1. AOPC-20 (2015)Atmos. Comp. JH Butler WMO/GAW Contributions to GCOS Greenhouse Gases  WMO/GAW Global Atmospheric CO 2 & CH 4 networks as baseline and comprehensive observing networks of GCOS;  WMO/GAW Global Atmospheric N 2 O network as a baseline and a comprehensive observing network of GCOS;  Q: Do we want to identify the Marine Boundary Layer Reference Network?  Q: Should we break out the minor gases into categories? Ozone (Reporting and Loss of Sites = main issues)  WMO/GAW Global Atmospheric Total Ozone network as a baseline observing network of GCOS; and  WMO/GAW Global Atmospheric Ozone profile network as a baseline observing network of GCOS. Aerosols. No “official” networks for Aerosols?

2. AOPC-20 (2015)Atmos. Comp. JH Butler GCOS Networks: general issues What does “GCOS” affiliation means for the network? Are all networks measuring ECV automatically considered as GCOS networks (e.g. AERONET seems to be linked from GCOS web site, did it go through GCOS AOPC approval)? How do networks get included in the list of networks measuring ECV in GCOS tables/documents (who is responsible for checking if a network follows GCOS principles or not). For the networks outside of WMO who ensures the quality and availability of data? How does GCOS treat applications from networks operating according to different protocols for the same ECV? How does GCOS treat composite networks? Who assigns GCOS affiliated data depositories? Who ensures that data are complete, freely available and are accompanied by proper metadata in those depositories if those depositories are outside of WMO responsibility?

3. AOPC-20 (2015)Atmos. Comp. JH Butler Main ozone Issue(s) -- Reporting Reporting delays  Brewer total ozone data from 57 stations down to 28 in 2014  Dobson spectrophotometer measurements dropped from 47 to 37 stations in same interval  No SAOZ data have been archived in WOUDC since 2012  Data from 19 filter instruments down from 26 to 19 in 2012-2013  Data in 2014 exist but submissions delayed by 4-6 months Lost stations?  17 Brewer, 6 Dobson, and 6 filter instrument stations have not reported data since 2012. These are largely instruments from Canada. The reason for missing data needs further investigation. Page 3

4. AOPC-20 (2015)Atmos. Comp. JH Butler GHG Issues Marine Boundary Layer Reference for CO 2 and CH 4  GCOS Reference Networks? Should GCOS include ”minor” GHGs? National Metrology Institutes  BIPM/WMO Agreement “ensures” coordination  “Restlessness” among NMI’s in pursuing GHG emissions Constructing an Adequate Global Network  Filling Gaps  Validating and interpreting remotely sensed retrievals  Urban “domes” – do they need separate guidelines? Page 4

5. AOPC-20 (2015)Atmos. Comp. JH Butler Aerosol Issues for GCOS Publication of the formal process for a network to become an "official" GCOS network; Clarification of the status as official GCOS networks of the networks mentioned at these web sites: http://gosic.org/content/gcos-atmospheric-composition-ecv-aerosols- properties http://www.wmo.int/pages/prog/gcos/index.php?name=ObservingSy stemsandData#composition ​ http://gosic.org/content/gcos-atmospheric-composition-ecv-aerosols- properties http://www.wmo.int/pages/prog/gcos/index.php?name=ObservingSy stemsandData#composition Status of GCOS response to SAG-Aerosol recommendation ​ that the "aerosol" ECV be elaborated as "Including, but not restricted to,  aerosol optical depth  light scattering and absorption coefficients, aerosol size distribution, and vertical distributions of aerosol backscattering and extinction."  ​ possibility of accepting AERONET as a GCOS comprehensive network, independent of GAW ​

6. AOPC-20 (2015)Atmos. Comp. JH Butler Surface Radiation (BSRN) Global distribution of sites remains an issue. Weighting of ownership remains an issue  US Department of Energy and ARM  Canada  US NOAA? Reporting remains an issue; BSRN scientists working internally to resolve that