Global carbon budget 2013

Background

“Global carbon budget 2013” updates the living carbon budget series through 2012, documenting continued growth in anthropogenic Carbon dioxide (CO2) emissions and atmospheric concentrations. Atmospheric CO2 rises from about 277 ppm in 1750 to 392.52 ± 0.10 ppm on average in 2012, with daily values exceeding 400 ppm at Mauna Loa in May 2013, symbolizing entry into a new high CO2 regime. The paper positions this trend against persistent fossil fuel dependence and ongoing land-use change, particularly deforestation.

Goals and Methods

The study aims to quantify fossil and land-use emissions, atmospheric growth, and land and ocean sinks for 1959-2012, emphasize the 2003-2012 decade, and project fossil emissions for 2013. Fossil emissions are estimated from Carbon Dioxide Information and Analysis Center (CDIAC) territorial inventories based on UN energy data, extended for recent years using BP energy statistics, and disaggregated by fuel and by territorial versus consumption-based accounting. Land-use change emissions combine land-cover change, deforestation-related fire activity, and bookkeeping models, while atmospheric CO2 growth is taken from NOAA records; the mean ocean sink is constrained by 1990s observations with anomalies from ocean models and new data products, and the residual land sink is compared with dynamic global vegetation model ensembles.

Conclusions and Takeaways

For 2003–2012, the budget finds mean fossil emissions of 8.6 ± 0.4 GtC yr⁻¹ and land-use change emissions of 0.9 ± 0.5 GtC yr⁻¹, balanced by atmospheric growth of 4.3 ± 0.1 GtC yr⁻¹, an ocean sink of 2.5 ± 0.5 GtC yr⁻¹, and a land sink of 2.8 ± 0.8 GtC yr⁻¹. In 2012 alone, fossil emissions reach 9.7 ± 0.5 GtC yr⁻¹ (2.2% above 2011), atmospheric growth rose to 5.1 ± 0.2 GtC yr⁻¹, and the ocean and land sinks were estimated at 2.9 ± 0.5 and 2.7 ± 0.9 GtC yr⁻¹, respectively, with a projected 2013 fossil increase of about 2.1% to 9.9 ± 0.5 GtC. Cumulative emissions for 1870–2013 were projected to reach ~535 ± 55 GtC (about 70% fossil, 30% land use), providing key inputs for remaining carbon budget calculations and offering practitioners transparent, annually updated diagnostics for mitigation planning, carbon accounting, and assessment of sink behavior.