The Global Climate Observing System (GCOS) has been established by four major international organisations in response to the perceived need to have a dedicated and co-ordinated international programme for the gathering and dissemination of high-precision, high-quality data for long-term climate studies, especially in relation to possible man-made effects. GCOS is concerned with all means of obtaining such data, but inevitably space observations will play an increasingly major part in its programme. GCOS will operate via a central planning and co-ordinating office, but will depend on member states and international agencies for the implementation of its programme. It will aim to make maximum use of existing and planned programmes, working towards closing gaps, converting selected short-term research programmes into long-term operational ones, and in general seeking to provide added-value to existing and currently planned programmes.