Global Carbon Budget 2016

Abstract. Accurate assessment of anthropogenic carbon dioxide (CO₂) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics, and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates and consistency within and among components, alongside methodology and data limitations. CO₂ emissions from fossil fuels and industry (E_FF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (E_LUC), mainly deforestation, are based on combined evidence from land-cover change data, fire activity associated with deforestation, and models. The global atmospheric CO₂ concentration is measured directly and its rate of growth (G_ATM) is computed from the annual changes in concentration. The mean ocean CO₂ sink (S_OCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in S_OCEAN is evaluated with data products based on surveys of ocean CO₂ measurements. The global residual terrestrial CO₂ sink (S_LAND) is estimated by the difference of the other terms of the global carbon budget and compared to results of independent dynamic global vegetation models. We compare the mean land and ocean fluxes and their variability to estimates from three atmospheric inverse methods for three broad latitude bands. All uncertainties are reported as ±1σ, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2006–2015), E_FF was 9.3 ± 0.5 GtC yr⁻¹, E_LUC 1.0 ± 0.5 GtC yr⁻¹, G_ATM 4.5 ± 0.1 GtC yr⁻¹, S_OCEAN 2.6 ± 0.5 GtC yr⁻¹, and S_LAND 3.1 ± 0.9 GtC yr⁻¹. For year 2015 alone, the growth in E_FF was approximately zero and emissions remained at 9.9 ± 0.5 GtC yr⁻¹, showing a slowdown in growth of these emissions compared to the average growth of 1.8 % yr⁻¹ that took place during 2006–2015. Also, for 2015, E_LUC was 1.3 ± 0.5 GtC yr⁻¹, G_ATM was 6.3 ± 0.2 GtC yr⁻¹, S_OCEAN was 3.0 ± 0.5 GtC yr⁻¹, and S_LAND was 1.9 ± 0.9 GtC yr⁻¹. G_ATM was higher in 2015 compared to the past decade (2006–2015), reflecting a smaller S_LAND for that year. The global atmospheric CO₂ concentration reached 399.4 ± 0.1 ppm averaged over 2015. For 2016, preliminary data indicate the continuation of low growth in E_FF with +0.2 % (range of −1.0 to +1.8 %) based on national emissions projections for China and USA, and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. In spite of the low growth of E_FF in 2016, the growth rate in atmospheric CO₂ concentration is expected to be relatively high because of the persistence of the smaller residual terrestrial sink (S_LAND) in response to El Niño conditions of 2015–2016. From this projection of E_FF and assumed constant E_LUC for 2016, cumulative emissions of CO₂ will reach 565 ± 55 GtC (2075 ± 205 GtCO₂) for 1870–2016, about 75 % from E_FF and 25 % from E_LUC. This living data update documents changes in the methods and data sets used in this new carbon budget compared with previous publications of this data set (Le Quéré et al., 2015b, a, 2014, 2013). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi:10.3334/CDIAC/GCP_2016).