Global Carbon Budget 2019

Abstract

Abstract. 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. Fossil CO2 emissions (EFF) are based on energy statistics and cement production data, while emissions from land use change (ELUC), mainly deforestation, are based on land use and land use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) and terrestrial CO2 sink (SLAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (BIM), 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 (2009–2018), EFF was 9.5±0.5 GtC yr−1, ELUC 1.5±0.7 GtC yr−1, GATM 4.9±0.02 GtC yr−1 (2.3±0.01 ppm yr−1), SOCEAN 2.5±0.6 GtC yr−1, and SLAND 3.2±0.6 GtC yr−1, with a budget imbalance BIM of 0.4 GtC yr−1 indicating overestimated emissions and/or underestimated sinks. For the year 2018 alone, the growth in EFF was about 2.1 % and fossil emissions increased to 10.0±0.5 GtC yr−1, reaching 10 GtC yr−1 for the first time in history, ELUC was 1.5±0.7 GtC yr−1, for total anthropogenic CO2 emissions of 11.5±0.9 GtC yr−1 (42.5±3.3 GtCO2). Also for 2018, GATM was 5.1±0.2 GtC yr−1 (2.4±0.1 ppm yr−1), SOCEAN was 2.6±0.6 GtC yr−1, and SLAND was 3.5±0.7 GtC yr−1, with a BIM of 0.3 GtC. The global atmospheric CO2 concentration reached 407.38±0.1 ppm averaged over 2018. For 2019, preliminary data for the first 6–10 months indicate a reduced growth in EFF of +0.6 % (range of −0.2 % to 1.5 %) based on national emissions projections for China, the USA, the EU, and India and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. Overall, the mean and trend in the five components of the global carbon budget are consistently estimated over the period 1959–2018, but discrepancies of up to 1 GtC yr−1 persist for the representation of semi-decadal variability in CO2 fluxes. A detailed comparison among individual estimates and the introduction of a broad range of observations shows (1) no consensus in the mean and trend in land use change emissions over the last decade, (2) a persistent low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) an apparent underestimation of the CO2 variability by ocean models outside the tropics. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this data set (Le Quéré et al., 2018a, b, 2016, 2015a, b, 2014, 2013). The data generated by this work are available at https://doi.org/10.18160/gcp-2019 (Friedlingstein et al., 2019).

The Global Distribution of Biological Nitrogen Fixation in Terrestrial Natural Ecosystems

“…The terrestrial carbon cycle is an important contributor to the uptake of atmospheric carbon, removing about a third of anthropogenic carbon emissions from the atmosphere (Friedlingstein et al, 2019;Le Quéré et al, 2018). Carbon fixation in the terrestrial biosphere is dependent on chlorophyll, of which nitrogen is a key component.…”

Soil Erosion and Gaseous Emissions

“…Important among these are climate [10,13], soil [15][16][17], terrain [18] and land use [13][14][15][19][20][21][22][23]. On the basis of some empirical data from 240 runoff plots studied over the entire rainy season from diverse global ecoregions, Mueller-Nedebock and Chaplot [18] estimated that the total amount of SOC displaced by sheet erosion from its source would be 1.32 ± 0.20 Pg C, or about 11.4% of the annual anthropogenic emission of 11.5 Pg C in 2019 [21]. Integrating all C fluxes for the EU agricultural soils, Lugato et al The author of [24] estimated a net C loss or gain of −2.28 Tg CO 2 e/yr.…”

“…Some examples of gaseous emissions from eroded and depositional sites are shown in (Table 5) [60,61]. Assuming an average flux of 300 mg CO 2 eq/m 2 ·h based on literature review, Oertel et al [62] estimated the global annual net soil emissions at ≥350 Pg CO 2 e, as compared with the 2018 anthropogenic emission of 42.1 Pg CO 2 e [21]. However, the large emissions from soil C transported by aeolian and alluvial processes are not considered in the global C budget (GCB), which creates a lot of uncertainty.…”

“…Erosion-induced transport of soil C (SOC and SIC) is a large and growing component with a strong impact on the GCB, but which is now being omitted [21]. However, the erosion-induced impact on soil C stock and flux, a large component comprising of multiple gases (CO 2 , CH 4 , N 2 O) and multiple processes (e.g., water, wind, gravity, and tillage), must be dually considered.…”

Spatial variations in CO<sub>2</sub> fluxes in the Saguenay Fjord (Quebec, Canada) and results of a water mixing model

“…The oceans, the largest CO 2 reservoir on Earth, have taken up ca. 30 % of the anthropogenic CO 2 emitted to the atmosphere since the beginning of the industrial era (Feely et al, 2004;Brewer and Peltzer, 2009;Doney et al, 2009;Orr, 2011;Friedlingstein et al, 2019), mitigating the impact of this greenhouse gas on global warming . On the other hand, the uptake of CO 2 by the oceans has led to modifications of the seawater carbonate chemistry and a decline in the average surface ocean pH by ∼ 0.1 units since pre-industrial times, a phenomenon dubbed ocean acidification (Caldeira and Wickett, 2005).…”