Increased maximum carbon release offsets half of the growth trend in annual land carbon sink
Abstract
The terrestrial carbon sink has strengthened in recent decades through enhanced maximum CO2 uptake (MCU) and a longer carbon uptake period (CUP), whereas maximum CO2 release (MCR) remains less quantified. Using atmospheric inversion estimates and 16 terrestrial biosphere models, we show that MCU and MCR both increased significantly from 1993 to 2022, with MCU rising faster globally (0.18 ± 0.04 versus 0.07 ± 0.01 g C m−2 yr−1). MCU increases were widespread, whereas MCR increases were strongest at mid- to high latitudes. Enhanced MCU and CUP increased annual net ecosystem productivity by 0.31 ± 0.09 g C m−2 yr−1, but rising MCR offset 44 ± 20% of this gain, leaving a net increase of 0.18 ± 0.06 g C m−2 yr−1. Elevated CO2 dominates long-term increases, while climate variability contributes to spatial heterogeneity. These findings highlight the importance of accounting for carbon release in projections of future terrestrial sink strength. This study shows that stronger maximum CO2 uptake and a longer carbon uptake period strengthen the terrestrial carbon sink but increasing maximum CO2 release offsets 44% of this gain, highlighting an important constraint on its future strength.
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Authors: Yu Bai, Zheng Fu, Josep Peñuelas, Philippe Ciais, Fangyue Zhang, Paul Stoy, Alessandro Cescatti, Stephen Sitch, Mirco Migliavacca, William K. Smith, Weize Tang, Yiqi Luo, Yulin Shangguan, Kai Wang, Michael O’Sullivan
Institutions: Chinese Academy of Sciences, Peking University, University of Exeter, Cornell University, Zhejiang University, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, University of Arizona, Centre National de la Recherche Scientifique, Beijing Normal University, University of Wisconsin–Madison, Université Paris-Saclay, CEA Paris-Saclay, Institute of Geographic Sciences and Natural Resources Research, Joint Research Centre, Université de Versailles Saint-Quentin-en-Yvelines, Laboratoire des Sciences du Climat et de l'Environnement, Centre for Research on Ecology and Forestry Applications, Czech Academy of Sciences, Global Change Research Institute, Global Ecology Unit CREAF-CSIC-UAB