Non-climatic factors and the environmental impact of volcanic volatiles: implications of the Laki fissure eruption of AD 1783

Studies of the potential of Icelandic volcanic eruptions to modify the environment of the British Isles have primarily concentrated on the degree of induced climate change, but models and temperature records suggest that the scale of such change may have been minimal. As a result it is difficult to account for change in the palaeoenvironmental and archaeological records, in response to a volcanic eruption, by invoking climate change alone. An additional mechanism is proposed by which Icelandic volcanic eruptions transport and deposit environmentally-significant levels of acid volatiles and halogens. Contemporary documentary evidence indicates a widespread dry, smoky haze throughout western Europe during the Laki fissure eruption in the summer of AD 1783, indicative of the presence of volcanically generated gases in the lower atmosphere. Severe damage to crops and trees occurred in a number of locations in Britain and western Europe, the descriptions of which are consistent with the impact of acid deposition. It is suggested that the deposition of acids and halogens emitted in Icelandic volcanic eruptions may be more significant than climatic perturbations for ecosystems in the British Isles.