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Vikings versus Climate Change

Page history last edited by Bryan Pettit 14 years, 6 months ago

 Climate and the Vikings: How are they Connected?


     Climate is defined most basically as the long-term weather patterns either locally or globally. Global climate change is a hot topic in the news today with an apparent warming over much of the earth. For example, Greenland is thought to be currently melting, which may increase the sea levels worldwide. Just recently, a small town in Alaska (Shishmaref) was in the news because coastal erosion is threatening to swallow up the town due to a loss of sea ice which usually protects the coast.


     In the same way in which current populations are having their lives modified by climate change, there have been perturbations in the past which might have had similar effects on the people of the time. In this study, I'll look at the climate (mainly in the Northern hemisphere) during the age of the vikings and look for ways in which the viking life may have been affected by climate changes of the past. As we learned in class, the era of viking dominance was mainly from roughly 800 A.D. to roughly 1200A.D. Therefore, I will focus on these dates when looking for correlations to climate and other aspects of the viking world which may have helped or hindered their dominance of the northern world.


How Do We Determine the Climate of the Past?


     Temperatures during historical periods can be estimated using various means. For example, tree rings (fig. 1) grow wider during warm, wet climatological periods and narrower during dry, cold times. Ice cores (fig. 2) can also be taken in polar regions, and the amount of oxygen isotopes trapped in bubbles correspond to the approximate temperature at which they formed (the Earth Observatory - NASA). These measurements are called proxy data; measurements of temperature-related environmental factors which indicate what the temperature was at the time of the formation of those factors.



Fig. 1: Norwegian Spruce (Picea abies) tree core sample. (Source: Wikimedia Commons)


Fig. 2: Portion of an Ice core sample from the Greenland Ice Sheet Project 2. (Source: Wikimedia Commons)



Temperature Reconstructions, Long-term


Fig. 3: Northern Hemisphere temperature anomaly reconstruction from 0 A.D. to 1980 A.D. compared to the average temperature from 1961-1991. (Source of data: Moberg, A., et al. 2005. 2,000-Year Northern Hemishphere Temperature Reconstruction. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2005-019. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.)


Fig. 4: Northern Hemisphere temperature anomaly reconstruction from 200 A.D. to 1980 A.D. compared to the average temperature from 1961-1991. (Source of data: Mann, M. E. and P. D. Jones, 2003, 2,000 Year Hemispheric Multi-proxy Temperature Reconstructions, IGBP  PAGES/World Data Center for Paleoclimatology Data Contribution Series #2003-051. NOAA/NGDC  Paleoclimatology Program, Boulder CO, USA.)


There Was No Census in Viking Times....


     so how do we know that climate change may have affected the rise and fall of the viking empire? Similar to using proxies for measuring historical climate conditions, data such as abundance of once-alive specimens (determined through studying fossilized bits of plants or animals) can be used to determine how climate at that time may have or may not have been conducive to life, including human settlement.


Betula pubescens - The beginning of Viking Settlement

     Downy Birch (also known as White Birch) is a tree species which has been present in Scandinavia for most of recorded history. Through looking at pollen accumulation in sediment samples, Erlendsson and Edwards (in The Holocene, 2009) showed that there were "rising values for the pollen of Betula pubescens for the period AD 600-800" (Erlendsson and Edwards). They determined that the increase in pollen they saw in that time period was generally due to improved flowering conditions for the plants, which they believe arose from overall climate warming and a decrease of early season cold and drought.


     Similarly to Betula pubescens, the human inhabitants of scandinavia would also benefit from fewer growing season cold snaps and climate warming in general. Spring is the growing season for both wild plants and agriculture alike, and any improvements in the growth of wild plants would translate nearly directly to improvements in agricultural conditions. In this case, the evidence of improved conditions for Betula pubescens serves as an indication that in the years immediately before the age of the vikings is a good indication that the climate was in the process of becoming favorable to population growth and demographic expansion.


     It is interesting to note that the increased abundance of Betula pubescens pollen was termed by the authors as "the final pre-settlement expansion of" Downy Birch in Iceland because upon settlement in Iceland, the vikings widely deforested the region for their natural resource needs such as housing, weapons, and ships.  


The Beginning of the End

     Although the viking dominance of the Northern world is largely thought to have occurred in roughly 1100 A.D., it is clear that the former-vikings were still living in relative peace in Iceland, Greenland, and other areas of the Northern world. Although their viking status was officially turning into a more docile centralized government of rural inhabitants, they were still living in relative peace in the same areas the had inhabited for hundreds of years. Soon, however, the very settlements which had once basked in viking dominance would cease to exist with the advent of the climate turning much colder than it once had been.



     Another species known to be present and widespread in Scandinavia during the time of the vikings were members of the chironomidae family, which are more commonly known as non-biting midges. These insects have tough, chitinous heads which survive the tests of time in sediment samples and can be identified and counted thousands of years after being deposited.


     Gathorne-Hardy et al. note that in their study of a sediment core from a shallow lake in Iceland, they found relatively high abundances of insects from the genuses Dicrotendipes and Ablabesmyia around 24cm to 32cm below the lake bottom (Gathorne-Hardy et al.). The two genuses indicated are known to survive better in warmer than average climates than other organisms in Iceland.


     Through looking at pollen accumulation rates and deposition of volcanic material, Gathorne-Hardy et al. concluded that the range in which Dicrotendipes and Ablabesmyia were more abundant in the fossil record than usual corresponded with the period between 1100 A.D. and 1300 A.D.  Following this period, the amount of warm-adapted insects began to decline in the fossil record of Iceland. Temperatures were turning colder and pressure was being exerted on both the small and the large animals - including humans.


Archaeological Evidence

     Ben Orlove wrote in Environmental Science and Policy that ice core records from Greeland show cold snaps in 1308-1318, 1324-1329, 1343-1362, and 1380-1384 (Orlove). These correspond with the above decline in Dicrotendipes and Ablabesmyia in Iceland. His study, however, focuses on archaeological evidence of the decline of the vikings.


     He notes that both low summer temperatures as well as cold winters would create hardships on the viking lifestyle. Hay production would decrease in the summers and increases in sea ice around Greenland's ports would make the life-sustaining trading with other scandinavian nations nearly impossible in the long winter season.


     Although the viking lifestyle of pillaging and plundering had largely ended by the beginning of the 12th century, it was the climate of the mid-14th century which would bring an end to post-viking settlements in Greenland. As Orlove explains, conditions soon got so dire for the former vikings that there is evidence of bones from hunting dogs in known viking settlements in Greenland which show signs of butchering; "demonstrat(ing) that the settlers were desperate enough to eat these animals". When things got bad enough to have to eat the very dogs which helped the vikings once look after their extensive livestock herds, the end of the vikings was finally taking place surely and swiftly. 


Conclusion: What is the connection between Vikings and Climate Change?


     It is clear from paleontological evidence such as tree-ring records, pollen counts, and ice core analyzation that the era in which the vikings began to settle the northern territories of Iceland and Greenland were exceptionally warm compared to their recent past. Exceptionally warm climates prompted the vikings to expand their empire outwards as their quest for resources and empire continued outwards from their original home of Norway.


     As for the downfall of the vikings, however, there seems to be no direct climate inference which can be made. By 1100 A.D. viking establishments were disappearing and centralized government was overtaking the individual spirit of the northmen. At best, by 1100 A.D. the temperatures in the northern hemisphere were just beginning to ttake turn downwards and would not yet have had an effect on the viking way of life.


     The immediate drop in Betula pubescens pollen in historic fossil records gives an indication of how the ecological factors in Iceland and Greenland could have had an effect on vikings. As soon as they arrived, native populations of White Birch crashed as the vikings harvested vast swaths of area for wood to burn and build ships and structures with.


     Due to this evidence, I hypothesize that the destruction on the natural resources in Iceland and Greenland overshadowed any effects which a climatological cool period (the Little Ice Age) would eventually have on the viking way of life. As abundance of natural resources waned in and around their settlements, the lush, individual lifestyle the vikings had enjoyed during the medieval warm period turned into a struggle to survive and by the time the Little Ice Age came around their population had already been crushed.


Works Cited


Erlendsson, Egill and Kevin J. Edwards. "The timing and causes of the final pre-settlement expansion of Betula pubescens in Iceland." The Holocene 19.7 (2009): 1083-1091.


Gathorne-Hardy, Freddy J., et al. "Lake sediment evidence for late Holocene climate change and landscape erosion in Western Iceland." Journal of Paleolimnology 42 (2009): 413-426. 


Orlove, Ben. "Human adaptation to climate change: a review of three historical cases and some general perspectives." Enviromental Science and Policy 8 (2005): 589-600.







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