Volcanic eruptions pose a significant risk to human lives, property and infrastructure, despite rapid advances in monitoring and early warning science and technology. Some elements of risk – such as the number of people living close to volcanoes – are increasing, and the unpredictable nature of eruptions may overwhelm the local response capacity and turn into a disaster, sometimes requiring international assistance. To deal effectively with these crises, the international humanitarian community needs a global, science-based early warning system that should assimilate the state-of-the-art monitoring and early warning techniques, as well as being able to provide a preliminary impact assessment, and issue appropriate and relevant alerts. Current volcano warning systems are either only local in context or are not suited to the needs of global early warning. In this paper we propose an outline for a volcano warning system aimed at issuing alerts to the humanitarian aid community. It is designed as a four-level system, incorporating the latest monitoring and hazard modelling techniques that are applicable on a global scale. Alerts are mainly based on the predicted humanitarian impact of the modelled hazards. Systematic handling of volcanic manifestations, such as thermal signals and ash clouds from space-borne instruments, make it possible to create such a system. The Global Disaster Alert and Coordination System (GDACS), a joint effort by the United Nations and the European Commission, has been operating in a similar spirit for other natural disasters for a number of years and could fulfil the role of the desired volcano system. This paper discusses the needs and issues of this undertaking.