Global Carbon Budget 2024

Background

“Global Carbon Budget 2024” assesses how anthropogenic carbon dioxide (CO2) emissions disrupt the global carbon cycle relative to pre-industrial conditions, when atmospheric CO2 was about 278 ppm in 1750. The study focuses on emissions from fossil fuels and land-use change and how these are partitioned between the atmosphere, ocean, and terrestrial biosphere. Recent changes, in the context of long-term trends since 1958, emphasize the role of deforestation, fossil fuel combustion, and climate variability, such as El Niño, in shaping CO2 fluxes.

Goals and Methods

This paper aims to quantify five major budget components: fossil CO2 emissions (EFO), land-use change emissions (ELUC), atmospheric CO2 growth (GATM), and the ocean (SOCEAN) and land (SLAND) sinks, including their uncertainties. EFOS is derived from energy statistics and cement production data, while ELUC is estimated with bookkeeping models (track carbon stock changes by combining land-use data (like deforestation maps) with established carbon density & decay rates for different land types, following IPCC guidelines Tier 3) based on land-use and land-use change datasets. Atmospheric CO2 is measured directly at monitoring stations, ocean uptake is estimated using global ocean biogeochemistry models and observation-based fugacity of carbon dioxide (fCO2) products, and land uptake is simulated with dynamic global vegetation models. Additional constraints come from atmospheric inversions, atmospheric oxygen, and Earth system models.

Conclusions and Takeaways

In 2023, total anthropogenic emissions reached 11.1 ± 0.9 GtC yr⁻¹, with 10.1 ± 0.5 GtC yr⁻¹ from fossil fuels and 1.0 ± 0.7 GtC yr⁻¹ from land-use change, while the budget imbalance is near zero, indicating internally consistent estimates. Preliminary 2024 data suggest fossil emissions increased by 0.8%, atmospheric CO2 rose to about 422.45 ppm, and the remaining carbon budget for a 50% chance of limiting warming to 1.5 °C falls to 65 GtC from early 2025, equivalent to roughly six years at 2024 emission levels. The ocean and land sinks combined continue to absorb about 56% of emissions, but show stagnation or strong variability since 2016, underscoring that sustained mitigation, reduced deforestation, and enhanced sinks are critical for practitioners designing climate policy, land management, and decarbonization pathways.