Global Carbon Budget 2017

The global atmospheric CO₂ concentration is measured directly and its rate of growth (G_ATM) is computed from the annual changes in concentration. The ocean CO₂ sink (S_OCEAN) and terrestrial CO₂ sink (S_LAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (B_IM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ.

For the last decade available (2007–2016), E_FF was 9.4±0.5GtCyr⁻¹, E_LUC 1.3±0.7GtCyr⁻¹, G_ATM 4.7±0.1GtCyr⁻¹, S_OCEAN 2.4±0.5GtCyr⁻¹, and S_LAND 3.0±0.8GtCyr⁻¹, with a budget imbalance B_IM of 0.6GtCyr⁻¹ indicating overestimated emissions and/or underestimated sinks. For year 2016 alone, the growth in E_FF was approximately zero and emissions remained at 9.9±0.5GtCyr⁻¹. Also for 2016, E_LUC was 1.3±0.7GtCyr⁻¹, G_ATM was 6.1±0.2GtCyr⁻¹, S_OCEAN was 2.6±0.5GtCyr⁻¹, and S_LAND was 2.7±1.0GtCyr⁻¹, with a small B_IM of −0.3GtC. G_ATM continued to be higher in 2016 compared to the past decade (2007–2016), reflecting in part the high fossil emissions and the small S_LAND consistent with El Niño conditions.

The global atmospheric CO₂ concentration reached 402.8±0.1ppm averaged over 2016. For 2017, preliminary data for the first 6–9 months indicate a renewed growth in E_FF of +2.0% (range of 0.8 to 3.0%) based on national emissions projections for China, USA, and India, and projections of gross domestic product (GDP) corrected for recent changes in the carbon intensity of the economy for the rest of the world.

This living data update documents changes in the methods and data sets used in this new global carbon budget compared with previous publications of this data set.