16.2.1 The Effects of Climate Change in the Fourteenth Century

Perhaps the greatest challenge in grasping the impact of climate change on the past is the limitations of traditional historical sources. Texts and other written source materials often provide scant information about environmental fluctuations of earlier centuries. To overcome these barriers, the field of historical climatology focuses on reconstructing and analyzing climates of the past and comparing them with modern conditions, allowing scholars to expand the traditional source base of historical research. Historians study references to crop yields and weather fluctuations in weather journals and tax records, along with scientific data drawn from tree rings and organic material trapped beneath ice sheets in different parts of the world, which offer information about past temperature fluctuations and rainfall patterns (Figure 16.9).

The investigation of such historical clues hidden in the natural world has enabled scholars to identify the ways in which environmental conditions and patterns of human migration and settlement have together shaped the course of human history. In the case of the calamitous fourteenth century, a series of unusual climatic changes led to a chain reaction of competition for resources and desperate attempts to mitigate the damage and despair that defined the century’s first decades.

At the beginning of the fourteenth century, subtle shifts in global mean temperature and rainfall had a profound impact on the climate of the Northern Hemisphere, unleashing devastating famines and plagues across Afro-Eurasia. These events caused significant human hardship, disrupted commerce, and contributed to the decline of once-great empires, even the seemingly impenetrable Mongol dynasty. Although premodern people did not understand these extraordinary environmental shifts, their lives were no less affected by them. In an era during which many people survived on subsistence agriculture, even the slightest change in seasonal weather patterns could devastate crops and result in widespread malnourishment and starvation. Poor nutrition weakens human immune systems, which—together with poor sanitation and the close quarters in which people lived in medieval towns—undoubtedly left many more vulnerable to the ravages of epidemic diseases. This was especially the case when the bubonic plague struck much of Afro-Eurasia by the middle of the century.

To place the dramatic meteorological changes of the fourteenth century in context, we must understand how they relate to larger climate patterns. Long-term weather fluctuations, during which periods of relative warmth and cold alternated over hundreds of years, have long been part of Earth’s ecological landscape and the narrative of environmental history. Within these longer periods of gradual climatological change, however, less predictable short-term fluctuations have also resulted from rapid changes in wind patterns, ocean currents, and seismic activity. From time to time, such erratic climatological shifts resulted in devastating reversals of typical weather patterns.

In the fourteenth century in particular, the Little Ice Age, a period of unusually cold weather that affected most of the Northern Hemisphere (Figure 16.10), led to significant variations in normal rainfall and a general drop in the mean annual temperature. Preceded by a Medieval Warm Period, a span of more temperate climate across the globe from the tenth through the thirteenth century, the cool temperatures and, in some areas, droughts radically reduced available resources and food supplies. Aggravated by rising population levels and declining agricultural productivity, food shortages caused significant hardship and financial distress as famine became commonplace and competition for resources intensified.

Although a consensus about the causes of the Little Ice Age remains elusive, possible triggers may have included changes in ocean circulation patterns, shifts in the earth’s orbit, and several massive volcanic eruptions in the tropics that released clouds of sulfate particles into the atmosphere and reflected solar energy back into space at the end of the thirteenth century. Ultimately, these environmental changes resulted in an advance of mountain glaciers and an overall mean global temperature decrease of 0.6°C (with some areas experiencing as much as a two-degree drop in annual temperature). This decrease may seem insignificant, but in the absence of modern agricultural and irrigation techniques, it led to catastrophic crop failures and widespread famine in many parts of the Northern Hemisphere within the first few decades of the fourteenth century. The increase in glacier growth, moreover, affected many regions of the world, because the more water turned to ice, the less was available to evaporate and turn into rain. As a result, even areas far from glacial mountains suffered prolonged periods of drought.

Despite their global impact, the effects of the Little Ice Age were not the same everywhere. In the Mediterranean and West Africa, irregular rainfall and periods of drought dramatically reduced crop yields, whereas in China and northern Europe, cold weather and the freezing of lakes and rivers were especially pronounced. Elsewhere in Europe and Asia, in 1314, extraordinary rains began to fall that introduced a period of abnormally cold and wet winters. This deluge of precipitation resulted in poor harvests as people struggled to cultivate already overworked land. Outside Afro-Eurasia, evidence suggests that the North American interior also suffered when established agricultural systems faltered under hotter summers with less rain and colder winters, leading to severe population loss in the southwestern region.

Although the Little Ice Age was especially devastating in the 1300s, its effects persisted for many centuries. In addition to its immediate impact on crops, late medieval climate change led to longer-term deforestation because more wood was used for heating, in the Northern Hemisphere in particular. The climate shift not only altered building designs and clothing styles, which became adapted to colder temperatures, but in some places it also ultimately precipitated the eventual adoption of coal for heating and the beginning of human reliance on fossil fuels.

The period known as the Great Famine of 1315–1317 was a direct result of the Little Ice Age in much of Europe north of the Alps, an area of roughly 400,000 square miles. This widespread and prolonged food shortage prompted one of the worst population collapses in Europe’s recorded history. It is virtually impossible to know the actual death toll, but it is likely that up to 10 percent of northern Europe’s population of more than thirty million perished. Even though crop yields began to rebound in 1317, it took several more years for them to return to prefamine levels. Beyond the devastating loss of lives and human suffering, prolonged food shortages also led to widespread political and economic instability. The prices of necessary food staples like grain skyrocketed, and competition for resources generated social tension, conflict, and an increase in crime. Ultimately, the Great Famine led many to question the ability of church officials and monarchs to respond effectively to crises and catastrophes, which had long-term effects on public trust in these institutions (Figure 16.11).

With very few options to remedy the devastation wrought by years of poor weather and famine, most people had little practical recourse other than migrating in search of better conditions. The collective anxiety and social tension of the era sometimes led to scapegoating, including persecutions of supposed witches based on the premise that they had the ability to control the weather as a means of causing others harm. Historians have traced connections between peaks of the Little Ice Age and spikes in witch-hunting activities. Although this type of persecution was by no means universal, it demonstrates the desperation many people must have felt in the face of unrelenting strife.