Fifty WMO member countries have contributed CO2 data to the GAW World Data Centre for Greenhouse Gases (WDCGG). Approximately 50% of the measurement records submitted to WDCGG are obtained at sites in the NOAA ESRL cooperative air sampling network. The rest of the network is maintained by Australia, Canada, China, Japan and many European countries. List of the WMO Global Atmosphere Watch (GAW) monitoring stations that contribute data to the Greenhouse Gas Bulletins is distributed as a List of Contributors on the WDCGG web page.