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GCOS, a system of systems for
the global observation of climate
Gilles Sommeria, GCOS Secretariat; John W. Zillman, Chairman, GCOS Steering Committee
and David Goodrich, Director, GCOS Secretariat
O
ne of the most important roles to be fulfilled by a fully
implemented GEOSS is provision of the Earth system
observations needed for understanding, assessing,
predicting, mitigating and adapting to natural climate variabil-
ity and human-induced climate change. The GEOSS 10-year
Implementation Plan identifies an extensive set of atmospheric,
oceanic and terrestrial variables needed in support of the climate
Societal Benefit Area (SBA). The Global Climate Observing
System (GCOS), which is itself a ‘system of systems’ built on the
climate-relevant parts of established observing systems of the
World
Meteorological
Organization
(WMO),
the
Intergovernmental Oceanographic Commission of the UNESCO
(IOC), the United Nations Environment Programme (UNEP) and
the International Council for Science (ICSU), was designed to
meet these needs and is thus an essential component of GEOSS.
This article describes the origin and historical development of
GCOS, summarizes its structure and concept of operation and
explains its role as the climate component of GEOSS.
Historical background and main objectives of GCOS
GCOS was established in 1992 as a joint initiative of WMO, IOC,
UNEP and ICSU, all now participating organisations in GEO, as a
response to the growing need for international cooperation in the
systematic observation of climate. It was designed as a ‘system of
systems’, built on existing global observing systems and aimed at
ensuring that data will collectively be improved or complemented
in order to fulfil its objectives.
The major established observing systems that contribute to GCOS
are the Global Observing System of the World Weather Watch, the
Global Atmospheric Watch and related atmospheric constituent
observing systems, the Global Ocean Observing System for physical
chemical and biological measurements of the oceans, and the Global
Terrestrial Observing System for land surface ecosystems, hydros-
phere and cryosphere measurements.
The objectives of GCOS have not changed significantly since its
establishment. As recalled and updated by the 2007 WMO Congress,
they are to ensure that climate observing systems provide adequate
data for:
• Climate system monitoring
• Climate change detection and attribution
• Research to improve understanding, modelling and prediction of
the climate system
• Operational climate prediction on seasonal-to-inter-annual
timescales
• Assessment of the impacts of, and vulnerability and
adaptation to, natural climate variability and human-
induced climate change
• Applications and services for sustainable economic
development
• Requirements of the UNFCCC and other interna-
tional conventions and agreements.
Main elements and achievements of GCOS
The first GCOS plan was published in 1995, and an
Implementation Plan (IP) for the Global Observing
System for Climate in support of the United Nations
Framework Convention on Climate Change
(UNFCCC) was published in 2004. The IP puts
together a number of guidelines developed during the
last ten years on the main variables to be observed, the
so-called ‘Essential Climate Variables’ and on the obser-
vation strategies, which should follow the so-called
‘GCOS Climate Monitoring Principles’. It provides
guidance and defines priorities for advances in the
observation of those variables on a five to ten year
time-scale.
The main items covered include the improvement of
key satellite and in situ networks, the generation of inte-
grated global products for climate analysis, the
enhancement of the participation of developing coun-
tries through system improvement and regional projects,
supported by an international cooperation mechanism,
and the necessary enhancement of the archival and
access to climate data for all. The IP has found broad
acceptance across a range of international bodies and
national organizations and thus represents the current
consensus document of the international community
regarding the global observing system for climate, in
support of the UNFCCC.
Major activities are going on with respect to the main-
tenance or improvement of observation networks and
satellite observation, which are intended to serve a
number of programs and activities representing a large
range of users of climate information. This includes
among others the research community represented by
the World Climate Research Programme (WCRP) and
the International Geosphere-Biosphere-Programme
(IGBP), the Intergovernmental Panel on Climate Change
GEOSS C
OMPONENTS
– O
BSERVING
S
YSTEMS