A New “Drought Atlas” Tracks Europe’s Extreme Weather Through History
The data, based on tree rings, fills in details about past events and could help improve climate modeling for the future
Central Europe suffered an extreme drought this year, with rainfall just 20 percent of normal in France and blistering heat across parts of the continent that was accompanied by water shortages, wildfires and poor harvests. The drought was the worst since 2003, and some climate experts considered it a sign of what could happen as climate change intensifies.
But the continent has seen even worse times in the last two millennia, from periods of extreme desiccation to famine-inducing downpours, according to a new study in Science Advances. The resulting “drought atlas” is a reminder that Earth can produce dangers more extreme than anything modern humans have experienced.
Edward Cook of Columbia University’s Lamont-Doherty Earth Observatory and his colleagues created their record from cross-sections of trees from across Europe. “Tree growth in the form of ring width is frequently limited by how much soil moisture from precipitation is available to use,” Cook says. That let the scientists produce centuries-long records of wet and dry times in Europe that they hope will improve climate modeling and “lead to improvements in what to anticipate in the future,” he says.
Scientists have previously produced drought atlases for North America and part of Asia and identified periods of megadrought that have not been experienced in modern times, Cook notes. While most of the extremes found in Europe were previously known from written records, the research fills in some details about these past events:
Crops need water, but there can be too much of a good thing. For more than two years in the 14th century, much of Europe received more than its usual share of rain. In 1315, crops failed across the continent, from England, west to Russia and south to Italy. These wet times are reflected in the drought atlas, which also shows that southern Italy was spared—matching historical records. Food became scarce and prices rose, quadrupling or more.
“The usual kinds of meat, suitable for eating, were too scarce; horse meat was precious; plump dogs were stolen. And, according to many reports, men and women in many places secretly ate their own children,” wrote Johannes de Trokelowe, an English monk. The quick population growth that preceded this time halted, and millions died. This great famine may also have undermined the campaign by Edward de Bruce in Ireland, putting out Irish dreams of ending English rule for centuries.
The drought that hit central and Eastern Europe in the 1500s has been described as a “worst case” by modern scientists, and the seeds of the dry times recorded in the tree rings may have been planted the year before. Chroniclers in northern Italy wrote that the 1539-40 winter was rain-free and “like in July.” People in Spain had begun praying for rain as early as October 1539. Heat continued through much of 1540, and even when the rains came, they don’t seem to have helped much.
Large rivers, such as the Rhine and the Seine, dried enough that people could easily wade across them in places. Brooks and wells went completely dry. Without water, cattle and other animals died, and mills could not grind grain. The earth dried out, and vegetation suffered from drought stress. Pierre de Teysseulh, a church official in Limoges, France, wrote that “the grapes were like roasted and the leaves of the vines had fallen to the ground like after a severe frost.” But the extreme heat may have been good for at least one vineyard in Germany, Würzburger Stein, which produced a vintage so fine that year that its reputation is still known today.
Less than a hundred years after the 1540 drought, the same region dried out again. Rivers again receded, and people marked the low levels in the Elbe River with “hunger stones” that can sometimes be seen when similar warm, dry conditions occur. The dry times, according to the tree rings, struck across much of central Europe, Germany and Switzerland.
This time period is known for the “Irish Famine,” which was actually worse than the infamous Irish Potato Famine that struck a century later. “This event has been attributed to unusually low winter and spring temperatures in 1740, resulting in crop failures and subsequent famine,” Cook and his colleagues note. But their tree ring analysis provided evidence that drought may also have played a role; spring and summer rainfall in 1741 was well below the modern average. Bad harvests and food shortages arrived quickly, and by May 1740, there were riots in Dublin. One author estimates that 38 percent of the Irish population died during the famine, a greater proportion than those claimed by the subsequent potato famine.
“Never within the memory of living men has it been so hot, and especially so dry, as during this ill-starred year,” wrote one person in the Paris Figaro on July 23, 1893. “The dreadful African heat has left not a handful of grass for the cattle, causing them to die off like flies.” Heat ruined crops in France and Germany, and written records include deaths from sunstroke. In England, several towns set records for the number of rainless days—including one spell lasting more than two months—that still have not been broken.