European hydroclimate response to volcanic eruptions over the past nine centuries

The climatic aftermath of the 1815 Tambora eruption in Europe suggests that large volcanic eruptions can introduce environmental and societal consequences in this region. Here, we analyse the European summer hydrological response to 31 tropical and 44 Northern Hemisphere mid-to-high latitude eruptions over the past nine centuries, using a newly published reconstruction of global volcanism and a proxy record of hydrological conditions (Old World Drought Atlas) together with a superposed epoch analysis. Our results show a significant wetting response (at the 95% confidence level) for year 0 and year +1 after tropical eruptions, followed by a significant drying in year +2. Spatially, wetting occurs in northeast and southern Europe, while a drying response develops in central and northwest Europe. Both the wetting and drying responses are more significant for the group of eruptions with higher sulphate injection magnitudes than the eruptions with low magnitudes. Large high latitude eruptions tend to cause a drying response in western-central Europe in year +2, which shifts south-eastwards in years +3 and +4. Correcting for the effects of El Nino does not noticeably change the response patterns. The response to eruptions counteracts the hydroclimate response to global warming in some regions, e.g. the Mediterranean, but exaggerates is in others, such as central Europe. Our results verify previous modelling studies from a longer term proxy perspective, and illuminate potential effects of stratospheric geoengineering in Europe.