Global Carbon Budget 2016 Academic Article uri icon

abstract

  • <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 – 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. CO<sub>2</sub> emissions from fossil fuels and industry (<i>E</i><sub>FF</sub>) are based on energy statistics and cement production data, respectively, 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 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. 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 ±1<i>?</i>, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2006–2015), <i>E</i><sub>FF</sub> was 9.3<span class="thinspace"></span>±<span class="thinspace"></span>0.5<span class="thinspace"></span>GtC<span class="thinspace"></span>yr<sup>?1</sup>, <i>E</i><sub>LUC</sub> 1.0<span class="thinspace"></span>±<span class="thinspace"></span>0.5<span class="thinspace"></span>GtC<span class="thinspace"></span>yr<sup>?1</sup>, <i>G</i><sub>ATM</sub> 4.5<span class="thinspace"></span>±<span class="thinspace"></span>0.1<span class="thinspace"></span>GtC<span class="thinspace"></span>yr<sup>?1</sup>, <i>S</i><sub>OCEAN</sub> 2.6<span class="thinspace"></span>±<span class="thinspace"></span>0.5<span class="thinspace"></span>GtC<span class="thinspace"></span>yr<sup>?1</sup>, and <i>S</i><sub>LAND</sub> 3.1<span class="thinspace"></span>±<span class="thinspace"></span>0.9<span class="thinspace"></span>GtC<span class="thinspace"></span>yr<sup>?1</sup>. For year 2015 alone, the growth in <i>E</i><sub>FF</sub> was approximately zero and emissions remained at 9.9<span class="thinspace"></span>±<span class="thinspace"></span>0.5<span class="thinspace"></span>GtC<span class="thinspace"></span>yr<sup>?1</sup>, showing a slowdown in growth of these emissions compared to the average growth of 1.8<span class="thinspace"></span>%<span class="thinspace"></span>yr<sup>?1</sup> that took place during 2006–2015. Also, for 2015, <i>E</i><sub>LUC</sub> was 1.3<span class="thinspace"></span>±<span class="thinspace"></span>0.5<span class="thinspace"></span>GtC<span class="thinspace"></span>yr<sup>?1</sup>, <i>G</i><sub>ATM</sub> was 6.3<span class="thinspace"></span>±<span class="thinspace"></span>0.2<span class="thinspace"></span>GtC<span class="thinspace"></span>yr<sup>?1</sup>, <i>S</i><sub>OCEAN</sub> was 3.0<span class="thinspace"></span>±<span class="thinspace"></span>0.5<span class="thinspace"></span>GtC<span class="thinspace"></span>yr<sup>?1</sup>, and <i>S</i><sub>LAND</sub> was 1.9<span class="thinspace"></span>±<span class="thinspace"></span>0.9<span class="thinspace"></span>GtC<span class="thinspace"></span>yr<sup>?1</sup>. <i>G</i><sub>ATM</sub> was higher in 2015 compared to the past decade (2006–2015), reflecting a smaller <i>S</i><sub>LAND</sub> for that year. The global atmospheric CO<sub>2</sub> concentration reached 399.4<span class="thinspace"></span>±<span class="thinspace"></span>0.1<span class="thinspace"></span>ppm averaged over 2015. For 2016, preliminary data indicate the continuation of low growth in <i>E</i><sub>FF</sub> with +0.2<span class="thinspace"></span>% (range of ?1.0 to +1.8<span class="thinspace"></span>%) 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 <i>E</i><sub>FF</sub> in 2016, the growth rate in atmospheric CO<sub>2</sub> concentration is expected to be relatively high because of the persistence of the smaller residual terrestrial sink (<i>S</i><sub>LAND</sub>) in response to El Niño conditions of 2015–2016. From this projection of <i>E</i><sub>FF</sub> and assumed constant <i>E</i><sub>LUC</sub> for 2016, cumulative emissions of CO<sub>2</sub> will reach 565<span class="thinspace"></span>±<span class="thinspace"></span>55<span class="thinspace"></span>GtC (2075<span class="thinspace"></span>±<span class="thinspace"></span>205<span class="thinspace"></span>GtCO<sub>2</sub>) for 1870–2016, about 75<span class="thinspace"></span>% from <i>E</i><sub>FF</sub> and 25<span class="thinspace"></span>% from <i>E</i><sub>LUC</sub>. 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 (<a href="http://dx.doi.org/10.3334/CDIAC/GCP_2016" target="_blank">doi:10.3334/CDIAC/GCP_2016</a>).</p>

authors

publication date

  • March 12, 2018