An accurate knowledge of the terrestrial component of the global carbon cycle has become a policy imperative for this and the forthcoming decades, both globally and for individual countries. At the global level, the main reason is recognition that the increasing atmospheric CO2 concentration is most likely affecting the variability and trend of regional and global climates. This recognition has led to important policy decisions. For example, the United Nations Framework Convention on Climate Change (UNFCCC) instituted inventories of the national greenhouse gas emissions, including terrestrial sources and sinks. More recently, the Kyoto Protocol acknowledged the role of terrestrial systems as carbon sinks and sources, and it provides a basis for developing future emission trading credits that involve C-sequestration in forests and potentially in other ecosystems. The effectiveness of the various policy instruments agreed upon by nations depends on the availability of specific observations related to the terrestrial component of the global carbon cycle. The observation needs are typically defined through a dialogue involving the policy and scientific communities, as a compromise between the desirable and the available or practically achievable information.
At the national level, in addition to the response of a country to the international or global policy agreements, the carbon cycle (expressed as vegetation productivity) has long been important to countries whose economic or social structure depend on biospheric resources. This motivation becomes stronger as an increasing portion of the global annual net primary production is employed in the economic sphere (now estimated to be ~40%) and with continuing concerns about the threats to sustainable use of terrestrial ecosystems. The national perspective and interest are very important to the implementation of global observation programmes since resources for implementation will ultimately need to be made available by national governments.
The basis for understanding the global carbon cycle and the role of terrestrial ecosystems has been provided through scientific research at national, regional and global levels. During the past decade, this research greatly accelerated under the leadership of the International Geosphere-Biosphere Programme (IGBP) and several of its core projects. The activities involve field research as well as modelling studies at various spatial scales. Through the Intergovernmental Panel on Climate Change (IPCC) process (IPCC, 1996), IGBP synthesis (e.g. Walker and Steffen, 1997), and other activities (e.g. IGBP Carbon Working Group, 1998), the scientific community also addressed specific questions and issues raised by the policy community. Based on these activities, it has also become evident that further progress in our understanding of the global carbon cycle and its likely future evolution depends on improved observations of the terrestrial carbon processes. Thus, commenting on the results of an inter-comparison of net primary productivity (NPP) models carried out by IGBP and guidance for future research, Cramer and Field (1999, p. iv) stated “...At the heart of these are enhanced experimental and monitoring systems (flux measurements, satellite sensors, field and laboratory experiments, global data archives) which are being identified by every single paper in this collection as being important for better parameterization of terrestrial biosphere models.”
The above policy as well as activities and interests depend on accurate, objective information about the state and changes in various parts of the terrestrial carbon cycle. Because of the many interacting factors affecting this cycle both above and below the soil surface, such information must be obtained frequently and with a high spatial resolution. Given the limitations of measurement techniques, this has simply not been possible in the past. The advent of new methods, including observing techniques and process models, makes the problem more tractable and has been a major reason for the increasing research interest in the observation and quantification of the terrestrial component of the global carbon cycle.
A substantial scientific effort has also taken place during the last decade. Since its inception in the late 1980s, IGBP has undertaken considerable research on the carbon cycle, both at the level of core projects (disciplinary aspects of the global cycle) and at the level of major sub-components of the global cycle (GAIM). As part of the IGBP synthesis/restructure project, begun in early 1998, IGBP formed a Carbon Working Group (CWG). The focus of the work of the CWG has been on the biophysical aspects of the carbon cycle, in keeping with IGBP’s emphasis on biogeochemical cycling. However, there are important aspects of research on the carbon cycle which benefit from the involvement of other communities. Examples include the effects of climate variability on carbon uptake or release (joint WCRP-IGBP issue) and the institutional challenges associated with management of components of the carbon cycle (IHDP issue).
Since the early 1990s, international organizations have been working towards the establishment of systematic, long-term observations of various components of the earth system: terrestrial environment, oceans, and climate. The need for such systems was evident during the preparation of the 1992 UN Conference on Environment and Development when scientists and policy makers were hindered by a lack of key data and information upon which to base targets and performance goals. The emerging global observing systems for oceans (GOOS), terrestrial environment (GTOS), and climate (GCOS) are intended to complement the existing atmospheric observation capabilities implemented as part of the Global Atmospheric Watch (GAW) through the World Meteorological Organization (WMO). Similarly as GAW, GCOS, GOOS and GTOS are designed to include space and in situ components. The close coordination of satellite and in situ observation programmes is therefore essential for the successful realisation of the observing systems.
To facilitate progress in the implementation process, space agencies and international agencies (both observation and research) have recently established a new coordination mechanism, the Integrated Observing Strategy Partnership (IGOS-P). The IGOS-Partnership includes GCOS, GTOS, GOOS, WCRP, IGBP, ICSU, FAO,UNEP, IOC,WMO, UNESCO, IGFA and CEOS, all of whom have signed a formal letter of partnership acknowledging their commitment to work together in the context of the Integrated Global Observing Strategy. IGOS-P has chosen to proceed by themes, rather than projects, with agreed criteria being established for the selection of themes. In June, 1999 IGOS-P agreed to consider a proposal for a terrestrial carbon theme by GTOS. The GTOS/GCOS Terrestrial Observation Panel for Climate (TOPC) prepared such a proposal for the November 1999 meeting of IGOS-P. At this meeting, IGOS-P made the following decisions:
* 4/5 GTOS with FAO support to lead the Terrestrial Carbon Cycle theme and to present a report to the Partners along the lines of the Oceans theme report.
* 4/6 GCOS, FAO, IGBP, ICSU, UNESCO, and CEOS to nominate representatives for the Terrestrial Carbon Cycle team by the end of November 1999.
* GOOS, GCOS, GTOS, IGBP, NASA to prepare proposals for the overarching Global Carbon Theme and to decide amongst themselves who should lead this activity.
The overall goal of the Terrestrial Carbon Observation (TCO) theme is to define observation requirements for an accurate estimation of the distribution of terrestrial carbon sources and sinks of the world with high spatial and temporal resolutions. To define the optimal system to achieve this goal requires strong scientific input, both from modelling studies and from ground-based process studies.
To initiate the process leading to the terrestrial carbon theme report, GTOS/TOPC in collaboration with IGBP and other IGOS-P members organised a workshop for February 8-11, 2000 in Ottawa, Canada. The specific objectives of the workshop were:
1. To assemble and summarize existing information on information requirements regarding the terrestrial component of the global carbon cycle.
2. To assemble and synthesize existing information on observation requirements needed to obtain the carbon cycle information, assuming that top-down (inversion modelling) and bottom-up (ecosystem modelling) strategies are employed in an integrated manner. All important data/observation requirements are to be considered (satellite, surface, atmospheric, etc.).
3. To evaluate the consistency, completeness, and reliability of the information on observation requirements defined above, and refine these to the extent possible.
4. To conduct initial evaluation of existing data or observations in relation to the observation requirements, identify major gaps or deficiencies, and propose solutions to the extent possible.
5. To identify actions that need to be taken in order to: complete the definition of observation requirements; complete the analysis of deficiencies of existing observations and needed remedies; link terrestrial and ocean carbon cycle observations; and prepare a report on the terrestrial carbon observation theme for IGOS-P.
6. Based on the above, to prepare a ‘straw man’ framework report as an input for a joint IGBP/GTOS meeting in May, 2000. This meeting will engage the scientific community more fully to complete the design of a comprehensive approach to terrestrial carbon observations and the links between terrestrial and ocean components of the global carbon cycle.
The GTOS-led preparations for global terrestrial carbon observations are an integral part of a larger international effort to undertake collaborative research on the global carbon cycle. This international research effort, which is led by the International Geosphere-Biosphere Programme in collaboration with the World Climate Research Programme (WCRP) and the International Human Dimensions Programme on Global Environmental Change (IHDP), consists of a linked suite of process level studies (e.g. experiments, field campaigns), observations, and modelling (development, evaluation, intercomparisons, etc.). The integrated international approach, which will also link strongly to national and regional carbon cycle research programmes, will contribute to an understanding of terrestrial, oceanic, and coastal process studies and modelling activities. Thus, the workshop agenda was planned to dovetail with subsequent international meetings that will take place during the year 2000, with the objective of completing the terrestrial carbon theme report to IGOS-P in October for consideration at the November meeting of IGOS-P.
This report contains information produced prior to and during the workshop. It is intended to support the further development of the IGOS carbon theme, particularly the theme report to be submitted in November 2000, as well as the Terrestrial Carbon Observation initiative led by GTOS. Results of group or plenary discussions are provided in the main report. Appendix III contains summaries of the contributions by participants prepared prior to the workshop.
