Field-experiment constraints on the enhancement of the terrestrial carbon sink by CO₂ fertilization

• Published in: Nature Geoscience
• Main Authors: Liu, Y., Piao, S., Gasser, T., Ciais, P., Yang, H., Wang, H., Keenan, T.F., Huang, M., Wan, S., Song, J., Wang, K., Janssens, I.A., Peñuelas, J., Huntingford, C., Wang, X., Altaf Arain, M., Fang, Y., Fisher, J.B., Huntzinger, D.N., Ito, A., Jain, A.K., Mao, J., Michalak, A.M., Peng, C., Poulter, B., Schwalm, C., Shi, X., Tian, H., Wei, Y., Zeng, N., Zhu, Q., Wang, T.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: NPG 2019
• Subjects: Arctic
• Online Access: http://pure.iiasa.ac.at/id/eprint/16069/

Clarifying how increased atmospheric CO₂ concentration (eCO₂) contributes to accelerated land carbon sequestration remains important since this process is the largest negative feedback in the coupled carbon–climate system. Here, we constrain the sensitivity of the terrestrial carbon sink to eCO₂ over the temperate Northern Hemisphere for the past five decades, using 12 terrestrial ecosystem models and data from seven CO₂ enrichment experiments. This constraint uses the heuristic finding that the northern temperate carbon sink sensitivity to eCO₂ is linearly related to the site-scale sensitivity across the models. The emerging data-constrained eCO₂ sensitivity is 0.64 ± 0.28 PgC yr−1 per hundred ppm of eCO₂. Extrapolating worldwide, this northern temperate sensitivity projects the global terrestrial carbon sink to increase by 3.5 ± 1.9 PgC yr−1 for an increase in CO2 of 100 ppm. This value suggests that CO₂ fertilization alone explains most of the observed increase in global land carbon sink since the 1960s. More CO₂ enrichment experiments, particularly in boreal, arctic and tropical ecosystems, are required to explain further the responsible processes.