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.

Accurate assessment of anthropogenic carbon dioxide (CO₂) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate is critical to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesize datasets and methodologies to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO₂ emissions (E_FOS) are based on energy statistics and cement production data, while emissions from land-use change (E_LUC) are based on land-use and land-use change data and bookkeeping models. Atmospheric CO₂ concentration is measured directly, and its growth rate (G_ATM) is computed from the annual changes in concentration. The global net uptake of CO₂ by the ocean (S_OCEAN, called the ocean sink) is estimated with global ocean biogeochemistry models and observation-based fCO₂ products (fCO₂ is the fugacity of CO₂). The global net uptake of CO₂ by the land (S_LAND, called the land sink) is estimated with dynamic global vegetation models. Additional lines of evidence on land and ocean sinks are provided by atmospheric inversions, atmospheric oxygen measurements, and Earth system models. The sum of all sources and sinks results in the carbon budget imbalance (B_IM), a measure of imperfect data and incomplete understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the year 2023, E_FOS increased by 1.3 % relative to 2022, with fossil emissions at 10.1 ± 0.5 GtC yr⁻¹ (10.3 ± 0.5 GtC yr⁻¹ when the cement carbonation sink is not included), and E_LUC was 1.0 ± 0.7 GtC yr⁻¹, for a total anthropogenic CO₂ emission (including the cement carbonation sink) of 11.1 ± 0.9 GtC yr⁻¹ (40.6 ± 3.2 GtCO₂ yr⁻¹). Also, for 2023, G_ATM was 5.9 ± 0.2 GtC yr⁻¹ (2.79 ± 0.1 ppm yr⁻¹; ppm denotes parts per million), S_OCEAN was 2.9 ± 0.4 GtC yr⁻¹, and S_LAND was 2.3 ± 1.0 GtC yr⁻¹, with a near-zero B_IM (−0.02 GtC yr⁻¹). The global atmospheric CO₂ concentration averaged over 2023 reached 419.31 ± 0.1 ppm. Preliminary data for 2024 suggest an increase in E_FOS relative to 2023 of +0.8 % (−0.2 % to 1.7 %) globally and an atmospheric CO₂ concentration increase by 2.87 ppm, reaching 422.45 ppm, 52 % above the pre-industrial level (around 278 ppm in 1750). Overall, the mean of and trend in the components of the global carbon budget are consistently estimated over the period 1959–2023, with a near-zero overall budget imbalance, although discrepancies of up to around 1 GtC yr⁻¹ persist for the representation of annual to semi-decadal variability in CO₂ fluxes. Comparison of estimates from multiple approaches and observations shows the following: (1) a persistent large uncertainty in the estimate of land-use change emissions, (2) low agreement between the different methods on the magnitude of the land CO₂ flux in the northern extra-tropics, and (3) a discrepancy between the different methods on the mean ocean sink. This living-data update documents changes in methods and datasets applied to this most recent global carbon budget as well as evolving community understanding of the global carbon cycle. The data presented in this work are available at https://doi.org/10.18160/GCP-2024 (Friedlingstein et al., 2024).

A decline in the carbon fertilization effect: One source of uncertainty in climate science is how the carbon fertilization effect (CFE) will contribute to mitigation of anthropogenic climate change. Wang et al. explored the temporal dynamics of CFE on vegetation photosynthesis at the global scale. There has been a decline over recent decades in the contribution of CFE to vegetation photosynthesis, perhaps owing to the limiting effects of plant nutrients such as nitrogen and phosphorus. This declining trend has not been adequately accounted for in carbon cycle models. CFE thus has limitations for long-term mitigation of climate change, and future warming might currently be underestimated. Science , this issue p. 1295

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

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, consistency within and among components, alongside methodology and data limitations. CO₂ emissions from fossil fuel combustion and cement production (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 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 (2004–2013), E_FF was 8.9 ± 0.4 GtC yr⁻¹, E_LUC 0.9 ± 0.5 GtC yr⁻¹, G_ATM 4.3 ± 0.1 GtC yr⁻¹, S_OCEAN 2.6 ± 0.5 GtC yr⁻¹, and S_LAND 2.9 ± 0.8 GtC yr⁻¹. For year 2013 alone, E_FF grew to 9.9 ± 0.5 GtC yr⁻¹, 2.3% above 2012, continuing the growth trend in these emissions, E_LUC was 0.9 ± 0.5 GtC yr⁻¹, G_ATM was 5.4 ± 0.2 GtC yr⁻¹, S_OCEAN was 2.9 ± 0.5 GtC yr⁻¹, and S_LAND was 2.5 ± 0.9 GtC yr⁻¹. G_ATM was high in 2013, reflecting a steady increase in E_FF and smaller and opposite changes between S_OCEAN and S_LAND compared to the past decade (2004–2013). The global atmospheric CO₂ concentration reached 395.31 ± 0.10 ppm averaged over 2013. We estimate that E_FF will increase by 2.5% (1.3–3.5%) to 10.1 ± 0.6 GtC in 2014 (37.0 ± 2.2 GtCO₂ yr⁻¹), 65% above emissions in 1990, based on projections of world gross domestic product and recent changes in the carbon intensity of the global economy. From this projection of E_FF and assumed constant E_LUC for 2014, cumulative emissions of CO₂ will reach about 545 ± 55 GtC (2000 ± 200 GtCO₂) for 1870–2014, about 75% from E_FF and 25% from E_LUC. This paper documents changes in the methods and data sets used in this new carbon budget compared with previous publications of this living data set (Le Quéré et al., 2013, 2014). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi:10.3334/CDIAC/GCP_2014).