“Dear diary, it was freezing outside today…” If someone today wrote that in their journal, it might seem like an innocuous enough line, perhaps never to be carefully considered again. But what if, 500 years from now, scientists used that entry about the weather to answer climate mysteries?
Researchers looking to the past have done just that, combing through diaries and other old documents to reconstruct the climate of 16th century Transylvania, part of modern-day Romania. What they found offers a glimpse at how a cooling period called the Little Ice Age may have affected people in the region, the team reports February 12 in Frontiers in Climate.
Previous studies of pollen, sediments and other materials have been used to reconstruct past climate change. But “what we wanted to do is to focus on how people at the time felt the climate,” says Tudor Caciora, a climatologist at the University of Oradea in Romania.
The Little Ice Age was a centuries-long climatic event that led to cooler temperatures from the 14th to the mid-19th century, with studies suggesting that average temperatures in Europe dropped by 0.5 degrees Celsius after 1560. Several studies have traced the effects of the phenomenon in Western Europe, but researchers have struggled to collect information about the event in Eastern Europe.
So the breadth of records kept by people living in 16th century Transylvania presented an opportunity. Caciora and his colleagues combed through diaries, chronicles and other records from the 1500s to search for local climate clues.
Documents were handwritten in different languages, including Hungarian, Turkish and Latin. Searching for keywords like “hot weather” was not an option, since the team found that people often wrote about the weather in distinct ways. A passage describing the effects of heavy rains during a siege, for example, read “a large river flowed through the city, which swelled every day and did not allow passage even for several hours.” The researchers had to read documents in their entirety, even if there were sparse mentions of the weather within them.
The documents paint a picture of a 16th century Transylvania that was marked by heat and droughts in the first half of the century, followed by a period of increased rainfall. The researchers also came across vivid written accounts that indicate how the climate may have affected people by influencing calamities like famine, locusts and disease.
One describes a famine in the summer of 1534 caused by an intense drought. People were “losing their minds because of hunger,” resorting to eating herbs, tree bark and carrion. Skeletal corpses were described as having the remains of grass in their mouths.
Warm weather recorded throughout the century led the team to suggest that the Little Ice Age may have been delayed in the region compared with Western Europe.
Beyond providing a better understanding of how the Little Ice Age may have affected people in the past, research like Caciora’s may foreshadow how extreme events could impact people experiencing climate change in the future.
“Imagine what happens when we have a similar event in a climate that’s already warmer by 2 degrees on average,” says Ulrich Foelsche, a climate scientist at the University of Graz in Austria who was not involved in the study. “These studies of past climates are especially important to understand the variability of climate and extremes, to better know what could be coming up in the future.”