Biogeosciences, 11, 3547–3602, 2014 www.biogeosciences.net/11/3547/2014/ doi:10.5194/bg-11-3547-2014 © Author(s) 2014. CC Attribution 3.0 License. Current systematic carbon-cycle observations and the need for implementing a policy-relevant carbon observing system P. Ciais1, A. J. Dolman2, A. Bombelli3, R. Duren4, A. Peregon1, P. J. Rayner5, C. Miller4, N. Gobron6, G. Kinderman7, G. Marland8, N. Gruber9, F. Chevallier1, R. J. Andres10, G. Balsamo11, L. Bopp1, F.-M. Bréon1, G. Broquet1, R. Dargaville5, T. J. Battin12, A. Borges13, H. Bovensmann14, M. Buchwitz14, J. Butler15, J. G. Canadell16, R. B. Cook10, R. DeFries17, R. Engelen11, K. R. Gurney18, C. Heinze19,20,21, M. Heimann22, A. Held23, M. Henry24, B. Law25, S. Luyssaert1, J. Miller15,26, T. Moriyama27, C. Moulin1, R. B. Myneni28, C. Nussli29, M. Obersteiner7, D. Ojima30, Y. Pan31, J.-D. Paris1, S. L. Piao32, B. Poulter1, S. Plummer33, S. Quegan34, P. Raymond35, M. Reichstein22, L. Rivier1, C. Sabine36, D. Schimel37, O. Tarasova38, R. Valentini3, R. Wang1, G. van der Werf2, D. Wickland39, M. Williams40, and C. Zehner41 1Laboratoire des Sciences du Climat et de l’Environnement, CEA-CNRS-UVSQ, UMR8212, 91191, Gif sur Yvette Cedex, France 2VU University Amsterdam, Amsterdam, the Netherlands 3Euro-Mediterranean Center for Climate Change, CMCC, Division Climate Change Impacts on Agriculture, Forests and Natural Ecosystems; via Augusto Imperatore 16, 73100 Lecce, Italy 4Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr, Pasadena, CA 91109, USA 5School of Earth Sciences, University of Melbourne, Australia 6Global Environmental Monitoring Unit, Institute for Environment and Sustainability, European Commission Joint Research Center, Ispra, Italy 7International Institute for Applied Systems Analysis (IIASA), Schlossplatz 1, Laxenburg, Austria 8Research Institute for Environment, Energy, and Economics, Appalachian State University, Boone, NC 28608, USA 9Institute of Biogeochemistry and Pollutant Dynamics and Center for Climate Systems Modeling, ETH Zürich, Zürich, Switzerland 10Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6290, USA 11European Centre for Medium-Range Weather Forecast (ECMWF), Shinfield Park, Reading, RG2 9AX, UK 12Department of Limnology, University of Vienna, A-1090 Vienna, Austria 13Chemical Oceanography Unit, University of Liège, Institute de Physique (B5), 4000 Liège, Belgium 14Institute of Environmental Physics (IUP), University of Bremen, Bremen, Germany 15NOAA Earth System Research Laboratory (ESRL), 325, Broadway, Boulder, CO 80305-3337, USA 16CSIRO Marine and Atmospheric Research, Canberra, ACT 2601, Australia 17Department of Geography and Environment, Boston University, Boston, MA 02115, USA 18School of Life Sciences, School of Sustainability, Arizona State University, Tempe, AZ 85287, USA 19Geophysical Institute, University of Bergen, Allégaten 70, 5007 Bergen, Norway 20Bjerknes Centre for Climate Research, Bergen, Norway 21Uni Bjerknes Centre, Uni Research, Bergen, Norway 22Max-Planck-Institute for Biogeochemistry, Jena, Germany 23AusCover Facility, Terrestrial Ecosystem Research Network – TERN, CSIRO, GPO Box 3023, Canberra ACT 2601, Australia 24Forestry Department, Food and Agriculture Organization of the United Nations, Via delle Terme di Caracalla, 00153 Rome, Italy 25Department of Forest Ecosystems and Society, 321 Richardson Hall, Oregon State University, Corvallis, OR 97331, USA 26Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA 27Japan Aerospace Exploration Agency (JAXA), Tokyo 28Department of Earth and Environment, Boston University, Boston, MA 02215, USA Published by Copernicus Publications on behalf of the European Geosciences Union. 3548 P. Ciais et al.: Current systematic carbon-cycle observations 29Thales Alenia Space, Toulouse, France 30Natural Resource Ecology Laboratory, Campus Mail 1499, Fort Collins, CO 80523-1499, USA 31US Department of Agriculture Forest Service, Newtown Square, PA 19073, USA 32Department of Ecology, Peking University, Beijing 100871, China 33ESA Climate Office, European Space Agency – Harwell, Didcot, Oxfordshire OX11 0QX, UK 34Centre for Terrestrial Carbon Dynamics, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, UK 35Yale School of Forestry and Environmental Studies, 195 Prospect Street, New Haven, CT 06511, USA 36Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric Administration, Seattle, WA 98115, USA 37National Ecological Observatory Network, Boulder, CO 80301, USA 38World Meteorological Organization, 7bis Avenue de la Paix, 1211 Geneva, Switzerland 39National Aeronautics and Space Administration, Suite 3B74, 300 E Street SW, Washington, DC 20546, USA 40School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3JN, UK 41ESA/ESRIN, Earth Observation Applications Engineer, Via Galileo Galilei CP, 64, Frascati Italy Correspondence to: P. Ciais ([email protected]) Received: 6 May 2013 – Published in Biogeosciences Discuss.: 10 July 2013 Revised: 6 March 2014 – Accepted: 21 March 2014 – Published: 3 July 2014 Abstract. A globally integrated carbon observation and anal- rently achieved for natural fluxes, although over a small land ysis system is needed to improve the fundamental under- area (cities, industrial sites, power plants), as well as the in- standing of the global carbon cycle, to improve our ability to clusion of fossil fuel CO2 proxy measurements such as ra- project future changes, and to verify the effectiveness of poli- diocarbon in CO2 and carbon-fuel combustion tracers. Addi- cies aiming to reduce greenhouse gas emissions and increase tionally, a policy-relevant carbon monitoring system should carbon sequestration. Building an integrated carbon obser- also provide mechanisms for reconciling regional top-down vation system requires transformational advances from the (atmosphere-based) and bottom-up (surface-based) flux esti- existing sparse, exploratory framework towards a dense, ro- mates across the range of spatial and temporal scales rele- bust, and sustained system in all components: anthropogenic vant to mitigation policies. In addition, uncertainties for each emissions, the atmosphere, the ocean, and the terrestrial bio- observation data-stream should be assessed. The success of sphere. The paper is addressed to scientists, policymakers, the system will rely on long-term commitments to monitor- and funding agencies who need to have a global picture of the ing, on improved international collaboration to fill gaps in the current state of the (diverse) carbon observations. We identify current observations, on sustained efforts to improve access the current state of carbon observations, and the needs and to the different data streams and make databases interopera- notional requirements for a global integrated carbon observa- ble, and on the calibration of each component of the system tion system that can be built in the next decade. A key conclu- to agreed-upon international scales. sion is the substantial expansion of the ground-based obser- vation networks required to reach the high spatial resolution for CO2 and CH4 fluxes, and for carbon stocks for address- ing policy-relevant objectives, and attributing flux changes 1 Introduction to underlying processes in each region. In order to establish Global mean atmospheric levels of CO have increased by flux and stock diagnostics over areas such as the southern 2 40 % from about 280 ppm in pre-industrial times (Etheridge oceans, tropical forests, and the Arctic, in situ observations et al., 1996) to 393.6 ppm by the end of 2012 (WMO, will have to be complemented with remote-sensing measure- 2010; Dlugokencky and Tans, 2012). Levels of CH reached ments. Remote sensing offers the advantage of dense spatial 4 1813 ± 2 ppb in 2011 (WMO, 2012), nearly 2.5 times their coverage and frequent revisit. A key challenge is to bring pre-industrial value of 700 ppb (Etheridge et al., 1996). The remote-sensing measurements to a level of long-term consis- increase of CO and CH is caused by fossil fuel combus- tency and accuracy so that they can be efficiently combined 2 4 tion and land use change. The primary anthropogenic CH in models to reduce uncertainties, in synergy with ground- 4 emissions are leaks from natural gas extraction and distribu- based data. Bringing tight observational constraints on fossil tion, the oil industry and coal extraction, livestock and rice fuel and land use change emissions will be the biggest chal- paddies, landfills and human-caused biomass burning (Den- lenge for deployment of a policy-relevant integrated carbon man et al., 2007). Natural emissions of CH are dominated observation system. This will require in situ and remotely 4 by wetlands and lakes, with smaller contributions from geo- sensed data at much higher resolution and density than cur- logical natural venting, wildfires, and termites. Biogeosciences, 11, 3547–3602, 2014 www.biogeosciences.net/11/3547/2014/ P. Ciais et al.: Current systematic carbon-cycle observations 3549 Fossil fuel emissions increased at a rate of 3.1 % per year design details of the monitoring system and their costs. Issues over the last decade (Le Quéré et al., 2013). Rates of land of economies of scale, i.e. single country or even projects use change CO2 emissions have slightly declined in the past versus a global system, and economies of scope generated decade (Friedlingstein et al., 2010). by constellations