Ice Core Research Reveals Climate Anomaly During WWI, 1918 Flu Epidemic

An international team of climate researchers and scientists affiliated with institutions like Harvard, the University of Maine, and the University of Nottingham have uncovered evidence of a six-year European climate anomaly, which impacted World War I and the 1918 Spanish flu pandemic.

Data obtained from historical records and an ice core, published with the Sept. 15 study, suggests that the presence of cold, salty air over Europe exacerbated casualties of the influenza pandemic and WWI.

Researchers in partnership with the Climate Change Institute at the University of Maine and the Initiative for the Science of the Human Past at Harvard study historical and natural data for evidence of climate anomalies. Glaciers and ice cores offer time capsules of global climate history, according to Alexander F. More, a co-author of the study and research associate in the Initiative for the Science of the Human Past at Harvard.

“Just like you smell it in your nose, the glacier smells it too,” More said. “The glacier traps whatever’s in the atmosphere — whether that’s human pollution, or dust from the Sahara, or salt from the ocean.”

The team uses new laser ablation technology from the University of Maine and a melting process called continuous flow analysis to date climate patterns observed in ice cores. The team’s recent discovery of high sodium and chlorine concentrations in the Colle Gnifetti glacier in the Swiss-Italian Alps indicated the presence of sea salt deposited in the early 20th century. According to More, this salt buildup demonstrated an extreme climate event.

“For the period of World War I, we saw the largest increase in sea salt in 100 years,” More said. “We looked into the historical accounts of World War I provided by my colleague Christopher P. Loveluck at the University of Nottingham and now had a much clearer picture of what was happening. It was a six-year anomaly where this cold, wet air from the North Atlantic really lingered over Europe.”

More and his colleagues discovered that the climate extreme was the result of a dominant marine air system, which forced cold marine air from the North Atlantic down onto Europe from 1914 until 1919. When the team compared this data with historical records, spikes in cold air matched spikes in mortality rates across Europe during WWI and the 1918 pandemic. The cold air damaged harvests, which had deadly consequences during the war and subsequent pandemic, according to History professor Michael McCormick, chair of the Initiative for the Science of the Human Past.

“Bad harvests promote frailty of health,” McCormick said. “One of the winters was called the ‘Turnip Year’ in Germany because everything failed, and they had only turnips to eat. So when your diet is poor, you are more susceptible to disease.”

Cold weather and increased precipitation also flooded trenches and destroyed battlefields, increasing casualties at the battles of the Somme and Verdun. An estimated 20 million died during WWI and 50 million died during the 1918 influenza pandemic.

In addition to informing the historical understanding of the spread of the Spanish flu, the findings of the study have implications on modern epidemics. Climate research increasingly represents an essential part of epidemiology due to rising concern over the effects of climate change, according to More.

The spread of Zika, Malaria, and COVID-19 also heighten the urgency of the work done by More, McCormick, and their team. Warming temperatures in the northeastern United States allowed tropical climate mosquitoes to spread the Zika virus all the way from Florida to New York, which More said showed that his team’s work is not only relevant to daily life, but vital.

“We have seen a connection between climate events and large outbreaks of disease multiple times,” he said. “We’re trying to figure it out. It’s the cutting edge of environmental health, and obviously, history.”