Global carbon budget 2013 Academic Article uri icon


  • <p><strong>Abstract.</strong> Accurate assessment of anthropogenic carbon dioxide (CO<sub>2</sub>) 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. CO<sub>2</sub> emissions from fossil-fuel combustion and cement production (<i>E</i><sub>FF</sub>) are based on energy statistics, while emissions from land-use change (<i>E</i><sub>LUC</sub>), mainly deforestation, are based on combined evidence from land-cover change data, fire activity associated with deforestation, and models. The global atmospheric CO<sub>2</sub> concentration is measured directly and its rate of growth (<i>G</i><sub>ATM</sub>) is computed from the annual changes in concentration. The mean ocean CO<sub>2</sub> sink (<i>S</i><sub>OCEAN</sub>) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in <i>S</i><sub>OCEAN</sub> is evaluated for the first time in this budget with data products based on surveys of ocean CO<sub>2</sub> measurements. The global residual terrestrial CO<sub>2</sub> sink (<i>S</i><sub>LAND</sub>) 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, CO<sub>2</sub> and land cover change (some including nitrogen–carbon interactions). All uncertainties are reported as ±1&amp;sigma;, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2003–2012), <i>E</i><sub>FF</sub> was 8.6 ± 0.4 GtC yr<sup>?1</sup>, <i>E</i><sub>LUC</sub> 0.9 ± 0.5 GtC yr<sup>?1</sup>, <i>G</i><sub>ATM</sub> 4.3 ± 0.1 GtC yr<sup>?1</sup>, <i>S</i><sub>OCEAN</sub> 2.5 ± 0.5 GtC yr<sup>?1</sup>, and <i>S</i><sub>LAND</sub> 2.8 ± 0.8 GtC yr<sup>?1</sup>. For year 2012 alone, <i>E</i><sub>FF</sub> grew to 9.7 ± 0.5 GtC yr<sup>?1</sup>, 2.2% above 2011, reflecting a continued growing trend in these emissions, <i>G</i><sub>ATM</sub> was 5.1 ± 0.2 GtC yr<sup>?1</sup>, <i>S</i><sub>OCEAN</sub> was 2.9 ± 0.5 GtC yr<sup>?1</sup>, and assuming an <i>E</i><sub>LUC</sub> of 1.0 ± 0.5 GtC yr<sup>?1</sup> (based on the 2001–2010 average), <i>S</i><sub>LAND</sub> was 2.7 ± 0.9 GtC yr<sup>?1</sup>. <i>G</i><sub>ATM</sub> was high in 2012 compared to the 2003–2012 average, almost entirely reflecting the high <i>E</i><sub>FF</sub>. The global atmospheric CO<sub>2</sub> concentration reached 392.52 ± 0.10 ppm averaged over 2012. We estimate that <i>E</i><sub>FF</sub> will increase by 2.1% (1.1–3.1%) to 9.9 ± 0.5 GtC in 2013, 61% above emissions in 1990, based on projections of world gross domestic product and recent changes in the carbon intensity of the economy. With this projection, cumulative emissions of CO<sub>2</sub> will reach about 535 ± 55 GtC for 1870–2013, about 70% from <i>E</i><sub>FF</sub> (390 ± 20 GtC) and 30% from <i>E</i><sub>LUC</sub> (145 ± 50 GtC). <br><br> This paper also documents any changes in the methods and data sets used in this new carbon budget from previous budgets (Le Quéré et al., 2013). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (<a href=""target="_blank">doi:10.3334/CDIAC/GCP_2013_V2.3</a>).</p>


publication date

  • June 17, 2014