GCOS is vital for:

• detecting and attributing climate change;
• assessing the impacts of climate variability and change;
• supporting research toward improved understanding, modelling and prediction of the climate system.

It addresses the total climate system including physical, chemical and biological properties, and atmospheric, oceanic, hydrologic, cryospheric and terrestrial processes.

GCOS builds upon, and works in partnership with, other existing and developing observing systems such as the  Global Ocean Observing System (GOOS), the  Global Terrestrial Observing System (GTOS), and the  Global Observing System (GOS) and  Global Atmospheric Watch (GAW) of the World Meteorological Organization.

It is co-sponsored by three UN bodies, the World Meteorological Organization (WMO), the Intergovernmental Oceanographic Commission (IOC) of the United Nations Educational, Scientific and Cultural Organization (UNESCO) and the United Nations Environmental Programme (UNEP) plus by the non-governmental organisation, the International Council for Science (ICSU).

The GCOS Joint Planning Office is based with the WMO Secretariat.

UK co-ordination of climate activities

In the UK climate change mitigation policy is managed (with energy policy) by  Department of Energy and Climate Change (DECC)

The  UK Climate Change Act (2008) established the  Committee on Climate Change as an independent body to advise the UK Government on setting and meeting carbon budgets and on preparing for the impacts of climate change.

UK commitments to GCOS

Various agencies in the UK contribute to the GCOS networks. These commitments, and additional contributions, to GCOS are described in the periodic reports on systematic observations for climate, prepared as part of the regular National Communication to the Conference of the Parties to the UN Framework Convention on Climate Change (UNFCCC).

Meteorological and atmospheric observations

• 11 GCOS Surface Network (GSN) stations (six in UK, five overseas).
• Six GCOS Upper Air (GUAN) stations (two in UK, four overseas).
• GUAN Data Centre.
• Two Baseline Surface Radiation (BSRN) stations (in UK).
• Observations from the UK Voluntary Observing fleet (approx. 350 ships).
• Global Collecting Centre (GCC) for marine climatological data.
• Drifting buoys contributing to the global drifter array.

In addition, ozone measurements from two stations (one in UK, one overseas) are also contributed to GCOS.

Oceanographic observations

• 11 sea-level (tide gauge) stations (three in UK, eight overseas) (operated as part of the National Tidal and Sea Level Facility).
• Permanent Service for Mean Sea Level.
• UK Argo floats contributing to the global Argo array.
• Reference mooring at the Porcupine Abyssal Plain Observatory site (contributing to OceanSites).
• Repeat hydrography.
• Ocean carbon measurements ( Atlantic Meridional Transect).
• Biogeochemical and ecosystem measurements ( Continuous Plankton Recorder survey)

Terrestrial observations

• Environmental Change Network
• 6 GTN-R (river run-off stations) (part of the National River Flow Archive)