Global Carbon Budget 2015

Background

The "Global Carbon Budget 2015” updates the global CO2 budget through 2014, a year when atmospheric CO2 reached 397.15 ppm and monthly values exceeded 400 ppm for the first time globally. The assessment highlights the continued dominance of fossil fuel and industrial CO2 emissions, with land-use change remaining a significant but smaller source. It places these trends within the broader industrial era, with CO2 increasing from about 277 ppm in 1750, and ongoing growth in energy use and economic activity.

Goals and Methods

This paper aims to quantify fossil and industrial emissions (EFF), land-use change emissions (ELUC), atmospheric growth (GATM), ocean uptake (SOCEAN), and the residual land sink (SLAND) for 1959–2014, focusing on the 2005–2014 decade and providing a 2015 emissions projection. EFF is estimated from Carbon Dioxide Information and Analysis Center (CDIAC) energy and cement data, extended with BP statistics, and disaggregated by fuel and by territorial versus consumption-based accounting informed by Global Trade Analysis Project (GTAP) trade matrices. ELUC relies on land-cover change data, deforestation-related fire activity, and bookkeeping models, while GATM is based on NOAA CO2 records; SOCEAN is constrained by 1990s observations with anomalies from ocean models and data products, and SLAND is the residual checked against dynamic global vegetation models.

Conclusions and Takeaways

For 2005–2014, the study reports average fossil and industrial emissions of 9.0 ± 0.5 GtC yr⁻¹ and land-use change emissions of 0.9 ± 0.5 GtC yr⁻¹, balanced by atmospheric growth of 4.4 ± 0.1 GtC yr⁻¹, an ocean sink of 2.6 ± 0.5 GtC yr⁻¹, and a land sink of 3.0 ± 0.8 GtC yr⁻¹. In 2014, fossil emissions reached 9.8 ± 0.5 GtC yr⁻¹ (0.6% above 2013), ELUC was 1.1 ± 0.5 GtC yr⁻¹, and the land sink strengthened to 4.1 ± 0.9 GtC yr⁻¹, producing a relatively low atmospheric growth of 3.9 ± 0.2 GtC yr⁻¹. Preliminary 2015 projections suggest near-zero growth in fossil emissions and cumulative emissions since 1870 of about 555 ± 55 GtC, offering practitioners key boundary conditions for remaining carbon budget analyses and for assessing whether observed emission slowdowns indicate structural decarbonization or short-term variability.