The main findings for 2024, as published in National Science Review.
Record CO2 growth in 2024 as land regions turned from sinks to sources
In 2024 the marine-boundary-layer CO2 growth rate reached a record 3.73 ppm yr−1 while fossil emissions grew by only 0.85%. Bottom-up models and OCO-2 inversions both show a strong weakening of the global net land sink and widespread transitions of terrestrial regions from sinks to sources.
- The CO2 growth rate from the NOAA marine boundary layer network reached a record 3.73 ± 0.08 ppm yr−1, a 38% increase over 2023, while fossil CO2 emissions increased by only 0.85%.
- The DGVMs estimate a net land source of 0.65 ± 0.85 GtC yr−1, the weakest net land flux since 1987; the OCO-2 inversions give a small sink of 0.29 ± 0.80 GtC yr−1.
- Tropical lands were a net source of 1.26 GtC yr−1 (DGVMs) and 0.95 GtC yr−1 (inversions); the Amazon (drought and fires) and central Africa had the largest source anomalies.
- The northern land sink (north of 30°N) continued its decline since 2015, to 0.90 GtC yr−1.
- Fire emissions were 0.50 GtC yr−1 above the 2015–2022 mean, about 20% of the land-sink reduction.
The budget at a glance
| Quantity | January–December 2024 | Notes |
|---|---|---|
| Atmospheric CO2 growth rate | 3.73 ± 0.08 ppm yr−1 | NOAA marine boundary layer; record high since 1959 |
| Fossil CO2 emissions | 10.19 ± 0.01 GtC yr−1 | +0.85% compared with 2023 |
| Net land flux (DGVMs) | −0.65 ± 0.85 GtC yr−1 | DGVMs: a net source, the weakest since 1987. OCO-2 inversions: a sink of 0.29 ± 0.80. The paper gives the mean of DGVMs and inversions as 0.18 ± 0.58 |
| Ocean sink | 2.48 ± 0.29 GtC yr−1 | Emulators 2.66 ± 0.55; inversions 2.30 ± 0.19 |
| Budget imbalance | 0.26 ± 1.03 GtC yr−1 | Bottom-up budget, against the marine boundary layer growth rate |
Values as published. Uncertainties are ±1σ across ensemble members. The ocean sink excludes the river-flux adjustment used in the Global Carbon Budget.
Models and data used
- Fossil CO2 emissions. Carbon Monitor and Global Carbon Budget 2024 projections
- Atmospheric growth rate. NOAA MBL; OCO-2 GRESO and inversion-implied growth as cross-checks
- Land, bottom-up. 4 DGVMs driven by ERA5: JULES, OCN, ORCHIDEE-MICT, LPJ-EOSIM; SiB4 (CTE-HR) as a cross-check
- Ocean, bottom-up. Machine-learning emulators of ocean models and data products
- Top-down. 3 OCO-2 inversions: CAMS, CMS-Flux, GONGGA
- Anomaly reference. 2015–2022
Publication
Ciais, P., Ke, P., Yao, Y., Sitch, S., Li, W., Xu, Y., et al. (2026). Low latency global carbon budget indicates reduced land carbon sink in the year 2024. National Science Review, 13(2), nwaf594. https://doi.org/10.1093/nsr/nwaf594