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Weak Northern and Strong Tropical Land Carbon Uptake from Vertical Profiles of Atmospheric CO₂

Stephens, Britton B., Gurney, Kevin R., Tans, Pieter P., Sweeney, Colm, Peters, Wouter, Bruhwiler, Lori, Ciais, Philippe, Ramonet, Michel, Bousquet, Philippe, Nakazawa, Takakiyo, Aoki, Shuji, Machida, Toshinobu, Inoue, Gen, Vinnichenko, Nikolay, Lloyd, Jon, Jordan, Armin, Heimann, Martin, Shibistova, Olga, Langenfelds, Ray L., Steele, L. Paul, Francey, Roger J., Denning, A. Scott
Science 2007 v.316 no.5832 pp. 1732-1735
carbon, carbon dioxide, ecosystems, greenhouse gas emissions, land use, latitude, models
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.