From the Swiss Federal Research Institute WSL: Tree-ring measurements have revealed a period of extreme cold in Eurasia between 536 and around 660 CE. It coincides strikingly with the Justinian plague, migrations of peoples and political turmoil in both Europe and Asia, reports an interdisciplinary team, led by the Swiss Federal Research Institute WSL and the Oeschger-Zentrum of the University of Bern, in the journal Nature Geoscience.
WSL dendroclimatologist Ulf Büntgen and his fellow researchers were able for the first time to precisely reconstruct the summer temperatures in central Asia for the past 2,000 years. This was made possible by new tree-ring measurements from the Altai mountains in Russia. The results complement the climatological history of the European Alps, stretching back 2,500 years, that Büntgen and collaborators published in 2011 in the journal Science. “The course temperatures took in the Altai mountains corresponds remarkably well to what we found for the Alps,” says Büntgen. The combined findings allow for the first time to infer summer temperatures for large parts of Eurasia over the past two millennia.
Tree-ring widths in old trees reflect the summer climate in any given year in the past. Looking at these, the researchers were particularly struck by a cold phase in the 6th century. It exhibited even lower temperatures, longer duration and larger expanse than the temperature drops in the Little Ice Age (13th to 19th centuries CE). “This was the most dramatic cooling in the Northern Hemisphere in the past 2,000 years,” explains Büntgen.
Climate and culture
In light of this, the researchers refer to the period from 536 to around 660 CE for the first time as the “Late Antique Little Ice Age” (LALIA). This was triggered by three major volcanic eruptions in 536, 540 and 547 CE[1], whose climatic impact was prolonged further by the retardant effect of the oceans and a minimum in solar activity.
According to the team of naturalists, historians and linguists, this period bore witness to a whole series of social upheavals. After famine, the Justinian plague established itself between 541 and 543 CE, killing millions of people in the centuries that followed and possibly contributing to the decline of the Eastern Roman Empire.
Migrations
Proto-Slavic-speaking people migrated, supposedly from the Carpathian region, into the eastern areas of modern-day Europe that had been abandoned by the Romans, thereby forming the Slavic language area. According to the researchers, this period of cool temperatures may also have fostered the expansion of the Arab Empire in the Middle East. The Arabian Peninsula received more rain, growing more vegetation, which may have sustained larger herds of camels used by the Arab armies for their campaigns.
In cooler areas, various peoples also migrated east towards China, maybe driven away by a lack of pastureland in central Asia. As a result, hostilities broke out in the steppe regions of northern China between nomadic groups and the local ruling powers. Subsequently, an alliance between these steppe populations and the Eastern Romans conquered the Sasanian Empire in Persia, leading to its collapse.
Strategies for modern-day climate change
While the researchers stress, however, that potential links between this period of cool temperatures and socio-political changes always need to be treated with great caution, they write that “the LALIA fits in well with the main transformative events that occurred in Eurasia during that time”.
Ulf Büntgen points out that their study serves as an example of how sudden climatological shifts can change existing political systems: “We can learn something from the speed and scale of the transformations that took place at that time,” he says. Knowledge about the effects of past climatic fluctuations could maybe contribute to developing strategies how to deal with modern climate change.
Cooling and societal change during the Late Antique Little Ice Age from 536 to around 660 AD
Ulf Büntgen,Vladimir S. Myglan,Fredrik Charpentier Ljungqvist,Michael McCormick,Nicola Di Cosmo,Michael Sigl,Johann Jungclaus,Sebastian Wagner,Paul J. Krusic,Jan Esper,Jed O. Kaplan,Michiel A. C. de Vaan,Jürg Luterbacher,Lukas Wacker,Willy Tegel& Alexander V. Kirdyanov
Climatic changes during the first half of the Common Era have been suggested to play a role in societal reorganizations in Europe1, 2 and Asia3, 4. In particular, the sixth century coincides with rising and falling civilizations1, 2, 3, 4, 5, 6, pandemics7, 8, human migration and political turmoil8, 9,10, 11, 12, 13. Our understanding of the magnitude and spatial extent as well as the possible causes and concurrences of climate change during this period is, however, still limited. Here we use tree-ring chronologies from the Russian Altai and European Alps to reconstruct summer temperatures over the past two millennia. We find an unprecedented, long-lasting and spatially synchronized cooling following a cluster of large volcanic eruptions in 536, 540 and 547 AD (ref. 14), which was probably sustained by ocean and sea-ice feedbacks15, 16, as well as a solar minimum17. We thus identify the interval from 536 to about 660 AD as the Late Antique Little Ice Age. Spanning most of the Northern Hemisphere, we suggest that this cold phase be considered as an additional environmental factor contributing to the establishment of the Justinian plague7, 8, transformation of the eastern Roman Empire and collapse of the Sasanian Empire1, 2, 5, movements out of the Asian steppe and Arabian Peninsula8, 11, 12, spread of Slavic-speaking peoples9, 10 and political upheavals in China13.
http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2652.html
h/t to Wim Rost
I have to wonder how much of the recent “warming” is simply due to increased growth due to CO2 fertilization. This would be particularly true at the tree line. Where air is thinnest, growth is limited by CO2 starvation (as for people it would be for O2 starvation). CO2 increase should push the treeline higher and also increase annual growth ring thickness.
I am very skeptical of attributing modern tree ring increases to temperature alone. I believe a good bit of it is due to CO2 fertilization.
Back door way of saying that the debate on tree ring and temperature is valid. The recent debate on tree ring widths that show the relationship between temperature and growth is invalid. I think some academic careers could be over for posing such a ridiculous argument. First the verified tree accounts only go back to 900 ce. It gets a little fuzzy going further back. Second, the only confirmed way of relating information about temperature and tree rings is through isotopic measurements. Any “real” scientist would know this and the paper when it was written. And by the way, it matches warming and cooling trends… worldwide. Which is why i am still waiting for an explanation of how that happened in the absence of major increases and decreases in co2. Further, if they can explain it, are those factors the same or different today. …
This is a garbage study, intending to support current garbage work trying to prove CAGW. Calling it CAGW now is fading since none of the catastrophic predictions/projections have occurred in the appointed time frame. It’s just AGW now, and that may be in the dust bin of history as well.
Much has been written about the extreme climactic events beginning in the 530’s; Justinian may have had a chance to restore Rome back to a semblance of itself if the lands had not been devastated by plague and many bad harvests. Also in historical circles, this era is sometimes referred to as the “Death of Nations”, since so many organized civilizations and peoples which had persisted for millennia simply disappeared, swallowed up, absorbed, or replaced by the invaders from the east – who were driven by starvation and warfare in their own lands.
It’s even thought that the Norse idea of a “Fimbulwinter”, which is entwined with the tales of Ragnarok, and essentially refers to a winter which lasts for years with no thaw, may be a distant memory of what transpired in the far north during the 6th century.
Hmmmm not sure what is wrong with my treemometer….. it doesn’t seem to be calibrated correctly I look out my window and it clearly shows 67.004 degrees F but my digital thermometer shows 72.5 degrees F…. can anyone help me calibrate my treemometers in my yard? Are the treemometers affected by wind chill?
/sarc off
Cheers,
Joe
A relevant book I read 20 odd years ago “Catastrophe” by David Keys.
Writing about the explosion of Krakatoa in Indonesia that blew up in 535AD. He writes about all of the changes that occurred (mass migration, plagues, climate change, famine etc.) bringing on the ‘dark ages’ lasting some 150 years.
He makes the case that these events cleared out the past and led to the start of our modern civilization.
Thanks for that, will check out his book. Keys has found many historical references to the Krakatoa event, also see the fascinating PBS documentary Catastrophe! available on-line: Part 1, Part 2. From Cassiodorus [Italy, 536AD] “The sun … seems to have lost its wonted light, and appears of a bluish colour. We marvel to see no shadows of our bodies at noon, to feel the mighty vigour of the sun’s heat wasted into feebleness, and the phenomena which accompany an eclipse prolonged through almost a whole year.
I’m a little disappointed that they don’t credit David Keys’ earlier thorough investigation of ice cores, tree rings, global historical records and other evidence, published in his book “Catastrophe”, in which essentially the same conclusions were reached.
Exactly! Posted similar reference earlier, Keyes has been there and thoroughly done that.
Admittedly, I haven’t been closely following progress on this topic, but my impression is that since David Keyes’ work, the main substantive progress has been the discovery that several massive volcanic eruptions occurred around the world in the same few years, including one in Central America.
Keyes thought on the basis of worldwide historic records and Indonesian legend that perhaps Krakatoa had erupted on a huge scale at this time. On site he filmed a deep layer of material due to such an eruption, but due to the absence of organic material within this mass, it was not possible to date this eruption to better than two or three thousand years, though he observed that 535 was in about the middle of this range.
So I guess the jury is still out concerning the date for that particular Krakatoa explosion.
Another question is why several widely distributed volcanoes were so violently active in the same interval. Is there a single geological or gravitational tidal phenomenon that can trigger that?
From what I’ve seen and read as a layman about tree ring data, while inclement weather of any type can affect ring growth, the effects are different enough to where examination of the growth under microscope (and sometimes, chemically) can indicate if the stunted growth was from too hot, too cold, too wet or too dry conditions, and combinations thereof – especially if you have modern data for the same tree species to correlate with.
The takeaway should be simply that this adds to the very large body of work inferring significant variability in the past. Regardless of the details, just this knowledge increases the uncertainty in claims that somehow the current warming period is unprecedented. Chalk up a credit for the skeptics.
“’This was the most dramatic cooling in the Northern Hemisphere in the past 2,000 years,’ explains Büntgen.” Which is to say Yamal all over again: the LIA is bogus; the hockey stick is vindicated. –AGF
“Tree-ring measurements have revealed a period of extreme cold in Eurasia between 536 and around 660 CE.”
No, they haven’t. Next.
Someone has to be asking this…………………….But where did they find 1400 year old trees………and did someone cut one down?
Fossilised, I guess.
There is little dispute that whatever happened in 535AD, it changed the human environment massively. It is notable that several texts already speak at length of these changes. One is “The Long Summer”, by Brian Fagan. It speaks of the movement of the “ecotone” between the Mediterranean air mass, and the Atlantic air mass, and the Continental air mass, each moving north and south. The effects that had on human politics were dramatic, because in agrarian societies all wealth was dependent on what crops could be grown, or not.
With wheat as the “imperial grain”, able to be stored and transported to feed armies with the least spoilage, the shift from the ecotone between the Mediterranean and Atlantic air masses was decisive for the Western Roman Empire. After 535, the ecotone moved long-term from what is now the English Channel to the coast of North Africa. The short, wet summers of the Atlantic Air Mass rarely allowed wheat the time to ripen and dry in the fields before harvest. As a result, the grain-fed cavalry armies of Justinian’s Constantinople-based Imperial Rome were not able to advance any farther North than grain from Egypt could be transported by ships. The Continental Air Mass that now predominated in the Eastern Mediterranean allowed sufficient time for one wheat crop a year, instead of the 2 of the Mediterranean Air Mass, and that allowed the Roman Empire of Constantinople to hold on, even after they lost their agriculturally most productive provinces after the Battle of the Yarmuk, with the Armies of the imperial Caliphate, the Arab copy of the Roman Empire of Constantinople.