Climatic Variability in Sixteenth-Century Europe and its Social Dimension: A Synthesis

Abstract

The introductory paper to this special issue of Climatic Change summarizes the results of an array of studies dealing with the reconstruction of climatic trends and anomalies in sixteenth-century Europe and their impact on the natural and the social world. Areas discussed include glacier expansion in the Alps, the frequency of natural hazards (floods in central and southern Europe and storms on the Dutch North Sea coast), the impact of climate deterioration on grain prices and wine production, and finally, witch-hunts.

The documentary data used for the reconstruction of seasonal and annual precipitation and temperatures in central Europe (Germany, Switzerland and the Czech Republic) include narrative sources, several types of proxy data and 32 weather diaries. Results were compared with long-term composite tree ring series and tested statistically by cross-correlating series of indices based on documentary data from the sixteenth century with those of simulated indices based on instrumental series (1901-1960). It was shown that series of indices can be taken as good substitutes for instrumental measurements.

A corresponding set of weighted seasonal and annual series of temperature and precipitation indices for central Europe was computed from series of temperature and precipitation indices for Germany, Switzerland and the Czech Republic, the weights being in proportion to the area of each country. The series of central European indices were then used to assess temperature and precipitation anomalies for the 1901-1960 period using transfer functions obtained from instrumental records. The statistical analysis of these series of estimated temperature and precipitation anomalies yielded features which are similar to those obtained from instrumental series.

Results show that winter temperatures remained below the 1901-1960 average except in the 1520s and 1550s. Springs fluctuated from 0.3°C to 0.8°C below this average. Summer climate was divided into three periods of almost equal length. The first was characterized by an alternation of cool and warmer seasons. The second interval was 0.3°C warmer and between 5 and 6% drier than in the 1901–1960 period. It is emphasized that this warm period included several cold extremes in contrast to the recent period of warming. Summers from 1560 were 0.4°C colder and 4% more humid. Autumns were 0.7°C colder in the 1510s and 20% wetter in the 1570s. The deterioration of summer climate in the late sixteenth century initiated a second period of enlarged glaciers in this millennium (the first having been in the fourteenth century) which did not end until the late nineteenth century.

An analysis of forcing factors (solar, volcanic, ENSO, greenhouse) points only to some volcanic forcing. In order to understand circulation patterns in the sixteenth century in terms of synoptic climatology, proxy information was mapped for a number of anomalous months. Attempts to compare circulation patterns in the sixteenth century with twentieth-century analogues revealed that despite broad agreements in pressure patterns, winters with distinct northeasterly patterns were more frequent in the sixteenth century, whereas the declining summer temperatures from the mid-1560s seem to be associated with a decreasing frequency of anticyclonic ridging from the Azores' center of action towards continental Europe. The number of severe storms on the Dutch North Sea coast was four times greater in the second half of the century than in the first. A more or less continuous increase in the number of floods over the entire century occurred in Germany and the Czech lands. The Iberian peninsula and the Garonne basin (France) had the greatest number of severe floods in the 1590s.

The analysis of the effects of climate on rye prices in four German towns involved a model that included monthly temperatures and precipitation values known to affect grain production. The correlation with rye prices was found significant for the entire century and reached its highest values between 1565 and 1600. From the 1580s to the turn of the century wine production slumped almost simultaneously in four regions over a distance of 800 kilometers (Lake Zurich to western Hungary). This had far-reaching consequences for the Habsburg treasury and promoted a temporary shift in drinking habits from wine to beer. Peasant communities which were suffering large collective damage from the effects of climatic change pressed authorities for the organization of witch-hunts. Seemingly most witches were burnt as scapegoats of climatic change.