title: 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.
authors.affiliation: National Center for Atmospheric Research, Boulder, CO 80305, USA. stephens@ucar.edu
authors.forename: Britton B
authors.initials: BB
authors.lastname: Stephens
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Gurney
authors.forename: Pieter P
authors.initials: PP
authors.lastname: Tans
authors.forename: Colm
authors.initials: C
authors.lastname: Sweeney
authors.forename: Wouter
authors.initials: W
authors.lastname: Peters
authors.forename: Lori
authors.initials: L
authors.lastname: Bruhwiler
authors.forename: Philippe
authors.initials: P
authors.lastname: Ciais
authors.forename: Michel
authors.initials: M
authors.lastname: Ramonet
authors.forename: Philippe
authors.initials: P
authors.lastname: Bousquet
authors.forename: Takakiyo
authors.initials: T
authors.lastname: Nakazawa
authors.forename: Shuji
authors.initials: S
authors.lastname: Aoki
authors.forename: Toshinobu
authors.initials: T
authors.lastname: Machida
authors.forename: Gen
authors.initials: G
authors.lastname: Inoue
authors.forename: Nikolay
authors.initials: N
authors.lastname: Vinnichenko
authors.forename: Jon
authors.initials: J
authors.lastname: Lloyd
authors.forename: Armin
authors.initials: A
authors.lastname: Jordan
authors.forename: Martin
authors.initials: M
authors.lastname: Heimann
authors.forename: Olga
authors.initials: O
authors.lastname: Shibistova
authors.forename: Ray L
authors.initials: RL
authors.lastname: Langenfelds
authors.forename: L Paul
authors.initials: LP
authors.lastname: Steele
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Francey
authors.forename: A Scott
authors.initials: AS
authors.lastname: Denning