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What have we learnt from global intercomparison programmes and what should we do next?

pubblicazioni - Articolo

What have we learnt from global intercomparison programmes and what should we do next?

and what should we do next? A. C. Manning 1 , A. Jordan 2 , R. F. Keeling 3 , I. Levin 4 , M. Schmidt 5 , R. E. M. Neubert 6 , A. Etchells 1 , B. Steinberg 2 , P. Ciais 5 , T. Aalto 7 , F. Apadula 8 , M. L. Bender 9 , K. Bracchi 3 , G. W. Brailsford 10 , W. A. Brand 2 , M. Delmotte 5 , A. Giorgio di Sarra 11 , B. Hall 12 , L. Haszpra 13 , L. Huang 14 , D. Kitzis 12 , S. van der Laan 6 , R. L. Langenfelds 15 , M. Leuenberger 16 , A. Lindroth 17 , T. Machida 18 , F. Meinhardt 19 , J. Moncrieff 20 , J. A. Morguí 21 , T. Nakazawa 22 , J. Necki 23 , W. J. Paplawsky 3 , M. Patecki 1 , E. Popa 2,24 , J. Richter 2 , L. Ries 19 , K. Rozanski 23 , R. Santaguida 25 , L. P. Steele 15 , B. B. Stephens 26,10 , J. Strom 27 , Y. Tohjima 18 , R. L. Thompson 2,5 , A. T. Vermeulen 24 , F. Vogel 4 , P. A. Wilson 1 and D. E. J. Worthy 14 15th WMO/IAEA Meeting of Experts on Carbon Dioxide, Other Greenhouse Gases, and Related Tracer Measurement Techniques Jena (Germany), 7-10 Settembre 2009 1 School of Environmental Sciences, University of East Anglia, United Kingdom 2 Max Planck Institute for Biogeochemistry, Germany 3 Scripps Institution of Oceanography, USA 4 Institut für Umweltphysik, University of Heidelberg, Germany 5 Laboratoire des Sciences du Climat et de l’Environnement, France 6 Centre for Isotope Research, University of Groningen, The Netherlands 7 Finnish Meteorological Institute, Finland 8 ENEA – Ricerca sul Sistema Elettrico (ERSE, ex CESI RICERCA), Italy 9 Department of Geosciences, Princeton University, USA 10 National Institute for Water and Atmospheric Research, New Zealand 11 ENEA/ACS, Italy 12 National Oceanic and Atmospheric Administration, USA 13 Hungarian Meteorological Service, Hungary 14 Environment Canada, Canada 15 CSIRO Marine Atmospheric Research, Australia 16 University of Bern, Switzerland 17 Lunds Universitet, Sweden 18 National Institute for Environmental Studies, Japan 19 Umweltbundesamt, Germany 20 School of GeoSciences, University of Edinburgh, United Kingdom 21 Laboratori de Recerca del Clima-Parc Científic de Barcelona, Spain 22 Center for Atmospheric and Oceanic Studies, Tohoku University, Japan 23 Environmental Physics Group, AGH University of Science and Technology, Poland 24 Dept. Air Quality, Energy Research Center of the Netherlands, The Netherlands 25 Italian Air Force Meteorological Service, Italy 26 National Center for Atmospheric Research, USA 27 Department of Meteorology, Stockholm University, Sweden The World Meteorological Organization has specified an “inter-laboratory comparability” of ±0.1 ppm and ±1 per meg for background atmospheric CO 2 and O 2 measurements respectively. This means that any given two laboratories (or field stations) measuring the same air sample should strive to obtain values within 0.1 ppm CO 2 (or 1 per meg O 2 ) of each other. Intercomparability goals also exist for the other major greenhouse gases and greenhouse-related tracers. Several intercomparison programmes, focussed on CO 2 , have existed for many years quantifying (and improving) such comparability between the few major greenhouse gas analysis laboratories around the world. No overarching programme existed, however, for assessing comparability between field stations or for O 2

measurements. Oxygen measurements further suffer from the non-existence of a common international calibration scale. The “GOLLUM” (Global Oxygen Laboratories Link Ultra-precise Measurements) and “Cucumber” intercomparison programmes were established to address these deficiencies. Each programme continuously circulates trios of high pressure cylinders of air of known concentrations to field stations and laboratories. We present 4 years of results from these programmes, where we quantify the CO 2 and O 2 comparability from 22 participating European field stations and 16 international laboratories. Results of other tracers are also presented. By highlighting concentration offsets, the programmes have assisted in improving the analytical procedures and thus the precision and accuracy at some stations. Comparability between any two given stations or laboratories is not constant over time, thus the programmes run indefinitely, and emphasis is given to rapid circulation between participants and for each station/laboratory to build up a time-history of comparability. In addition to continuing the programmes and improving technical aspects of the measurements, next steps must consider quantitative adjustments to existing atmospheric concentration data, thus allowing one to merge formerly disparate datasets. This would lead to spatially and temporally denser datasets which would be invaluable to many aspects of carbon cycle science, for example by reducing uncertainty in atmospheric inverse models used to quantify global and regional carbon sinks.

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