Tree ring sampling shows cold spells in Eastern Europe led to unrest over past thousand years

Tree ring sampling shows cold spells in Eastern Europe led to unrest over past thousand years
Annually resolved variations of May-June temperature between 1040 and 2011 AD, based on 545 samples of living trees and historical timbers (Larix decidua Mill.) from the Slovakian Tatra Mountains in the northwestern Carpathian arc. Credit: Ulf Büntgen (WSL)
(—A team of Swiss, Czech, Canadian and German researchers has found that prolonged cold spells in Eastern Europe over the last thousand years has led to wars, plagues and civil unrest. In their paper published in the Proceedings of the National Academy of Sciences, the team compares evidence from tree ring samples taken from the Tatra region in Eastern Europe dating back to 1040 A.D., with archival histories to track human activities during the same period.

In the study, led by paleoclimatologist Ulf Büntgen, of the Swiss Federal Research Institute, the researchers examined ring samples from 282 living trees and 263 from wood used in construction of old wood buildings – wider rings indicate , narrower, cooler. In analyzing the data, they were able to plot spring-time temperatures in the region going back nearly a thousand years. Next they compared average temperatures over extended cold periods and found they coincided with historical events such as the French invasion of Russia, the plague and the Thirty Years War. The group suggests food shortages during repeated cold springs might have led to civil unrest and the spread of diseases.

Predictably, the team also found that over the past five decades exceed anything they saw in the historical record they had created, adding yet another piece of evidence to the mountain of data already in existence that suggests the planet is truly experiencing an unprecedented period of global warming.

The team made clear also that cold snaps aren't necessarily an indicator of sudden unrest, more that extended periods of have in the past tended to lead to some very bad times for the people that lived through them or in many cases died as a result of the changes that were wrought.

Creating a from tree rings in Eastern Europe has an increased significance over some other areas, the team adds, because written historical records don't go back in time as far as those for Western Europe and other parts of the world. To gain an accurate picture of average global temperatures over a given period, they suggest, requires gathering evidence from a variety of locations that cover a significant amount of time, rather than relying on data from just a few locations.

Explore further

Climate in northern Europe reconstructed for the past 2,000 years

More information: Filling the Eastern European gap in millennium-long temperature reconstructions, PNAS, Published online before print January 14, 2013, doi: 10.1073/pnas.1211485110

Tree ring–based temperature reconstructions form the scientific backbone of the current global change debate. Although some European records extend into medieval times, high-resolution, long-term, regional-scale paleoclimatic evidence is missing for the eastern part of the continent. Here we compile 545 samples of living trees and historical timbers from the greater Tatra region to reconstruct interannual to centennial-long variations in Eastern European May–June temperature back to 1040 AD. Recent anthropogenic warming exceeds the range of past natural climate variability. Increased plague outbreaks and political conflicts, as well as decreased settlement activities, coincided with temperature depressions. The Black Death in the mid-14th century, the Thirty Years War in the early 17th century, and the French Invasion of Russia in the early 19th century all occurred during the coldest episodes of the last millennium. A comparison with summer temperature reconstructions from Scandinavia, the Alps, and the Pyrenees emphasizes the seasonal and spatial specificity of our results, questioning those large-scale reconstructions that simply average individual sites.

Press release

© 2013

Citation: Tree ring sampling shows cold spells in Eastern Europe led to unrest over past thousand years (2013, January 15) retrieved 19 May 2019 from
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

Jan 15, 2013
May be we could turn it around too . In warm periods there is plenty of food with a lot of offspring which leads to wars because more territory is needed for expansion . Cold or warm it does not matter . In fact in history a lot of offspring leads to wars . Now in europe with most families with two children all of a sudden it has been quite peace full the past 60 years . All so wars on planet earth at this moment are only in countries which have a population boom .

Jan 15, 2013
" All so wars on planet earth at this moment are only in countries which have a population boom."- perry

I see it as countries that have oil and poppy fields.

Jan 15, 2013
The creation of 'Europe' had much more influence on war or peace between countries.

Jan 15, 2013
Nit-picking: If this is Tatra in former Czhechoslovakia, it would be more correct to say Central Europe.
-So the Black Death was pre-dated by a cold spell that would have lead to malnourishment and reduced disease resistance. Maybe Poland was saved by having had a relative abundance of food, coupled with encountering a weaker strain of the pathogen.
Also, Norway was much harder hit than Sweden. This could also have been a matter of poor nutrition, following a period of poor crops.
Alas, comparing different strains of the pathogen is now impossible, but this factor would also have been relevant for differences in how the Black Death hit.

Jan 15, 2013
Wars are caused by fear. Fear of starvation, fear of ideas, fear of loss of power, fear, fear, fear....

That turns into desperation, which leads to a rationalization of "self preservation" (whether or not that's physical preservation or preserving your mental picture and ideology in the face of an alternative). I suspect the people who understand this and are "well placed" in a society or civilization find it all too easy to whip up the masses into legitimized mass murder of fellow human beings.

Jan 15, 2013
-So the Black Death was pre-dated by a cold spell that would have lead to malnourishment and reduced disease resistance.

With disease and war at roughly the same time it's hard to say which predated which.

War often leads to siege situations which are perfect breeding grounds for diseases (within the walls where food and water are scarce and long time food stores start to rot...but also in the military camps outside the gates with less than stellar sanitation. To the point where throwing diseased corpses to and fro between the camps via catapult was not an uncommon practice).

Also you get a lot of people fleeing from combat areas which means that diseases that are normally confined to a local group now have a chance to spread. And with the Black Death it was then a problem that people would tend to flee cities where it broke out - speading it quickly even further.

Jan 15, 2013
Which explains how and why a nation of cowards, The U.S., is in a state of perpetual war with the rest of the world.

"Wars are caused by fear. Fear of starvation, fear of ideas, fear of loss of power, fear, fear, fear..." - Mystic

Jan 15, 2013
Perhaps I can expand your scenario further. Instead of just warm, what about bleeding hot, then freezing cold, then droughts for 10 years then floods for the next 5? People and critics alike are fools thinking that GW is just about heating up. In fact, it is about the climate goes to crazy extremes, as it is beginning to show on the world's weather's news these days. Take the mess that I mentioned above, then fights will start for water, energy sources for heating and cooling. The havoc of ruined crops and shortage of food, sickness, diseases and death for people not acclimatized to extreme climatic variability and other bugs-born diseases such as malaria will be daily news. And tempers will be short for everyone because you won't be able to plant, or plan a thing without getting it ruined by..."just the weather", as climate change critics will say! The crap is hitting the fan. Everybody on this planet will get sprayed. Critics, don't think that you will get off scot-free.

Jan 15, 2013
"what about bleeding hot, then freezing cold, then droughts for 10 years"

It was 110-120f all summer, and now the lows have been in the 20s all week. I'm sure I speak for all of phoenix that we would all be rioting out on the streets right now if we weren't afraid of frostbite.

I'm freezing my ass off even with my heavy travel coat that I normally only use when I go to Europe or the East Coast.

Jan 16, 2013
Everybody is so panicked about climate change meanwhile basement bio-hacking is a growing cottage industry and the first viruses were built from scratch all the way back in 2003.
How much longer until it only takes one sociopath (psychopath?) to "print" a virus design that actually accomplishes a /- 90% fatality rate?


Jan 20, 2013
More pronouncements of what causes wars. First, religion is blamed for all the wars, then famine, overpopulation, fear. None of these caused World Wat I, which stemmed more from the crowned heads of Europe all being closely related, becuase of Queen Victoria's intermarrying her children. or the Revolutionary War, or World War II, or Korea or Vietnam of the invasion of Iraq, and so on. Also, which may please climate change deniers, this material may be suspect because, in the last few decades, dendroclimatology has seen chalolenges caused by the fact that ring width no longer correlates even approximately with temperature. Maybe trees are changing, maybe chemtrail poisoning of the air caused it. It was downplaying this fact that led to charges of fraud in the so called "climategate" affair.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more