Global Carbon Budget 2025

Background

“Global Carbon Budget 2025” extends the living dataset on anthropogenic carbon dioxide (CO2) emissions and their redistribution among atmosphere, ocean, and land, updating trends through 2024, and providing preliminary 2025 estimates. Atmospheric CO2 has risen from about 278 ppm in 1750 to 422.8 ± 0.1 ppm in 2024, with recent growth amplified by the 2023–2024 El Niño event. This paper highlights the continued dominance of fossil fuel emissions, persistent sources of land-use change, and climate-driven modulation of land and ocean sinks within the broader carbon-climate system.

Goals and Methods

The authors aim to quantify annual and decadal means, variability, and trends in fossil emissions, land-use change emissions, atmospheric growth, and land and ocean sinks, as well as the resulting budget imbalance. Fossil emissions are estimated from energy statistics and cement production, including a cement carbonation sink, while land-use change emissions rely on updated bookkeeping models that now use transient carbon densities and an adjusted model ensemble. Atmospheric growth is derived from surface CO2 networks, ocean uptake from global biogeochemical models and observation-based fCO2 products, and land uptake from dynamic global vegetation models, complemented by atmospheric inversions, oxygen measurements, and Earth system model simulations that close the global balance.

Conclusions and Takeaways

In 2024, the study reported fossil emissions of 10.3 ± 0.5 GtC yr⁻¹ and land-use change emissions of 1.3 ± 0.7 GtC yr⁻¹, yielding total anthropogenic emissions of 11.6 ± 0.9 GtC yr⁻¹, and an unusually large negative budget imbalance, suggesting either overestimated sinks or growth rate that year. Preliminary 2025 estimates indicate fossil emissions grew by 1.1%, to about 10.4 GtC yr⁻¹, atmospheric CO2 reached roughly 425.7 ppm, and the remaining carbon budget for a 50% chance of limiting warming to 1.5 °C shrinks to about 50 GtC (≈4 years at 2025 emissions), with budgets for 1.7 °C and 2 °C also sharply reduced. The ocean and land sinks take up about 29% and 21% of emissions, respectively, over 2015–2024, but are weakened by climate change. A growing number of countries show declining fossil emissions with rising GDP, providing important signals and data products for policymakers, modelers, and practitioners working on mitigation strategies and carbon accounting.