GCOS Implementation Plan - WMO

Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC
(2010 Update)
The overall atmospheric climate observing system comprises a complementary mix of in situ 62 and
satellite-based subsystems. To characterise the atmosphere at the land- and ocean-surface,
measurements of temperature, water vapour, wind, pressure, and precipitation are needed.
Observations of atmospheric composition ECVs, such as carbon dioxide, methane and aerosols, are
a critical need because of their changing concentrations and impact on the radiative forcing of climate.
Some ECVs, such as precipitation, are highly-variable in space and time, and require high-resolution
observations to create an accurate picture. Satellite observations are a unique source of attaining
global coverage of virtually all atmospheric climate variables but in most cases do not extend
sufficiently far back in time to give a full historical perspective and need to be complemented by in situ
measurements, especially at lower levels over land. Emerging arrangements for the calibration of data
and the formation of satellite data records for climate purposes have been outlined in section 3.4.
Furthermore instrumental and palaeo-reconstructions of temperature and precipitation are essential to
provide the long-term perspective.
The in situ atmospheric observing systems are largely based on the WMO WWW networks for surface
and upper-air observations, and the WMO GAW networks for atmospheric composition. The GCOS
implementation strategy has placed an initial emphasis on the full implementation of baseline
networks. These include, as subsets of the WMO WWW/GOS networks, the GSN and the GUAN for
the surface and upper-air meteorological variables, and the phased establishment of GAW networks
for all the composition variables. The latter has made progress but needs to be completed. Full
implementation of the emerging GRUAN is also needed as a key component that provides climate
data of intrinsic high value and contributes to the calibration of data from both the general in situ
networks and the satellite subsystems.
The careful management of data and their associated metadata are vital aspects of the baseline and
other climate networks, with real-time monitoring centres, delayed-mode analysis centres and
reanalysis programmes complementing the work of the International Data Centres which hold the
basic archives. For most atmospheric ECVs, such centres and programmes currently exist; however,
as pointed out below, there are several gaps and weaknesses that need to be addressed.
Users of climate information require products that meet their requirements for quality, scope and
coverage. Many of these products are generated through the integration of data from different
sources. Integration of data from the complete mix of in situ networks and satellite subsystems is
achieved through the process of reanalysis, which by consistently incorporating historical data
provides the potential to yield homogeneous, consistent, multivariate products with either global or
more-detailed regional coverage (see discussed in section 3.5). Some products, however, are
independent of modelling frameworks and based on single-source datasets, which have been
processed to correct for artefacts and to provide a continuous picture over space and time.
4.1. Atmospheric Domain – Surface
Observations at the surface of the Earth are vitally important as they characterise the climate of the
layer of the atmosphere in which we live, and where many impacts of climate change will be felt and
necessitate adaptation. Climate analysis has traditionally placed emphasis on surface temperature,
precipitation and pressure data. Temperature and precipitation have the greatest impact on natural
systems and human activities, with pressure allowing a perspective on the meteorological systems
that drive the weather. More recently, wind speed, wind direction and sunshine data have become
increasingly important as Parties consider measures to adapt to future climate change, as these data
are also essential for the design of renewable energy systems, which include wind and solar farms as
well as hydroelectric systems. Wind, water vapour, sunshine and surface radiation are also
associated with a range of direct impacts.
There is an increasing need for local, high-frequency surface atmospheric data on climate, to
characterise extremes for the purposes of monitoring and research, and more generally to meet
needs relating to impacts, vulnerabilities and adaptive responses. This Plan identifies a number of
Actions to improve the availability of the required observations and data products for precipitation. It
also identifies Actions to enhance the frequency of reporting and general operation of the WWW/GOS
62 The term in situ is used to denote any ground-based or air-borne measuring system, including non-satellite remote-sensing
systems.
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