Reconciling the climate and ozone response to the 1257 CE Mount Samalas eruption

The Mount Samalas eruption in 1257, one of the largest explosive volcanic eruptions in the Common Era, has proven a complex case for climate models which have generally overestimated the climate response compared with proxy data. Here we perform Earth system model simulations of the impacts of the Mount Samalas eruption using a range of SO₂ and halogen emission scenarios. Reported halogen emissions are considerable from the eruption, but using our model simulations and reconstructed climate response we can rule out all but minor halogen emissions reaching the stratosphere. Including a minor fraction of the halogen inventory reaching the stratosphere captures the observed "muted" climate response but results in significant ozone depletion with implications for ultraviolet exposure and human health.