This document presents an additional compilation and synthesis of the national reports submitted by Annex I Parties by 30 September, 2002. It is based on 12 separate reports and 11 reports provided as a part of the third national communications. In addition to the report by the GCOS secretariat (FCCC/SBSTA/2002/MISC.10), the GCOS web site provides further reference material. This report analyses the information from Annex I Parties on their actions regarding global climate observing systems; the status and development of the networks; international data exchange; provision of metadata; adherence to GCOS monitoring principles and GCOS best practices; achievements, deficiencies and characteristics of the systems; and support for non-Annex I Parties. It also provides an assessment of compliance of the submitted information with the UNFCCC guidelines on global climate observing systems, identifies good practices in reporting, and provides some views on the possibility of using the information to assess the state of climate observing systems globally. This report follows the structure recommended in the UNFCCC guidelines for individual Party reports. It describes the general approach taken by Parties to meet the needs identified by the GCOS and its partner programmes, and analyses information on meteorological and atmospheric, oceanographic, terrestrial and space-based observations. The annexes contain lists of compilation tables and of abbreviations used in the report