the last 2,500 thousands years, was, according to historian Robert Shoch, caused by excessive rainfall, witnessed also by the research of ….. , proving that the Sahara or Sahel 5000 BP, used to have an inland lake and cattle grazing. http://www.nature.com/news/pottery-shards-put-a-date-on-africa-s-dairying-1.10863 [Now this original Sapienza University research has been re-dated to 7.000-10.000 BP]
Now what could cause heavy rainfall from heavier cloud-cover, if NOT by global warming? It could only have been by a unique mechanism, sofar unmentioned, to wit: oceanic warming! If the oceans had warmed say by ten degrees Celsius, it would lead to higher evaporation & more cloud cover and thus more rain, yet the Earth would not get significantly warmer.
Perhaps there was at that time greater volcanic activity under the ocean, which led to more rainfall for a long time, but then the oceans cooled down enough to stop the heavy rain which caused draught in the areas mentioned in the comments, Egypt, Sahara, Meso America, Northern Australia, Harrapan Indus valley, Egypt, And mesopotamia.
There is something else that heavier rainfall and cloudcover would cause, more snowfall on the greater landmass in the North, without a chanche to melt in the warmer water, like in the South!
ANd that would lead to a thickening of the snow, layer by layer, which would turn into an extended icecap of several KM thickness, depressing the Northern continents leading to more tectonic activity! That, empirical scientists, came to call the Ice Age, which led to a decrease of the ocean levels of 130 M. or 300 Ft. but it ended as recent as the Snail research indicated, at least 4000 years ago, and NOT 10-12.000 years ago!
Actually when we look more closely under the oceans, we will find many submerged cities fords, ceremonial platforms, walls, houses, roads, like for example of the coasts of Spain, Palestine, Greece, here in Taiwan (Yonaguni) and Japan, Near Dwarka, and under the Black Sea. The Hindu religion tells us that there was a landbridge between Ceylon (Sri Lanka) and India and there was a city of Krishna that perished in a very short time by sinking beneath the waves. Are we to suppose that Krishna was a hunter gatherer or caveman of 12.000 years BP? Of course not!
The ruins under the black sea date from the same time as when the Dardanelles were formed by a Tsunami breakthrough when also the floods of Ogygys and Deucalion took place at the time of King Dardanus just before the founding of Troy. That was the Bronze Age and not 12000 years BP!
The problem in all these things is the dating. The dating is to say it sweetly, very arbitrary and highly fluctuating. But the ruins under the Black Sea near Sochi are of the same kind as the megalithic walls in Peru for example. King Dardanus’ Life and the overflowing of the Black Sea took place around 1500 BC. (Coins with his image still exist) The ruins under water of the coast of Spain, Bimini, Alexandria, Lebanon date from the same time.
And of course according to Plato (although he mis-dated it also), the cause of the sinking of the Atlantic oceanic empire Atlantis, between the Atlas mountains and the Antilles, Atlan, and the Doggersbank or -land which is now the North Sea! Before that time Bordeaux was linked with a geographically united Ireland-England! These global inundations were caused by the at least 200 year lasting melting of the Northern Icecaps! Around 1500 BC, the time of the Exodus, and the drying out of the formerly rain-blessed civilisations. The readjusting of the Earth’s crust led eventually to the explosion of Santorini around that same time!
But what could have caused this significant volcanic warming of the oceans? The same event that Govt. Astronomer George Dodwell of Australia found recorded in the solar corridors of many ancient solar temples (like Karnak) which showed that the Sun had moved 3 degrees away from the initial 26.5 degrees of the Earth’s tilt in 2345 BC. Which by the way was also recorded in the dendrochronological tree-ring research by Prof (Emeritus) Mike Baillie, who arrived at the same conclusion!
Something had caused the Earth to tilt, as Chinese mythology recorded that Nuwa (Noah) had to fix the sky because it had tilted! And that tilt was NOT caused by a small insignificant event! yet that event has been ostracised, politically incorrect-ised, and ostracised, and obfuscated, and ignored, not as and elephant in the room, but as the proverbial MAMMOTH in the historical and geological livingroom, even though attested to by its survivors in over 500 ethnic narratives and legends, of course mystified and embellished by those who obviously were not the survivors themselves but only knew it from hear-say!
Yes, we’re talking here about a global Deluge that left its marks in 2-4 KM deep layers of mud turned to rock mixed with flora and fauna rests instantly fossilised under its pressure. If those layers came from an inch per year over many many many years, where could these trillions of cubic kilometers dirt have originated from?
Science is not so confusing, as long as there is no political or philosophical agenda preventing mankind to see its true origins, repeated by over 500 of its small early tribes-turned-into the few high civilisations scattered in rain-blessed areas! Like the Egyptians! They were astronomical wizards that recorded the basic earth dimensions into the blueprints of the Great Pyramid, which we are still unable to copy! They were sea faring savants like Atlas who traveled the entire globe mapping it with trigonometry before Antarctica was ever frozen over! (Piri Reis map)
So that is why the snails and civilisations changed! DROUGHT! For more information check out the Ancient History articles on our website!
{Moderator this last paragraph you may cut off if you let it pass! 🙂 ]
I could go on and on, but waste my time as politically incorrect stuff will most likely not be allowed to pass the moderators. I implore you though to let it pass, even as just a fun mocking-point of the many Darwinians among your readers. It should be great fun! Why not! Aw come on! Give this one a chance to pass the grade. Pretty please? I know…the Global Warmistas might accuse you of becoming “creationists” (even though I am NOT!) and that would be bad for the cause, of course. But then again, this IS backed up by lots and lots of research!
Interesting article. However, I’ve got some news for the authors. According to the UN’s Framework Convention on Climate Change (FCCC) and the British government’s Department of Energy and Climate Change (DECC) there was no climate change prior to the industrial revolution by definition. These official human authorities on global truth and reality have redefined “climate change” to be all man-made! The UN’s redefinition can be found on page 3 of the Glossary attached to AR4 under the entry for “climate change” here:
http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-annexes.pdf
and the British government’s redefinition can be found on page 16 of the DECC Guide to Carbon Offsetting under the Glossary entry for “climate change” again here:
ccs.cabinetoffice.gov.uk/sites/default/files/contracts/DECC%20guide%20to%20carbon%20offsetting.pdf
Isn’t Newspeak fascinating? But in the light of the above report, doesn’t this example of it make climate change deniers of the UN and the British government? I really do wish that the Emperor would put his clothes back on.
Perhaps the authors should now turn their attention to investigating what really brought down the Tower of Babel. Wasn’t that said to be something to do with a “confusion of tongues”? Or maybe it was about “climate change” too!
There’s a problem with that, during colder periods when the mean position of the jet stream is further south, more warm water is transported into the Arctic. It is more likely that during extended extreme cold periods that the oceanic inflow to Arctic, and very importantly the outflow of sea ice off the east coast of Greenland is inhibited by ice shelves spreading out from the land.
Note that I’m not talking about the jet stream, I’m talking about the Gulf Stream — water, not air. It isn’t clear precisely what forces might shift the Gulf Stream, but there is some evidence that it might have shifted further south and/or slowed during the LIA.
Outside of that, outspreading of ice is certainly a plausible assertion as a feedback/amplification of some OTHER process that gets the ice started, and could easily be a factor that “switches” semi-permanently once enough ice is in place to create a new stable circulation that leaves the north cold(er).
There is actually an interesting documentary here:
http://topdocumentaryfilms.com/gulf-stream-next-ice-age/
that asserts that global warming, by diluting the North Sea and Arctic Ocean with freshwater that dilutes the surface sea water sufficiently that it will no longer sink at the northmost extent of the circulation, could interrupt the thermohaline circulation through the critical arctic bight which would effectively cause a massive southward deflection of the turning point in the northward surface current and which might create the initial conditions that would LEAD to the freeze you suggest, making the deflection “permanent” even after the freshwater dilution terminates as the area re-freezes. As I noted, this is one of the hypotheses for the Younger Dryas — an enormous freshwater lake formed from the melting of the kilometer-thick glaciers broke through an ice berm and rapidly drained enough freshwater into the northern atlantic and arctic ocean that thermohaline circulation contributing to the early Holocene thaw was stopped dead in its tracks for almost 1000 years before conditions again overwhelmed the cooling.
Note that I don’t assert that these things are true — it is too difficult to get conclusive evidence, and humans are natural born storytellers but even a great story can end up not being true. But they are “plausible”, and there is at least moderate evidence for them even when it is insufficient to make the stories “known fact”. It does make me keep an open mind about the vast range of responses possible to even comparatively small perturbations of a highly nonlinear system.
rgb
http://www.nature.com/news/2006/061127/full/news061127-8.html
Yet another article (one pointing to some of the actual hard evidence) for linkage between the Gulf Stream and the LIA. East Coast drought (which reached historic proportions, BTW, in the early 1600s, wiping out colonies and native Americans alike) is itself probably linked to ENSO and the major decadal oscillations. The Younger Dryas was a period of profound drought on the North American continent — vast, decade-long dust storms are recorded in the silt layers of e.g. North Carolina streamways that correspond to that event. The article also notes the dilution hypothesis (without mentioning the YD by name).
Willis is very fond of negative feedbacks in the climate system, and this is yet another one that may have been neglected in all of the climate models. Transient warming in the Arctic may well dynamically feed back into the speed of the Gulf Stream, so that melting land ice actively increases area cooling by slowing the delivery of warmth, with a lag of at most a few years. But the big issue is whether or not there is a “catastrophe” lurking there in the sense of “catastrophe theory”, not in the sense of “climate catastrophe” — a major switch of the global climate system from one set of attractors to another, where the new one could either accelerate warming or accelerate cooling substantially.
rgb
Jimbo says:
February 27, 2014 at 2:35 am
——————————————–
Thanks for the historical rainfall link. That is great info. I would love to see the current chart of that Epochal Pattern.
“The largest number of settlements of the “Harappan” civilisation were located along the Saraswati river. The river slowly dried up, as is well attested in the Vedas, Upanishads, etc, and confirmed by modern geology.”
Here we go, the Hinduist nationalist fruitloops arrive – who haven’t even read the Vedas and Upanishads except in bastardized 10th-hand translations, or who recite but don’t understand them as Hindu priests have been doing for millennia.
Note: just like some nationalist Japanese, nationalist Hindu Indians are obsessed with ‘proving’ they belong to ‘the world’s most ancient culture’. As a result, recent archeology finding ‘ancient cities’ underwater etc from both places is not to be taken seriously. Even the once respected Indian archeologist BB Lal besmirched his career in his declining years with sentimental claptrap.
All who are interested in this matter should consult the GISP2 graph of Holocene
temps. Enlarge the temp swings to exactly see the rapid up and downs. Interesting
are the top temp spikes as well as the bottom temp spikes. All megadroughts set
in (I will write an aridification paper next year) as long as the temp drop period is on.
In this case of the Harrapians as the Sumerians/Akkadians, the rapid temp drop
was the result of the devastating asteroid impact of 2,193 BC, which sent global
temps down for 300 years until 1900 BC. As soon as the bottom temp spike was reached
in 1900 BC, the megadroughts ended abruptly and new human settlements sprang up in
the belt from Spain to Egypt, to West Asia and Pakistan….. After all major cosmic impacts,
of which we identified 14, temps went down in a spike, with a simultaneous aridification
period lasting exactly to bottom of the temp drop spike and immediately turning into a good precipitation period for the following centuries of the temp rebounce period. The latest
work of Harvey Weiss : “Seven generations since the Fall of Akkad” (2012) explains those megadrought observations with measurements conducted in West Asia. Cometary details can
be found in our paper on climate forcing. JS
I also believe that the wandering Jews came from India because they were treated as lower class. There are similiar words like Siva in both Jedish and Hindu. They left India and headed NW towards the mediteranian.
rgbatduke says:
“Note that I’m not talking about the jet stream, I’m talking about the Gulf Stream — water, not air. It isn’t clear precisely what forces might shift the Gulf Stream, but there is some evidence that it might have shifted further south and/or slowed during the LIA.”
Reconstructions show a very warm AMO in the Spörer and Maunder minimums, and during the late 1800’s during weaker solar cycles. So despite what the Gulf stream may have been doing, poleward warm water transport tends to increase during colder periods for the mid latitudes.
http://snag.gy/loCBw.jpg
Here we go, the Hinduist nationalist fruitloops arrive – who haven’t even read the Vedas and Upanishads except in bastardized 10th-hand translations, or who recite but don’t understand them as Hindu priests have been doing for millennia.
Well, yes, but even though India is my second country (I grew up there) I didn’t really want to say it. Besides, there is no need — India is the site of several the world’s oldest known urban civilizations. Whether they “beat” Mesopotamia, or Egypt, or China is hardly important. But there is little doubt that e.g. Mohenjo-Daro is quite ancient, and it is reasonably probable that there were semi-urban settlements that preceded it by a fair bit in the Holocene. India’s climate — alternating drought and monsoon flood — is such that entire civilizations could be buried deep in silt somewhere and who would know?
Once you get on the far side of 3000 years ago, it is all pretty ancient and in some sense prehistoric.
But to the best of my recollection, while the Upanishads are fairly definitely “recent” — circa 500 BCE, during the same religious upheaval that produced Buddhism from much the same physical part of India — the Vedas proper are an oral tradition that wasn’t even written down until the middle ages. So when one talks about sanskrit “writings” of the Vedas, one is not referring to any ancient manuscripts because there are none. They are dated back to 1500-1700 BCE, but that is pure guesswork, as are similar estimates of the books of the Old Testament. Buddhism at least has the pillars of Ashoka to date its written tradiation back to the third century BCE, although the Pali Canons are similarly an oral tradition.
Reconstructions show a very warm AMO in the Spörer and Maunder minimums, and during the late 1800′s during weaker solar cycles. So despite what the Gulf stream may have been doing, poleward warm water transport tends to increase during colder periods for the mid latitudes.
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Note that the top article is on just how difficult it is to measure either SST or mid-ocean temperature reconstructions to depth now with modern instrumentation making measurements at precise locations in space and time. Difficulties I’ve pointed out include sparsity of data, spatiotemporal resolution issues, bias introduced by correlations in measurement sites, and don’t even include possible instrumental error or the kind of post-processing Fred has discussed, lopping off measurements that are “too low” but leaving ones that are “too high”.
Forgive me if I doubt that any reconstruction of oceanic temperatures and currents 400 to 500 years ago has sufficient accuracy or spatiotemporal extent to permit any broad conclusions to be drawn with a great deal of confidence from that era. That isn’t to say that attempts to obtain a picture of what was happening are without merit, and may tell a story, it is just that it is difficult to know how much confidence to place in the story they tell.
By the time error bars reach 1-2C, they are out there with the signal one hopes to discern. IMO it is very, very difficult to argue that our knowledge of past climate — as opposed to very much localized conditions at a very restricted number of sites where good fortune preserved a proxy that isn’t too confoundingly multivariate and that doesn’t have too many diluting Bayesian priors — is much more accurate than that at any point substantially before the thermometric record. Even when I look at, and direct people too, the various “best guess” climate reconstructions of e.g. the Holocene or the last 600 million years, I do so with a number of very large grains of salt.
In a way, it is strangely similar to the problem with e.g. the Rig Vedas or the Pentateuch. “Tradition” holds that they have thus and such a date, but evidence usually directly contradicts the dates assigned by tradition. Tubal Cain was an artificer of iron, for example, which rather limits the time frame for Genesis to the Iron Age, thousands of years later than the supposed time of the events of Genesis. Similarly, tree rings often show a given supposed thermal history — until one looks carefully at how well they do against the actual thermal history as recorded by actual thermometers, where there are amusing exchanges in the various climategate documents IIRC between dendroclimatologists whose kids didn’t even get a good science fair climate record out of trees cut in their own back yard.
So are the various proxies for oceanic temperature any good? I don’t know. Maybe. Maybe sometimes but not other times. Maybe some places, but not other places. Maybe at low resolution, but not high resolution. And good or not, how accurate or “global” are they?
For better or worse, IMO we have “good” surface data stretching back at most 35 years, “adequate” surface data going back maybe 60 years, adequate data on certain reasonably globally distributed locations stretching back another 50 or so years, and then we hit the 19th century and all bets are off — Anarctica, China, Siberia, Australia, Tibet, much of Africa, large chunks of North and South America all terra incognita, the oceans miserably sampled with terrible instrumentation and practice in tiny stretches near the shipping lanes. Global Temperature in the 1600s? We have at best a guess — we are pretty sure Europe was cold, and we have enough evidence that the planet itself was pretty cold then to name it the LIA with some confidence as being a Lot Colder than Today, but was it 1C colder? 2C colder? 3C colder? That’s really difficult to say. Maybe it was a time of Antarctic thaw and Arctic freeze, just as the Arctic is generally warming and Antarctica cooling at the moment. Maybe Africa was having horrendous heat waves. Maybe ENSO was stoking up half of the world’s oceans, even as major continents were cooling. The problem is that we just don’t know, and probably can’t know.
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rgbatduke says: “,…”
I agree with your comment. and many other comments i have read from you.
My thing has been this: if some study into the past, finds that some time (approx 4000 yrs ago this study) in the past some event has occured that if it happens now that it’s somehow change. It seems to me that unprecedented climatic events have all happened before.
Thanks to WUWT for the interesting articles and for the opportunity to add my virtual cents.
I think my mom taught me to be polite.
the belt from Spain to Egypt, to West Asia and Pakistan….. After all major cosmic impacts,
of which we identified 14, temps went down in a spike, with a simultaneous aridification
period lasting exactly to bottom of the temp drop spike and immediately turning into a good precipitation period for the following centuries of the temp rebounce period.
So, was there a cosmic impact that precipitated the LIA? In the 16th century, most of the world was unknown to western civilization, and an oceanic impact or continental impact in many of the world’s continents might have gone unnoticed.
I have read no really good explanations for the LIA, which is the coldest single stretch in the entire Holocene post YD, although there was a similar scale dip around 9000 years BP. Also, while we have some good modern-era reason to think that there are climate bobbles associated with major volcanism, e.g. Tambora or Krakatoa, we lack information on such events before the 17th century for most of the globe. Their effect seems not to be century-scale persistent, although Tambora was a significant explosion no matter how you slice it, certainly comparable to all but a truly significant asteroid strike. What explains the long lasting effects of an asteroid compared to e.g. Tambora, which pulverized something like 16 cubic miles of rock?
rgb