Seawater cultures were conducted in large volume (36 1) gas impermeable tri-laminate bags for the purpose of empirically deriving bacterial growth efficiency (BGE) and carbon conversion factors (CCF) in the south central Ross Sea. Thls experimental design allowed for concomitant nleasurements of metabolic reactants (loss of total and dissolved organic carbon [TOC and DOC]) and products (gain of total carbon dioxide [TCOz] and bacterial biomass) to be made from a single incubation vessel. Some previous studies have relied on proxy measurements (e.g. 02, 3H-thymidine incorporation and cell abundance) to determine BGE and CCF rather than direct carbon measurements. Our experimental design enabled a complete carbon budget to be constructed and eliminated variability associated with normally employed parallel bottle incubations. Uhlization of TOC was well balanced by the production of TC02, in 7 of 8 experiments, validating the use of tri-laminate bags for measuring microbial respiration. In 3 experiments, where TOC, DOC, TCOzand bacterial biovolume were directly measured, carbon mass balance yielded BGE estimates of 12, 32 and 38% and bacterial CCF of 77, 95 and 134 fg C pm-3 In experiments where independent DOC measurements were not made we used our empirically derived CCF values to determine bacterial carbon production and calculated DOC concentrations and BGE for these remaining experiments. The BGE derived from all the bag experiments conducted throughout the austral spring and summer 1995-1997 ranged from 9 to 38%. Our experimental design and carbon mass balance approach could be applied to other aquatic systems to empirically derive the BGE and CCF, factors essential for determining carbon flux through bacterioplankton.

Abstract. 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 data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFOS) 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) is estimated with global ocean biogeochemistry models and observation-based data-products. The terrestrial CO2 sink (SLAND) is estimated with dynamic global vegetation models. 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 first time, an approach is shown to reconcile the difference in our ELUC estimate with the one from national greenhouse gases inventories, supporting the assessment of collective countries’ climate progress. For the year 2020, EFOS declined by 5.4 % relative to 2019, with fossil emissions at 9.5 ± 0.5 GtC yr−1 (9.3 ± 0.5 GtC yr−1 when the cement carbonation sink is included), ELUC was 0.9 ± 0.7 GtC yr−1, for a total anthropogenic CO2 emission of 10.2 ± 0.8 GtC yr−1 (37.4 ± 2.9 GtCO2). Also, for 2020, GATM was 5.0 ± 0.2 GtC yr−1 (2.4 ± 0.1 ppm yr−1), SOCEAN was 3.0 ± 0.4 GtC yr−1 and SLAND was 2.9 ± 1 GtC yr−1, with a BIM of −0.8 GtC yr−1. The global atmospheric CO2 concentration averaged over 2020 reached 412.45 ± 0.1 ppm. Preliminary data for 2021, suggest a rebound in EFOS relative to 2020 of +4.9 % (4.1 % to 5.7 %) globally. Overall, the mean and trend in the components of the global carbon budget are consistently estimated over the period 1959–2020, but discrepancies of up to 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: (1) a persistent large uncertainty in the estimate of land-use changes emissions, (2) a 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 strength of the ocean sink over the last decade. 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 (Friedlingstein et al., 2020; Friedlingstein et al., 2019; Le Quéré et al., 2018b, 2018a, 2016, 2015b, 2015a, 2014, 2013). The data presented in this work are available at https://doi.org/10.18160/gcp-2021 (Friedlingstein et al., 2021).

Modafinil had no effect on cancer-related fatigue and should not be prescribed outside a clinical trial setting. Its use was associated with a clinically significant placebo effect.