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48    The Viking Age in Denmark

Europcan meteorological data for earlier periods. For instance, the mcdieval warm climate ends in Greenland in the beginning of the eleventh cen tury, but in England it ends in about 1300 according to the historical record. Furthermore, the Greenland curve shows the same trend towards poorer conditions of weathcr, at intervals of about 250 years, as the Danish bogs.

We shall not investigate the reasons, but only notę that there seems to be a corrclation between climatic periods and transgressions of the sea.³ According to the Greenland medium-frequency curve, the temperatures seem to be high in the eighth cen tury, before the onset of the Viking Age, Iow in the ninth and in generał warm again in the tenth, with a cooling in the eleventh (Fig. 9). By comparison these changes should also hołd true for north-west Europę. On the long-term level in Greenland, eliminating the 250-year time lag, we also have a cold ninth century, the period of the Danish raids on west Europę, a warmer trend throughout the tenth century and a drop towards a lower yearly average in about 1100.

Returning to the humification of the Danish bogs, there is support herc from comparisons of temperaturę between Greenland and north-west Europę for prehistorie periods. To a high degree the changes towards a colder and/or morę humid climate in the bog-series tum out to be parallel to the cold recessions of the Greenland temperaturę curve.⁴ This reveals temperaturę as the main factor behind the fluctuations in humification, and we tend to read the humification curve of Denmark, especially in outline, as a scalę of temperaturę differences.

In Draved bog, for instance, in south-western Jylland, we have a drop in humification in the later part of the Bronze Age (Periods IV-V, about 11 (X) to 700 B.C.) (Fig. 10). At exactly this time the distribution of burials shows that marginal lands in western Jylland have been given up.⁵ The next drastic recession takes place around 200 A.D., at a time when a large number of early Iron Age settlemcnts, especially on the poor lands to the west, were abandoned, and the field system was changed.⁶ The centuries at the tum of the first millennium B.C. on the other hand, were warm and probably dry, and rich in settlcments on the same soils. Apparently the problcms of a colder climate in south Scandinavia were greater than the benefits that sandy soils would gain from possible inerease in precipitation. The climatic and environ-mental data show that a poorer harvest, the leaching out of the soil for nutrients and mulldrift have caused the settlement system in the west to break down. In south Jylland, 01mer’s dyke, protecting the rich eastern areas from the west, was set up in the third century A.D.⁷ The same datę applies to an underwater blockade from the Haderslev inlet, fifty kilomctres to the north-east of 01mer’s dyke.^H Moreover we kno w of a number of sometimes very large offerings of weapons and other equipment for war parties in the bogs of the western border of the rich clay arca in central and western Denmark.⁹ Ali this points to an inerease in hostilities, probably centring on the west.

We do not believc that these changes altcred the generał character of the societies, which was much the same during both the Bronze Age and the early Iron Age (as compared with the period of the Viking Age State). For instance, valuable objects were being disposed of in large quantities in graves and sacred places, like the bogs, never to be regained. It is striking how both these practices disappear around 400-600, at the onset of the late Iron Age and the development of morę stable societies which eventually lacked these glaring, but redundant, ways of underlining personal status, either at individual burials or in public rituals like the bog-offerings.

Nor should the differences between the burial and the common public ritual be overlooked. Rich burials tend to be concentrated in the early Bronze Age warm period and to disappear during the late Bronze Age climatic recession, only to return before the turn of the millennium at the optimum of the early Iron Age.¹⁰ They vanish again after about 300 A.D., where offerings, often ofweapons, are common. Furthermore, the late Bronze Age and the beginning of the early Iron Age have many offerings of valuable objects. In short, there seems to be a correlation between periods of expansion of the settlement, stable subsistence production and conspicuous individual gravcs. The periods of recession stress public rituals and communion, and may in some ways have a firmer social system; but squandering of wealth in individual graves was suppressed, probably as a result of morę concrete Systems of inheritance.

These considerations cannot be directly applied to the end of pre-history. The Viking Age does have a number of wealthy gravcs and lacks bog-offerings; but the graves are all from the tenth century and refer to new statuses within the west Danish Jelling State. Between about 600 and 900 rich graves (as well as bog finds) are practically unknown, although the settlement was markedly expanding during the Viking Age climatic optimum and even during the preceding one or two centuries; this is apparent, in particular, from the many new place-names. The ninth century, however, may have been a period of some hardship, to judge from the Greenland evidence. The decades after the death of King Godfred in 810, with internal struggles for power, accompanied by the raids on western Europę and some settling abroad, would then fali within a shorter period of recession. The political expansion of the tenth-century Jelling dynasty, on the other hand, was bolstered by fine climatic conditions for subsistence production. To conclude this sector, we should point out that King Olaf ‘Hunger’ of Denmark late in the eleventh century reigned during years of severe crop failure, which fits into another recession in the Greenland series of temperaturę. Such detailed evidence has not been produced from the study of bogs; yet these yield the prime data for the