Showing papers by "Michel Ramonet published in 2007"

Saturation of the Southern Ocean CO2 Sink Due to Recent Climate Change

Abstract: Based on observed atmospheric carbon dioxide (CO2) concentration and an inverse method, we estimate that the Southern Ocean sink of CO2 has weakened between 1981 and 2004 by 0.08 petagrams of carbon per year per decade relative to the trend expected from the large increase in atmospheric CO2. We attribute this weakening to the observed increase in Southern Ocean winds resulting from human activities, which is projected to continue in the future. Consequences include a reduction of the efficiency of the Southern Ocean sink of CO2 in the short term (about 25 years) and possibly a higher level of stabilization of atmospheric CO2 on a multicentury time scale.

Weak northern and strong tropical land carbon uptake from vertical profiles of atmospheric CO2

Abstract: Measurements of midday vertical atmospheric CO2 distributions reveal annual-mean vertical CO2 gradients that are inconsistent with atmospheric models that estimate a large transfer of terrestrial carbon from tropical to northern latitudes. The three models that most closely reproduce the observed annual-mean vertical CO2 gradients estimate weaker northern uptake of –1.5 petagrams of carbon per year (Pg C year–1) and weaker tropical emission of +0.1 Pg C year–1 compared with previous consensus estimates of –2.4 and +1.8 Pg C year–1, respectively. This suggests that northern terrestrial uptake of industrial CO2 emissions plays a smaller role than previously thought and that, after subtracting land-use emissions, tropical ecosystems may currently be strong sinks for CO2.

Retrieval of average CO2 fluxes by combining in situ CO2 measurements and backscatter lidar information

Abstract: [1] The present paper deals with a boundary layer budgeting method which makes use of observations from various in situ and remote sensing instruments to infer regional average net ecosystem exchange (NEE) of CO2. Measurements of CO2 within and above the atmospheric boundary layer (ABL) by in situ sensors, in conjunction with a precise knowledge of the change in ABL height by lidar and radiosoundings, enable to infer diurnal and seasonal NEE variations. Near-ground in situ CO measurements are used to discriminate natural and anthropogenic contributions of CO2 diurnal variations in the ABL. The method yields mean NEE that amounts to 5 μmol m−2 s−1 during the night and −20 μmol m−2 s−1 in the middle of the day between May and July. A good agreement is found with the expected NEE accounting for a mixed wheat field and forest area during winter season, representative of the mesoscale ecosystems in the Paris area according to the trajectory of an air column crossing the landscape. Daytime NEE is seen to follow the vegetation growth and the change in the ratio diffuse/direct radiation. The CO2 vertical mixing flux during the rise of the atmospheric boundary layer is also estimated and seems to be the main cause of the large decrease of CO2 mixing ratio in the morning. The outcomes on CO2 flux estimate are compared to eddy-covariance measurements on a barley field. The importance of various sources of error and uncertainty on the retrieval is discussed. These errors are estimated to be less than 15%; the main error resulted from anthropogenic emissions.

The CARIBIC aircraft system for detailed, long-term, global-scale measurement of trace gases and aerosol in a changing atmosphere

Abstract: Contributed by Carl Brenninkmeijer (carlb@mpchmainz.mpg.de), Franz Slemr (slemr@mpch-mainz. mpg.de), Tanja Schuck (schuck@mpch-mainz.mpg.de), Dieter Scharffe (scharffe@mpch-mainz.mpg.de), Claus Koeppel, (koeppel@mpch-mainz.mpg.de), Martin Pupek (pupek@mpch-mainz.mpg.de), Patrick Jockel (Joeckel@mpch-mainz.mpg.de), Jos Lelieveld (lelieveld@mpch-mainz.mpg.de) and Paul Crutzen (crutzen@mpch-mainz.mpg. de), Max Planck Institute for Chemistry, Mainz, Germany, Tae Siek Rhee (rhee@ kopri.re.kr), Korea Polar Institute, Incheon, Korea, Markus Hermann (Hermann@tropos.de), Andreas Weigelt (andreas.weigelt@tropos.de), Manuela Reichelt (reichelt@chemie.uni-leipzig.de) and Jost Heintzenberg (jost@tropos.de), Leibniz Institute for Tropospheric Research, Leipzig, Germany, Andreas Zahn (zahn@imk.fzk.de), Detlev Sprung (sprung@ imk.fzk.de) and Herbert Fischer (Fischer@imk.fzk. de), Institute for Meteorology and Climate Research, Karslruhe, Germany, Helmut Ziereis (helmut.ziereis@ dlr.de), Hans Schlager (hans.schlager@dlr.de) and Ulrich Schumann (ulrich. schumann@dlr.de), Institute for Atmospheric Physics, DLR, Oberpfaffenhofen, Germany, Barbara Dix (bdix@iup.uni-heidelberg. de), Udo Friess (udo.friess@ iup.uni-heidelberg.de) and Ulrich Platt (Platt@iup.uniheidelberg.de), University of Heidelberg, Heidelberg, Germany, Ralf Ebinghaus (ralf.ebinghaus@gkss.de), GKSS, Geesthacht, Germany, Bengt Martinsson (bengt. martinsson@nuclear.lu.se) and Hung N. Nguyen (hung. ng uye n _ ngo c @ pi xe . l t h . se), Department of Nuclear Physics, University of Lund, Lund, Sweden, David Oram (d.e.oram@uea.ac.uk), Debbie O’Sullivan (debbie. osullivan@metoffice.gov.uk) and Stuart Penkett (M.Penkett@uea.ac.uk), University of East Anglia, Norwich, England, Peter van Velthoven (velthove@ knmi.nl) KNMI, de Bilt, the Netherlands, Thomas Rockmann (T.Roeckmann@phys.uu.nl) and Gerben Pieterse (G.Pieterse@phys.uu.nl), University of Utrecht, the Netherlands, Sergey Assonov (sergey.assonov@ ec.europa.eu), IRMM, Geel, Belgium, Michel Ramonet (michel.ramonet@cea.fr), Irene Xueref-Remy (irene. xueref@cea.fr) and Philippe Ciais (ciais@cea.fr), LSCE/ CEA/CNRS, Paris, France, Stefan Reimann (Stefan. Reimann@empa.ch) and Martin Vollmer (Martin. Vollmer@empa.ch), EMPA, Dubendorf, Switzerland, Markus Leuenberger (mleu@climate.unibe. ch) and Francesco Luca Valentino ( F r a n c e s c o L u c a .Va l e n t i n o @ insightful.com), University of Bern, Bern, Switzerland.