It is fifteen years since the formal agreement to establish a Global Climate Observing System (GCOS) was concluded between three United Nations System Organisations and the non-governmental international science community and since some 170 countries committed themselves to its implementation by building on their existing atmospheric, oceanographic and terrestrial (including hydrological) observing systems. The need for an enhanced global observing system for climate was articulated in the margins of the Second World Climate Conference in Geneva in October 1990, the concept for GCOS was developed at an historic meeting at Winchester (UK) in January 1991, and the international institutional framework for its implementation put in place over the following two years through sessions of the governing bodies of its four sponsors the World Meteorological Organization (WMO), the Intergovernmental Oceanographic Commission (IOC) of UNESCO, the United Nations Environment Programme (UNEP) and the International Council for Science, (ICSU). By 1993 it had been identified as one of the four main foci of the international Climate Agenda.

Much has happened over the past fifteen years. The basic rationale for a global climate observing system has changed with the international politicisation of climate, the original concept of GCOS has been interpreted in many different ways – as a system of systems, as a sub-set of systems, as a stand-alone system and as a gap-filling system – and its implementation has been approached at many different levels and through many different mechanisms. Its relation to its institutional sponsors and to both its component systems and its user communities has also evolved over time and, in some quarters at least, a community which did not exist at the time of its establishment has come to be seen as its major client. And, as a cross-cutting system spanning the main earth system domains of atmosphere, ocean and surface land and water, it set the stage for the even more ambitious concept of a Global Earth Observation System of Systems (GEOSS) which has emerged over the past five years and of which it can be seen as the ‘climate component'.

The successful implementation of such globally co-ordinated systems represents a major challenge for their international sponsor organisations, for their Member nations and stakeholder communities, for the scientific and engineering communities on whose research and technology development their success depends. And, perhaps more than anything, their success depends on effective linkage mechanisms with their end-user communities. In the case of GCOS, this means, in particular, through the effectiveness of the aggregate of local, national, regional and global data assimilation and product delivery and application systems that collectively make up the World Climate Programme (including the World Climate Research Programme) as well as the various scientific assessment mechanisms and policy organs such as the Intergovernmental Panel on Climate Change (IPCC) and the Conference of the Parties to the Framework Convention on Climate Change (FCCC).

This presentation will analyse and evaluate the GCOS concept fifteen years on from its inception and attempt to map out a contemporary framework and strategy for its ongoing implementation and enhancement in support of user needs.