medieval-atlas/introductory/20

Transcription

Climatic changes Much of the infonnation presented in the rest of the atlas comprises data derived from archive sources unlikely to be changed in radical ways by future finds of fresh material. In contrast, since historical documentary evidence for climate change tends to be indirect and problematic, palaeoclimatologists actively pursue new data, from a whole range of laboratory and field sciences. Because ofconcern over global warming, governments are now financing extensive research into fonner climatic changes, in the hope that the past may cast its shadow into the future. Our picture of climatic change is thus under constant reassessment, so no definitive model can be offered here. Nonetheless, as historians we would be injudicious to neglect the basic fact that the physical environment which was the context for the activities of our forebears was characterised by almost constant change. The aim of what follows is therefore to give a general indication of the nature of the variations involved, with the proviso that revisions may certainly be expected. Before exploring the sequences of change, it is important to emphasise that the interaction between Scotland's global . position and physiography produces a basic climate, with characteristic regional subdivisions, and that the patterns illustrated in the previous pages have been largely characteristic of Scotland during the whole period covered by the atlas. These patterns have been modified but never obliterated by the postglacial climatic variations. Thus, while the margins between zones have been shifting almost continuously, the major positive and nega ',· . . . Cold polar air D. . . tive core areas of high and low "climatic productivity potential" have remained dominant features of our Scottish landscapes, throughout medieval and recent times. A basic fact of life in Scotland of which we must not lose sight is that a large portion of the country has always remained a harsh environment for subsistence agriculturalists. Nevertheless, what people actually choose to do is by no means necessarily·synonymous with what is theoretically possible in tenns of their physical environment. For example, people may farm farther up the hill even in climatically adverse periods because they rate the risks of using more marginal land as being less dangerous than the hazard of living down in the lowlands in time of strife. Alternatively, people may descend from the hills even in times of better climate if more land becomes available below, because of forest or peat clearance, say. Furthennore, pressure on land resources may change through demographic trends much less dramatic than, say, the Black Death. Changes in spatial patterns may also arise from alterations in the balance between subsistence agriculture and more commercially oriented types of land use. These in turn may reflect either relatively local economic changes, or large scale changes of the pattern of international markets, and of political access to them. In considering relationships between people and their environments, it seems that we must keep in mind changes in climates of opinion as much as changes in meteorological ones. Northern hemisphere circulation pattern -1- /' ----I --

  Transcribers who have contributed to this page.

None