Modèle de note technique en anglais

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CARBONES
20-year re-analysis of CARBON fluxES and pools over Europe
and the Globe
SUMMARY FOR POLICY-MAKERS
Context
The increasing atmospheric concentration of greenhouse gases is the main driver of
the on-going climate change. Since the beginning of the industrial revolution, CO 2
concentrations have increased by 30 %, N 2O by 20 %, and CH4 by 300%. These
changes are caused by human activities, especially through fossil fuel combustion and
modifications of global vegetation related to land-use change. On an average, only
half of the CO2 from anthropogenic emissions has remained in the atmosphere until
now. The land and oceans have sequestered the other half, in approximately equal
proportions. However, the apportionment of carbon fluxes between ocean and land
varies in time and space, and continental sources are particularly heterogeneous.
The present quantification of CO2 sources and sinks is based on inventories of forest
biomass and on energy statistics. This pragmatic quantification is too simple to
correctly represent the atmospheric signatures of CO2 variability. Detailed information
on CO2 fluxes and carbon pools, under the form of well resolved maps and their
variabilities, are necessary. This need is expressed both by the members of the
climate modelling community who want to understand and quantify the carbon cycles
at global and regional scales, and by policy makers who want to make well-informed
decisions on CO2 emissions at regional and local scales.
Objectives
CARBONES is a global information system that provides comprehensive information on
the spatial and temporal distribution of carbon fluxes and pools over the Globe. The
aim of CARBONES is to deliver, through the use of data assimilation techniques, stateof-the-art information on the history of the carbon cycle, using available observations
of the terrestrial and oceanic carbon-cycles: ocean surface CO 2 partial pressure,
atmospheric CO2 concentrations, remotely-sensed vegetation properties and in situ
ecologic data. The main CARBONES product takes the form of a calibrated, highresolution 20 year-long reanalysis of space and time variations of carbon fluxes and
stocks. This reanalysis includes the surface-atmosphere CO2 fluxes (net and gross
fluxes), leaf area and biomass stocks in various categories of land ecosystems. The
service potentially serves as a benchmark for core services carbon products and
provides a baseline for predicting future responses of the carbon-cycle.
Scientific approach The CARBONES reanalysis system is based upon a pivotal triad of advanced processbased models of the carbon cycle: the atmosphere (LMDz General Circulation
Transport Model), the land ecosystems (ORCHIDEE biosphere model) and the oceans
(OCVR neural network framework). These models, which describe the complex
biological, chemical and physical processes that regulate the exchange of CO2 over
each point of the globe, are optimized with the help of a full-fledged 4D-var
assimilation system by using long-term in situ and satellite observations.
Four 'observation pillars' are used to constrain the 20-years long reanalysis of the
carbon cycle:
1) Long term satellite monitoring of the ocean colour and of land greenness,
measuring respectively phytoplankton and terrestrial vegetation activity;
2) Eddy covariance networks with in-situ measurements of CO2 and water fluxes;
3) Surface measurements of partial pressure of CO2 in the ocean from shipboard
(SOCAT database);
4) Atmospheric CO2 concentrations networks.
In addition, the CARBONES service uses as inputs gridded climate and weather data,
as well as land cover and vegetation maps.
Special emphasis is placed on evaluating the carbon fluxes and pools at continental
breakdown and for specific ocean regions like the North Atlantic, by taking advantage
of the wealth of carbon observations recently collected by EU-funded projects, such as
CARBOEUROPE and CARBOOCEAN. The combination of these data sets with processbased atmospheric, land and ocean models enables to obtain fluxes at high spatial
(100 km) and temporal (3-hourly) resolutions necessary to capture the details of the
rapid changes in carbon cycles at regional and local scales. Moreover, the system also
integrates tropical deforestation fluxes and global fire emissions data as well as
anthropogenic emission inventories: a very high-resolution inventory over Europe, and
moderate-resolution inventories over the rest of the globe.
In order to provide an integrated view of the carbon cycle, CARBONES provides the
added value of using multiple data streams together to constrain the carbon cycle
compared with existing FP7 programs that integrate space-based information on CO 2
atmospheric composition (MACC), land surface biophysical state (GEOLAND) and
ocean bio-geochemical and dynamic state (MYOCEAN).
Added-value
The CARBONES data products, diagnostics and dissemination material directed at both
experts and the general public are available through a user-friendly web portal:
http://www.carbones.eu/wcmqs/. Several interactive tools for data visualisation
and data downloading have been integrated in this web interface in order to give
potential users (e.g. climate modellers, policy experts, and also the general public) the
possibility to take full advantage of the reanalysis generated. In particular, the
interactive visualisation tools allow creating both maps as well as time series of the
selected components of the carbon fluxes and stocks. The users can thus identify, for
example, the regions which act as strong sources or sinks of carbon, analyse the
contributions of individual processes (e.g. anthropogenic fluxes, natural fluxes, fluxes
from photosynthesis or respiration, etc.) and plot the time evolution for preselected
regions. An indication of the product uncertainty is provided and the plotting tool can
be used to compare the CARBONES products against products from independent
approaches.
Product example
The following figure illustrates the typical land carbon fluxes that are obtained with
the CARBONES data assimilation system. The upper panel shows the annual global
land carbon flux variations over the past two decades (natural exchange and biomass
burning emissions) and the contributions from northern (above 30°N), tropical (30°S30°N) and southern (below 30°S) regions. The Northern hemisphere appears to be
the major land carbon sink with a flux around -1.7 PgC/yr. The tropical land is more
neutral with a carbon uptake by the ecosystem compensating the emissions from
biomass burning (around 1. PgC/yr) with large inter-annual variations due to El-Nino
events 1997-1998). The southern land is on an average a small land carbon sink
(around -0.5 PgC/yr) with large inter-annual variations.
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The lower panel provides a split of the northern land flux into North American,
European and North Asian components. While the three regions have a mean sink
around 0.5 PgC/yr, the year-to year-variations appear to be relatively large and not in
phase between the three regions. It should be noted that at this continental scale, the
annual fluxes are still associated to large uncertainties. Finally, the CARBONES
products indicate an increase in ecosystem uptake from 2000 to 2009 in North
America and Eurasia that needs to be challenged against independent observations.
Figure 1: The
annual land carbon flux (including natural ecosystem exchange and biomass burning emissions,
fossil fuel burning is not included) variations from 1990 to 2009.
Upper graph: Global flux as well as contributions from the northern (above 30°N), tropical (30°S-30°N) and
southern (below 30°S) regions.
Lower graph: contributions from North America, Europe and Asia. Positive values indicate the release of the
CO2 into the atmosphere while negative values correspond to the uptake of atmospheric CO 2 by the
ecosystems. The units are Peta (1015)g of Carbon/year.
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PROJECT IDENTITY
Coordinator
Scientific coordinator
1. NOVELTIS (Coordinator), SME, France
2. Commissariat à l'Energie Atomique (CEA) - Laboratoire des Sciences du Climat et
de l'Environnement (LSCE), France
Consortium
1. NOVELTIS (Coordinator), SME, France
2. Commissariat à l'Energie Atomique (CEA) - Laboratoire des Sciences du Climat et
de l'Environnement (LSCE), France
3. Cambridge Environmental Research Consultants (CERC), UK
4. Max Planck Institute for Biochemistry, Jena, Germany
5. Ricardo-AEA, UK
6. Thales Alenia Space, France
7. Federal Institute of Technology (ETH), Zurich, Switzerland
8. ALTERRA- Dienst Landbouwkundig Onderzoek, the Netherlands
9. University of Stuttgart, Germany
10. Peking University, China
11. University of Aberdeen, UK
12. Met Office, UK
13. European Forest Institute (EFI), Finland
14. CLIMMOD, SME, France
Duration
April 1, 2010 – March 31, 2013 (36 months)
Funding scheme
Collaborative Project – FP7-SPACE-2009-01 N° 242316
Budget
3.491 Meuros, including EC contribution: 2.561 Meuros
Website
www.carbones.eu
More information
[email protected]
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