The main findings for July 2023 to June 2024, as published in iScience.
The 2023/24 El Niño drove a record CO2 growth rate through a weaker tropical land sink
Extending the budget through the decay phase of the 2023/24 El Niño, this edition finds the highest July-to-July CO2 growth rate since 1979. The growth-rate anomaly was driven by a 2.24 GtC yr−1 weakening of the net land sink, 97.5% of it in the tropics, partly offset by stronger ocean uptake.
- From July 2023 to June 2024 atmospheric CO2 grew by 3.66 ± 0.09 ppm yr−1, the highest July-to-July rate since 1979; after detrending, the anomaly (1.1 ppm yr−1) was comparable to the 1997/98 and 2015/16 El Niño events.
- The anomaly was mainly driven by a 2.24 GtC yr−1 weakening of the net land sink, partly offset by 0.38 GtC yr−1 stronger ocean uptake.
- The tropics accounted for 97.5% of the land anomaly, led by the Amazon, central Africa and Southeast Asia.
- The land-sink weakening persisted through the first half of 2024, beyond the late-2023 Amazon drought, with new source anomalies in tropical Africa and Southeast Asia.
- ERA5-driven DGVMs give larger tropical losses than the OCO-2 inversions; emulators of 19 GCB DGVMs and the SiB4 model sit closer to the inversions.
The budget at a glance
| Quantity | July 2023–June 2024 | Notes |
|---|---|---|
| Atmospheric CO2 growth rate | 3.66 ± 0.09 ppm yr−1 | NOAA marine boundary layer, July–June; highest since 1979 |
| Fossil CO2 emissions | 10.14 GtC yr−1 | Range 10.14–10.15 across two estimates |
| Net land flux | −0.34 ± 0.33 GtC yr−1 | A net source. DGVMs −0.59 ± 0.60; inversions −0.09 ± 0.26 (negative = source) |
| Ocean sink | 2.56 ± 0.33 GtC yr−1 | Emulators 2.87 ± 0.56; inversions 2.25 ± 0.33 |
| Budget imbalance | 0.09 GtC yr−1 | Bottom-up budget, against the marine boundary layer growth rate |
Values as published, for July 2023–June 2024. Uncertainties are ±1σ across ensemble members.
Models and data used
- Fossil CO2 emissions. Carbon Monitor and the Global Carbon Budget method; monthly split from IEA-EDGAR
- Atmospheric growth rate. NOAA MBL (June–July); OCO-2 GRESO and inversion-implied growth as cross-checks
- Land, bottom-up. 4 DGVMs driven by ERA5: JULES, OCN, ORCHIDEE-MICT, LPJ-EOSIM; cross-checks from SiB4 (CTE-HR) and emulators of 19 GCB 2024 DGVMs
- Ocean, bottom-up. Machine-learning emulators of GCB 2022 ocean models and data products
- Top-down. 3 OCO-2 inversions: CAMS, CMS-Flux, GONGGA
- Anomaly reference. 2015–2022, same calendar window
Publication
Ke, P., Ciais, P., Yao, Y., Sitch, S., Li, W., Xu, Y., et al. (2026). Low latency global carbon budget reveals land sink decline during 2023 to 2024 El Niño. iScience, 29(8), 117053. https://doi.org/10.1016/j.isci.2026.117053