Volcanic activity is taking place in many different forms and scales, from silent degassing to huge eruptions. During recent years volcanic activity has attracted increasing attention in the Geosciences community. This is with respect to climate forcing, as the most prominent forcing factor for natural climate variability of the last millennium, as a proxy for potential geo-engineering activities and as a test bed for climate models. Further, with ever increasing air traffic, the hazards from volcanic ash plumes become greater and also hazards arising from ash fall, pyroclastic flows and other processes, directly linked to eruptive activity become more important due to the increasing number of people settling in the more endangered areas. The question of the influence of volcanic gases on atmospheric chemistry and dynamics, the hydrological cycle and marine and terrestrial vegetation has been discussed in the literature, but many questions remain un-answered. During the last few years the development of models covering the most relevant parts of the Earth System (i.e. Atmosphere-Ocean-Land-Vegetation-Chemistry-...) made very good progress and it is now the time to review first results from such models with
respect to volcanic activity. Other models and other observational methods were developed to study the less dramatic but long-lasting effects of degassing and smaller eruptions and their results should be compared and fiscussed.

Hence we would like to invite scientists from a variety of fields: climate modellers, data analysts, in-situ and remote sensing specialists, process modelers to review and discuss their results of volcanic activity and its impact on the Earth system.