The Global Climate Observing System (GCOS) science panels and secretariat prepared an Implementation Plan (GCOS-92) for the Global Observing Systems for Climate in support of the UN Framework Convention on Climate Change which was given strong support by the UNFCCC in December 2004. This plan was subject to open review by the community and was prepared in cooperation with GCOS's many partner bodies, observing systems and programs and also in coordination with the GEO. It proposed an integrated climate observing system with a balance of in-situ and satellite observations. Since then this plan has received good attention from the various communities involved including the satellite agencies. In the last year GCOS has prepared a supplement that gives further details the satellite-based component of the Implementation Plan. This report (GCOS-107, available from http://www.wmo.int/web/gcos/gcoshome.html ) sets out in more detail the satellite observations and the strategy proposed. This supplement has been used by the Committee on Earth Observation from Space (CEOS) to assist them in reporting on their response to the Implementation Plan. This presentation will seek to provide an overview of this supplement.

In particular, the supplement seeks to highlight, in generic form, the particular satellite data records needed to enable the construction of long term homogeneous climate products, such as for upper-air temperature, precipitation, or land use change. To achieve these records, it is essential that the related satellite observations meet requirements for resolution, accuracy, and stability, and that they are acquired with good attention to the GCOS climate monitoring principles, i.e. adhering to basic principles of consistency and continuity. The report also notes many other valuable observations from satellites which, although ideally measured in the same sustained way, are, for reasons of priority and cost, suggested in the Plan to be made at intervals of time with a view to assisting in the interpretation of changes in the climate system. Whilst indicative details of the satellite observation requirements are given, the process of providing detailed specifications for satellite instruments needs is a very complex issue which depends on the various approaches taken in generating end products. For this reason the supplement stresses the need to ensure appropriate structural arrangements to ensure links between satellite agencies, end users and those scientific groups involved in the creation of products.