One can only imagine one single general answer to this almost complete coincidence: changes in climate. Today they are no longer dismissed by academics as a joke. Recent detailed research by historians and meteorologists shows constant fluctuations in temperature, pressure systems and rainfall. These variations affect trees, rivers, glaciers, the level of the seas, and the growth of rice and corn, olive trees and vines, men and animals.
Now the world between the fifteenth and eighteenth centuries consisted of one vast peasantry, where between 80% and 90% of people lived from the land and from nothing else. The rhythm, quality and deficiency of harvests ordered all material life. Sudden climatic catastrophes are reflected in the growth-rings of trees - and in the population figures of mankind. And some of these changes occur everywhere at the same time, although as yet we can only explain them by short-lived hypotheses (such as the now abandoned theory of variations in the speed of the jet-stream). There was a general cooling down of the northern hemisphere, for example, in the fourteenth century. The glaciers advanced, icefloes were more numerous and winters became more severe. The Vikings’ route to America was cut off by dangerous icebergs: ‘Now the ice has come … no one can sail by the old route without risking death’, writes a Norwegian priest in mid-fourteenth century. This climatic drama appears to have interrupted Scandinavian colonization in Greenland: the bodies of the last survivors, found in the frozen earth, are thought to be poignant testimony of this.
Similarly the ‘little ice age’ (to use Dr Shove’s expressiori) during Louis XIV’s reign was more of a tyrant than the Sun King. Everything moved to its rhythm: cereal-growing Europe and the rice fields and steppes of Asia; the olive groves of Provence and the Scandinavian countries where snow and ice lingered till late in the year and autumn returned so promptly that the corn no longer had time to ripen: this was the case in the terrible decade of the 1690s, the cold est for seven hundred years. Natural disasters also multiplied in China in the
middle of the seventeenth century disastrous droughts, plagues of locusts - and a succession of peasant uprisings occurred in the interior provinces, as in France under Louis XIII. All this gives additional meaning to the fluctuations in
material life and may explain their simultaneous appearance. The possibility of
a physical coherence of the world and the generalization of a certain biological history common to all mankind suggests one way in which the globe could be said to be unified, long before the voyages of discovery, the industrial revolution or the interpenetration of economies.
If, as I am inclined to think, the climatic explanation has some truth in it, we must take care not to over-simplify it. Climate is a very complex system and its effect on the lives of plants, animals and people only comes about via very devious routes that vary according to place, crop and season. In temperate Western Europe, for example, there is ‘a negative correlation between the quantity of rainfall from 10 June to 20 July’ and ‘a positive correlation between the percentage [of sunny days] in the period from 20 March to 10 May and the number of grains [on an ear] of corn’. And if one seeks to argue that serious consequences resulted from a deterioration of the climate, one has to prove first that such deterioration occurred in the countries of the temperate zone, the most densely populated and in the past ‘the most important for Western Europe’s food supply’. That may seem obvious. But the examples of direct influence of the climate on harvests so far put forward by historians too often relate to marginal regions or crops, such as corn in Sweden. In the present fragmentary state of research, it is impossible to generalize. But we should not prejudge too hastily the answers the future may provide. And we should bear in mind the
congenital frailty of man compared to the colossal forces of nature. Whether it favours him or not, the calendar is man’s master. Historians of the ancien regime are quite right to regard it as punctuated by the succession of good, not so good or bad harvests. These were the regular drumbeats which set in motion enormous fluctuations of prices on which so many other things depended. And who could fail to agree that this insistent background music was in part determined by the changing history of the climate? We know how vitally important the date of the monsoon still is today: a mere delay can cause irreparable harm in India. If the same thing happens two or three years running, it means famine. Here man has still not been able to free himself from these terrible shackles. But we would also do well not to forget the damage inflicted by the drought of I976 in France and Western Europe, or the abnormal change in wind patterns which caused a catastrophic drought east of the Rocky Mountains, in the United States in I964
It is amusing to think that the men of former times would not have been put out by this climatic explanation, implicating as it does the heavens. They found it all too tempting to explain the course of everything terrestrial, including individual or collective destinies and disease, by the stars. In I55I Oronce Finé,
a mathematician and dabbler in the occult, made the following diagnosis in the name of astrology: ‘If the Sun, Venus and the Moon are in conjunction in the sign of Gemini (the Twins), writers will earn little for that year and servants will rebel against their masters and lords. But there will be a great abundance of
wheat on the land and roads will be unsafe because of the abundance of thieves.