Satellite records combined with global ecosystem models show a persistent and widespread greening over 25-50% of the global vegetated area; less than 4% of the globe is browning. CO2 fertilization explains 70% of the observed greening trend.

The difference is found at the margins: The terrestrial biosphere absorbs about a quarter of all anthropogenic carbon dioxide emissions, but the amount that they take up varies from year to year. Why? Combining models and observations, Ahlström et al. found that marginal ecosystems—semiarid savannas and low-latitude shrublands—are responsible for most of the variability. Biological productivity in these semiarid regions is water-limited and strongly associated with variations in precipitation, unlike wetter tropical areas. Understanding carbon uptake by these marginal lands may help to improve predictions of variations in the global carbon cycle. Science , this issue p. 895

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).

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 the five major components of the global carbon budget and their uncertainties. 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 land-cover change data and bookkeeping 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 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 ± 0.5 GtC yr⁻¹, E_LUC 1.3 ± 0.7 GtC yr⁻¹, G_ATM 4.7 ± 0.1 GtC yr⁻¹, S_OCEAN 2.4 ± 0.5 GtC yr⁻¹, and S_LAND 3.0 ± 0.8 GtC yr⁻¹, with a budget imbalance B_IM of 0.6 GtC yr⁻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 ± 0.5 GtC yr⁻¹. Also for 2016, E_LUC was 1.3 ± 0.7 GtC yr⁻¹, G_ATM was 6.1 ± 0.2 GtC yr⁻¹, S_OCEAN was 2.6 ± 0.5 GtC yr⁻¹, and S_LAND was 2.7 ± 1.0 GtC yr⁻¹, with a small B_IM of −0.3 GtC. 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 ± 0.1 ppm 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 (Le Quéré et al., 2016, 2015b, a, 2014, 2013). All results presented here can be downloaded from https://doi.org/10.18160/GCP-2017 (GCP, 2017).

Accurate assessment of anthropogenic carbon dioxide (CO₂) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere 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 a 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 as well as 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, 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 forced by observed climate, CO₂, and land-cover change (some including nitrogen–carbon interactions). 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 (2005–2014), E_FF was 9.0 ± 0.5 GtC yr⁻¹, E_LUC was 0.9 ± 0.5 GtC yr⁻¹, G_ATM was 4.4 ± 0.1 GtC yr⁻¹, S_OCEAN was 2.6 ± 0.5 GtC yr⁻¹, and S_LAND was 3.0 ± 0.8 GtC yr⁻¹. For the year 2014 alone, E_FF grew to 9.8 ± 0.5 GtC yr⁻¹, 0.6 % above 2013, continuing the growth trend in these emissions, albeit at a slower rate compared to the average growth of 2.2 % yr⁻¹ that took place during 2005–2014. Also, for 2014, E_LUC was 1.1 ± 0.5 GtC yr⁻¹, G_ATM was 3.9 ± 0.2 GtC yr⁻¹, S_OCEAN was 2.9 ± 0.5 GtC yr⁻¹, and S_LAND was 4.1 ± 0.9 GtC yr⁻¹. G_ATM was lower in 2014 compared to the past decade (2005–2014), reflecting a larger S_LAND for that year. The global atmospheric CO₂ concentration reached 397.15 ± 0.10 ppm averaged over 2014. For 2015, preliminary data indicate that the growth in E_FF will be near or slightly below zero, with a projection of −0.6 [range of −1.6 to +0.5] %, based on national emissions projections for China and the USA, and projections of gross domestic product corrected for recent changes in the carbon intensity of the global economy for the rest of the world. From this projection of E_FF and assumed constant E_LUC for 2015, cumulative emissions of CO₂ will reach about 555 ± 55 GtC (2035 ± 205 GtCO₂) for 1870–2015, 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., 2015, 2014, 2013). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi:10.3334/CDIAC/GCP_2015).

Accurate assessments of anthropogenic carbon dioxide (CO₂) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere is important to better understand the global carbon cycle, support the climate policy process, and project future climate change. Present-day analysis requires the combination of a range of data, algorithms, statistics and model estimates and their interpretation by a broad scientific community. Here we describe datasets and a methodology developed by the global carbon cycle science community to quantify all major components of the global carbon budget, including their uncertainties. We discuss changes compared to previous estimates, consistency within and among components, and methodology and data limitations. CO₂ emissions from fossil fuel combustion and cement production (E_FF) are based on energy statistics, while emissions from Land-Use Change (E_LUC), including deforestation, are based on combined evidence from land cover change data, fire activity in regions undergoing deforestation, and models. The global atmospheric CO₂ concentration is measured directly and its rate of growth (G_ATM) is computed from the 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. Finally, the global residual terrestrial CO₂ sink (S_LAND) is estimated by the difference of the other terms. For the last decade available (2002–2011), E_FF was 8.3 ± 0.4 PgC yr⁻¹, E_LUC 1.0 ± 0.5 PgC yr⁻¹, G_ATM 4.3 ± 0.1 PgC yr⁻¹, S_OCEAN 2.5 ± 0.5 PgC yr⁻¹, and S_LAND 2.6 ± 0.8 PgC yr⁻¹. For year 2011 alone, E_FF was 9.5 ± 0.5 PgC yr⁻¹, 3.0 percent above 2010, reflecting a continued trend in these emissions; E_LUC was 0.9 ± 0.5 PgC yr⁻¹, approximately constant throughout the decade; G_ATM was 3.6 ± 0.2 PgC yr⁻¹, S_OCEAN was 2.7 ± 0.5 PgC yr⁻¹, and S_LAND was 4.1 ± 0.9 PgC yr⁻¹. G_ATM was low in 2011 compared to the 2002–2011 average because of a high uptake by the land probably in response to natural climate variability associated to La Niña conditions in the Pacific Ocean. The global atmospheric CO₂ concentration reached 391.31 ± 0.13 ppm at the end of year 2011. We estimate that E_FF will have increased by 2.6% (1.9–3.5%) in 2012 based on projections of gross world product and recent changes in the carbon intensity of the economy. All uncertainties are reported as ±1 sigma (68% confidence assuming Gaussian error distributions that the real value lies within the given interval), reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. This paper is intended to provide a baseline to keep track of annual carbon budgets in the future. All data presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi:10.3334/CDIAC/GCP_V2013). Global carbon budget 2013