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There is an increasing demand for scientific support on climate-related decisions, in particular for providing societies and policy-makers with reliable and up-to-date information about atmospheric greenhouse gas (GHG) emissions and natural sinks. The Global Carbon Project now reports annually on the evolution of COsources and sinks, their uncertainties and the resulting Global Carbon Budget, in phase with the United Nations Framework Convention on Climate Change (UNFCCC) annual Conference of the Parties (COP). 

Figure 1: Perturbation of the global carbon cycle caused by anthropogenic activities, averaged globally for the decade 2008–2017 (GtCO2/yr) (LeQuéré et al., 2018, ESSD)

Global stocktaking as defined by the Paris Agreement further requires information about regional GHG budgets that should be consistent with the global budgets and regularly updated. Still, the latest global carbon budget (LeQuéré et al., 2018, ESSD) estimates a budget imbalance (knowledge-gap) of ca. 2.1PgC each year (Figure). Top-down and bottom-up estimates also show important discrepancies over different latitudinal bands and a non-negligible fraction of the global carbon budget variability remains to be captured by land and ocean models. This underscores the need for regional studies to better constrain key processes/regions in the global C-cycle.

This pilot project from ESA-CCI aims at supporting, in cooperation with the GCP, the scientific synthesis and assessment activities of regional carbon budgets and their drivers of the ‘REgional Carbon Cycle Assessment and Processes’, phase 2 (RECCAP-2) project by making use of regional cuts of annually updated global terrestrial and ocean carbon models, and atmospheric CO2 inversions, taking stock of new satellite-based surface monitoring products of climate and ecological variables now available within the framework of ESA-CCI.


The goal of the CCI project RECCAP-2 is to support and accelerate the analysis of regional carbon budgets based on the results of data-driven models and process-oriented Global Dynamic Vegetation Models used by the Global Carbon Project by operationalizing the production and uncertainty assessment of regional CO2 budgets, taking stock of newly available land surface and atmospheric remote sensing data to constrain and improve model results. The RECCAP-2 project specifically aims:

  1. To provide higher spatial resolution and annual updates for the global and regional carbon balance with the aim of improving the quantification and understanding of drivers, processes, and hot spot regions essential for predicting the future evolution of any carbon-climate feedback;
  2. To build on the experience from the RECCAP analysis that lasted from 2009 to 2012 to address the growing demand for the capacity to measure, report on, and verify the evolution of regional fluxes and the outcomes of climate mitigation policies;
  3. To respond to the demand of ESA and other space agencies for the better appropriation and effective use of remote sensing products in climate science. Here specifically, we will use a variety of remote sensing products to directly constrain carbon fluxes in data-driven models, and to be used as input or to evaluate process-based ecosystem models.

Latest news

RECCAP-2 session at the 2019 AGU Fall meeting​

Global and regional fluxes from Global Carbon Budget 2018 available
The land-surface CO2 fluxes from the five inversions and 14 dynamic global vegetation models from GCB2018 (Le Quéré et al. 2018) can now be explored in the Global Carbon Atlas (see Resources)

First all RECCAP-2 Workshop, Gotemba, Japan 18-21 March
18-21 March 2019, Gotemba (at the foothill of Mount Fuji), Japan

The workshop will gather scientists with expertise on regional and global budgets of GHGs (CO2, CH4, N2O), including atmospheric inversions, vegetation, soils and ocean models, existing and emerging observations, data mining and synthesis, from different regions of the globe. The main goal will be the planning to deliver (and explore the feasibility for regular updates) of regional assessment of GHG budgets based on scientific evidence, considering uncertainties, understanding of drivers, and retrospective analysis of recent trends. Additionally, key global assessments will be developed for their own value and in support to the regional GHG budgets. See one-page Justification and Objectives of RECCAP2.

This meeting is supported by the National Institute for Environmental Studies (which will cover your accommodation, local transport and food in Japan), the European Space Agency (ESA), and the Global Carbon Project. We hope you will be able to cover your airfare, but we do have a limited budget to support some airfares which will be allocated on the basis of the most needed. Our Japanese hosts are Nobuko Saigusa from NIES and Prabir Patra from JAMSTEC.

RECCAP2 Science Committee: Philippe Ciais, Niki Gruber, Prabir Patra, Ana Bastos, Judith Hauck, Masao Ishii, Rob Jackson, Ben Poulter, Nobuko Saigusa, Pep Canadell

RECCAP-2 session at the 2018 AGU Fall meeting

About the project

The project is based on CO2 fluxes data-streams from three different approaches to deliver annual updates of land-atmosphere CO2 fluxes at global and regional scales (Tier 1), consistent with the global carbon budget assessment from the Global Carbon Project (GCP) and with regional details in space and time to analyze the underlying drivers (Tier 2, Figure 2 below).

These data-streams are

  1. atmospheric inversions of CO2 concentration gradients based on surface in situ networks and satellite remote sensing, with currently three “high resolution” global inversions being used by the Global Carbon Budget annual assessment;
  2. Output from process-based terrestrial ecosystem models from the TRENDY inter-comparison, these models being driven by climate fields and land cover change;  
  3. Output of “data-driven” bottom-up approach machine learning methods like artificial neural networks or regression tree ensembles in the FLUXCOM project.

RECCAP2 Tier 2

Figure 2: Approaches to global and regional scale land-atmosphere CO2 fluxes.

These three approaches are largely independent; even though inversions use as prior the output from process-based models, they usually do not use specifically the TRENDY models’ output. TRENDY models and data-driven models also share climate forcing as input.

The project will update the output of regional land carbon fluxes from the three approaches each year for the previous year, synchronized with the availability of in situ CO2 data for inversions. ESA CCI available products for burned area, land cover, and soil moisture will be used until 2014 to evaluate the results from TRENDY models. ESA CCI satellite GHG column concentrations of CO2 (XCO2) have been produced by ESA CCI until 2015 and similar retrieval products will be available in near-real-time to perform atmospheric inversions for the period of the project through the Copernicus project CAMS41.

The scale of the RECCAP-2 regional analysis will have increased detail compared to those in RECCAP-1. The analysis will also focus on spatially explicit maps of monthly CO2 fluxes from TRENDY, data driven models and from inversions.

The project team

The Consortium is based on a close collaboration between the following partners:

  • Laboratoire des Sciences du Climat et de l’Environnement, France

  • University of Exeter, United Kingdom

  • Max-Planck Institute for Biogeochemistry, Germany

  • Global Carbon Project via Future Earth, Sweden

Resources, data and documents



IPCC Special Report on Climate Change and Land

ESA-CCI RECCAP-2 (M. O'Sullivan and A. Bastos) contributed to the IPCC Special Report on Climate Change and Land Chapters 1 and 2 with regional estimates of natural sinks and land-use change emissions.



Impact of the 2015/2016 El Niño on the terrestrial carbon cycle constrained by bottom-up and top-down approaches

In this work, we evaluated the response of the terrestrial carbon cycle to the extreme El-Niño event in 2015/16 using atmospheric inversions and land-surface models. 

Evaluating the response of the land carbon sink to the anomalies in temperature and drought imposed by El Niño events provides insights into the present-day carbon cycle and its climate-driven variability. It is also a necessary step to build confidence in terrestrial ecosystems models' response to the warming and drying stresses expected in the future over many continents, and particularly in the tropics. Here we present an in-depth analysis of the response of the terrestrial carbon cycle to the 2015/2016 El Niño that imposed extreme warming and dry conditions in the tropics and other sensitive regions. First, we provide a synthesis of the spatio-temporal evolution of anomalies in net land–atmosphere CO2 fluxes estimated by two in situ measurements based on atmospheric inversions and 16 land-surface models (LSMs) from TRENDYv6. Simulated changes in ecosystem productivity, decomposition rates and fire emissions are also investigated. Inversions and LSMs generally agree on the decrease and subsequent recovery of the land sink in response to the onset, peak and demise of El Niño conditions and point to the decreased strength of the land carbon sink: by 0.4–0.7 PgC yr−1 (inversions) and by 1.0 PgC yr−1 (LSMs) during 2015/2016. LSM simulations indicate that a decrease in productivity, rather than increase in respiration, dominated the net biome productivity anomalies in response to ENSO throughout the tropics, mainly associated with prolonged drought conditions. anomalies in terrestrial net CO2 uptake by terrestrial ecosystems during the 2015/16 El Nino event, seen by two atmospheric inversions and an ensemble of land-surface models

Figure 3: Anomalies in terrestrial net CO2 uptake by terrestrial ecosystems during the2015/16 El-Niño event, seen by two atmospheric inversions and an ensemble of land-surface models.

This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’.

Global Carbon Atlas

The Global Carbon Atlas allows for quick time-series and map visualisation of the carbon fluxes from the datasets used in RECCAP-2.  

The Global Carbon Atlas is an online platform to explore, visualize and interpret global and regional carbon data arising from both human activities and natural processes. The graphics and data sources are made available in the belief that their wide dissemination will lead to new knowledge and better-informed decisions to limit and cope with human-induced climate change. The Global Carbon Atlas is a community effort under the umbrella of the Global Carbon Project based on the contributions of many research institutions and individual scientists around the world who make available observations, models, and interpretation skills. 

The land-surface CO2 fluxes from the five inversions and 14 dynamic global vegetation models from GCB2018 (Le Quéré et al. 2018) can now be explored in the Global Carbon Atlas:




For data access, please contact:

- Inversions: see product tooltip or




The project contributed to the benchmarking of TRENDY DGVMs using the International Land Model Benchmarking (ILAMB) software ( We outline the use of ESA-CCI data in evaluating the ability of DGVMs to simulate carbon-cycle related variables. The ESA-CCI project provides information on ‘essential climate variables’ (ECVs) from across the Earth system. Surface soil moisture, burned area, land cover type, and forest biomass are four ECVs that can be used to evaluate DGVM performance.

Results from the DGVM benchmarking for burned area, biomass and forest cover can be explored online here

Contact us / support

Please use the following emails to contact the RECCAP-2 team:

  • Science Leader(s): Philippe Ciais (philippe.ciais[at] / Ana Bastos (ana.bastos[at]
  • ESA technical officer: Stephen Plummer (stephen.plummer[at]