title: A comprehensive estimate of recent carbon sinks in China using both top-down and bottom-up approaches.
abstract: Atmospheric inversions use measurements of atmospheric CO2 gradients to constrain regional surface fluxes. Current inversions indicate a net terrestrial CO2 sink in China between 0.16 and 0.35 PgC/yr. The uncertainty of these estimates is as large as the mean because the atmospheric network historically contained only one high altitude station in China. Here, we revisit the calculation of the terrestrial CO2 flux in China, excluding emissions from fossil fuel burning and cement production, by using two inversions with three new CO2 monitoring stations in China as well as aircraft observations over Asia. We estimate a net terrestrial CO2 uptake of 0.39-0.51 PgC/yr with a mean of 0.45 PgC/yr in 2006-2009. After considering the lateral transport of carbon in air and water and international trade, the annual mean carbon sink is adjusted to 0.35 PgC/yr. To evaluate this top-down estimate, we constructed an independent bottom-up estimate based on ecosystem data, and giving a net land sink of 0.33 PgC/yr. This demonstrates closure between the top-down and bottom-up estimates. Both top-down and bottom-up estimates give a higher carbon sink than previous estimates made for the 1980s and 1990s, suggesting a trend towards increased uptake by land ecosystems in China.
authors.affiliation: Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, International Institute for Earth System Science, Nanjing University, Nanjing 210046, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Jiang
authors.affiliation: Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, International Institute for Earth System Science, Nanjing University, Nanjing 210046, China.|Department of Geography, University of Toronto, Ontario M5S3G3, Canada.
authors.forename: Jing M
authors.initials: JM
authors.lastname: Chen
authors.affiliation: Chinese Academy of Meteorological Sciences, China Meteorological Administration, Beijing 100081, China.
authors.forename: Lingxi
authors.initials: L
authors.lastname: Zhou
authors.affiliation: Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, International Institute for Earth System Science, Nanjing University, Nanjing 210046, China.
authors.forename: Weimin
authors.initials: W
authors.lastname: Ju
authors.affiliation: State Key Laboratory of Resources and Environment Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Huifang
authors.initials: H
authors.lastname: Zhang
authors.affiliation: National Institute for Environmental Studies, 305-8506 Tsukuba, Japan.
authors.forename: Toshinobu
authors.initials: T
authors.lastname: Machida
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnement, CEA CNRS UVSQ, 91191 Gif sur Yvette, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Ciais
authors.affiliation: Department of Meteorology and Air Quality, Wageningen University and Research Center, 6708 PB Wageningen, The Netherlands.|University of Groningen, Centre for Isotope Research, 9747 AG Groningen, The Netherlands.
authors.forename: Wouter
authors.initials: W
authors.lastname: Peters
authors.affiliation: Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, International Institute for Earth System Science, Nanjing University, Nanjing 210046, China.
authors.forename: Hengmao
authors.initials: H
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Resources and Environment Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Baozhang
authors.initials: B
authors.lastname: Chen
authors.affiliation: Chinese Academy of Meteorological Sciences, China Meteorological Administration, Beijing 100081, China.
authors.forename: Lixin
authors.initials: L
authors.lastname: Liu
authors.affiliation: Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology, International Institute for Earth System Science, Nanjing University, Nanjing 210046, China.|School of Geography and Planning, Ludong University, Yantai 264025, China.
authors.forename: Chunhua
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Geochemical Research Department, Meteorological Research Institute, Tsukuba 305-0052, Japan.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Matsueda
authors.affiliation: Geochemical Research Department, Meteorological Research Institute, Tsukuba 305-0052, Japan.
authors.forename: Yousuke
authors.initials: Y
authors.lastname: Sawa