An AOGCM simulation of the climate response to a volcanic super-eruption

Abstract

Volcanic ‘super-eruptions’ have been suggested to have significantly influenced the Earth’s climate, perhaps causing glaciations and impacting on the human population. Climatic changes following a hypothetical ‘super-eruption’ are simulated using a coupled atmosphere ocean general circulation model, incorporating scaled volcanic stratospheric aerosols. Assumptions are made about the stratospheric sulphate aerosol loading, size distribution, lifetime, chemical make up and spatial distribution. As this study is concentrating on the physical climatological impacts over long timescales, microphysics and chemical interactive processes are not simulated. Near-surface temperatures fall by as much as 10 K globally for a few months and a considerable deviation from normal temperatures continues for several decades. A warming pattern is evident over northern land masses during the winter due to increased longwave forcing and a positive AO mode. The overturning rate of the North Atlantic thermohaline circulation doubles in intensity. Snow and ice increases in extent to a maximum coverage of 35% of the Earth. Despite these and other impacts longer term climatic changes that could lead to a transition to a glaciation do not occur, for present day boundary conditions and one possible plausible aerosol loading.