See Jones et al. (2021) for a detailed description of this dataset and the core methods used to produce it. Key details are provided below. Product Description GCP-GridFED (version 2021.3) is a gridded fossil emissions dataset that is consistent with the national CO2 emissions reported by the Global Carbon Project (GCP). GCP-GridFEDv2021.3 provides monthly fossil CO2 emissions for the period 1959-2020 at a spatial resolution of 0.1° × 0.1°. The gridded emissions estimates are provided separately for fossil CO2 emitted by the oxidation of oil, coal and natural gas, with mixed international bunker fuels considered separately, as well as for the calcination of limestone during cement production. GCP-GridFED also includes gridded uncertainties in CO2 emission, incorporating differences in uncertainty across emissions sectors and countries, and gridded estimates of corresponding O2 uptake based on oxidative ratios for oil, coal and natural gas. Core Methodology in Brief GCP-GridFEDv2021.3 was produced by scaling monthly gridded emissions for the year 2010, from the Emissions Database for Global Atmospheric Research (EDGAR v4.3.2; Janssens-Maenhout et al., 2019), to the national annual emissions estimates compiled as part of the 2020 global carbon budget (GCP-NAE) for the years 1959-2020 (Friedlingstein et al., in preparation [Earth System Science Data]), an update from the 2020 global carbon budget (Friedlingstein et al., 2020). GCP-GridFEDv2021.3 uses a preliminary release of GCP-NAE covering the years 1959-2020 (timestamp 31st July 2021). The GCP-NAE estimates for year 2020 are based on data available on 31st July 2021 and the estimates are thus expected to differ somewhat from those that will be presented by Friedlingstein et al. (in preparation [Earth System Science Data]), which will adopt updates to GCP-NAE since 31st July 2021. From October 2021, Andrew and Peters (2021) began to publish regular updates of their GCP-NAE dataset, including regular updates. For full details of the core methodology, see Jones et al. (2021). New Methodology for Years 2019-2020 using Carbon Monitor Data GCP-GridFEDv2021.3 features methodological changes beyond the core methods presented by Jones et al. (2021) in this version of GCP-GridFED because the seasonality of CO2 emissions was drastically affected by the lockdowns implemented to deal with the COVID-19 pandemic. Hitherto, GCP-GridFED has adopted the seasonality (that is, the monthly distribution of emissions) from EDGAR v4.3.2 (year 2010; Janssens-Maenhout et al., 2019) and applied a small correction based on heating/cooling degree days to account for inter-annual climate variability which effects emissions in some sectors (see Jones et al., 2021). Due to international responses to the COVID-19 pandemic, the typical seasonal pattern was broken in the year 2020. Hence, we now adopt the seasonality of CO2 emissions at the national level from Carbon Monitor (Liu et al., 2020), with state-level data for large countries. We apply this change in methodology to the years included in the Carbon Monitor dataset; 2019-2020. Nonetheless, the national annual emissions remain consistent with GCP-NAE (timestamp 31st July 2021) in 2019 and 2020. Corrections to O2 emissions in v2021.3 In GridFEDv2021.3, we make a correction to the oxidative ratios (OR) used to estimate O2 consumption per unit CO2 emitted (g O2 g-1 CO2). OR values now accurately match the values reported by Steinbach et al. (2012) and are 1.05 g O2 g-1 CO2 for oil (and bunker fuels), 0.85 g O2 g-1 CO2 for coal, and 1.42 g O2 g-1 CO2 for gas. The gridded values of O2 consumption are negative and indicate that the flux of O2 is from atmosphere to surface (in contrast to +ve fluxes of CO2).

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