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Abstract

Large volcanic eruptions are an important driving factor of natural climate variability. A sound assessment of the role of volcanoes in the climate system in comparison to other forcing factors is therefore a prerequisite for understanding future and past climate variability. New advances in understanding volcanic climate effects have been achieved by using comprehensive climate and Earth system models. New insights have been gained over the last decade about volcanic impacts on atmospheric composition and dynamics, but most notably also about their impact on ocean dynamics, the hydrological and the carbon cycle and on marine and terrestrial biogeochemistry. An important achievement is the improved understanding of the volcanic imprint on decadal to multidecadal time scales. Climate model simulations of past eruptions are highly dependent not only on the quality of the model and of the volcanologcial input data but also on the treatment of the aerosol size distribution in chemistry and radiation calculations. Further knowledge has to be achieved about the relation between the initial climate state at the time of the eruption and the volcanic climatic impact. A challenging task for climate models is also the simulation of the Northern Hemisphere winter climate response after a large tropical eruption. Model intercomparison studies and cross validations of model simulations with observations are essential to better constrain the radiative forcing of large volcanic eruptions and their climate impact.