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Weak Northern and Strong Tropical Land Carbon Uptake from Vertical Profiles of Atmospheric CO2
Britton B. Stephens,1*Kevin R. Gurney,2Pieter P. Tans,3Colm Sweeney,3Wouter Peters,3Lori Bruhwiler,3Philippe Ciais,4Michel Ramonet,4Philippe Bousquet,4Takakiyo Nakazawa,5Shuji Aoki,5Toshinobu Machida,6Gen Inoue,7Nikolay Vinnichenko,8Jon Lloyd,9Armin Jordan,10Martin Heimann,10Olga Shibistova,11Ray L. Langenfelds,12L. Paul Steele,12Roger J. Francey,12A. Scott Denning13
Measurements of midday vertical atmospheric CO2 distributionsreveal annual-mean vertical CO2 gradients that are inconsistentwith atmospheric models that estimate a large transfer of terrestrialcarbon from tropical to northern latitudes. The three modelsthat most closely reproduce the observed annual-mean verticalCO2 gradients estimate weaker northern uptake of –1.5petagrams of carbon per year (Pg C year–1) and weakertropical emission of +0.1 Pg C year–1 compared with previousconsensus estimates of –2.4 and +1.8 Pg C year–1,respectively. This suggests that northern terrestrial uptakeof industrial CO2 emissions plays a smaller role than previouslythought and that, after subtracting land-use emissions, tropicalecosystems may currently be strong sinks for CO2.
1 National Center for Atmospheric Research, Boulder, CO 80305, USA. 2 Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, IN 47907, USA. 3 National Oceanic and Atmospheric Administration, Boulder, CO 80305, USA. 4 Le Laboratoire des Sciences du Climat et l'Environnement, 91191 Gif sur Yvette, France. 5 Center for Atmospheric and Oceanic Studies, Tohoku University, Sendai 980-8578, Japan. 6 National Institute for Environmental Studies, Onogawa, Tsukuba 305-8506, Japan. 7 Graduate School of Environmental Studies, Nagoya University, Nagoya City 464-8601, Japan. 8 Central Aerological Observatory, Dolgoprudny, 141700, Russia. 9 School of Geography, University of Leeds, West Yorkshire, LS2 9JT, UK. 10 Max Planck Institute for Biogeochemistry, 07701 Jena, Germany. 11 Sukachev Institute of Forest, Krasnoyarsk, 660036, Russia. 12 Commonwealth Scientific and Industrial Research Organisation (CSIRO) Marine and Atmospheric Research, Aspendale, Victoria 3195, Australia. 13 Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523, USA.
Deceased.
* To whom correspondence should be addressed. E-mail: stephens{at}ucar.edu
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Climate Change, Deforestation, and the Fate of the Amazon.
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Deceased. 
