Three scientific panels, reporting to the Steering Committee, were established to define the observations needed in each of the main global domains (atmosphere, oceans and land), to prepare specific programme elements and to make recommendations for implementation:

• Atmospheric Observation Panel for Climate (AOPC)
• Ocean Observations Physics and Climate Panel (OOPC)
• Terrestrial Observation Panel for Climate (TOPC)

The scientific panels gather experts in the respective areas to generate inputs from these fields to the climate observing community.

The Terms of Reference for GCOS Panels were revised by GCOS SC-30 (Decision 30/7) and they came into force in 2023. Below, the section specifying the composition and terms for Panel members and chairs, common to the three panels, is presented. Specific terms to each of the panels (specifying their activities and so on) can be found under the AOPC, OOPC and TOPC webpages.

Section 1: Terms of Reference for GCOS Panel Members and Panel Chairs and composition of GCOS panels
The GCOS panels are composed of core members and ex-officio members. The panels are led by a chair. The chair of each panel can decide to nominate a co-chair, or a deputy chair, selected from the core panel members. Ex-officio members will be appointed by relevant programmes and/or networks. The chair of a panel may invite additional experts to contribute to specific tasks.

GCOS Panel Members
1. Membership of the panels will consist of:
  a. Up to 15 core members including the panel chair and co-chair or deputy chair;
  b. Ex-officio members: No more than 6 or not exceeding one third of the core membership if it is less than 15;
  c. A representative of each panel sponsor at their own expense.

Panel Chairs:
1. The Panel Chair shall be appointed by the GCOS Steering Committee with the approval of the panel sponsoring programmes of each of the panels.
2. The Panel Chair shall serve for 3 years. Subject to approval of the GCOS Steering Committee this may be extended for an additional 3-year period. After 6 years of service, the GCOS Steering Committee and the panel sponsoring programmes may approve an extraordinary 3-year extension.
3. The Panel Chair may nominate a co-chair or a deputy chair, selected from the panel members. This nomination will be subject to approval by the GCOS SC and the panel sponsoring programmes.
Panel Chairs shall:
4. Lead the panel, guiding and prioritizing the panel’s agenda and work, with the support of the GCOS Secretariat.
5. Preside over the annual panel session and respond to its requests and decisions.
6. Act on behalf of the panel between meetings.
7. Present the panel’s activities at the annual GCOS Steering Committee.
8. Follow up on the actions of the panel supported by the secretariats.
9. Assist the GCOS Secretariat in reviewing the membership and nominating new candidate members.

Core Members:
10. Members of the panels should be technical experts in their individual capacity. Specific duties of the panel members are specified in the Panel Member ToR (Sections 2, 3 and 4 of this document).
11. Membership should provide for geographical and gender representation.
12. New members should be selected by the Panel Chair and shall be appointed by mutual consent of the GCOS Steering Committee Chair, the Director of GCOS and the Chair(s) of the panel sponsoring programmes.
13. Members shall serve for 3 years. Subject to approval of the Panel Chair this may be extended by an additional 3 years. After 6 years of service, further extensions may be possible, but these must be approved by the GCOS Steering Committee.
14. At the request of the Panel Chair and with the approval of the GCOS Steering Committee Chair and the Chair(s) of the panel sponsoring programmes, members that will not have satisfactory discharged the expectations as described in this section can be dismissed from the role of GCOS Panel Members at any time.
15. The GCOS Secretariat will support travel to meetings and related costs.
Members of the GCOS Panels shall:
16. Lead the evolution of sustained and systematic observations of the global climate system in accordance with their expertise, as part of a GCOS expert panel.
17. In agreement with the Panel Chair(s), take responsibility to report to the panel for one, or a few, Essential Climate Variables and/or networks on:
  a. The ECV requirements for long-term monitoring of the Earth’s climate;
  b. The adequacy of observing networks (in-situ, satellite-based), compared with the ECV requirements;
  c. Progress on actions contained on the latest GCOS Implementation Plan.
18. Contribute to the revision of the ECV, based on user needs for climate monitoring, adaptation and mitigation.
19. Contribute to the regular updating of the GCOS Status Report and Implementation Plan.
20. Liaise with relevant research, operational, and user communities.
21. Undertake, in agreement with the Panel Chair(s) other tasks in line with the panel Terms of Reference (Sections 2, 3 and 4)
22. The total commitment is expected to be about 10 days per year, including:
  a. One panel meeting a year;
  b. Taking part in panel teleconferences as decided by the Panel Chair(s), (expected to be at least 4 times a year).

Ex-officio Members:
In addition to the Panel Core Members, related programmes/organizations/networks will be invited to nominate ex-officio experts based on the work programme of the relevant GCOS Panel. The GCOS Steering Committee shall have oversight of the ex-officio experts in the three panels.
23. Panel Chair(s) can, on annual basis, propose programmes/organizations/networks to be represented by ex-officio members at panel meetings. These proposals shall be approved by the Steering Committee.
24. Ex-officio members should be technical experts. Specific duties are the same as for a Core Members. Ex-officio members shall ensure a connection between the panel and the organization they represent and shall regularly report to the organization and to the panel.
25. Following approval of the proposed ex-officio member by the Steering Committee, the GCOS Secretariat shall inform the programme/organization/network and invite them to nominate an expert. Nominations shall be confirmed, in writing, and invitations copied to the programme/organization.
26. The duration of the ex-officio member appointment depends on the nominating organization who at any time can nominate a different expert.
27. Ex-officio members shall be invited to participate to all panel meetings.
28. In general, the nominating organization shall provide travel support to the panel meetings.
Additional experts:
29. Panel Chair(s) can, on an ad hoc basis, invite individual experts to the panel sessions and to contribute to the panel work. In general, GCOS Secretariat will not support travel to meetings and relative costs for the additional experts.

General Procedures
30. Invitations to Panel sessions should be sent out from the GCOS Secretariat to all panel members and copied to the Chair(s) of all other GCOS panels.
31. The GCOS Secretariat shall issue letters of appointment for new members on behalf of the panel sponsoring programmes.
32. The GCOS Secretariat shall issue letters of thanks for leaving members on behalf of the panel sponsoring programmes.
33. The GCOS Secretariat shall organize a panel meeting in person or by teleconference at least once a year.
34. The GCOS Secretariat shall publish a report after the panel meeting.