It tends to come in autumn. The Venetians call it acqua alta–the seemingly seasonal flooding of their historic city center. But a paper published in the Journal of Geophysical Research Atmospheres suggests that Italians eager to predict the next flood shouldn’t study the Earth’s seasons, but should instead look at the sun.
A project led by David Barriopedro at the Universidade de Lisboa in Lisbon, Portugal analyzed hourly recordings of water levels in the city from 1948 to 2008. His team noted a correlation of these “high-surge events” and the eleven-year solar cycle: Periods of maximum solar activity, when sun spots usually appear, seemed to herald the acqua alta.