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are obtained and made available to all users. The focus
was on better understanding the climate system for better
decision-making. To meet this goal GCOS defined a set of
approximately 44 essential climate variables (ECVs) that
should be systematically monitored in order to quantify the
state of our climate in an objective and effective way.
Over the last decade GCOS has published a series
of adequacy reports assessing the gaps in the existing
climate observation system, as well as an implementa-
tion plan to deliver high-quality reliable climate data
sets of the ECVs. The international community recog-
nizes the vital role played by Earth observation satellites
in globally monitoring the climate system, as well as
in delivering consistent and homogeneous long-term
climate data records. GCOS articulates the data needs
for a subset of about 25 ECV products in terms of the
‘Fundamental Climate Data Records’, which relate ECVs
to the observables measured by space-borne sensors.
In 2006, the Committee of Earth Observation Satellites
(CEOS) – being the primary international forum for
coordination of space-based Earth observation missions
– provided a coordinated response by space agencies
to the data needs expressed through GCOS, identifying
more than 50 actions to be performed by space agen-
cies all over the world. In this context, ESA took on
the commitment to contribute to GCOS’s implemen-
ready to be launched during 2009. Another four Explorers are currently
in the development stage. The missions are selected and developed in
close cooperation with the scientific community, which allows science
needs to be directly translated into the space-based instruments.
The quest to aid scientists in better understanding the Earth’s
climate continues with the European Union’s (EU) preparation of
the Global Monitoring for Environment and Security initiative. ESA
has taken up the responsibility of implementing and coordinating
the space component of this initiative. Dedicated satellites, called
Sentinels, will provide the operational continuity needed to support
European policies on environment and security issues. Climate
constitutes a large part of this; not only is it a fundamental factor
in our environment, but climate change and the human reaction
to it also has a large social and security impact. Land, ocean and
atmospheric chemistry monitoring, climate quality observations and
many more factors are therefore key in preparing for and adapting to
future challenges. The partnership with the EU (representing user
interests) aims to provide the necessary basis for sustainability.
The importance of global observation for understanding climate change
has also triggered action on the international scene – a fact long recog-
nized by the United Nations Framework Convention on Climate Change
(UNFCCC). As a result, the Global Climate Observing System (GCOS)
was established in 1992 by the World Meteorological Organization
(WMO), Intergovernmental Oceanographic Commission, UnitedNations
Environment Programme and International Council for Science to ensure
that the high-quality observations needed to address climate-related issues
Envisat ASAR data mosaic showing sea-ice coverage as of mid-August 2008. The red line indicates the all-time minimum Arctic sea ice coverage in September 2007
Image: ESA