Coordinating action in space

European Space Agency

Essential Climate Variables (ECV), deduced from space, have been defined as a result of the coordinated actions of international space agencies through the Committee on Earth Observing Satellites (CEOS), responding to requirements expressed by the Global Climate Observing System (GCOS), on behalf of parties to the UNFCCC.

Meeting objectives

The European Space Agency (ESA) is steering its Earth Observation programmes to directly meet these objectives. The “Global Monitoring of the Environment and Security (GMES) Space Component” programme is establishing dedicated operational constellations of complementary Earth Observing satellites – the Sentinel series. GMES is a partnership between ESA and the European Union to provide data to support Europe’s policy goals on environment and security for the next 25 years.

ESA is also starting a dedicated Climate Change Initiative (CCI) to enable scientists to access and re-analyse its global satellite data archives. This programme aims to generate the most complete, consistent and well-characterised global records of ECVs possible, and make them freely available to climate research and modelling communities worldwide. It responds explicitly to the GCOS requirements.

The GCOS-82 document divided 44 of these ECVs into three categories: atmospheric, ocean, and terrestrial. The objective of the CCI programme element is to ”realize the full potential of the long-term global Earth Observation archives that ESA together with its Member states have established over the last thirty years, as a significant and timely contribution to the ECV databases required by UNFCCC”.

It will ensure full capital is derived from ongoing and planned ESA missions for climate purposes, including ERS, Envisat, the Earth Explorer missions and, in due course, the GMES Space Component. Its essential feature will be to implement a coherent and continuous suite of actions that encompasses all steps necessary for the systematic generation of relevant ECVs, and ensures their regular updating on timescales corresponding to the increasingly urgent needs of the international climate change community.

This demands a major sustained, and coordinated scientific effort to review, improve and, in some cases develop new underlying algorithm, processing and validation methods.

The users of the ECV data products are the scientific, research, and (in a limited number of cases) operational organisations from the UNFCCC countries responsible for climate research, modelling, assessment and prediction within nationally and internationally funded research programmes. Many, but not all, of these scientists, organisations and programmes are already users of ESA Earth Observation data products. The following 11 ECVs have been selected and shall be implemented as a series of subprojects.

In the previous issue of RTCC, we highlighted the potential of remote sensing for land cover (GlobCover) and fire disturbance (ATSR World Fire Atlas), we would like to give further example of satellite possible long time series measurements.

1. Counting Carbon (Figure 1: click here): Carbon is both captured and emitted by the ocean and land through several processes. The photosynthesis process is at the basis of chlorophyll development into the ocean and over land. Understanding both the capacity of the ocean and land to uptake or release carbon is one of the major uncertainties of the carbon budget. Analysis of in-situ trends as the Mauna Loa or derived from the ENVISAT satellite show a clear seasonality of carbon dioxin in the air with the seasonal vegetation growing season in the northern hemisphere where two thirds of the land surfaces are present. In addition to the natural seasonal trends, changes in land use and forestry management may either reduce or increase the overall load of carbon in the atmosphere which long-term increase is due to fossil fuel emissions.

2. An Ocean of Change (Figure 2: click here): One of the best-known change from an increase of temperature is the sea-level rise from first the temperature-dependant sea expansion and pouring of fresh water release from melting glaciers or ice caps flow acceleration (Antartica and Groenland). The continuous global measurements of sea level by a constellation of altimeters from various space agencies allow for a cross-calibrated constant global and local monitoring of the sea-level rise. These constant measurements span almost 20 years and determine the understanding of the future risk of small island states or river basin deltas.

3. Ice Signals (Figure 3: click here): The last three years have shown the lower artic ice extend coverage at the end of the summer, allowing the north-west and north-east passage in some cases to be free of ice. Beyond navigational routes and oil exploitation, an ice-free artic is also drastically changing the air / sea interaction and therefore the radiation budget at the air / sea interface leading to change in ocean circulation.

4. Answer from the Ocean (Figure 4: click here): Last but not least, satellite system are able to capture the sea surface temperature evolution over time. This in fact is an image of the ocean overall thermal machinery that carries heat from the warm latitude to the pole allowing Europe to have a mild climate.

Perspectives

ESA’s planned GMES satellites will extend these and other time series long into the future, using enhanced sensors. For example, the Sentinel-3 satellite, to be launched in 2013, will have significantly enhanced coverage and sensitivity to ensure long-term continuity of the global sea surface temperature, ocean colour, sea level, aerosol, cloud, land cover and fire records for the next 25 years. In the meantime, the ESA CCI will enable scientists to improve the accuracy and extend the time duration of the present records of these and other ECVs by using existing satellites and data archives. With these major new programmes, ESA is substantially contributing towards meeting the GCOS requirements, strengthening the GCOS and thereby supporting the overall goals of UNFCCC.

European Space Agency
W: www.esa.int