Global carbon budget 2014

摘要

Accurate assessment of anthropogenic carbon dioxide (CO₂) emissions andtheir redistribution among the atmosphere, ocean, and terrestrial biosphereis important to better understand the global carbon cycle, support thedevelopment of climate policies, and project future climate change. Here wedescribe data sets and a methodology to quantify all major components of theglobal carbon budget, including their uncertainties, based on the combinationof a range of data, algorithms, statistics, and model estimates and theirinterpretation by a broad scientific community. We discuss changes comparedto previous estimates, consistency within and among components, alongsidemethodology and data limitations. CO₂ emissions from fossil fuelcombustion and cement production (E_FF) are based on energystatistics and cement production data, respectively, while emissions fromland-use change (E_LUC), mainly deforestation, are based oncombined evidence from land-cover-change data, fire activity associated withdeforestation, and models. The global atmospheric CO₂ concentration ismeasured directly and its rate of growth (G_ATM) is computed fromthe annual changes in concentration. The mean ocean CO₂ sink(S_OCEAN) is based on observations from the 1990s, while theannual anomalies and trends are estimated with ocean models. The variabilityin S_OCEAN is evaluated with data products based on surveys ofocean CO₂ measurements. The global residual terrestrial CO₂ sink(S_LAND) is estimated by the difference of the other terms of theglobal carbon budget and compared to results of independent dynamic globalvegetation models forced by observed climate, CO₂, and land-cover-change(some including nitrogen–carbon interactions). We compare the mean land andocean fluxes and their variability to estimates from three atmosphericinverse methods for three broad latitude bands. All uncertainties arereported as ±1σ, reflecting the current capacity to characterisethe annual estimates of each component of the global carbon budget. For thelast decade available (2004–2013), E_FF was8.9 ± 0.4 GtC yr?1, E_LUC 0.9 ± 0.5 GtC yr?1, G_ATM4.3 ± 0.1 GtC yr?1, S_OCEAN2.6 ± 0.5 GtC yr?1, and S_LAND2.9 ± 0.8 GtC yr?1. For year 2013 alone, E_FF grew to9.9 ± 0.5 GtC yr?1, 2.3% above 2012, continuing the growthtrend in these emissions, E_LUC was0.9 ± 0.5 GtC yr?1, G_ATM was5.4 ± 0.2 GtC yr?1, S_OCEAN was2.9 ± 0.5 GtC yr?1, and S_LAND was2.5 ± 0.9 GtC yr?1. G_ATM was high in 2013, reflectinga steady increase in E_FF and smaller and opposite changes betweenS_OCEAN and S_LAND compared to the past decade(2004–2013). The global atmospheric CO₂ concentration reached395.31 ± 0.10 ppm averaged over 2013. We estimate that E_FFwill 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 inthe carbon intensity of the global economy. From this projection ofE_FF and assumed constant E_LUC for 2014, cumulativeemissions of CO₂ will reach about 545 ± 55 GtC(2000 ± 200 GtCO₂) for 1870–2014, about 75% fromE_FF and 25% from E_LUC. This paper documentschanges in the methods and data sets used in this new carbon budget comparedwith previous publications of this living data set (Le Quéré et al.,2013, 2014). All observations presented