The Regional Carbon Cycle Assessment and Processes (RECCAP; http://www.globalcarbonproject.org/reccap/) is an ongoing international assessment designed and coordinated by the Global Carbon Project, and involving many of the world’s leading scientists in carbon cycle research. RECCAP serves the scientific needs of providing a higher spatial resolution of the global carbon balance with the aim to improve the attribution to processes and to identify hot-spot regions essential to understand its future evolution. This is important in the context of a growing demand for a capacity to Measure, Report, and Verify (MRV) the evolution of regional fluxes and the outcomes of climate mitigation policies. RECCAP also supports the capacity building needs in regions with regional carbon balances of significant global influence but with little or no technical capabilities. Finally, RECCAP responds to the Group on Earth Observations (GEO) in establishing a global carbon observation system to track the evolution of natural and anthropogenic carbon sources and sinks.

RECCAP Scope and Regions

The scope of RECCAP lies at establishing the mean carbon balance of large regions of the globe on the scale of continents and large ocean basins, including their component fluxes. It is achieved through using and comparing bottom-up estimates with the results of regional top-down atmospheric inversions, and thereby testing the compatibility of regional bottom-up estimates with global atmospheric constraints. It evaluates the regional 'hot-spots' of inter-annual variability and possibly the trends and underlying processes over the past two decades by combining available long-term observations and modeling. The RECCAP assessment period is variable but, for carbon budget, it encompasses the period between 1990 and 2009 and for trends analyses it is between 1958–2009. However, information on ocean trend observations is available only for 1983–2009. RECCAP uses multiple constraints to understand one carbon budget. From top-down, information from atmospheric CO₂ inversion models and GHG observations is utilized while, from bottom-up, the regional carbon budget in land and ocean is provided by a number of models and observations (e.g. in-situ and remote sensing). RECCAP has established fourteen regions in this synthesis of which ten are for land (Africa, the Arctic tundra, Australia, Europe, Russia, East Asia, South Asia, Southeast Asia, Central and South America, and North America), and four are ocean regions (Atlantic and Arctic, Indian, Pacific, and Southern oceans).

RECCAP Syntheses Structures

In RECCAP, each region is analyzed both for its long term mean carbon budget over the target period, and also, wherever possible, for its rate of inter-annual variability and trends. RECCAP ‘Global’ Syntheses cover and analyze the globe subdivided into large regions using a globally homogeneous approach. Global syntheses include topics such as fossil fuel emissions, land-use change emissions, global atmospheric budget, global ocean surface CO₂, global ocean storage, coastal ocean, rivers fluxes and embedded fluxes in international trade. The RECCAP ‘regional’ syntheses are composed of land and ocean. The land syntheses cover topics such as estimates of the long-term mean carbon budget; estimates of the average monthly seasonal cycle of ecosystem fluxes and disturbance-related emissions; breakdown of the long-term mean carbon budget into component gross fluxes of GPP, NPP, RH and disturbance emissions for major land cover types including at least croplands, grassland and forests; estimation of the inter-annual flux anomalies and an overview of the dominant underlying processes leading to sources and sinks of sub-regional hot spots. On the ocean front, RECCAP regional syntheses cover topics such as estimates of the long-term mean carbon budget over the past two decades including interior ocean; estimates of the natural and anthropogenic CO₂ fluxes; estimates of the average seasonal cycle of CO₂ fluxes; breakdown of the long-term mean carbon budget into component gross fluxes of primary production, export production, thermal component and physical transport; estimation of the inter-annual flux anomalies since 1983 and an overview of the dominant underlying processes generating sources and sinks and sub-regional hot spots. RECCAP’s ‘final’ synthesis (a ‘synthesis’ of the different syntheses) draws upon the results of the syntheses described above. A number of synthesis chapters are foreseen to integrate top-down inversions results with the state of the art of bottom-up long-term mean fluxes and their inter-annual variability, possibly also the long-term trends in key regions. Areas where these two approaches converge or differ will be identified, and uncertainties will be assessed into a coherent framework. A discussion of the different processes contributing regionally (e.g. CO₂ fertilization versus the legacy from past land-use change and climate change) will be provided. Finally, the synthesis aims to make essential recommendations for reducing errors in the future, for example, organizing data exchange protocols, tailored model inter-comparisons or model-data comparison, identifying regions where key information is missing, and suggesting ways to reduce uncertainties in a 5–10 year time-frame.

The RECCAP assessment is being realized through a large scale global coordination effort with the involvement of about 200 key experts globally. A “soft protocol” has been prepared and deliberated to guide and ensure consistency among regional syntheses. The assessment relies, primarily, on existing analyses, regional and national programs (e.g., North American Carbon Synthesis, CarboEurope and COCOS, China and East Asia budgets, Australian North American Carbon Assessment and Syntheses, The Large-Scale Biosphere Atmosphere Experiment in Amazonia), global modeling and synthesis efforts (e.g. GCP Annual Global Carbon Budget, GCP-TRENDY, TRANSCOM). Secondarily, it relies on the establishment of new synthesis teams in regions where there is no established carbon program with the support of active regions, such as South and South East Asia. RECCAP’s plans and scope were prepared in mid-2007 followed by a series of community consultations. The invitations for lead authors were sent out in December 2009. The first lead authors’ workshop of RECCAP took place in October 2010 at Viterbo, Italy, which laid out the basic process and plans. The second lead authors’ workshop of RECCAP took place at the Training Center of US Fisheries and Wildlife Services in West Virginia, USA on 23–27 May 2011. This workshop presented the zero-order draft of the various chapters and discussed the progress made so far within and across teams, cross cutting harmonization needs, and deliberated on the high level ‘synthesis’ of the regional and global syntheses made so far. The RECCAP assessment is aimed to be completed by the early to mid-2012 and will publish a total of 25 synthesis papers in the form of a journal special issue and high level synthesis papers in top journals.

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