Lunar eclipses illuminate timing and climate impact of medieval volcanism
Résumé
Volcanism is a key factor in climate variability from interannual to centennial timescales. Understanding the far-field societal impacts of eruption-forced climaticchange requires firm event chronologies and reliable estimates of both the burden and the altitude (that is, tropospheric versus stratospheric) of volcanic sulfateaerosol. However, despite progress in ice-core dating, uncertainties remain in these key factors. This particularly hinders investigation of the role of temporally clustered large eruptions during the High Medieval Period (HMP, 1100–1300 CE), which have been implicated in the transition from the warm Medieval Climate Anomaly to the Little Ice Age. Here we shed new light on volcanism during the HMP, drawing on analysis of contemporary reports of total lunar eclipses, from which we derive a time series of stratospheric turbidity. By combining this new record with aerosol model simulations and tree-ring-based climate proxies, we refine the estimated dates of five considerable eruptions and associate each with stratospheric aerosol veils. Five further eruptions, including one responsible for high sulfur deposition in Greenland circa 1182 CE, affected only the troposphere and had muted climatic consequences. Our findings offer support for further investigation of the decadal-scale to centennial-scale climate response to volcanic eruptions.
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