Abstract. The H1N1 “Spanish influenza” pandemic of 1918–1919 caused the highest known number of deaths recorded for a single pandemic in human history.  Several theories have been offered to explain the virulence and spread of the disease, but the environmental context remains underexamined.  In this study, we present a new environmental record from a European, Alpine ice core, showing a significant climate anomaly that affected the continent from 1914 to 1919.  Incessant torrential rain and declining temperatures increased casualties in the battlefields of World War I (WWI), setting the stage for the spread of the pandemic at the end of the conflict.  Multiple independent records of temperature, precipitation, and mortality corroborate these findings.

Plain Language Summary. A new, high-resolution climate record from Europe shows a once-in-a-century climate anomaly that occurred during the years of World War I and the Spanish flu pandemic.  Mortality data from all causes show increases in times of worsening weather, precipitation, and temperatures, a factor in many of the major battles of WWI, as well as a possible exacerbating factor for the virulence of the pandemic.

The full article appeared on the American Geophysical Union website at https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2020GH000277