The world was not a fun place between 1914 and 1920. As if the horrors of the First World War (1914-1918) were not hellish enough, much of the world then had to deal with the “Spanish flu” outbreak, a pandemic that’s thought to have wiped out over 50 million people worldwide. It turns out this unfortunate series of events might have been worsened by a short but sharp blip in the Earth’s climate that resulted in freakishly cold and wet weather in northern Europe. 

In a new study published in Geohealth, an international team of scientists studied a 72-meter-long (236-foot-long) ice core taken from the Colle Gnifetti glacier in the Swiss-Italian Alps and discovered a “once?in?a?century climate anomaly” that resulted in increased wet and cold conditions from the north Atlantic during the First World War. 

Within the 2,000 years of climate history embedded in the ice core, the researchers discovered notable changes in the levels of sodium and chlorine, components found in sea salt, in the layers that related to the years 1915 to 1918. According to the researchers, this clearly indicates the Alps and much of northwestern Europe were likely hit by a strong influx of cold North Atlantic sea air, bringing in colder air and a deluge of rain. 

Other sources from the time, such as written documents or photographs, often portray this period as a deary and grey time, with barbed-wire lined trenches filled with rainwater and mud. It appears this image might not be far from the truth. 

In turn, the researchers argue that this harsh bout of weather might have further deepened the hardship and casualties brought on by World War One. Along with the threat of bullets and mortars, soldiers fighting this arduous war also had to deal with disease and trench foot, a nasty condition when the feet are wet for long periods of time. These dangers would have been made significantly worse from the harsh weather experienced at the time, say the researchers. 

“We found that mortality in Europe peaked three times during the war, and these peaks occurred during or soon after periods of cold temperatures and heavy rain caused by extremely unusual influxes of ocean air in the winters of 1914-15, 1915-16 and 1917-18, together providing a once in a 100-year anomaly,” Dr Alex More, study author from Harvard University and the Climate Change Institute, University of Maine, and associate professor in environmental health at Long Island University, New York, explained in a statement. 

Furthermore, they also link this climate anomaly to the strong waves of the Spanish flu. Not only would more humid conditions favor the spread of respiratory disease but the unusual climatic conditions may have also had a profound effect on mallard ducks, one of the main animal reservoirs for the H1N1 strain of influenza. The researchers argue that the migrations of mallard ducks and other migratory birds would have been profoundly disturbed during the war years, meaning they were more likely to stay in Europe where they could easily transmit influenza to humans by water contaminated with their poop. Clearly, this is just one small piece of the puzzle, but the researchers argue it could have played some role in the disease outbreak.

“These atmospheric reorganizations happen and they affect people,” Dr More said in another press release. “They affect how we move, how much water is available, what animals are around. Animals bring their own diseases with them in their movements, and their migrations are due to the environment and how it changes, or how we change it.”

“I think it’s a very credible, provocative study that makes us think in new ways about the interplay between infectious diseases and the environment,” added Philip Landrigan, a director of the Global Public Health Program at Boston College who was not involved in the new study.