European Space Agency

Observations from space are a unique source of global information for understanding and responding to climate change and an uninterrupted long-term record of such observations is essential for future decision-making. It is clear that an international programme to sustain the long-term availability of such observations is needed. Significant advances in this direction are being made 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 the parties to the UNFCCC (United Nations Framework Convention on Climate Change).

Fig 1: Global Land Cover derived from the ENVISAT MERIS Full Resolution images acquired from January 2005 to June 2006

The G8 Heads of State underlined the importance of such actions during their July 2008 summit in Tokyo: “To respond to the growing demand for Earth Observation data, we will accelerate efforts within the Global Earth Observation System of Systems (GEOSS)… in priority areas, inter alia, climate change and water resources management, by strengthening observation, prediction and data sharing”. Europe is contributing to this by developing a powerful suite of new global observing satellites, by improving data access, and by strengthening scientific analysis of long-term data archives.

Leading the way

The European Space Agency is leading the way by steering its Earth Observation programmes to directly meet these objectives. At the end of this year ESA will invite its member states to undertake three major new programmes in Earth Observation:

1. The “Meteosat Third Generation” programme (MTG), will implement a new series of advanced Geostationary Meteorological satellites for Europe and Africa. MTG is a partnership between ESA and the European Meteorological Satellite organisation EUMETSAT.

2. The “GMES Space Component” programme will establish dedicated operational constellations of complementary Earth Observing satellites (Sentinels 1-5) and will also access data from other contributing satellites. 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.

3. ESA is also proposing a dedicated “Climate Change Initiative” that will 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 “Essential Climate Variables” possible, and make them freely available to climate research and modelling communities worldwide. It responds explicitly to the GCOS requirements and will be implemented in close cooperation with CEOS and GEOSS.

These new programmes underscore the strong, collective commitment of ESA Member States to ensure that global observations of climate from space will be sustained and exploited, now and in the future.

Fig 2: The ATSR World Fire Atlas fire distribution in 1998

Land and fire

We illustrate the practical value of these developments with two examples of Essential Climate Variables derived from space: Global Land Cover and Global Fire Disturbance. Each is associated with significant uncertainty in the understanding of the climate system. For each, space offers the only realistic source of reliable, long-term global observations. Over the last few years ESA has been working with the science community to derive improved estimates of these two variables, through the “Globcover” and “ATSR World Fire Atlas” projects respectively, using data from the ERS and ENVISAT missions.

The GlobCover Project

Earth’s land cover has been charted from space before. However, GlobCover provides a resolution 10 times sharper than any of its predecessors. Scientists, who will use the data to plot worldwide land-cover trends, study natural and managed ecosystems, and model climate change extent and impacts, are hailing the product as a milestone. An international network of partners is working with ESA on the project, including the UN Environment Programme (UNEP), the UN Food and Agriculture Organisation (FAO), the European Commission’s Joint Research Centre (JRC), the European Environmental Agency (EEA), the International Geosphere Biosphere Programme (IGBP) and the Global Observations of Forest Cover and Global Observations of Land Dynamics (GOFC-GOLD) Implementation Team Project Office.

Building on the success of the previous GLC-2000 project (Global Land Cover map for the year 2000), coordinated by the EC Joint Research Centre, ESA launched the GlobCover initiative in early 2004, as part of its Data User Element (DUE). The GlobCover system was developed by a European consortium including Medias-France, Brockmann Consult (Germany), Université Catholique de Louvain, and partners. It is a major step forward in global land cover, primarily because the products are generated automatically. This guarantees that the results are repeatable, and can be quantitatively inter-compared to estimate global land cover changes with time. The products also take full advantage of the high quality data from the Meris sensor on ESA’s ENVISAT satellite to deliver finer spatial resolution and more detailed thematic content than ever before achieved.

The GlobCover product (Fig 1) is the first freely available global land cover product at 300m resolution, and is thus a milestone for a broad stakeholder community. There are 22 different land cover types shown in the map, including croplands, wetlands, forests, artificial surfaces, water bodies and permanent snow and ice. For maximum user benefit, the map’s thematic legend is compatible with the UN Land Cover Classification System (LCCS). All data are freely accessible on www.esa.int/due/ionia/globcover.

More than a simple map

GlobCover is much more than a simple map: It is a scientific and technical demonstration of the first automated mapping of land cover on a global scale. It provides a basis for the detailed description of land surface states needed for regional climate modelling. Information on land cover is also needed for sustainable management of natural resources, environmental protection, food security, and humanitarian programmes. GlobCover is now being used in long-term studies of land-cover and land-use dynamics, notably to improve understanding of nature-society dynamics of land management. Such information products will play an increasingly important role in regional and global modelling in future, and are thus vital for climate impact and sustainability research.

Fig 3: Off shore gas flaring in North Sea has a reduction trend of 12 %

The ATSR World Fire Atlas Project

Worldwide information on fire disturbance is needed to calculate the net carbon sink. This may account for the large observed inter-annual variations in carbon emissions from ecosystems. However, the interplay between climate, likelihood of disturbance, phenological status, severity of disturbance, and disturbance return is highly complex. These factors all control the emissions, vegetation recovery trajectories and thus the likelihood of future change. Disturbance has both direct and indirect effects on patterns of tree establishment, future vegetation composition and structure, hydrology and carbon cycling. It is highly temporally variable, occurring in temporal clusters, both within the active fire season, and between years. This clustering is associated with weather patterns such as low precipitation and high temperature. It is also closely linked to anthropogenic activities.

Disturbance, especially fire, represents a major source of uncertainty and presents a major challenge for models of global vegetation and of atmospheric chemistry. All efforts to incorporate disturbance in such models face the difficulty of obtaining sufficiently long-time series of reliable, global observations.

The ESA ATSR World Fire Atlas (Fig 1) is the longest time series of global fire data currently available. It provides an uninterrupted global record of fire location and timing since 1995. The data used are those recorded at night-time by the second Along Track Scanning Radiometer (ATSR-2) on ESA’s ERS-2 satellite and, since 2003, by the follow-on Advanced Along Track Scanning Radiometer (AATSR) on ENVISAT. Each record is comprised of the date, latitude and longitude of a 1 km by 1 km pixel when the brightness temperature in the 3.7μm channel superseded either 312 (algorithm 1) or 308 (algorithm 2) degrees K with pixels being revisited on average every 3 days. These records are available as monthly ASCII files direct from the ATSR World Fire Atlas web site http://dup.esrin.esa.it/ionia/wfa/

It should be noted that the records represent all pixels superseding the above thresholds, with no subsequent elimination of pixels. The interpretation of these records as vegetation fires is left for the user to perform. These data are already being used by many different groups worldwide for monitoring global change and diverse processes – including vegetation, atmosphere, biosphere, habitats and human development – all of which are impacted by fire disturbance. One striking example of their use for monitoring reductions or increases of gas flaring during offshore oil extraction is shown in Figure 3. Figure 4 shows a quantitative measure of the dramatic increase of forest fire outbreaks in Greece during summer 2007.

Fig 4: The ATSR World Fire Atlas fire distribution over southern Europe highlighting the Greece fire event anomaly of August 2007

Going into the future

Through GlobCover and the ATSR Wold Fire Atlas ESA is already providing scientists with high quality global information on land cover and fire disturbance, to inform policy decisions on climate change mitigation and adaptation. To reinforce this process the initial GlobCover and ATSR World Fire Atlas time series need to be extended well into the future and backward into the past by exploiting archives. Their quality and coverage needs to be further improved by including data from other satellite sources.

ESA’s planned GMES satellites will extend these and other time-series long into the future, using enhanced sensors, specifically designed for globally monitoring many of the Essential Climate Variables called for by GCOS. For example, the Sentinel-3 satellite, which is being prepared for launch in 2012, will have significantly enhanced coverage and sensitivity to ensure long-term continuity of the Global Land Cover and Global fire disturbance records illustrated here. In the meantime, the ESA Climate Change initiative will enable scientists to improve the accuracy and extend the time duration of the present record of these and other Essential Climate Variables by using existing satellites and data archives.

With these major new programmes ESA is preparing substantial contributions towards meeting the GCOS requirements, strengthening the GEOSS system, and thereby supporting the overall goals of UNFCCC.

W: www.esa.int