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1
Introduction:
Climate background and Eem visitors
1.1 Setting the stage
One sometimes sees history divided into the period with written sources, the period for which cultural objects have been found, and the period with no such tangible evidence. The first two periods are sometimes called “the historical period” and “the archaeological period”.
I do not think these distinctions are particularly useful. The period with no written or archaeological finds still allows a number of conclusions to be reached (e.g. regarding conditions for life and diversity). Methods may involve climate reconstructions, geological models, genetic development models and simulation of resource competition and niche occupancies. Some of these models may even allow falsification by suitable observations in nature or experiments.
In the period with archaeological findings, an approach needs to be adopted that prevents the actual finds from overshadowing other (and perhaps more important) factors. For example, there could be other types of artefacts, which have not survived or physically could not have survived until present society, and these artefacts might have delivered a substantially different picture of the society in which they functioned. We are preoccupied with the stone tools of the palaeolithic period, because of their abundance, but talk little of what clothes and shelter were used during time periods too far away to have delivered evidence of such items. For high-latitude ice age human survival, these are key factors, and our research becomes enriched once we begin to study scenarios for survival in the winter of Saalian France at −20 °C with different types of footwear. Finding the boots is not a condition for insight, and the colleague who tells you that the Neanderthals could not have worn tight footwear because the sewing needle had not been invented may have to yield. The challenges do not become smaller as one passes from the period of museum artefacts to the period of prolific writing. Written documents are of course perfect tools for attempting to manipulate history. Kings and emperors, religious institutions and political figures will do anything to improve their image or that of their cause in history, and other historical agents are keen to follow suit. Historical research is a continuous struggle to see through such attempts at history falsification and get to the bottom of the matter. The volume of written documentation rarely tells which things are important and which are not. Today, nonsense documents are sometimes produced with the sole purpose of hiding more important issues, and even if there is not any conspiracy involved, written junk information still surpasses the true information by orders of magnitude.
Thus my overall suggestion is that all of the historical periods, with written, archaeological or no tangible sources, have large margins of uncertainty and an immense need for somebody to sort true from false by a maximum of unbiased scientific analysis and synthesis.
In this work, I have used Denmark as a case study for the energy history of a region. “Denmark” should be taken in a flexible sense, as the notion of nations only exists in a relatively short and recent period. Even during this period, Denmark has, like most other European nations, not had a constant size. Most European countries have, at some point in time, been a dominant force on the continent, and have subsequently lost that position. During most of its existence, Denmark comprised the Jutland peninsula and most of the surrounding islands, the provinces of Skåne, Halland and Blekinge (conquered by Sweden a little over 300 years ago), and the provinces of Schleswig and Holstein (which have been handed back and forth between Denmark and various German states, in connection with wars and for the most recent border adjustment by popular referendum). In the context of this book, former colonies such as Greenland (now making the transition from being part of the Danish state over extensive home rule to independent status) are not included, and nor are the Norwegian remnants (such as Iceland) adopted by Denmark when the union between Denmark and Norway was broken by the Swedish appropriation of Norway proper.
The alternative of defining “Denmark” as where the Danes live would be equally difficult, because nearly all populations in Europe have been through several migration phases, sometimes moving from one end of the continent to the opposite one. At the modern origin some 4000–5000 years ago, the people living in the south of Jutland are referred to as Germanian. They presumably descended from the Stone Age people living in this area at earlier times, and these had again come from regions further south in Europe. They subsequently spread both north and south, to the rest of Denmark and Scandinavia and to the North of current Germany. Neither culture nor language allows a precise delimitation of what is Danish. Just over 2000 years ago, another wave of Danes, the Cimbrians and the Teutons, marched south and tried to settle near current Belgrade. The next waves were those of Angles, Jutes and Vikings (also coming from other parts of Scandinavia), settling between 400 and 1100 in England and France, and establishing strongholds from Ireland to Portugal, Spain and Italy (Kinder and Hilgemann, 1964). In this way, through many earlier and subsequent movements in south and central Europe, a beautifully multicultural Europe was formed and readied to serve as a basis for current cooperation. Some time after 700, a proper Danish state was formed.
In the palaeolithic era there is even less point in singling out the people living in Denmark. The European population moved north and south in response to climate change, and the interaction, not least through trade, with people in the Near East was a most important source of new ideas. In consequence, this study will simply focus on a Denmark similar to that which exists today, but will make excursions to adjacent areas whenever relevant.
The style of history-telling will be very selective: to explore living conditions to the extent required to determine energy use, and occasionally to identify impacts of energy issues on other traits of society. This means following everyday life and when society becomes stratified, then to explore the effects of this on energy provision and energy usage, but not to go into much detail on issues such as wars, fights over thrones and territories, and exploitation and revolt between the classes.
The rest of this chapter gives an overview of environmental conditions induced by changes in climate and then concentrates on the development of human (Neanderthal) societies in Europe during the warm interglacial period called the Eem period. Exploring the energy conditions during this part of the Stone Age will set the stage for several of the following chapters by introducing methods and illustrating climate development, population size and available technology across the time periods, to be subjected to further scrutiny in the subsequent chapters.
1.2 Climatic conditions in the European interglacial period
During the interglacial period from about 130 000 years to about 115 000 years ago (130–115 ky BP), a modest number of humans, presumably Neanderthals, ventured to exploit the hunting possibility in the northern parts of Europe.* It is likely that at the higher latitudes they were only seasonal visitors, although a few may have stayed over during the winter to avoid the long march back to where they came from (perhaps in current mid-Germany, where a fairly large amount of Neanderthal remains have been found).
What were the environmental conditions these people had to cope with, and how did conditions change during the following millennia? The conditions of interest include temperature, solar radiation, precipitation, windiness, land and sea distribution and topology, soil type, vegetation and fauna, ice and glaciers, and, for several of these quantities, their seasonal variation.
Let me begin with temperature and solar radiation. The major cyclic behaviour in solar radiation (the 105 000-year Milankovitch cycle induced by changes in eccentricity of the Earth’s orbit) has caused periodic shifts between warming and cooling, with periods of extensive glaciation accompanied by changes in atmospheric carbon dioxide content and ocean salinity. Increased ice cover changes the surface albedo (to make the surface reflect more sunlight) and thereby provides a feedback to surface temperatures (Jansen et al., 2007; Sørensen, 2004). Further changes in the obliquity of the Earth’s orbit and the precession of its perihelion cause variations in the geographical distribution of solar radiation, with periods of 41 000 years and 23 000 to 19 000 years. The changes in temperature that may be inferred from ice core samples and ocean sediment analysis are depicted in Figs. 1.1, 1.3 and 1.4, where they have been adjusted by an overall shift to give an approximate temperature profile relevant for the location of Denmark. The variation in solar radiation due to variations in the Earth’s orbital parameters is shown in Fig. 1.2, also for Denmark.
Figure 1.1. Temperatures in Denmark deduced from 50-year averages of ice core data from NGRIP, Greenland (based on Huber et al., 2006).
Figure 1.2. Historical and near-future levels of solar radiation in Denmark, calculated from variations in orbital parameters and without attenuation in the atmosphere (based on data from Berger et al., 2007).
Figure 1.3. 250 000 years of temperature estimates (shifted to Danish average temperatures for easy comparison with Fig. 1.1) based on δ2H data from Vostok, Antarctica (based on Petit et al., 1999).
Figure 1.4. Average benthic δ 18O, with shift to Danish temperature scale imposed for illustration (based on Lisiecki and Raymo, 2005).
Figure 1.1 shows that mean temperatures in Denmark may have varied by over 30 °C between the most severe part of the last ice age (just under 30 000 years ago) and the warm Eem period some 125 000 years BP, and that even during the middle of the recent (Weichselian) ice age, temperatures varied up and down by up to 20 °C over fairly short intervals of time. How certain are we that the Greenland ice records reflect temperatures in Denmark? The presence of various amounts of the oxygen isotope variant 18O in the water falling as snow in Greenland and being incorporated in the ice cores (drilled vertically down to the bottom of the ice sheet covering Greenland) constitutes the basic measured data. The 18O is then interpreted as having been incorporated somewhere else into the clouds responsible for the Greenland snow, say over Europe, and is thus reflecting the conditions at that location. Temperature is an important determinant for the amount of 18O in the water that forms clouds and the Greenland ice core measurements therefore tell us something of the temperature – not in Greenland, but in the regions where the water came from. A typical path with today’s climate for water to arrive in Greenland is, in winter, from middle Europe northeast to the Barents Sea, then turning west to the Denmark Strait and finally turning north across Greenland. In summer, a typical path goes east from the central North American continent, then turning north towards Cape Farewell and further north into Greenland. The “18O-temperature” seen at the NGRIP borehole in mid-Greenland will be lower in winter than in summer. Going back in time (deeper into the borehole), the ice will become increasingly compressed, and after a while seasonal variations can no longer be seen. The lowering of sea level due to ice formation at peaks in the glacial periods may alter ocean current paths as well as wind circulation patterns, and the bore-hole 18O-temperature may at such times be reflecting real temperatures at other locations than currently. The large temperature variations of the ice core records (e.g. during the period from 50 000 to 30 000 years BP) may therefore reflect changes in posting locations combined with modest changes in circulation, or they may reflect real abrupt temperature changes (e.g. in Europe).
In Antarctica, where few large land masses are adjacent, one does not see quite such large variations in ice core 2H-temperatures, and the overall temperature excursions during the last 300 000 years are also much smaller than in the Arctic records (Fig. 1.3): some 12 °C versus 35 °C in the north. On the other hand, the recent excursion around 14 000 years BP in the Greenland record (Fig. 1.1) is corroborated by pollen data from Denmark, as discussed in the following chapter on the latest deglaciation period. A reasonable conclusion is that the Antarctic data do not tell us much about detailed climate change in the north, but only about the rough extent of ice ages.
A third indicator of temperature is from the 18O-analysis of benthic cores. They are cores drilled at ocean bottom...
