In Europe, intensities of hydrological extreme events were influenced by volcanic SO2
concentrations in the Northern Hemisphere. SO2
-rich eruptions, similar to the Bárðarbunga 2014–15 eruption (Iceland), by affecting Ocean-atmosphere heat exchange, affected the intensity of the NAO with effects on rainfall and flood intensities. SO2
effects, superimposed to climate change, could enhance frequencies and intensities of extreme events, thus increasing the natural risks in densely populated area.