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 CO 2 uptake (MCU) and a longer carbon uptake period (CUP), whereas maximum CO 2 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 CO 2 dominates longterm 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.
Terrestrial ecosystems act as major carbon sinks, offsetting approximately 30% of anthropogenic CO 2 emissions 1,2 . The long-term increase in global terrestrial carbon uptake has mostly been attributed to enhanced peak photosynthetic activity and lengthened growing seasons, but the stability of this sink under ongoing climate change remains uncertain, particularly because the processes of both carbon uptake and release are being altered simultaneously 3-9 . How processes of carbon release have changed over recent decades and how these concurrent changes interact with processes of carbon uptake to influence the long-term dynamics and stability of terrestrial carbon sinks remain insufficiently quantified.
Previous studies have predominantly focused on metrics of carbon uptake, showing that increases in the maximum CO 2 uptake (MCU, defined as the annual maximum of monthly net ecosystem productivity) and the carbon uptake period (CUP, Fig. S1a) have strongly contributed to the long-term enhancement of annual net ecosystem productivity (NEP annual ) 10-12 . Even small relative changes in MCU are often indicative of substantial changes in annual net carbon uptake 13-16 . Short-term peak values in daily or weekly fluxes (e.g., net ecosystem productivity [NEP] or gross primary productivity [GPP]) correlate closely with their annual totals 13 . NEP annual covaries with peak lightsaturated GPP at long-term European observational sites 17 . Similarly, many recent studies have also advanced our knowledge of how ecosystem phenology and thereby CUP influence the terrestrial carbon sinks 4,11,18,19 . Collectively, these studies consistently reported higher
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BibTeX
@article{bai2026increased,
title = {{Increased maximum carbon release offsets half of the growth trend in annual land carbon sink}},
author = {Yu Bai and Zheng Fu and Josep Peñuelas and Philippe Ciais and Fangyue Zhang and Paul C Stoy and Alessandro Cescatti and Stephen Sitch and Mirco Migliavacca and William K Smith and Weize Tang and Yiqi Luo and Yulin Shangguan and Kai Wang and Michael O’sullivan},
journal = {Nature Communications},
year = {2026},
month = sep,
doi = {10.1038/s41467-026-77462-8},
url = {https://hal.science/hal-05820810v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Increased maximum carbon release offsets half of the growth trend in annual land carbon sink
AU - Yu Bai
AU - Zheng Fu
AU - Josep Peñuelas
AU - Philippe Ciais
AU - Fangyue Zhang
AU - Paul C Stoy
AU - Alessandro Cescatti
AU - Stephen Sitch
AU - Mirco Migliavacca
AU - William K Smith
AU - Weize Tang
AU - Yiqi Luo
AU - Yulin Shangguan
AU - Kai Wang
AU - Michael O’sullivan
PY - 2026
DA - 2026/09/02
JO - Nature Communications
DO - 10.1038/s41467-026-77462-8
UR - https://hal.science/hal-05820810v1
AB - The terrestrial carbon sink has strengthened in recent decades through enhanced maximum CO 2 uptake (MCU) and a longer carbon uptake period (CUP), whereas maximum CO 2 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 CO 2 dominates longterm 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. Terrestrial ecosystems act as major carbon sinks, offsetting approximately 30% of anthropogenic CO 2 emissions 1,2 . The long-term increase in global terrestrial carbon uptake has mostly been attributed to enhanced peak photosynthetic activity and lengthened growing seasons, but the stability of this sink under ongoing climate change remains uncertain, particularly because the processes of both carbon uptake and release are being altered simultaneously 3-9 . How processes of carbon release have changed over recent decades and how these concurrent changes interact with processes of carbon uptake to influence the long-term dynamics and stability of terrestrial carbon sinks remain insufficiently quantified. Previous studies have predominantly focused on metrics of carbon uptake, showing that increases in the maximum CO 2 uptake (MCU, defined as the annual maximum of monthly net ecosystem productivity) and the carbon uptake period (CUP, Fig. S1a) have strongly contributed to the long-term enhancement of annual net ecosystem productivity (NEP annual ) 10-12 . Even small relative changes in MCU are often indicative of substantial changes in annual net carbon uptake 13-16 . Short-term peak values in daily or weekly fluxes (e.g., net ecosystem productivity [NEP] or gross primary productivity [GPP]) correlate closely with their annual totals 13 . NEP annual covaries with peak lightsaturated GPP at long-term European observational sites 17 . Similarly, many recent studies have also advanced our knowledge of how ecosystem phenology and thereby CUP influence the terrestrial carbon sinks 4,11,18,19 . Collectively, these studies consistently reported higher
SN - 2041-1723
SN - 2041-1723
ER -